Merge remote-tracking branch 'upstream/master' into gcc-7

Conflicts:
	pkgs/development/compilers/gcc/7/default.nix
	pkgs/development/libraries/SDL2/default.nix
	pkgs/top-level/all-packages.nix

8 files changed, 1454 insertions, 1753 deletions

diff --git a/pkgs/development/compilers/gcc/4.5/default.nix b/pkgs/development/compilers/gcc/4.5/default.nix
index e7b188ad71b8..6b2718f5e692 100644
--- a/pkgs/development/compilers/gcc/4.5/default.nix
+++ b/pkgs/development/compilers/gcc/4.5/default.nix
@@ -25,6 +25,7 @@
 , libpthread ? null, libpthreadCross ? null  # required for GNU/Hurd
 , stripped ? true
 , buildPlatform, hostPlatform, targetPlatform
+, buildPackages
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -63,59 +64,68 @@ let version = "4.5.4";
 
     javaAwtGtk = langJava && gtk2 != null;
 
+    /* Platform flags */
+    platformFlags = let
+        gccArch = targetPlatform.platform.gcc.arch or null;
+        gccCpu = targetPlatform.platform.gcc.cpu or null;
+        gccAbi = targetPlatform.platform.gcc.abi or null;
+        gccFpu = targetPlatform.platform.gcc.fpu or null;
+        gccFloat = targetPlatform.platform.gcc.float or null;
+        gccMode = targetPlatform.platform.gcc.mode or null;
+      in
+        optional (gccArch != null) "--with-arch=${gccArch}" ++
+        optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
+        optional (gccAbi != null) "--with-abi=${gccAbi}" ++
+        optional (gccFpu != null) "--with-fpu=${gccFpu}" ++
+        optional (gccFloat != null) "--with-float=${gccFloat}" ++
+        optional (gccMode != null) "--with-mode=${gccMode}";
+
     /* Cross-gcc settings */
-    gccArch = stdenv.lib.attrByPath [ "gcc" "arch" ] null targetPlatform;
-    gccCpu = stdenv.lib.attrByPath [ "gcc" "cpu" ] null targetPlatform;
-    gccAbi = stdenv.lib.attrByPath [ "gcc" "abi" ] null targetPlatform;
-    withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-    withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-    withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
     crossMingw = (targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt");
 
     crossConfigureFlags =
-      withArch +
-      withCpu +
-      withAbi +
       # Ensure that -print-prog-name is able to find the correct programs.
-      " --with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as" +
-      " --with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" +
-      (if crossMingw && crossStageStatic then
-        " --with-headers=${libcCross}/include" +
-        " --with-gcc" +
-        " --with-gnu-as" +
-        " --with-gnu-ld" +
-        " --with-gnu-ld" +
-        " --disable-shared" +
-        " --disable-nls" +
-        " --disable-debug" +
-        " --enable-sjlj-exceptions" +
-        " --enable-threads=win32" +
-        " --disable-win32-registry"
-        else if crossStageStatic then
-        " --disable-libssp --disable-nls" +
-        " --without-headers" +
-        " --disable-threads " +
-        " --disable-libmudflap " +
-        " --disable-libgomp " +
-        " --disable-shared" +
-        " --disable-decimal-float" # libdecnumber requires libc
-        else
-        " --with-headers=${libcCross}/include" +
-        " --enable-__cxa_atexit" +
-        " --enable-long-long" +
-        (if crossMingw then
-          " --enable-threads=win32" +
-          " --enable-sjlj-exceptions" +
-          " --enable-hash-synchronization" +
-          " --enable-version-specific-runtime-libs" +
-          " --disable-libssp" +
-          " --disable-nls" +
-          " --with-dwarf2"
-          else
-          " --enable-threads=posix" +
-          " --enable-nls" +
-          " --disable-decimal-float") # No final libdecnumber (it may work only in 386)
-        );
+      [ "--with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as"
+        "--with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" ] ++
+      (if crossMingw && crossStageStatic then [
+        "--with-headers=${libcCross}/include"
+        "--with-gcc"
+        "--with-gnu-as"
+        "--with-gnu-ld"
+        "--with-gnu-ld"
+        "--disable-shared"
+        "--disable-nls"
+        "--disable-debug"
+        "--enable-sjlj-exceptions"
+        "--enable-threads=win32"
+        "--disable-win32-registry"
+      ] else if crossStageStatic then [
+        "--disable-libssp"
+        "--disable-nls"
+        "--without-headers"
+        "--disable-threads"
+        "--disable-libmudflap"
+        "--disable-libgomp"
+        "--disable-shared"
+        "--disable-decimal-float" # libdecnumber requires libc
+      ] else [
+        "--with-headers=${libcCross}/include"
+        "--enable-__cxa_atexit"
+        "--enable-long-long"
+      ] ++
+        (if crossMingw then [
+          "--enable-threads=win32"
+          "--enable-sjlj-exceptions"
+          "--enable-hash-synchronization"
+          "--enable-version-specific-runtime-libs"
+          "--enable-libssp"
+          "--disable-nls"
+          "--with-dwarf2"
+        ] else [
+          "--enable-threads=posix"
+          "--enable-nls"
+          "--disable-decimal-float" # No final libdecnumber (it may work only in 386)
+        ]));
     stageNameAddon = if crossStageStatic then "-stage-static" else
       "-stage-final";
     crossNameAddon = if targetPlatform != hostPlatform then "-${targetPlatform.config}" + stageNameAddon else "";
@@ -219,11 +229,22 @@ stdenv.mkDerivation ({
   inherit noSysDirs profiledCompiler staticCompiler langJava
     libcCross crossMingw;
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
   nativeBuildInputs = [ texinfo which gettext ]
     ++ optional (perl != null) perl;
 
-  buildInputs = [ gmp mpfr libmpc libelf ]
-    ++ (optional (ppl != null) ppl)
+  # For building runtime libs
+  depsBuildTarget =
+    if hostPlatform == buildPlatform then [
+      targetPackages.stdenv.cc.bintools # newly-built gcc will be used
+    ] else assert targetPlatform == hostPlatform; [ # build != host == target
+      stdenv.cc
+    ];
+
+  buildInputs = [
+    gmp mpfr libmpc libelf
+    targetPackages.stdenv.cc.bintools # For linking code at run-time
+  ] ++ (optional (ppl != null) ppl)
     ++ (optional (cloogppl != null) cloogppl)
     ++ (optional (zlib != null) zlib)
     ++ (optional langJava boehmgc)
@@ -237,79 +258,27 @@ stdenv.mkDerivation ({
   # TODO(@Ericson2314): Always pass "--target" and always prefix.
   configurePlatforms =
     # TODO(@Ericson2314): Figure out what's going wrong with Arm
-    if hostPlatform == targetPlatform && targetPlatform.isArm
+    if buildPlatform == hostPlatform && hostPlatform == targetPlatform && targetPlatform.isArm
     then []
     else [ "build" "host" ] ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
 
-  configureFlags = "
-    ${if enableMultilib then "" else "--disable-multilib"}
-    ${if enableShared then "" else "--disable-shared"}
-    ${if ppl != null then "--with-ppl=${ppl}" else ""}
-    ${if cloogppl != null then "--with-cloog=${cloogppl}" else ""}
-    ${if langJava then
-      "--with-ecj-jar=${javaEcj} " +
-
-      # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
-      # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
-      "--enable-java-home --with-java-home=\${prefix}/lib/jvm/jre "
-      else ""}
-    ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-    ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr}" else ""}
-    --with-gmp=${gmp.dev}
-    --with-mpfr=${mpfr.dev}
-    --with-mpc=${libmpc}
-    ${if libelf != null then "--with-libelf=${libelf}" else ""}
-    --disable-libstdcxx-pch
-    --without-included-gettext
-    --with-system-zlib
-    --enable-languages=${
-      concatStrings (intersperse ","
-        (  optional langC        "c"
-        ++ optional langCC       "c++"
-        ++ optional langFortran  "fortran"
-        ++ optional langJava     "java"
-        ++ optional langAda      "ada"
-        ++ optional langVhdl     "vhdl"
-        )
-      )
-    }
-    ${ # Trick that should be taken out once we have a mips64el-linux not loongson2f
-      if targetPlatform == hostPlatform && stdenv.system == "mips64el-linux" then "--with-arch=loongson2f" else ""}
-    ${if langAda then " --enable-libada" else ""}
-    ${if targetPlatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-    ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-  ";
-
-  targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
-
-  crossAttrs = {
-    AR = "${targetPlatform.config}-ar";
-    LD = "${targetPlatform.config}-ld";
-    CC = "${targetPlatform.config}-gcc";
-    CXX = "${targetPlatform.config}-gcc";
-    AR_FOR_TARGET = "${targetPlatform.config}-ar";
-    LD_FOR_TARGET = "${targetPlatform.config}-ld";
-    CC_FOR_TARGET = "${targetPlatform.config}-gcc";
-    NM_FOR_TARGET = "${targetPlatform.config}-nm";
-    CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
-    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
-    dontStrip = true;
-    configureFlags = ''
-      ${if enableMultilib then "" else "--disable-multilib"}
-      ${if enableShared then "" else "--disable-shared"}
-      ${if ppl != null then "--with-ppl=${ppl.crossDrv}" else ""}
-      ${if cloogppl != null then "--with-cloog=${cloogppl.crossDrv}" else ""}
-      ${if langJava then "--with-ecj-jar=${javaEcj.crossDrv}" else ""}
-      ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-      ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr.crossDrv}" else ""}
-      --with-gmp=${gmp.crossDrv}
-      --with-mpfr=${mpfr.crossDrv}
-      --with-mpc=${libmpc.crossDrv}
-      --disable-libstdcxx-pch
-      --without-included-gettext
-      --with-system-zlib
-      --enable-languages=${
+  configureFlags =
+    # Basic dependencies
+    [
+      "--with-gmp=${gmp.dev}"
+      "--with-mpfr=${mpfr.dev}"
+      "--with-mpc=${libmpc}"
+    ] ++
+    optional (libelf != null) "--with-libelf=${libelf}" ++
+    optional (!(crossMingw && crossStageStatic))
+      "--with-native-system-header-dir=${getDev stdenv.cc.libc}/include" ++
+
+    # Basic configuration
+    [
+      "--disable-libstdcxx-pch"
+      "--without-included-gettext"
+      "--with-system-zlib"
+      "--enable-languages=${
         concatStrings (intersperse ","
           (  optional langC        "c"
           ++ optional langCC       "c++"
@@ -319,31 +288,61 @@ stdenv.mkDerivation ({
           ++ optional langVhdl     "vhdl"
           )
         )
-      }
-      ${if langAda then " --enable-libada" else ""}
-      ${if targetplatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-      ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-    '';
-  };
- 
+      }"
+    ] ++
+    optional (!enableMultilib) "--disable-multilib" ++
+    optional (!enableShared) "--disable-shared" ++
+
+    # Optional features
+    optional (cloogppl != null) "--with-cloog=${cloogppl}" ++
+    optional (ppl != null) "--with-ppl=${ppl}" ++
 
-  # Needed for the cross compilation to work
-  AR = "ar";
-  LD = "ld";
-  CC = "gcc";
+    # Java options
+    optionals langJava [
+      "--with-ecj-jar=${javaEcj}"
 
-  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find
-  # the library headers and binaries, regarless of the language being
-  # compiled.
+      # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
+      # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
+      "--enable-java-home"
+      "--with-java-home=\${prefix}/lib/jvm/jre"
+    ] ++
+    optional javaAwtGtk "--enable-java-awt=gtk" ++
+    optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}" ++
 
-  # Note: When building the Java AWT GTK+ peer, the build system doesn't
-  # honor `--with-gmp' et al., e.g., when building
-  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just
-  # add them to $CPATH and $LIBRARY_PATH in this case.
+    # Ada
+    optional langAda "--enable-libada" ++
+
+    platformFlags ++
+    optional (targetPlatform != hostPlatform) crossConfigureFlags ++
+
+    # Platform-specific flags
+    optional (targetPlatform == hostPlatform && targetPlatform.isi686) "--with-arch=i686" ++
+    # Trick that should be taken out once we have a mips64el-linux not loongson2f
+    optional (targetPlatform == hostPlatform && stdenv.system == "mips64el-linux") "--with-arch=loongson2f"
+  ;
+
+  targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
+
+  /* For cross-built gcc (build != host == target) */
+  crossAttrs = {
+    dontStrip = true;
+  };
+
+  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
+  # library headers and binaries, regarless of the language being compiled.
+  #
+  # Note: When building the Java AWT GTK+ peer, the build system doesn't honor
+  # `--with-gmp' et al., e.g., when building
+  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just add
+  # them to $CPATH and $LIBRARY_PATH in this case.
   #
   # Likewise, the LTO code doesn't find zlib.
+  #
+  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
+  # compiler (after the specs for the cross-gcc are created). Having
+  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.
 
-  CPATH = makeSearchPathOutput "dev" "include" ([]
+  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
@@ -354,42 +353,44 @@ stdenv.mkDerivation ({
     # On GNU/Hurd glibc refers to Mach & Hurd
     # headers.
     ++ optionals (libcCross != null && libcCross ? propagatedBuildInputs)
-                 libcCross.propagatedBuildInputs);
+                 libcCross.propagatedBuildInputs
+  ));
 
-  LIBRARY_PATH = makeLibraryPath ([]
+  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
-    ++ optional (libpthread != null) libpthread);
-
-  EXTRA_TARGET_CFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-idirafter ${libcCross.dev}/include"
-      ]
-      ++ optionals (! crossStageStatic) [
-        "-B${libcCross.out}/lib"
-      ]
-    else null;
-
-  EXTRA_TARGET_LDFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-Wl,-L${libcCross.out}/lib"
-      ]
-      ++ (if crossStageStatic then [
+    ++ optional (libpthread != null) libpthread)
+  );
+
+  EXTRA_TARGET_FLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-idirafter ${libcCross.dev}/include"
+    ] ++ optionals (! crossStageStatic) [
+      "-B${libcCross.out}/lib"
+    ]);
+
+  EXTRA_TARGET_LDFLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-Wl,-L${libcCross.out}/lib"
+    ] ++ (if crossStageStatic then [
         "-B${libcCross.out}/lib"
       ] else [
         "-Wl,-rpath,${libcCross.out}/lib"
         "-Wl,-rpath-link,${libcCross.out}/lib"
-      ])
-      ++ optionals (libpthreadCross != null) [
-        "-L${libpthreadCross}/lib"
-        "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
-      ]
-    else null;
-
-  passthru = { inherit langC langCC langAda langFortran langVhdl
-      enableMultilib version; isGNU = true; };
+    ]) ++ optionals (libpthreadCross != null) [
+      "-L${libpthreadCross}/lib"
+      "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
+    ]);
+
+  passthru = {
+    inherit langC langCC langAda langFortran langVhdl enableMultilib version;
+    isGNU = true;
+    hardeningUnsupportedFlags = [ "stackprotector" ];
+  };
 
   enableParallelBuilding = !langAda;
 
diff --git a/pkgs/development/compilers/gcc/4.8/default.nix b/pkgs/development/compilers/gcc/4.8/default.nix
index ab91528049c4..0105a159877a 100644
--- a/pkgs/development/compilers/gcc/4.8/default.nix
+++ b/pkgs/development/compilers/gcc/4.8/default.nix
@@ -23,7 +23,7 @@
 , x11Support ? langJava
 , gnatboot ? null
 , enableMultilib ? false
-, enablePlugin ? true             # whether to support user-supplied plug-ins
+, enablePlugin ? hostPlatform == buildPlatform # Whether to support user-supplied plug-ins
 , name ? "gcc"
 , libcCross ? null
 , crossStageStatic ? false
@@ -33,6 +33,7 @@
 , gnused ? null
 , darwin ? null
 , buildPlatform, hostPlatform, targetPlatform
+, buildPackages
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -109,105 +110,78 @@ let version = "4.8.5";
 
     /* Platform flags */
     platformFlags = let
-        gccArch = stdenv.platform.gcc.arch or null;
-        gccCpu = stdenv.platform.gcc.cpu or null;
-        gccAbi = stdenv.platform.gcc.abi or null;
-        gccFpu = stdenv.platform.gcc.fpu or null;
-        gccFloat = stdenv.platform.gcc.float or null;
-        gccMode = stdenv.platform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
+        gccArch = targetPlatform.platform.gcc.arch or null;
+        gccCpu = targetPlatform.platform.gcc.cpu or null;
+        gccAbi = targetPlatform.platform.gcc.abi or null;
+        gccFpu = targetPlatform.platform.gcc.fpu or null;
+        gccFloat = targetPlatform.platform.gcc.float or null;
+        gccMode = targetPlatform.platform.gcc.mode or null;
       in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode;
-
-    /* Cross-gcc settings */
+        optional (gccArch != null) "--with-arch=${gccArch}" ++
+        optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
+        optional (gccAbi != null) "--with-abi=${gccAbi}" ++
+        optional (gccFpu != null) "--with-fpu=${gccFpu}" ++
+        optional (gccFloat != null) "--with-float=${gccFloat}" ++
+        optional (gccMode != null) "--with-mode=${gccMode}";
+
+    /* Cross-gcc settings (build == host != target) */
     crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";
     crossDarwin = targetPlatform != hostPlatform && targetPlatform.libc == "libSystem";
-    crossConfigureFlags = let
-        gccArch = targetPlatform.gcc.arch or null;
-        gccCpu = targetPlatform.gcc.cpu or null;
-        gccAbi = targetPlatform.gcc.abi or null;
-        gccFpu = targetPlatform.gcc.fpu or null;
-        gccFloat = targetPlatform.gcc.float or null;
-        gccMode = targetPlatform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
-      in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode +
-        # Ensure that -print-prog-name is able to find the correct programs.
-        " --with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as" +
-        " --with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" +
-        (if crossMingw && crossStageStatic then
-          " --with-headers=${libcCross}/include" +
-          " --with-gcc" +
-          " --with-gnu-as" +
-          " --with-gnu-ld" +
-          " --with-gnu-ld" +
-          " --disable-shared" +
-          " --disable-nls" +
-          " --disable-debug" +
-          " --enable-sjlj-exceptions" +
-          " --enable-threads=win32" +
-          " --disable-win32-registry"
-          else if crossStageStatic then
-          " --disable-libssp --disable-nls" +
-          " --without-headers" +
-          " --disable-threads " +
-          " --disable-libmudflap " +
-          " --disable-libgomp " +
-          " --disable-libquadmath" +
-          " --disable-shared" +
-          " --disable-libatomic " +  # libatomic requires libc
-          " --disable-decimal-float" # libdecnumber requires libc
-          else
-          (if crossDarwin then " --with-sysroot=${libcCross.out}/share/sysroot"
-           else                " --with-headers=${libcCross.dev}/include") +
-          # Ensure that -print-prog-name is able to find the correct programs.
-          " --enable-__cxa_atexit" +
-          " --enable-long-long" +
-          (if crossMingw then
-            " --enable-threads=win32" +
-            " --enable-sjlj-exceptions" +
-            " --enable-hash-synchronization" +
-            " --disable-libssp" +
-            " --disable-nls" +
-            " --with-dwarf2" +
-            # I think noone uses shared gcc libs in mingw, so we better do the same.
-            # In any case, mingw32 g++ linking is broken by default with shared libs,
-            # unless adding "-lsupc++" to any linking command. I don't know why.
-            " --disable-shared" +
-            # To keep ABI compatibility with upstream mingw-w64
-            " --enable-fully-dynamic-string"
-            else (if targetPlatform.libc == "uclibc" then
-              # In uclibc cases, libgomp needs an additional '-ldl'
-              # and as I don't know how to pass it, I disable libgomp.
-              " --disable-libgomp" else "") +
-            " --enable-threads=posix" +
-            " --enable-nls" +
-            " --disable-decimal-float") # No final libdecnumber (it may work only in 386)
-          );
+    crossConfigureFlags =
+      # Ensure that -print-prog-name is able to find the correct programs.
+      [ "--with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as"
+        "--with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" ] ++
+      (if crossMingw && crossStageStatic then [
+        "--with-headers=${libcCross}/include"
+        "--with-gcc"
+        "--with-gnu-as"
+        "--with-gnu-ld"
+        "--with-gnu-ld"
+        "--disable-shared"
+        "--disable-nls"
+        "--disable-debug"
+        "--enable-sjlj-exceptions"
+        "--enable-threads=win32"
+        "--disable-win32-registry"
+      ] else if crossStageStatic then [
+        "--disable-libssp"
+        "--disable-nls"
+        "--without-headers"
+        "--disable-threads"
+        "--disable-libgomp"
+        "--disable-libquadmath"
+        "--disable-shared"
+        "--disable-libatomic"  # libatomic requires libc
+        "--disable-decimal-float" # libdecnumber requires libc
+      ] else [
+        (if crossDarwin then "--with-sysroot=${getLib libcCross}/share/sysroot"
+         else                "--with-headers=${getDev libcCross}/include")
+        "--enable-__cxa_atexit"
+        "--enable-long-long"
+      ] ++
+        (if crossMingw then [
+          "--enable-threads=win32"
+          "--enable-sjlj-exceptions"
+          "--enable-hash-synchronization"
+          "--enable-libssp"
+          "--disable-nls"
+          "--with-dwarf2"
+          # To keep ABI compatibility with upstream mingw-w64
+          "--enable-fully-dynamic-string"
+        ] else
+          optionals (targetPlatform.libc == "uclibc") [
+            # In uclibc cases, libgomp needs an additional '-ldl'
+            # and as I don't know how to pass it, I disable libgomp.
+            "--disable-libgomp"
+          ] ++ [
+          "--enable-threads=posix"
+          "--enable-nls"
+          "--disable-decimal-float" # No final libdecnumber (it may work only in 386)
+        ]));
     stageNameAddon = if crossStageStatic then "-stage-static" else "-stage-final";
     crossNameAddon = if targetPlatform != hostPlatform then "-${targetPlatform.config}" + stageNameAddon else "";
 
-    bootstrap = targetPlatform == hostPlatform && !hostPlatform.isArm && !hostPlatform.isMips;
+    bootstrap = targetPlatform == hostPlatform;
 
 in
 
@@ -293,6 +267,7 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler langJava
     libcCross crossMingw;
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
   nativeBuildInputs = [ texinfo which gettext ]
     ++ (optional (perl != null) perl)
     ++ (optional javaAwtGtk pkgconfig);
@@ -325,67 +300,90 @@ stdenv.mkDerivation ({
   # TODO(@Ericson2314): Always pass "--target" and always prefix.
   configurePlatforms =
     # TODO(@Ericson2314): Figure out what's going wrong with Arm
-    if hostPlatform == targetPlatform && targetPlatform.isArm
+    if buildPlatform == hostPlatform && hostPlatform == targetPlatform && targetPlatform.isArm
     then []
     else [ "build" "host" ] ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
 
-  configureFlags = "
-    ${if hostPlatform.isSunOS then
-      " --enable-long-long --enable-libssp --enable-threads=posix --disable-nls --enable-__cxa_atexit " +
-      # On Illumos/Solaris GNU as is preferred
-      " --with-gnu-as --without-gnu-ld "
-      else ""}
-    --enable-lto
-    ${if enableMultilib then "--disable-libquadmath" else "--disable-multilib"}
-    ${if enableShared then "" else "--disable-shared"}
-    ${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
-    ${optionalString (isl != null) "--with-isl=${isl}"}
-    ${optionalString (cloog != null) "--with-cloog=${cloog} --disable-cloog-version-check --enable-cloog-backend=isl"}
-    ${if langJava then
-      "--with-ecj-jar=${javaEcj} " +
+  configureFlags =
+    # Basic dependencies
+    [
+      "--with-gmp-include=${gmp.dev}/include"
+      "--with-gmp-lib=${gmp.out}/lib"
+      "--with-mpfr-include=${mpfr.dev}/include"
+      "--with-mpfr-lib=${mpfr.out}/lib"
+      "--with-mpc=${libmpc}"
+    ] ++
+    optional (libelf != null) "--with-libelf=${libelf}" ++
+    optional (!(crossMingw && crossStageStatic))
+      "--with-native-system-header-dir=${getDev stdenv.cc.libc}/include" ++
+
+    # Basic configuration
+    [
+      "--enable-lto"
+      "--disable-libstdcxx-pch"
+      "--without-included-gettext"
+      "--with-system-zlib"
+      "--enable-static"
+      "--enable-languages=${
+        concatStrings (intersperse ","
+          (  optional langC        "c"
+          ++ optional langCC       "c++"
+          ++ optional langFortran  "fortran"
+          ++ optional langJava     "java"
+          ++ optional langAda      "ada"
+          ++ optional langVhdl     "vhdl"
+          ++ optional langGo       "go"
+          ++ optional langObjC     "objc"
+          ++ optional langObjCpp   "obj-c++"
+          ++ optionals crossDarwin [ "objc" "obj-c++" ]
+          )
+        )
+      }"
+    ] ++
+
+    (if enableMultilib
+      then ["--enable-multilib" "--disable-libquadmath"]
+      else ["--disable-multilib"]) ++
+    optional (!enableShared) "--disable-shared" ++
+    (if enablePlugin
+      then ["--enable-plugin"]
+      else ["--disable-plugin"]) ++
+
+    # Optional features
+    optional (isl != null) "--with-isl=${isl}" ++
+    optionals (cloog != null) [
+      "--with-cloog=${cloog}"
+      "--disable-cloog-version-check"
+      "--enable-cloog-backend=isl"
+    ] ++
+
+    # Java options
+    optionals langJava [
+      "--with-ecj-jar=${javaEcj}"
 
       # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
       # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
-      "--enable-java-home --with-java-home=\${prefix}/lib/jvm/jre "
-      else ""}
-    ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-    ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr}" else ""}
-    --with-gmp-include=${gmp.dev}/include
-    --with-gmp-lib=${gmp.out}/lib
-    --with-mpfr-include=${mpfr.dev}/include
-    --with-mpfr-lib=${mpfr.out}/lib
-    --with-mpc=${libmpc}
-    ${if libelf != null then "--with-libelf=${libelf}" else ""}
-    --disable-libstdcxx-pch
-    --without-included-gettext
-    --with-system-zlib
-    --enable-static
-    --enable-languages=${
-      concatStrings (intersperse ","
-        (  optional langC        "c"
-        ++ optional langCC       "c++"
-        ++ optional langFortran  "fortran"
-        ++ optional langJava     "java"
-        ++ optional langAda      "ada"
-        ++ optional langVhdl     "vhdl"
-        ++ optional langGo       "go"
-        ++ optional langObjC     "objc"
-        ++ optional langObjCpp   "obj-c++"
-        ++ optionals crossDarwin [ "objc" "obj-c++" ]
-        )
-      )
-    }
-    ${if targetPlatform == hostPlatform
-      then if hostPlatform.isDarwin
-        then " --with-native-system-header-dir=${darwin.usr-include}"
-        else " --with-native-system-header-dir=${getDev stdenv.cc.libc}/include"
-      else ""}
-    ${if langAda then " --enable-libada" else ""}
-    ${if targetPlatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-    ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-    ${if !bootstrap then "--disable-bootstrap" else ""}
-    ${if targetPlatform == hostPlatform then platformFlags else ""}
-  ";
+      "--enable-java-home"
+      "--with-java-home=\${prefix}/lib/jvm/jre"
+    ] ++
+    optional javaAwtGtk "--enable-java-awt=gtk" ++
+    optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}" ++
+
+    # Ada
+    optional langAda "--enable-libada" ++
+
+    platformFlags ++
+    optional (targetPlatform != hostPlatform) crossConfigureFlags ++
+    optional (!bootstrap) "--disable-bootstrap" ++
+
+    # Platform-specific flags
+    optional (targetPlatform == hostPlatform && targetPlatform.isi686) "--with-arch=i686" ++
+    optionals hostPlatform.isSunOS [
+      "--enable-long-long" "--enable-libssp" "--enable-threads=posix" "--disable-nls" "--enable-__cxa_atexit"
+      # On Illumos/Solaris GNU as is preferred
+      "--with-gnu-as" "--without-gnu-ld"
+    ]
+  ;
 
   targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
 
@@ -398,84 +396,30 @@ stdenv.mkDerivation ({
     then "install-strip"
     else "install";
 
-  crossAttrs = let
-    xgccArch = targetPlatform.gcc.arch or null;
-    xgccCpu = targetPlatform.gcc.cpu or null;
-    xgccAbi = targetPlatform.gcc.abi or null;
-    xgccFpu = targetPlatform.gcc.fpu or null;
-    xgccFloat = targetPlatform.gcc.float or null;
-    xwithArch = if xgccArch != null then " --with-arch=${xgccArch}" else "";
-    xwithCpu = if xgccCpu != null then " --with-cpu=${xgccCpu}" else "";
-    xwithAbi = if xgccAbi != null then " --with-abi=${xgccAbi}" else "";
-    xwithFpu = if xgccFpu != null then " --with-fpu=${xgccFpu}" else "";
-    xwithFloat = if xgccFloat != null then " --with-float=${xgccFloat}" else "";
-  in {
-    AR = "${targetPlatform.config}-ar";
-    LD = "${targetPlatform.config}-ld";
-    CC = "${targetPlatform.config}-gcc";
-    CXX = "${targetPlatform.config}-gcc";
-    AR_FOR_TARGET = "${targetPlatform.config}-ar";
-    LD_FOR_TARGET = "${targetPlatform.config}-ld";
-    CC_FOR_TARGET = "${targetPlatform.config}-gcc";
-    NM_FOR_TARGET = "${targetPlatform.config}-nm";
-    CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
-    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
+  /* For cross-built gcc (build != host == target) */
+  crossAttrs =  {
     dontStrip = true;
-    configureFlags = ''
-      ${if enableMultilib then "" else "--disable-multilib"}
-      ${if enableShared then "" else "--disable-shared"}
-      ${if cloog != null then "--with-cloog=${cloog.crossDrv} --enable-cloog-backend=isl" else ""}
-      ${if langJava then "--with-ecj-jar=${javaEcj.crossDrv}" else ""}
-      ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-      ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr.crossDrv}" else ""}
-      --with-gmp=${gmp.crossDrv}
-      --with-mpfr=${mpfr.crossDrv}
-      --with-mpc=${libmpc.crossDrv}
-      --disable-libstdcxx-pch
-      --without-included-gettext
-      --with-system-zlib
-      --enable-languages=${
-        concatStrings (intersperse ","
-          (  optional langC        "c"
-          ++ optional langCC       "c++"
-          ++ optional langFortran  "fortran"
-          ++ optional langJava     "java"
-          ++ optional langAda      "ada"
-          ++ optional langVhdl     "vhdl"
-          ++ optional langGo       "go"
-          )
-        )
-      }
-      ${if langAda then " --enable-libada" else ""}
-      ${xwithArch}
-      ${xwithCpu}
-      ${xwithAbi}
-      ${xwithFpu}
-      ${xwithFloat}
-    '';
     buildFlags = "";
   };
 
-
-  # Needed for the cross compilation to work
-  AR = "ar";
-  LD = "ld";
   # http://gcc.gnu.org/install/specific.html#x86-64-x-solaris210
-  CC = if stdenv.system == "x86_64-solaris" then "gcc -m64" else "gcc";
-
-  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find
-  # the library headers and binaries, regarless of the language being
-  # compiled.
+  ${if hostPlatform.system == "x86_64-solaris" then "CC" else null} = "gcc -m64";
 
-  # Note: When building the Java AWT GTK+ peer, the build system doesn't
-  # honor `--with-gmp' et al., e.g., when building
-  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just
-  # add them to $CPATH and $LIBRARY_PATH in this case.
+  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
+  # library headers and binaries, regarless of the language being compiled.
+  #
+  # Note: When building the Java AWT GTK+ peer, the build system doesn't honor
+  # `--with-gmp' et al., e.g., when building
+  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just add
+  # them to $CPATH and $LIBRARY_PATH in this case.
   #
   # Likewise, the LTO code doesn't find zlib.
+  #
+  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
+  # compiler (after the specs for the cross-gcc are created). Having
+  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.
 
-  CPATH = makeSearchPathOutput "dev" "include" ([]
+  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
@@ -486,42 +430,44 @@ stdenv.mkDerivation ({
     # On GNU/Hurd glibc refers to Mach & Hurd
     # headers.
     ++ optionals (libcCross != null && libcCross ? propagatedBuildInputs)
-                 libcCross.propagatedBuildInputs);
+                 libcCross.propagatedBuildInputs
+  ));
 
-  LIBRARY_PATH = makeLibraryPath ([]
+  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
-    ++ optional (libpthread != null) libpthread);
-
-  EXTRA_TARGET_CFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-idirafter ${libcCross.dev}/include"
-      ]
-      ++ optionals (! crossStageStatic) [
-        "-B${libcCross.out}/lib"
-      ]
-    else null;
-
-  EXTRA_TARGET_LDFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-Wl,-L${libcCross.out}/lib"
-      ]
-      ++ (if crossStageStatic then [
+    ++ optional (libpthread != null) libpthread)
+  );
+
+  EXTRA_TARGET_FLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-idirafter ${libcCross.dev}/include"
+    ] ++ optionals (! crossStageStatic) [
+      "-B${libcCross.out}/lib"
+    ]);
+
+  EXTRA_TARGET_LDFLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-Wl,-L${libcCross.out}/lib"
+    ] ++ (if crossStageStatic then [
         "-B${libcCross.out}/lib"
       ] else [
         "-Wl,-rpath,${libcCross.out}/lib"
         "-Wl,-rpath-link,${libcCross.out}/lib"
-      ])
-      ++ optionals (libpthreadCross != null) [
-        "-L${libpthreadCross}/lib"
-        "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
-      ]
-    else null;
-
-  passthru =
-    { inherit langC langCC langObjC langObjCpp langAda langFortran langVhdl langGo version; isGNU = true; };
+    ]) ++ optionals (libpthreadCross != null) [
+      "-L${libpthreadCross}/lib"
+      "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
+    ]);
+
+  passthru = {
+    inherit langC langCC langObjC langObjCpp langAda langFortran langVhdl langGo version;
+    isGNU = true;
+    hardeningUnsupportedFlags = [ "stackprotector" ];
+  };
 
   inherit enableParallelBuilding enableMultilib;
 
diff --git a/pkgs/development/compilers/gcc/4.9/default.nix b/pkgs/development/compilers/gcc/4.9/default.nix
index 794d809fa727..1b1492686d0e 100644
--- a/pkgs/development/compilers/gcc/4.9/default.nix
+++ b/pkgs/development/compilers/gcc/4.9/default.nix
@@ -23,7 +23,7 @@
 , x11Support ? langJava
 , gnatboot ? null
 , enableMultilib ? false
-, enablePlugin ? true             # whether to support user-supplied plug-ins
+, enablePlugin ? hostPlatform == buildPlatform # Whether to support user-supplied plug-ins
 , name ? "gcc"
 , libcCross ? null
 , crossStageStatic ? false
@@ -33,6 +33,7 @@
 , gnused ? null
 , darwin ? null
 , buildPlatform, hostPlatform, targetPlatform
+, buildPackages
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -100,106 +101,81 @@ let version = "4.9.4";
 
     /* Platform flags */
     platformFlags = let
-        gccArch = stdenv.platform.gcc.arch or null;
-        gccCpu = stdenv.platform.gcc.cpu or null;
-        gccAbi = stdenv.platform.gcc.abi or null;
-        gccFpu = stdenv.platform.gcc.fpu or null;
-        gccFloat = stdenv.platform.gcc.float or null;
-        gccMode = stdenv.platform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
+        gccArch = targetPlatform.platform.gcc.arch or null;
+        gccCpu = targetPlatform.platform.gcc.cpu or null;
+        gccAbi = targetPlatform.platform.gcc.abi or null;
+        gccFpu = targetPlatform.platform.gcc.fpu or null;
+        gccFloat = targetPlatform.platform.gcc.float or null;
+        gccMode = targetPlatform.platform.gcc.mode or null;
       in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode;
-
-    /* Cross-gcc settings */
+        optional (gccArch != null) "--with-arch=${gccArch}" ++
+        optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
+        optional (gccAbi != null) "--with-abi=${gccAbi}" ++
+        optional (gccFpu != null) "--with-fpu=${gccFpu}" ++
+        optional (gccFloat != null) "--with-float=${gccFloat}" ++
+        optional (gccMode != null) "--with-mode=${gccMode}";
+
+    /* Cross-gcc settings (build == host != target) */
     crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";
     crossDarwin = targetPlatform != hostPlatform && targetPlatform.libc == "libSystem";
-    crossConfigureFlags = let
-        gccArch = targetPlatform.gcc.arch or null;
-        gccCpu = targetPlatform.gcc.cpu or null;
-        gccAbi = targetPlatform.gcc.abi or null;
-        gccFpu = targetPlatform.gcc.fpu or null;
-        gccFloat = targetPlatform.gcc.float or null;
-        gccMode = targetPlatform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
-      in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode +
-        # Ensure that -print-prog-name is able to find the correct programs.
-        " --with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as" +
-        " --with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" +
-        (if crossMingw && crossStageStatic then
-          " --with-headers=${libcCross}/include" +
-          " --with-gcc" +
-          " --with-gnu-as" +
-          " --with-gnu-ld" +
-          " --with-gnu-ld" +
-          " --disable-shared" +
-          " --disable-nls" +
-          " --disable-debug" +
-          " --enable-sjlj-exceptions" +
-          " --enable-threads=win32" +
-          " --disable-win32-registry"
-          else if crossStageStatic then
-          " --disable-libssp --disable-nls" +
-          " --without-headers" +
-          " --disable-threads " +
-          " --disable-libgomp " +
-          " --disable-libquadmath" +
-          " --disable-shared" +
-          " --disable-libatomic " +  # libatomic requires libc
-          " --disable-decimal-float" # libdecnumber requires libc
-          else
-          (if crossDarwin then " --with-sysroot=${libcCross.out}/share/sysroot"
-           else                " --with-headers=${libcCross.dev}/include") +
-          " --enable-__cxa_atexit" +
-          " --enable-long-long" +
-          (if crossMingw then
-            " --enable-threads=win32" +
-            " --enable-sjlj-exceptions" +
-            " --enable-hash-synchronization" +
-            " --disable-libssp" +
-            " --disable-nls" +
-            " --with-dwarf2" +
-            # I think noone uses shared gcc libs in mingw, so we better do the same.
-            # In any case, mingw32 g++ linking is broken by default with shared libs,
-            # unless adding "-lsupc++" to any linking command. I don't know why.
-            " --disable-shared" +
-            # To keep ABI compatibility with upstream mingw-w64
-            " --enable-fully-dynamic-string"
-            else (if targetPlatform.libc == "uclibc" then
-              # libsanitizer requires netrom/netrom.h which is not
-              # available in uclibc.
-              " --disable-libsanitizer" +
-              # In uclibc cases, libgomp needs an additional '-ldl'
-              # and as I don't know how to pass it, I disable libgomp.
-              " --disable-libgomp" else "") +
-            " --enable-threads=posix" +
-            " --enable-nls" +
-            " --disable-decimal-float") # No final libdecnumber (it may work only in 386)
-          );
+    crossConfigureFlags =
+      # Ensure that -print-prog-name is able to find the correct programs.
+      [ "--with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as"
+        "--with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" ] ++
+      (if crossMingw && crossStageStatic then [
+        "--with-headers=${libcCross}/include"
+        "--with-gcc"
+        "--with-gnu-as"
+        "--with-gnu-ld"
+        "--with-gnu-ld"
+        "--disable-shared"
+        "--disable-nls"
+        "--disable-debug"
+        "--enable-sjlj-exceptions"
+        "--enable-threads=win32"
+        "--disable-win32-registry"
+      ] else if crossStageStatic then [
+        "--disable-libssp"
+        "--disable-nls"
+        "--without-headers"
+        "--disable-threads"
+        "--disable-libgomp"
+        "--disable-libquadmath"
+        "--disable-shared"
+        "--disable-libatomic"  # libatomic requires libc
+        "--disable-decimal-float" # libdecnumber requires libc
+      ] else [
+        (if crossDarwin then "--with-sysroot=${getLib libcCross}/share/sysroot"
+         else                "--with-headers=${getDev libcCross}/include")
+        "--enable-__cxa_atexit"
+        "--enable-long-long"
+      ] ++
+        (if crossMingw then [
+          "--enable-threads=win32"
+          "--enable-sjlj-exceptions"
+          "--enable-hash-synchronization"
+          "--enable-libssp"
+          "--disable-nls"
+          "--with-dwarf2"
+          # To keep ABI compatibility with upstream mingw-w64
+          "--enable-fully-dynamic-string"
+        ] else
+          optionals (targetPlatform.libc == "uclibc") [
+            # libsanitizer requires netrom/netrom.h which is not
+            # available in uclibc.
+            "--disable-libsanitizer"
+            # In uclibc cases, libgomp needs an additional '-ldl'
+            # and as I don't know how to pass it, I disable libgomp.
+            "--disable-libgomp"
+          ] ++ [
+          "--enable-threads=posix"
+          "--enable-nls"
+          "--disable-decimal-float" # No final libdecnumber (it may work only in 386)
+        ]));
     stageNameAddon = if crossStageStatic then "-stage-static" else "-stage-final";
     crossNameAddon = if targetPlatform != hostPlatform then "-${targetPlatform.config}" + stageNameAddon else "";
 
-  bootstrap = targetPlatform == hostPlatform;
+    bootstrap = targetPlatform == hostPlatform;
 
 in
 
@@ -286,12 +262,23 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler langJava
     libcCross crossMingw;
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
   nativeBuildInputs = [ texinfo which gettext ]
     ++ (optional (perl != null) perl)
     ++ (optional javaAwtGtk pkgconfig);
 
-  buildInputs = [ gmp mpfr libmpc libelf ]
-    ++ (optional (cloog != null) cloog)
+  # For building runtime libs
+  depsBuildTarget =
+    if hostPlatform == buildPlatform then [
+      targetPackages.stdenv.cc.bintools # newly-built gcc will be used
+    ] else assert targetPlatform == hostPlatform; [ # build != host == target
+      stdenv.cc
+    ];
+
+  buildInputs = [
+    gmp mpfr libmpc libelf
+    targetPackages.stdenv.cc.bintools # For linking code at run-time
+  ] ++ (optional (cloog != null) cloog)
     ++ (optional (isl != null) isl)
     ++ (optional (zlib != null) zlib)
     ++ (optionals langJava [ boehmgc zip unzip ])
@@ -322,65 +309,89 @@ stdenv.mkDerivation ({
   # TODO(@Ericson2314): Always pass "--target" and always prefix.
   configurePlatforms =
     # TODO(@Ericson2314): Figure out what's going wrong with Arm
-    if hostPlatform == targetPlatform && targetPlatform.isArm
+    if buildPlatform == hostPlatform && hostPlatform == targetPlatform && targetPlatform.isArm
     then []
     else [ "build" "host" ] ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
 
-  configureFlags = "
-    ${if hostPlatform.isSunOS then
-      " --enable-long-long --enable-libssp --enable-threads=posix --disable-nls --enable-__cxa_atexit " +
-      # On Illumos/Solaris GNU as is preferred
-      " --with-gnu-as --without-gnu-ld "
-      else ""}
-    --enable-lto
-    ${if enableMultilib then "--enable-multilib --disable-libquadmath" else "--disable-multilib"}
-    ${if enableShared then "" else "--disable-shared"}
-    ${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
-    ${optionalString (isl != null) "--with-isl=${isl}"}
-    ${optionalString (cloog != null) "--with-cloog=${cloog} --disable-cloog-version-check --enable-cloog-backend=isl"}
-    ${if langJava then
-      "--with-ecj-jar=${javaEcj} " +
+  configureFlags =
+    # Basic dependencies
+    [
+      "--with-gmp-include=${gmp.dev}/include"
+      "--with-gmp-lib=${gmp.out}/lib"
+      "--with-mpfr=${mpfr.dev}"
+      "--with-mpc=${libmpc}"
+    ] ++
+    optional (libelf != null) "--with-libelf=${libelf}" ++
+    optional (!(crossMingw && crossStageStatic))
+      "--with-native-system-header-dir=${getDev stdenv.cc.libc}/include" ++
+
+    # Basic configuration
+    [
+      "--enable-lto"
+      "--disable-libstdcxx-pch"
+      "--without-included-gettext"
+      "--with-system-zlib"
+      "--enable-static"
+      "--enable-languages=${
+        concatStrings (intersperse ","
+          (  optional langC        "c"
+          ++ optional langCC       "c++"
+          ++ optional langFortran  "fortran"
+          ++ optional langJava     "java"
+          ++ optional langAda      "ada"
+          ++ optional langVhdl     "vhdl"
+          ++ optional langGo       "go"
+          ++ optional langObjC     "objc"
+          ++ optional langObjCpp   "obj-c++"
+          ++ optionals crossDarwin [ "objc" "obj-c++" ]
+          )
+        )
+      }"
+    ] ++
+
+    (if enableMultilib
+      then ["--enable-multilib" "--disable-libquadmath"]
+      else ["--disable-multilib"]) ++
+    optional (!enableShared) "--disable-shared" ++
+    (if enablePlugin
+      then ["--enable-plugin"]
+      else ["--disable-plugin"]) ++
+
+    # Optional features
+    optional (isl != null) "--with-isl=${isl}" ++
+    optionals (cloog != null) [
+      "--with-cloog=${cloog}"
+      "--disable-cloog-version-check"
+      "--enable-cloog-backend=isl"
+    ] ++
+
+    # Java options
+    optionals langJava [
+      "--with-ecj-jar=${javaEcj}"
 
       # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
       # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
-      "--enable-java-home --with-java-home=\${prefix}/lib/jvm/jre "
-      else ""}
-    ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-    ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr}" else ""}
-    --with-gmp=${gmp.dev}
-    --with-mpfr=${mpfr.dev}
-    --with-mpc=${libmpc}
-    ${if libelf != null then "--with-libelf=${libelf}" else ""}
-    --disable-libstdcxx-pch
-    --without-included-gettext
-    --with-system-zlib
-    --enable-static
-    --enable-languages=${
-      concatStrings (intersperse ","
-        (  optional langC        "c"
-        ++ optional langCC       "c++"
-        ++ optional langFortran  "fortran"
-        ++ optional langJava     "java"
-        ++ optional langAda      "ada"
-        ++ optional langVhdl     "vhdl"
-        ++ optional langGo       "go"
-        ++ optional langObjC     "objc"
-        ++ optional langObjCpp   "obj-c++"
-        ++ optionals crossDarwin [ "objc" "obj-c++" ]
-        )
-      )
-    }
-    ${if targetPlatform == hostPlatform
-      then if hostPlatform.isDarwin
-        then " --with-native-system-header-dir=${darwin.usr-include}"
-        else " --with-native-system-header-dir=${getDev stdenv.cc.libc}/include"
-      else ""}
-    ${if langAda then " --enable-libada" else ""}
-    ${if targetPlatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-    ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-    ${if !bootstrap then "--disable-bootstrap" else ""}
-    ${if targetPlatform == hostPlatform then platformFlags else ""}
-  ";
+      "--enable-java-home"
+      "--with-java-home=\${prefix}/lib/jvm/jre"
+    ] ++
+    optional javaAwtGtk "--enable-java-awt=gtk" ++
+    optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}" ++
+
+    # Ada
+    optional langAda "--enable-libada" ++
+
+    platformFlags ++
+    optional (targetPlatform != hostPlatform) crossConfigureFlags ++
+    optional (!bootstrap) "--disable-bootstrap" ++
+
+    # Platform-specific flags
+    optional (targetPlatform == hostPlatform && targetPlatform.isi686) "--with-arch=i686" ++
+    optionals hostPlatform.isSunOS [
+      "--enable-long-long" "--enable-libssp" "--enable-threads=posix" "--disable-nls" "--enable-__cxa_atexit"
+      # On Illumos/Solaris GNU as is preferred
+      "--with-gnu-as" "--without-gnu-ld"
+    ]
+  ;
 
   targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
 
@@ -393,84 +404,30 @@ stdenv.mkDerivation ({
     then "install-strip"
     else "install";
 
-  crossAttrs = let
-    xgccArch = targetPlatform.gcc.arch or null;
-    xgccCpu = targetPlatform.gcc.cpu or null;
-    xgccAbi = targetPlatform.gcc.abi or null;
-    xgccFpu = targetPlatform.gcc.fpu or null;
-    xgccFloat = targetPlatform.gcc.float or null;
-    xwithArch = if xgccArch != null then " --with-arch=${xgccArch}" else "";
-    xwithCpu = if xgccCpu != null then " --with-cpu=${xgccCpu}" else "";
-    xwithAbi = if xgccAbi != null then " --with-abi=${xgccAbi}" else "";
-    xwithFpu = if xgccFpu != null then " --with-fpu=${xgccFpu}" else "";
-    xwithFloat = if xgccFloat != null then " --with-float=${xgccFloat}" else "";
-  in {
-    AR = "${targetPlatform.config}-ar";
-    LD = "${targetPlatform.config}-ld";
-    CC = "${targetPlatform.config}-gcc";
-    CXX = "${targetPlatform.config}-gcc";
-    AR_FOR_TARGET = "${targetPlatform.config}-ar";
-    LD_FOR_TARGET = "${targetPlatform.config}-ld";
-    CC_FOR_TARGET = "${targetPlatform.config}-gcc";
-    NM_FOR_TARGET = "${targetPlatform.config}-nm";
-    CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
-    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
+  /* For cross-built gcc (build != host == target) */
+  crossAttrs = {
     dontStrip = true;
-    configureFlags = ''
-      ${if enableMultilib then "" else "--disable-multilib"}
-      ${if enableShared then "" else "--disable-shared"}
-      ${if cloog != null then "--with-cloog=${cloog.crossDrv} --enable-cloog-backend=isl" else ""}
-      ${if langJava then "--with-ecj-jar=${javaEcj.crossDrv}" else ""}
-      ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-      ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr.crossDrv}" else ""}
-      --with-gmp=${gmp.crossDrv}
-      --with-mpfr=${mpfr.crossDrv}
-      --with-mpc=${libmpc.crossDrv}
-      --disable-libstdcxx-pch
-      --without-included-gettext
-      --with-system-zlib
-      --enable-languages=${
-        concatStrings (intersperse ","
-          (  optional langC        "c"
-          ++ optional langCC       "c++"
-          ++ optional langFortran  "fortran"
-          ++ optional langJava     "java"
-          ++ optional langAda      "ada"
-          ++ optional langVhdl     "vhdl"
-          ++ optional langGo       "go"
-          )
-        )
-      }
-      ${if langAda then " --enable-libada" else ""}
-      ${xwithArch}
-      ${xwithCpu}
-      ${xwithAbi}
-      ${xwithFpu}
-      ${xwithFloat}
-    '';
     buildFlags = "";
   };
 
-
-  # Needed for the cross compilation to work
-  AR = "ar";
-  LD = "ld";
   # http://gcc.gnu.org/install/specific.html#x86-64-x-solaris210
-  CC = if stdenv.system == "x86_64-solaris" then "gcc -m64" else "gcc";
-
-  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find
-  # the library headers and binaries, regarless of the language being
-  # compiled.
+  ${if hostPlatform.system == "x86_64-solaris" then "CC" else null} = "gcc -m64";
 
-  # Note: When building the Java AWT GTK+ peer, the build system doesn't
-  # honor `--with-gmp' et al., e.g., when building
-  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just
-  # add them to $CPATH and $LIBRARY_PATH in this case.
+  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
+  # library headers and binaries, regarless of the language being compiled.
+  #
+  # Note: When building the Java AWT GTK+ peer, the build system doesn't honor
+  # `--with-gmp' et al., e.g., when building
+  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just add
+  # them to $CPATH and $LIBRARY_PATH in this case.
   #
   # Likewise, the LTO code doesn't find zlib.
+  #
+  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
+  # compiler (after the specs for the cross-gcc are created). Having
+  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.
 
-  CPATH = makeSearchPathOutput "dev" "include" ([]
+  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
@@ -481,39 +438,38 @@ stdenv.mkDerivation ({
     # On GNU/Hurd glibc refers to Mach & Hurd
     # headers.
     ++ optionals (libcCross != null && libcCross ? propagatedBuildInputs)
-                 libcCross.propagatedBuildInputs);
+                 libcCross.propagatedBuildInputs
+  ));
 
-  LIBRARY_PATH = makeLibraryPath ([]
+  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
-    ++ optional (libpthread != null) libpthread);
-
-  EXTRA_TARGET_CFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-idirafter ${libcCross.dev}/include"
-      ]
-      ++ optionals (! crossStageStatic) [
-        "-B${libcCross.out}/lib"
-      ]
-    else null;
-
-  EXTRA_TARGET_LDFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-Wl,-L${libcCross.out}/lib"
-      ]
-      ++ (if crossStageStatic then [
+    ++ optional (libpthread != null) libpthread)
+  );
+
+  EXTRA_TARGET_FLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-idirafter ${getDev libcCross}/include"
+    ] ++ optionals (! crossStageStatic) [
+      "-B${libcCross.out}/lib"
+    ]);
+
+  EXTRA_TARGET_LDFLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-Wl,-L${libcCross.out}/lib"
+    ] ++ (if crossStageStatic then [
         "-B${libcCross.out}/lib"
       ] else [
         "-Wl,-rpath,${libcCross.out}/lib"
         "-Wl,-rpath-link,${libcCross.out}/lib"
-      ])
-      ++ optionals (libpthreadCross != null) [
-        "-L${libpthreadCross}/lib"
-        "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
-      ]
-    else null;
+    ]) ++ optionals (libpthreadCross != null) [
+      "-L${libpthreadCross}/lib"
+      "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
+    ]);
 
   passthru =
     { inherit langC langCC langObjC langObjCpp langAda langFortran langVhdl langGo version; isGNU = true; };
diff --git a/pkgs/development/compilers/gcc/5/default.nix b/pkgs/development/compilers/gcc/5/default.nix
index 345e2baf6718..0636ce7381ae 100644
--- a/pkgs/development/compilers/gcc/5/default.nix
+++ b/pkgs/development/compilers/gcc/5/default.nix
@@ -23,7 +23,7 @@
 , x11Support ? langJava
 , gnatboot ? null
 , enableMultilib ? false
-, enablePlugin ? true             # whether to support user-supplied plug-ins
+, enablePlugin ? hostPlatform == buildPlatform # Whether to support user-supplied plug-ins
 , name ? "gcc"
 , libcCross ? null
 , crossStageStatic ? false
@@ -49,9 +49,6 @@ assert libelf != null -> zlib != null;
 # Make sure we get GNU sed.
 assert hostPlatform.isDarwin -> gnused != null;
 
-# Need c++filt on darwin
-assert hostPlatform.isDarwin -> targetPackages.stdenv.cc.bintools or null != null;
-
 # The go frontend is written in c++
 assert langGo -> langCC;
 
@@ -104,106 +101,81 @@ let version = "5.5.0";
 
     /* Platform flags */
     platformFlags = let
-        gccArch = stdenv.platform.gcc.arch or null;
-        gccCpu = stdenv.platform.gcc.cpu or null;
-        gccAbi = stdenv.platform.gcc.abi or null;
-        gccFpu = stdenv.platform.gcc.fpu or null;
-        gccFloat = stdenv.platform.gcc.float or null;
-        gccMode = stdenv.platform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
+        gccArch = targetPlatform.platform.gcc.arch or null;
+        gccCpu = targetPlatform.platform.gcc.cpu or null;
+        gccAbi = targetPlatform.platform.gcc.abi or null;
+        gccFpu = targetPlatform.platform.gcc.fpu or null;
+        gccFloat = targetPlatform.platform.gcc.float or null;
+        gccMode = targetPlatform.platform.gcc.mode or null;
       in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode;
-
-    /* Cross-gcc settings */
+        optional (gccArch != null) "--with-arch=${gccArch}" ++
+        optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
+        optional (gccAbi != null) "--with-abi=${gccAbi}" ++
+        optional (gccFpu != null) "--with-fpu=${gccFpu}" ++
+        optional (gccFloat != null) "--with-float=${gccFloat}" ++
+        optional (gccMode != null) "--with-mode=${gccMode}";
+
+    /* Cross-gcc settings (build == host != target) */
     crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";
     crossDarwin = targetPlatform != hostPlatform && targetPlatform.libc == "libSystem";
-    crossConfigureFlags = let
-        gccArch = targetPlatform.gcc.arch or null;
-        gccCpu = targetPlatform.gcc.cpu or null;
-        gccAbi = targetPlatform.gcc.abi or null;
-        gccFpu = targetPlatform.gcc.fpu or null;
-        gccFloat = targetPlatform.gcc.float or null;
-        gccMode = targetPlatform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
-      in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode +
-        # Ensure that -print-prog-name is able to find the correct programs.
-        " --with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as" +
-        " --with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" +
-        (if crossMingw && crossStageStatic then
-          " --with-headers=${libcCross}/include" +
-          " --with-gcc" +
-          " --with-gnu-as" +
-          " --with-gnu-ld" +
-          " --with-gnu-ld" +
-          " --disable-shared" +
-          " --disable-nls" +
-          " --disable-debug" +
-          " --enable-sjlj-exceptions" +
-          " --enable-threads=win32" +
-          " --disable-win32-registry"
-          else if crossStageStatic then
-          " --disable-libssp --disable-nls" +
-          " --without-headers" +
-          " --disable-threads " +
-          " --disable-libgomp " +
-          " --disable-libquadmath" +
-          " --disable-shared" +
-          " --disable-libatomic " +  # libatomic requires libc
-          " --disable-decimal-float" # libdecnumber requires libc
-          else
-          (if crossDarwin then " --with-sysroot=${getLib libcCross}/share/sysroot"
-           else                " --with-headers=${getDev libcCross}/include") +
-          " --enable-__cxa_atexit" +
-          " --enable-long-long" +
-          (if crossMingw then
-            " --enable-threads=win32" +
-            " --enable-sjlj-exceptions" +
-            " --enable-hash-synchronization" +
-            " --disable-libssp" +
-            " --disable-nls" +
-            " --with-dwarf2" +
-            # I think noone uses shared gcc libs in mingw, so we better do the same.
-            # In any case, mingw32 g++ linking is broken by default with shared libs,
-            # unless adding "-lsupc++" to any linking command. I don't know why.
-            " --disable-shared" +
-            # To keep ABI compatibility with upstream mingw-w64
-            " --enable-fully-dynamic-string"
-            else (if targetPlatform.libc == "uclibc" then
-              # libsanitizer requires netrom/netrom.h which is not
-              # available in uclibc.
-              " --disable-libsanitizer" +
-              # In uclibc cases, libgomp needs an additional '-ldl'
-              # and as I don't know how to pass it, I disable libgomp.
-              " --disable-libgomp" else "") +
-            " --enable-threads=posix" +
-            " --enable-nls" +
-            " --disable-decimal-float") # No final libdecnumber (it may work only in 386)
-          );
+    crossConfigureFlags =
+      # Ensure that -print-prog-name is able to find the correct programs.
+      [ "--with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as"
+        "--with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" ] ++
+      (if crossMingw && crossStageStatic then [
+        "--with-headers=${libcCross}/include"
+        "--with-gcc"
+        "--with-gnu-as"
+        "--with-gnu-ld"
+        "--with-gnu-ld"
+        "--disable-shared"
+        "--disable-nls"
+        "--disable-debug"
+        "--enable-sjlj-exceptions"
+        "--enable-threads=win32"
+        "--disable-win32-registry"
+      ] else if crossStageStatic then [
+        "--disable-libssp"
+        "--disable-nls"
+        "--without-headers"
+        "--disable-threads"
+        "--disable-libgomp"
+        "--disable-libquadmath"
+        "--disable-shared"
+        "--disable-libatomic"  # libatomic requires libc
+        "--disable-decimal-float" # libdecnumber requires libc
+      ] else [
+        (if crossDarwin then "--with-sysroot=${getLib libcCross}/share/sysroot"
+         else                "--with-headers=${getDev libcCross}/include")
+        "--enable-__cxa_atexit"
+        "--enable-long-long"
+      ] ++
+        (if crossMingw then [
+          "--enable-threads=win32"
+          "--enable-sjlj-exceptions"
+          "--enable-hash-synchronization"
+          "--enable-libssp"
+          "--disable-nls"
+          "--with-dwarf2"
+          # To keep ABI compatibility with upstream mingw-w64
+          "--enable-fully-dynamic-string"
+        ] else
+          optionals (targetPlatform.libc == "uclibc") [
+            # libsanitizer requires netrom/netrom.h which is not
+            # available in uclibc.
+            "--disable-libsanitizer"
+            # In uclibc cases, libgomp needs an additional '-ldl'
+            # and as I don't know how to pass it, I disable libgomp.
+            "--disable-libgomp"
+          ] ++ [
+          "--enable-threads=posix"
+          "--enable-nls"
+          "--disable-decimal-float" # No final libdecnumber (it may work only in 386)
+        ]));
     stageNameAddon = if crossStageStatic then "-stage-static" else "-stage-final";
     crossNameAddon = if targetPlatform != hostPlatform then "-${targetPlatform.config}" + stageNameAddon else "";
 
-  bootstrap = targetPlatform == hostPlatform;
+    bootstrap = targetPlatform == hostPlatform;
 
 in
 
@@ -220,8 +192,6 @@ stdenv.mkDerivation ({
     inherit sha256;
   };
 
-  hardeningDisable = [ "format" ];
-
   inherit patches;
 
   outputs = [ "out" "lib" "man" "info" ];
@@ -230,6 +200,8 @@ stdenv.mkDerivation ({
 
   libc_dev = stdenv.cc.libc_dev;
 
+  hardeningDisable = [ "format" ];
+
   # This should kill all the stdinc frameworks that gcc and friends like to
   # insert into default search paths.
   prePatch = stdenv.lib.optionalString hostPlatform.isDarwin ''
@@ -302,17 +274,27 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler langJava
     libcCross crossMingw;
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
   nativeBuildInputs = [ texinfo which gettext ]
     ++ (optional (perl != null) perl)
     ++ (optional javaAwtGtk pkgconfig);
 
-  buildInputs = [ gmp mpfr libmpc libelf ]
-    ++ (optional (isl != null) isl)
+  # For building runtime libs
+  depsBuildTarget =
+    if hostPlatform == buildPlatform then [
+      targetPackages.stdenv.cc.bintools # newly-built gcc will be used
+    ] else assert targetPlatform == hostPlatform; [ # build != host == target
+      stdenv.cc
+    ];
+
+  buildInputs = [
+    gmp mpfr libmpc libelf
+    targetPackages.stdenv.cc.bintools # For linking code at run-time
+  ] ++ (optional (isl != null) isl)
     ++ (optional (zlib != null) zlib)
     ++ (optionals langJava [ boehmgc zip unzip ])
     ++ (optionals javaAwtGtk ([ gtk2 libart_lgpl ] ++ xlibs))
     ++ (optionals (targetPlatform != hostPlatform) [targetPackages.stdenv.cc.bintools])
-    ++ (optionals (buildPlatform != hostPlatform) [buildPackages.stdenv.cc])
     ++ (optionals langAda [gnatboot])
     ++ (optionals langVhdl [gnat])
 
@@ -336,66 +318,85 @@ stdenv.mkDerivation ({
   # TODO(@Ericson2314): Always pass "--target" and always prefix.
   configurePlatforms =
     # TODO(@Ericson2314): Figure out what's going wrong with Arm
-    if hostPlatform == targetPlatform && targetPlatform.isArm
+    if buildPlatform == hostPlatform && hostPlatform == targetPlatform && targetPlatform.isArm
     then []
     else [ "build" "host" ] ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
 
-  configureFlags = "
-    ${if hostPlatform.isSunOS then
-      " --enable-long-long --enable-libssp --enable-threads=posix --disable-nls --enable-__cxa_atexit " +
-      # On Illumos/Solaris GNU as is preferred
-      " --with-gnu-as --without-gnu-ld "
-      else ""}
-    --enable-lto
-    ${if enableMultilib then "--enable-multilib --disable-libquadmath" else "--disable-multilib"}
-    ${if enableShared then "" else "--disable-shared"}
-    ${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
-    ${optionalString (isl != null) "--with-isl=${isl}"}
-    ${if langJava then
-      "--with-ecj-jar=${javaEcj} " +
+  configureFlags =
+    # Basic dependencies
+    [
+      "--with-gmp-include=${gmp.dev}/include"
+      "--with-gmp-lib=${gmp.out}/lib"
+      "--with-mpfr-include=${mpfr.dev}/include"
+      "--with-mpfr-lib=${mpfr.out}/lib"
+      "--with-mpc=${libmpc}"
+    ] ++
+    optional (libelf != null) "--with-libelf=${libelf}" ++
+    optional (!(crossMingw && crossStageStatic))
+      "--with-native-system-header-dir=${getDev stdenv.cc.libc}/include" ++ 
+
+    # Basic configuration
+    [
+      "--enable-lto"
+      "--disable-libstdcxx-pch"
+      "--without-included-gettext"
+      "--with-system-zlib"
+      "--enable-static"
+      "--enable-languages=${
+        concatStrings (intersperse ","
+          (  optional langC        "c"
+          ++ optional langCC       "c++"
+          ++ optional langFortran  "fortran"
+          ++ optional langJava     "java"
+          ++ optional langAda      "ada"
+          ++ optional langVhdl     "vhdl"
+          ++ optional langGo       "go"
+          ++ optional langObjC     "objc"
+          ++ optional langObjCpp   "obj-c++"
+          ++ optionals crossDarwin [ "objc" "obj-c++" ]
+          )
+        )
+      }"
+    ] ++
+
+    (if enableMultilib
+      then ["--enable-multilib" "--disable-libquadmath"]
+      else ["--disable-multilib"]) ++
+    optional (!enableShared) "--disable-shared" ++
+    (if enablePlugin
+      then ["--enable-plugin"]
+      else ["--disable-plugin"]) ++
+
+    # Optional features
+    optional (isl != null) "--with-isl=${isl}" ++
+
+    # Java options
+    optionals langJava [
+      "--with-ecj-jar=${javaEcj}"
 
       # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
       # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
-      "--enable-java-home --with-java-home=\${prefix}/lib/jvm/jre "
-      else ""}
-    ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-    ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr}" else ""}
-    --with-gmp-include=${gmp.dev}/include
-    --with-gmp-lib=${gmp.out}/lib
-    --with-mpfr-include=${mpfr.dev}/include
-    --with-mpfr-lib=${mpfr.out}/lib
-    --with-mpc=${libmpc}
-    ${if libelf != null then "--with-libelf=${libelf}" else ""}
-    --disable-libstdcxx-pch
-    --without-included-gettext
-    --with-system-zlib
-    --enable-static
-    --enable-languages=${
-      concatStrings (intersperse ","
-        (  optional langC        "c"
-        ++ optional langCC       "c++"
-        ++ optional langFortran  "fortran"
-        ++ optional langJava     "java"
-        ++ optional langAda      "ada"
-        ++ optional langVhdl     "vhdl"
-        ++ optional langGo       "go"
-        ++ optional langObjC     "objc"
-        ++ optional langObjCpp   "obj-c++"
-        ++ optionals crossDarwin [ "objc" "obj-c++" ]
-        )
-      )
-    }
-    ${if targetPlatform == hostPlatform
-      then if hostPlatform.isDarwin
-        then " --with-native-system-header-dir=${darwin.usr-include}"
-        else " --with-native-system-header-dir=${getDev stdenv.cc.libc}/include"
-      else ""}
-    ${if langAda then " --enable-libada" else ""}
-    ${if targetPlatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-    ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-    ${if !bootstrap then "--disable-bootstrap" else ""}
-    ${if targetPlatform == hostPlatform then platformFlags else ""}
-  ";
+      "--enable-java-home"
+      "--with-java-home=\${prefix}/lib/jvm/jre"
+    ] ++
+    optional javaAwtGtk "--enable-java-awt=gtk" ++
+    optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}" ++
+
+    # Ada
+    optional langAda "--enable-libada" ++
+
+    platformFlags ++
+    optional (targetPlatform != hostPlatform) crossConfigureFlags ++
+    optional (!bootstrap) "--disable-bootstrap" ++
+
+    # Platform-specific flags
+    optional (targetPlatform == hostPlatform && targetPlatform.isi686) "--with-arch=i686" ++
+    optionals hostPlatform.isSunOS [
+      "--enable-long-long" "--enable-libssp" "--enable-threads=posix" "--disable-nls" "--enable-__cxa_atexit"
+      # On Illumos/Solaris GNU as is preferred
+      "--with-gnu-as" "--without-gnu-ld"
+    ]
+  ;
 
   targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
 
@@ -408,85 +409,32 @@ stdenv.mkDerivation ({
     then "install-strip"
     else "install";
 
-  crossAttrs = let
-    xgccArch = targetPlatform.gcc.arch or null;
-    xgccCpu = targetPlatform.gcc.cpu or null;
-    xgccAbi = targetPlatform.gcc.abi or null;
-    xgccFpu = targetPlatform.gcc.fpu or null;
-    xgccFloat = targetPlatform.gcc.float or null;
-    xwithArch = if xgccArch != null then " --with-arch=${xgccArch}" else "";
-    xwithCpu = if xgccCpu != null then " --with-cpu=${xgccCpu}" else "";
-    xwithAbi = if xgccAbi != null then " --with-abi=${xgccAbi}" else "";
-    xwithFpu = if xgccFpu != null then " --with-fpu=${xgccFpu}" else "";
-    xwithFloat = if xgccFloat != null then " --with-float=${xgccFloat}" else "";
-  in {
-    AR = "${targetPlatform.config}-ar";
-    LD = "${targetPlatform.config}-ld";
-    CC = "${targetPlatform.config}-gcc";
-    CXX = "${targetPlatform.config}-gcc";
-    AR_FOR_TARGET = "${targetPlatform.config}-ar";
-    LD_FOR_TARGET = "${targetPlatform.config}-ld";
-    CC_FOR_TARGET = "${targetPlatform.config}-gcc";
-    NM_FOR_TARGET = "${targetPlatform.config}-nm";
-    CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
-    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
+  /* For cross-built gcc (build != host == target) */
+  crossAttrs = {
     dontStrip = true;
-    configureFlags = ''
-      ${if enableMultilib then "" else "--disable-multilib"}
-      ${if enableShared then "" else "--disable-shared"}
-      ${if langJava then "--with-ecj-jar=${javaEcj.crossDrv}" else ""}
-      ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-      ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr.crossDrv}" else ""}
-      --with-gmp=${gmp.crossDrv}
-      --with-mpfr=${mpfr.crossDrv}
-      --with-mpc=${libmpc.crossDrv}
-      --disable-libstdcxx-pch
-      --without-included-gettext
-      --with-system-zlib
-      --enable-languages=${
-        concatStrings (intersperse ","
-          (  optional langC        "c"
-          ++ optional langCC       "c++"
-          ++ optional langFortran  "fortran"
-          ++ optional langJava     "java"
-          ++ optional langAda      "ada"
-          ++ optional langVhdl     "vhdl"
-          ++ optional langGo       "go"
-          )
-        )
-      }
-      ${if langAda then " --enable-libada" else ""}
-      ${xwithArch}
-      ${xwithCpu}
-      ${xwithAbi}
-      ${xwithFpu}
-      ${xwithFloat}
-    '';
     buildFlags = "";
   };
 
-
-  # Needed for the cross compilation to work
-  AR = "ar";
-  LD = "ld";
   # http://gcc.gnu.org/install/specific.html#x86-64-x-solaris210
-  CC = if stdenv.system == "x86_64-solaris" then "gcc -m64" else "gcc";
-
-  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find
-  # the library headers and binaries, regarless of the language being
-  # compiled.
+  ${if hostPlatform.system == "x86_64-solaris" then "CC" else null} = "gcc -m64";
 
-  # Note: When building the Java AWT GTK+ peer, the build system doesn't
-  # honor `--with-gmp' et al., e.g., when building
-  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just
-  # add them to $CPATH and $LIBRARY_PATH in this case.
+  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
+  # library headers and binaries, regarless of the language being compiled.
+  #
+  # Note: When building the Java AWT GTK+ peer, the build system doesn't honor
+  # `--with-gmp' et al., e.g., when building
+  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just add
+  # them to $CPATH and $LIBRARY_PATH in this case.
   #
   # Likewise, the LTO code doesn't find zlib.
+  #
+  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
+  # compiler (after the specs for the cross-gcc are created). Having
+  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.
 
-  CPATH = makeSearchPathOutput "dev" "include" ([]
+  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
     ++ optional (zlib != null) zlib
-    ++ optionals langJava [ boehmgc ]
+    ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
     ++ optional (libpthread != null) libpthread
@@ -495,39 +443,38 @@ stdenv.mkDerivation ({
     # On GNU/Hurd glibc refers to Mach & Hurd
     # headers.
     ++ optionals (libcCross != null && libcCross ? propagatedBuildInputs)
-                 libcCross.propagatedBuildInputs);
+                 libcCross.propagatedBuildInputs
+  ));
 
-  LIBRARY_PATH = makeLibraryPath ([]
+  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
-    ++ optional (libpthread != null) libpthread);
-
-  EXTRA_TARGET_CFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-idirafter ${getDev libcCross}/include"
-      ]
-      ++ optionals (! crossStageStatic) [
-        "-B${libcCross.out}/lib"
-      ]
-    else null;
-
-  EXTRA_TARGET_LDFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-Wl,-L${libcCross.out}/lib"
-      ]
-      ++ (if crossStageStatic then [
+    ++ optional (libpthread != null) libpthread)
+  );
+
+  EXTRA_TARGET_FLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-idirafter ${getDev libcCross}/include"
+    ] ++ optionals (! crossStageStatic) [
+      "-B${libcCross.out}/lib"
+    ]);
+
+  EXTRA_TARGET_LDFLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-Wl,-L${libcCross.out}/lib"
+    ] ++ (if crossStageStatic then [
         "-B${libcCross.out}/lib"
       ] else [
         "-Wl,-rpath,${libcCross.out}/lib"
         "-Wl,-rpath-link,${libcCross.out}/lib"
-      ])
-      ++ optionals (libpthreadCross != null) [
-        "-L${libpthreadCross}/lib"
-        "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
-      ]
-    else null;
+    ]) ++ optionals (libpthreadCross != null) [
+      "-L${libpthreadCross}/lib"
+      "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
+    ]);
 
   passthru =
     { inherit langC langCC langObjC langObjCpp langAda langFortran langVhdl langGo version; isGNU = true; };
diff --git a/pkgs/development/compilers/gcc/6/default.nix b/pkgs/development/compilers/gcc/6/default.nix
index 03c6b3834ea4..2614e96e1b7c 100644
--- a/pkgs/development/compilers/gcc/6/default.nix
+++ b/pkgs/development/compilers/gcc/6/default.nix
@@ -23,7 +23,7 @@
 , x11Support ? langJava
 , gnatboot ? null
 , enableMultilib ? false
-, enablePlugin ? true             # whether to support user-supplied plug-ins
+, enablePlugin ? hostPlatform == buildPlatform # Whether to support user-supplied plug-ins
 , name ? "gcc"
 , libcCross ? null
 , crossStageStatic ? false
@@ -34,6 +34,7 @@
 , cloog # unused; just for compat with gcc4, as we override the parameter on some places
 , darwin ? null
 , buildPlatform, hostPlatform, targetPlatform
+, buildPackages
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -48,9 +49,6 @@ assert libelf != null -> zlib != null;
 # Make sure we get GNU sed.
 assert hostPlatform.isDarwin -> gnused != null;
 
-# Need c++filt on darwin
-assert hostPlatform.isDarwin -> targetPackages.stdenv.cc.bintools or null != null;
-
 # The go frontend is written in c++
 assert langGo -> langCC;
 
@@ -101,106 +99,81 @@ let version = "6.4.0";
 
     /* Platform flags */
     platformFlags = let
-        gccArch = stdenv.platform.gcc.arch or null;
-        gccCpu = stdenv.platform.gcc.cpu or null;
-        gccAbi = stdenv.platform.gcc.abi or null;
-        gccFpu = stdenv.platform.gcc.fpu or null;
-        gccFloat = stdenv.platform.gcc.float or null;
-        gccMode = stdenv.platform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
+        gccArch = targetPlatform.platform.gcc.arch or null;
+        gccCpu = targetPlatform.platform.gcc.cpu or null;
+        gccAbi = targetPlatform.platform.gcc.abi or null;
+        gccFpu = targetPlatform.platform.gcc.fpu or null;
+        gccFloat = targetPlatform.platform.gcc.float or null;
+        gccMode = targetPlatform.platform.gcc.mode or null;
       in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode;
-
-    /* Cross-gcc settings */
+        optional (gccArch != null) "--with-arch=${gccArch}" ++
+        optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
+        optional (gccAbi != null) "--with-abi=${gccAbi}" ++
+        optional (gccFpu != null) "--with-fpu=${gccFpu}" ++
+        optional (gccFloat != null) "--with-float=${gccFloat}" ++
+        optional (gccMode != null) "--with-mode=${gccMode}";
+
+    /* Cross-gcc settings (build == host != target) */
     crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";
     crossDarwin = targetPlatform != hostPlatform && targetPlatform.libc == "libSystem";
-    crossConfigureFlags = let
-        gccArch = targetPlatform.gcc.arch or null;
-        gccCpu = targetPlatform.gcc.cpu or null;
-        gccAbi = targetPlatform.gcc.abi or null;
-        gccFpu = targetPlatform.gcc.fpu or null;
-        gccFloat = targetPlatform.gcc.float or null;
-        gccMode = targetPlatform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
-      in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode +
-        # Ensure that -print-prog-name is able to find the correct programs.
-        " --with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as" +
-        " --with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" +
-        (if crossMingw && crossStageStatic then
-          " --with-headers=${libcCross}/include" +
-          " --with-gcc" +
-          " --with-gnu-as" +
-          " --with-gnu-ld" +
-          " --with-gnu-ld" +
-          " --disable-shared" +
-          " --disable-nls" +
-          " --disable-debug" +
-          " --enable-sjlj-exceptions" +
-          " --enable-threads=win32" +
-          " --disable-win32-registry"
-          else if crossStageStatic then
-          " --disable-libssp --disable-nls" +
-          " --without-headers" +
-          " --disable-threads " +
-          " --disable-libgomp " +
-          " --disable-libquadmath" +
-          " --disable-shared" +
-          " --disable-libatomic " +  # libatomic requires libc
-          " --disable-decimal-float" # libdecnumber requires libc
-          else
-          (if crossDarwin then " --with-sysroot=${getLib libcCross}/share/sysroot"
-           else                " --with-headers=${getDev libcCross}/include") +
-          " --enable-__cxa_atexit" +
-          " --enable-long-long" +
-          (if crossMingw then
-            " --enable-threads=win32" +
-            " --enable-sjlj-exceptions" +
-            " --enable-hash-synchronization" +
-            " --disable-libssp" +
-            " --disable-nls" +
-            " --with-dwarf2" +
-            # I think noone uses shared gcc libs in mingw, so we better do the same.
-            # In any case, mingw32 g++ linking is broken by default with shared libs,
-            # unless adding "-lsupc++" to any linking command. I don't know why.
-            " --disable-shared" +
-            # To keep ABI compatibility with upstream mingw-w64
-            " --enable-fully-dynamic-string"
-            else (if targetPlatform.libc == "uclibc" then
-              # libsanitizer requires netrom/netrom.h which is not
-              # available in uclibc.
-              " --disable-libsanitizer" +
-              # In uclibc cases, libgomp needs an additional '-ldl'
-              # and as I don't know how to pass it, I disable libgomp.
-              " --disable-libgomp" else "") +
-            " --enable-threads=posix" +
-            " --enable-nls" +
-            " --disable-decimal-float") # No final libdecnumber (it may work only in 386)
-          );
+    crossConfigureFlags =
+      # Ensure that -print-prog-name is able to find the correct programs.
+      [ "--with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as"
+        "--with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" ] ++
+      (if crossMingw && crossStageStatic then [
+        "--with-headers=${libcCross}/include"
+        "--with-gcc"
+        "--with-gnu-as"
+        "--with-gnu-ld"
+        "--with-gnu-ld"
+        "--disable-shared"
+        "--disable-nls"
+        "--disable-debug"
+        "--enable-sjlj-exceptions"
+        "--enable-threads=win32"
+        "--disable-win32-registry"
+      ] else if crossStageStatic then [
+        "--disable-libssp"
+        "--disable-nls"
+        "--without-headers"
+        "--disable-threads"
+        "--disable-libgomp"
+        "--disable-libquadmath"
+        "--disable-shared"
+        "--disable-libatomic"  # libatomic requires libc
+        "--disable-decimal-float" # libdecnumber requires libc
+      ] else [
+        (if crossDarwin then "--with-sysroot=${getLib libcCross}/share/sysroot"
+         else                "--with-headers=${getDev libcCross}/include")
+        "--enable-__cxa_atexit"
+        "--enable-long-long"
+      ] ++
+        (if crossMingw then [
+          "--enable-threads=win32"
+          "--enable-sjlj-exceptions"
+          "--enable-hash-synchronization"
+          "--enable-libssp"
+          "--disable-nls"
+          "--with-dwarf2"
+          # To keep ABI compatibility with upstream mingw-w64
+          "--enable-fully-dynamic-string"
+        ] else
+          optionals (targetPlatform.libc == "uclibc") [
+            # libsanitizer requires netrom/netrom.h which is not
+            # available in uclibc.
+            "--disable-libsanitizer"
+            # In uclibc cases, libgomp needs an additional '-ldl'
+            # and as I don't know how to pass it, I disable libgomp.
+            "--disable-libgomp"
+          ] ++ [
+          "--enable-threads=posix"
+          "--enable-nls"
+          "--disable-decimal-float" # No final libdecnumber (it may work only in 386)
+        ]));
     stageNameAddon = if crossStageStatic then "-stage-static" else "-stage-final";
     crossNameAddon = if targetPlatform != hostPlatform then "-${targetPlatform.config}" + stageNameAddon else "";
 
-  bootstrap = targetPlatform == hostPlatform;
+    bootstrap = targetPlatform == hostPlatform;
 
 in
 
@@ -300,12 +273,23 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler langJava
     libcCross crossMingw;
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
   nativeBuildInputs = [ texinfo which gettext ]
     ++ (optional (perl != null) perl)
     ++ (optional javaAwtGtk pkgconfig);
 
-  buildInputs = [ gmp mpfr libmpc libelf ]
-    ++ (optional (isl != null) isl)
+  # For building runtime libs
+  depsBuildTarget =
+    if hostPlatform == buildPlatform then [
+      targetPackages.stdenv.cc.bintools # newly-built gcc will be used
+    ] else assert targetPlatform == hostPlatform; [ # build != host == target
+      stdenv.cc
+    ];
+
+  buildInputs = [
+    gmp mpfr libmpc libelf
+    targetPackages.stdenv.cc.bintools # For linking code at run-time
+  ] ++ (optional (isl != null) isl)
     ++ (optional (zlib != null) zlib)
     ++ (optionals langJava [ boehmgc zip unzip ])
     ++ (optionals javaAwtGtk ([ gtk2 libart_lgpl ] ++ xlibs))
@@ -337,155 +321,120 @@ stdenv.mkDerivation ({
   # TODO(@Ericson2314): Always pass "--target" and always prefix.
   configurePlatforms =
     # TODO(@Ericson2314): Figure out what's going wrong with Arm
-    if hostPlatform == targetPlatform && targetPlatform.isArm
+    if buildPlatform == hostPlatform && hostPlatform == targetPlatform && targetPlatform.isArm
     then []
     else [ "build" "host" ] ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
 
-  configureFlags = "
-    ${if hostPlatform.isSunOS then
-      " --enable-long-long --enable-libssp --enable-threads=posix --disable-nls --enable-__cxa_atexit " +
-      # On Illumos/Solaris GNU as is preferred
-      " --with-gnu-as --without-gnu-ld "
-      else ""}
-    --enable-lto
-    ${if enableMultilib then "--enable-multilib --disable-libquadmath" else "--disable-multilib"}
-    ${if enableShared then "" else "--disable-shared"}
-    ${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
-    ${optionalString (isl != null) "--with-isl=${isl}"}
-    ${if langJava then
-      "--with-ecj-jar=${javaEcj} " +
+  configureFlags =
+    # Basic dependencies
+    [
+      "--with-gmp-include=${gmp.dev}/include"
+      "--with-gmp-lib=${gmp.out}/lib"
+      "--with-mpfr-include=${mpfr.dev}/include"
+      "--with-mpfr-lib=${mpfr.out}/lib"
+      "--with-mpc=${libmpc}"
+    ] ++
+    optional (libelf != null) "--with-libelf=${libelf}" ++
+    optional (!(crossMingw && crossStageStatic))
+      "--with-native-system-header-dir=${getDev stdenv.cc.libc}/include" ++
+
+    # Basic configuration
+    [
+      "--enable-lto"
+      "--disable-libstdcxx-pch"
+      "--without-included-gettext"
+      "--with-system-zlib"
+      "--enable-static"
+      "--enable-languages=${
+        concatStrings (intersperse ","
+          (  optional langC        "c"
+          ++ optional langCC       "c++"
+          ++ optional langFortran  "fortran"
+          ++ optional langJava     "java"
+          ++ optional langAda      "ada"
+          ++ optional langVhdl     "vhdl"
+          ++ optional langGo       "go"
+          ++ optional langObjC     "objc"
+          ++ optional langObjCpp   "obj-c++"
+          ++ optionals crossDarwin [ "objc" "obj-c++" ]
+          )
+        )
+      }"
+    ] ++
+
+    (if enableMultilib
+      then ["--enable-multilib" "--disable-libquadmath"]
+      else ["--disable-multilib"]) ++
+    optional (!enableShared) "--disable-shared" ++
+    (if enablePlugin
+      then ["--enable-plugin"]
+      else ["--disable-plugin"]) ++
+
+    # Optional features
+    optional (isl != null) "--with-isl=${isl}" ++
+
+    # Java options
+    optionals langJava [
+      "--with-ecj-jar=${javaEcj}"
 
       # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
       # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
-      "--enable-java-home --with-java-home=\${prefix}/lib/jvm/jre "
-      else ""}
-    ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-    ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr}" else ""}
-    --with-gmp-include=${gmp.dev}/include
-    --with-gmp-lib=${gmp.out}/lib
-    --with-mpfr-include=${mpfr.dev}/include
-    --with-mpfr-lib=${mpfr.out}/lib
-    --with-mpc=${libmpc}
-    ${if libelf != null then "--with-libelf=${libelf}" else ""}
-    --disable-libstdcxx-pch
-    --without-included-gettext
-    --with-system-zlib
-    --enable-static
-    --enable-languages=${
-      concatStrings (intersperse ","
-        (  optional langC        "c"
-        ++ optional langCC       "c++"
-        ++ optional langFortran  "fortran"
-        ++ optional langJava     "java"
-        ++ optional langAda      "ada"
-        ++ optional langVhdl     "vhdl"
-        ++ optional langGo       "go"
-        ++ optional langObjC     "objc"
-        ++ optional langObjCpp   "obj-c++"
-        ++ optionals crossDarwin [ "objc" "obj-c++" ]
-        )
-      )
-    }
-    ${if targetPlatform == hostPlatform
-      then if hostPlatform.isDarwin
-        then " --with-native-system-header-dir=${darwin.usr-include}"
-        else " --with-native-system-header-dir=${getDev stdenv.cc.libc}/include"
-      else ""}
-    ${if langAda then " --enable-libada" else ""}
-    ${if targetPlatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-    ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-    ${if !bootstrap then "--disable-bootstrap" else ""}
-    ${if targetPlatform == hostPlatform then platformFlags else ""}
-  ";
+      "--enable-java-home"
+      "--with-java-home=\${prefix}/lib/jvm/jre"
+    ] ++
+    optional javaAwtGtk "--enable-java-awt=gtk" ++
+    optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}" ++
+
+    # Ada
+    optional langAda "--enable-libada" ++
+
+    platformFlags ++
+    optional (targetPlatform != hostPlatform) crossConfigureFlags ++
+    optional (!bootstrap) "--disable-bootstrap" ++
+
+    # Platform-specific flags
+    optional (targetPlatform == hostPlatform && targetPlatform.isi686) "--with-arch=i686" ++
+    optionals hostPlatform.isSunOS [
+      "--enable-long-long" "--enable-libssp" "--enable-threads=posix" "--disable-nls" "--enable-__cxa_atexit"
+      # On Illumos/Solaris GNU as is preferred
+      "--with-gnu-as" "--without-gnu-ld"
+    ]
+  ;
 
   targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
 
-  buildFlags = if bootstrap then
-    (if profiledCompiler then "profiledbootstrap" else "bootstrap")
-    else "";
+  buildFlags =
+    optional bootstrap (if profiledCompiler then "profiledbootstrap" else "bootstrap");
 
   installTargets =
     if stripped
     then "install-strip"
     else "install";
 
-  crossAttrs = let
-    xgccArch = targetPlatform.gcc.arch or null;
-    xgccCpu = targetPlatform.gcc.cpu or null;
-    xgccAbi = targetPlatform.gcc.abi or null;
-    xgccFpu = targetPlatform.gcc.fpu or null;
-    xgccFloat = targetPlatform.gcc.float or null;
-    xwithArch = if xgccArch != null then " --with-arch=${xgccArch}" else "";
-    xwithCpu = if xgccCpu != null then " --with-cpu=${xgccCpu}" else "";
-    xwithAbi = if xgccAbi != null then " --with-abi=${xgccAbi}" else "";
-    xwithFpu = if xgccFpu != null then " --with-fpu=${xgccFpu}" else "";
-    xwithFloat = if xgccFloat != null then " --with-float=${xgccFloat}" else "";
-  in {
-    AR = "${targetPlatform.config}-ar";
-    LD = "${targetPlatform.config}-ld";
-    CC = "${targetPlatform.config}-gcc";
-    CXX = "${targetPlatform.config}-gcc";
-    AR_FOR_TARGET = "${targetPlatform.config}-ar";
-    LD_FOR_TARGET = "${targetPlatform.config}-ld";
-    CC_FOR_TARGET = "${targetPlatform.config}-gcc";
-    NM_FOR_TARGET = "${targetPlatform.config}-nm";
-    CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
-    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
+  /* For cross-built gcc (build != host == target) */
+  crossAttrs = {
     dontStrip = true;
-    configureFlags = ''
-      ${if enableMultilib then "" else "--disable-multilib"}
-      ${if enableShared then "" else "--disable-shared"}
-      ${if langJava then "--with-ecj-jar=${javaEcj.crossDrv}" else ""}
-      ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-      ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr.crossDrv}" else ""}
-      --with-gmp=${gmp.crossDrv}
-      --with-mpfr=${mpfr.crossDrv}
-      --with-mpc=${libmpc.crossDrv}
-      --disable-libstdcxx-pch
-      --without-included-gettext
-      --with-system-zlib
-      --enable-languages=${
-        concatStrings (intersperse ","
-          (  optional langC        "c"
-          ++ optional langCC       "c++"
-          ++ optional langFortran  "fortran"
-          ++ optional langJava     "java"
-          ++ optional langAda      "ada"
-          ++ optional langVhdl     "vhdl"
-          ++ optional langGo       "go"
-          )
-        )
-      }
-      ${if langAda then " --enable-libada" else ""}
-      ${xwithArch}
-      ${xwithCpu}
-      ${xwithAbi}
-      ${xwithFpu}
-      ${xwithFloat}
-    '';
     buildFlags = "";
   };
 
-
-  # Needed for the cross compilation to work
-  AR = "ar";
-  LD = "ld";
   # http://gcc.gnu.org/install/specific.html#x86-64-x-solaris210
-  CC = if stdenv.system == "x86_64-solaris" then "gcc -m64" else "gcc";
-
-  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find
-  # the library headers and binaries, regarless of the language being
-  # compiled.
+  ${if hostPlatform.system == "x86_64-solaris" then "CC" else null} = "gcc -m64";
 
-  # Note: When building the Java AWT GTK+ peer, the build system doesn't
-  # honor `--with-gmp' et al., e.g., when building
-  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just
-  # add them to $CPATH and $LIBRARY_PATH in this case.
+  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
+  # library headers and binaries, regarless of the language being compiled.
+  #
+  # Note: When building the Java AWT GTK+ peer, the build system doesn't honor
+  # `--with-gmp' et al., e.g., when building
+  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just add
+  # them to $CPATH and $LIBRARY_PATH in this case.
   #
   # Likewise, the LTO code doesn't find zlib.
+  #
+  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
+  # compiler (after the specs for the cross-gcc are created). Having
+  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.
 
-  CPATH = makeSearchPathOutput "dev" "include" ([]
+  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
@@ -496,39 +445,38 @@ stdenv.mkDerivation ({
     # On GNU/Hurd glibc refers to Mach & Hurd
     # headers.
     ++ optionals (libcCross != null && libcCross ? propagatedBuildInputs)
-                 libcCross.propagatedBuildInputs);
+                 libcCross.propagatedBuildInputs
+  ));
 
-  LIBRARY_PATH = makeLibraryPath ([]
+  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
-    ++ optional (libpthread != null) libpthread);
-
-  EXTRA_TARGET_CFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-idirafter ${getDev libcCross}/include"
-      ]
-      ++ optionals (! crossStageStatic) [
-        "-B${libcCross.out}/lib"
-      ]
-    else null;
-
-  EXTRA_TARGET_LDFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-Wl,-L${libcCross.out}/lib"
-      ]
-      ++ (if crossStageStatic then [
+    ++ optional (libpthread != null) libpthread)
+  );
+
+  EXTRA_TARGET_FLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-idirafter ${getDev libcCross}/include"
+    ] ++ optionals (! crossStageStatic) [
+      "-B${libcCross.out}/lib"
+    ]);
+
+  EXTRA_TARGET_LDFLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-Wl,-L${libcCross.out}/lib"
+    ] ++ (if crossStageStatic then [
         "-B${libcCross.out}/lib"
       ] else [
         "-Wl,-rpath,${libcCross.out}/lib"
         "-Wl,-rpath-link,${libcCross.out}/lib"
-      ])
-      ++ optionals (libpthreadCross != null) [
-        "-L${libpthreadCross}/lib"
-        "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
-      ]
-    else null;
+    ]) ++ optionals (libpthreadCross != null) [
+      "-L${libpthreadCross}/lib"
+      "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
+    ]);
 
   passthru =
     { inherit langC langCC langObjC langObjCpp langAda langFortran langVhdl langGo version; isGNU = true; };
diff --git a/pkgs/development/compilers/gcc/7/default.nix b/pkgs/development/compilers/gcc/7/default.nix
index 7d1ac4aa536e..9ce3808b73f2 100644
--- a/pkgs/development/compilers/gcc/7/default.nix
+++ b/pkgs/development/compilers/gcc/7/default.nix
@@ -23,7 +23,7 @@
 , x11Support ? langJava
 , gnatboot ? null
 , enableMultilib ? false
-, enablePlugin ? true             # whether to support user-supplied plug-ins
+, enablePlugin ? hostPlatform == buildPlatform # Whether to support user-supplied plug-ins
 , name ? "gcc"
 , libcCross ? null
 , crossStageStatic ? false
@@ -33,7 +33,9 @@
 , gnused ? null
 , cloog # unused; just for compat with gcc4, as we override the parameter on some places
 , darwin ? null
+, flex ? null
 , buildPlatform, hostPlatform, targetPlatform
+, buildPackages
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -48,9 +50,6 @@ assert libelf != null -> zlib != null;
 # Make sure we get GNU sed.
 assert hostPlatform.isDarwin -> gnused != null;
 
-# Need c++filt on darwin
-assert hostPlatform.isDarwin -> targetPackages.stdenv.cc.bintools or null != null;
-
 # The go frontend is written in c++
 assert langGo -> langCC;
 
@@ -98,106 +97,81 @@ let version = "7.2.0";
 
     /* Platform flags */
     platformFlags = let
-        gccArch = stdenv.platform.gcc.arch or null;
-        gccCpu = stdenv.platform.gcc.cpu or null;
-        gccAbi = stdenv.platform.gcc.abi or null;
-        gccFpu = stdenv.platform.gcc.fpu or null;
-        gccFloat = stdenv.platform.gcc.float or null;
-        gccMode = stdenv.platform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
+        gccArch = targetPlatform.platform.gcc.arch or null;
+        gccCpu = targetPlatform.platform.gcc.cpu or null;
+        gccAbi = targetPlatform.platform.gcc.abi or null;
+        gccFpu = targetPlatform.platform.gcc.fpu or null;
+        gccFloat = targetPlatform.platform.gcc.float or null;
+        gccMode = targetPlatform.platform.gcc.mode or null;
       in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode;
-
-    /* Cross-gcc settings */
+        optional (gccArch != null) "--with-arch=${gccArch}" ++
+        optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
+        optional (gccAbi != null) "--with-abi=${gccAbi}" ++
+        optional (gccFpu != null) "--with-fpu=${gccFpu}" ++
+        optional (gccFloat != null) "--with-float=${gccFloat}" ++
+        optional (gccMode != null) "--with-mode=${gccMode}";
+
+    /* Cross-gcc settings (build == host != target) */
     crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";
     crossDarwin = targetPlatform != hostPlatform && targetPlatform.libc == "libSystem";
-    crossConfigureFlags = let
-        gccArch = targetPlatform.gcc.arch or null;
-        gccCpu = targetPlatform.gcc.cpu or null;
-        gccAbi = targetPlatform.gcc.abi or null;
-        gccFpu = targetPlatform.gcc.fpu or null;
-        gccFloat = targetPlatform.gcc.float or null;
-        gccMode = targetPlatform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
-      in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode +
-        # Ensure that -print-prog-name is able to find the correct programs.
-        " --with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as" +
-        " --with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" +
-        (if crossMingw && crossStageStatic then
-          " --with-headers=${libcCross}/include" +
-          " --with-gcc" +
-          " --with-gnu-as" +
-          " --with-gnu-ld" +
-          " --with-gnu-ld" +
-          " --disable-shared" +
-          " --disable-nls" +
-          " --disable-debug" +
-          " --enable-sjlj-exceptions" +
-          " --enable-threads=win32" +
-          " --disable-win32-registry"
-          else if crossStageStatic then
-          " --disable-libssp --disable-nls" +
-          " --without-headers" +
-          " --disable-threads " +
-          " --disable-libgomp " +
-          " --disable-libquadmath" +
-          " --disable-shared" +
-          " --disable-libatomic " +  # libatomic requires libc
-          " --disable-decimal-float" # libdecnumber requires libc
-          else
-          (if crossDarwin then " --with-sysroot=${getLib libcCross}/share/sysroot"
-           else                " --with-headers=${getDev libcCross}/include") +
-          " --enable-__cxa_atexit" +
-          " --enable-long-long" +
-          (if crossMingw then
-            " --enable-threads=win32" +
-            " --enable-sjlj-exceptions" +
-            " --enable-hash-synchronization" +
-            " --disable-libssp" +
-            " --disable-nls" +
-            " --with-dwarf2" +
-            # I think noone uses shared gcc libs in mingw, so we better do the same.
-            # In any case, mingw32 g++ linking is broken by default with shared libs,
-            # unless adding "-lsupc++" to any linking command. I don't know why.
-            " --disable-shared" +
-            # To keep ABI compatibility with upstream mingw-w64
-            " --enable-fully-dynamic-string"
-            else (if targetPlatform.libc == "uclibc" then
-              # libsanitizer requires netrom/netrom.h which is not
-              # available in uclibc.
-              " --disable-libsanitizer" +
-              # In uclibc cases, libgomp needs an additional '-ldl'
-              # and as I don't know how to pass it, I disable libgomp.
-              " --disable-libgomp" else "") +
-            " --enable-threads=posix" +
-            " --enable-nls" +
-            " --disable-decimal-float") # No final libdecnumber (it may work only in 386)
-          );
+    crossConfigureFlags =
+      # Ensure that -print-prog-name is able to find the correct programs.
+      [ "--with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as"
+        "--with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" ] ++
+      (if crossMingw && crossStageStatic then [
+        "--with-headers=${libcCross}/include"
+        "--with-gcc"
+        "--with-gnu-as"
+        "--with-gnu-ld"
+        "--with-gnu-ld"
+        "--disable-shared"
+        "--disable-nls"
+        "--disable-debug"
+        "--enable-sjlj-exceptions"
+        "--enable-threads=win32"
+        "--disable-win32-registry"
+      ] else if crossStageStatic then [
+        "--disable-libssp"
+        "--disable-nls"
+        "--without-headers"
+        "--disable-threads"
+        "--disable-libgomp"
+        "--disable-libquadmath"
+        "--disable-shared"
+        "--disable-libatomic"  # libatomic requires libc
+        "--disable-decimal-float" # libdecnumber requires libc
+      ] else [
+        (if crossDarwin then "--with-sysroot=${getLib libcCross}/share/sysroot"
+         else                "--with-headers=${getDev libcCross}/include")
+        "--enable-__cxa_atexit"
+        "--enable-long-long"
+      ] ++
+        (if crossMingw then [
+          "--enable-threads=win32"
+          "--enable-sjlj-exceptions"
+          "--enable-hash-synchronization"
+          "--enable-libssp"
+          "--disable-nls"
+          "--with-dwarf2"
+          # To keep ABI compatibility with upstream mingw-w64
+          "--enable-fully-dynamic-string"
+        ] else
+          optionals (targetPlatform.libc == "uclibc") [
+            # libsanitizer requires netrom/netrom.h which is not
+            # available in uclibc.
+            "--disable-libsanitizer"
+            # In uclibc cases, libgomp needs an additional '-ldl'
+            # and as I don't know how to pass it, I disable libgomp.
+            "--disable-libgomp"
+          ] ++ [
+          "--enable-threads=posix"
+          "--enable-nls"
+          "--disable-decimal-float" # No final libdecnumber (it may work only in 386)
+        ]));
     stageNameAddon = if crossStageStatic then "-stage-static" else "-stage-final";
     crossNameAddon = if targetPlatform != hostPlatform then "-${targetPlatform.config}" + stageNameAddon else "";
 
-  bootstrap = targetPlatform == hostPlatform;
+    bootstrap = targetPlatform == hostPlatform;
 
 in
 
@@ -296,12 +270,23 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler langJava
     libcCross crossMingw;
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
   nativeBuildInputs = [ texinfo which gettext ]
     ++ (optional (perl != null) perl)
     ++ (optional javaAwtGtk pkgconfig);
 
-  buildInputs = [ gmp mpfr libmpc libelf ]
-    ++ (optional (isl != null) isl)
+  # For building runtime libs
+  depsBuildTarget =
+    if hostPlatform == buildPlatform then [
+      targetPackages.stdenv.cc.bintools # newly-built gcc will be used
+    ] else assert targetPlatform == hostPlatform; [ # build != host == target
+      stdenv.cc
+    ];
+
+  buildInputs = [
+    gmp mpfr libmpc libelf flex
+    targetPackages.stdenv.cc.bintools # For linking code at run-time
+  ] ++ (optional (isl != null) isl)
     ++ (optional (zlib != null) zlib)
     ++ (optionals langJava [ boehmgc zip unzip ])
     ++ (optionals javaAwtGtk ([ gtk2 libart_lgpl ] ++ xlibs))
@@ -329,66 +314,85 @@ stdenv.mkDerivation ({
   # TODO(@Ericson2314): Always pass "--target" and always prefix.
   configurePlatforms =
     # TODO(@Ericson2314): Figure out what's going wrong with Arm
-    if hostPlatform == targetPlatform && targetPlatform.isArm
+    if buildPlatform == hostPlatform && hostPlatform == targetPlatform && targetPlatform.isArm
     then []
     else [ "build" "host" ] ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
 
-  configureFlags = "
-    ${if hostPlatform.isSunOS then
-      " --enable-long-long --enable-libssp --enable-threads=posix --disable-nls --enable-__cxa_atexit " +
-      # On Illumos/Solaris GNU as is preferred
-      " --with-gnu-as --without-gnu-ld "
-      else ""}
-    --enable-lto
-    ${if enableMultilib then "--enable-multilib --disable-libquadmath" else "--disable-multilib"}
-    ${if enableShared then "" else "--disable-shared"}
-    ${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
-    ${optionalString (isl != null) "--with-isl=${isl}"}
-    ${if langJava then
-      "--with-ecj-jar=${javaEcj} " +
+  configureFlags =
+    # Basic dependencies
+    [
+      "--with-gmp-include=${gmp.dev}/include"
+      "--with-gmp-lib=${gmp.out}/lib"
+      "--with-mpfr-include=${mpfr.dev}/include"
+      "--with-mpfr-lib=${mpfr.out}/lib"
+      "--with-mpc=${libmpc}"
+    ] ++
+    optional (libelf != null) "--with-libelf=${libelf}" ++
+    optional (!(crossMingw && crossStageStatic))
+      "--with-native-system-header-dir=${getDev stdenv.cc.libc}/include" ++
+
+    # Basic configuration
+    [
+      "--enable-lto"
+      "--disable-libstdcxx-pch"
+      "--without-included-gettext"
+      "--with-system-zlib"
+      "--enable-static"
+      "--enable-languages=${
+        concatStrings (intersperse ","
+          (  optional langC        "c"
+          ++ optional langCC       "c++"
+          ++ optional langFortran  "fortran"
+          ++ optional langJava     "java"
+          ++ optional langAda      "ada"
+          ++ optional langVhdl     "vhdl"
+          ++ optional langGo       "go"
+          ++ optional langObjC     "objc"
+          ++ optional langObjCpp   "obj-c++"
+          ++ optionals crossDarwin [ "objc" "obj-c++" ]
+          )
+        )
+      }"
+    ] ++
+
+    (if enableMultilib
+      then ["--enable-multilib" "--disable-libquadmath"]
+      else ["--disable-multilib"]) ++
+    optional (!enableShared) "--disable-shared" ++
+    (if enablePlugin
+      then ["--enable-plugin"]
+      else ["--disable-plugin"]) ++
+
+    # Optional features
+    optional (isl != null) "--with-isl=${isl}" ++
+
+    # Java options
+    optionals langJava [
+      "--with-ecj-jar=${javaEcj}"
 
       # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
       # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
-      "--enable-java-home --with-java-home=\${prefix}/lib/jvm/jre "
-      else ""}
-    ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-    ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr}" else ""}
-    --with-gmp-include=${gmp.dev}/include
-    --with-gmp-lib=${gmp.out}/lib
-    --with-mpfr-include=${mpfr.dev}/include
-    --with-mpfr-lib=${mpfr.out}/lib
-    --with-mpc=${libmpc}
-    ${if libelf != null then "--with-libelf=${libelf}" else ""}
-    --disable-libstdcxx-pch
-    --without-included-gettext
-    --with-system-zlib
-    --enable-static
-    --enable-languages=${
-      concatStrings (intersperse ","
-        (  optional langC        "c"
-        ++ optional langCC       "c++"
-        ++ optional langFortran  "fortran"
-        ++ optional langJava     "java"
-        ++ optional langAda      "ada"
-        ++ optional langVhdl     "vhdl"
-        ++ optional langGo       "go"
-        ++ optional langObjC     "objc"
-        ++ optional langObjCpp   "obj-c++"
-        ++ optionals crossDarwin [ "objc" "obj-c++" ]
-        )
-      )
-    }
-    ${if targetPlatform == hostPlatform
-      then if hostPlatform.isDarwin
-        then " --with-native-system-header-dir=${darwin.usr-include}"
-        else " --with-native-system-header-dir=${getDev stdenv.cc.libc}/include"
-      else ""}
-    ${if langAda then " --enable-libada" else ""}
-    ${if targetPlatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-    ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-    ${if !bootstrap then "--disable-bootstrap" else ""}
-    ${if targetPlatform == hostPlatform then platformFlags else ""}
-  ";
+      "--enable-java-home"
+      "--with-java-home=\${prefix}/lib/jvm/jre"
+    ] ++
+    optional javaAwtGtk "--enable-java-awt=gtk" ++
+    optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}" ++
+
+    # Ada
+    optional langAda "--enable-libada" ++
+
+    platformFlags ++
+    optional (targetPlatform != hostPlatform) crossConfigureFlags ++
+    optional (!bootstrap) "--disable-bootstrap" ++
+
+    # Platform-specific flags
+    optional (targetPlatform == hostPlatform && targetPlatform.isi686) "--with-arch=i686" ++
+    optionals hostPlatform.isSunOS [
+      "--enable-long-long" "--enable-libssp" "--enable-threads=posix" "--disable-nls" "--enable-__cxa_atexit"
+      # On Illumos/Solaris GNU as is preferred
+      "--with-gnu-as" "--without-gnu-ld"
+    ]
+  ;
 
   targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
 
@@ -401,83 +405,30 @@ stdenv.mkDerivation ({
     then "install-strip"
     else "install";
 
-  crossAttrs = let
-    xgccArch = targetPlatform.gcc.arch or null;
-    xgccCpu = targetPlatform.gcc.cpu or null;
-    xgccAbi = targetPlatform.gcc.abi or null;
-    xgccFpu = targetPlatform.gcc.fpu or null;
-    xgccFloat = targetPlatform.gcc.float or null;
-    xwithArch = if xgccArch != null then " --with-arch=${xgccArch}" else "";
-    xwithCpu = if xgccCpu != null then " --with-cpu=${xgccCpu}" else "";
-    xwithAbi = if xgccAbi != null then " --with-abi=${xgccAbi}" else "";
-    xwithFpu = if xgccFpu != null then " --with-fpu=${xgccFpu}" else "";
-    xwithFloat = if xgccFloat != null then " --with-float=${xgccFloat}" else "";
-  in {
-    AR = "${targetPlatform.config}-ar";
-    LD = "${targetPlatform.config}-ld";
-    CC = "${targetPlatform.config}-gcc";
-    CXX = "${targetPlatform.config}-gcc";
-    AR_FOR_TARGET = "${targetPlatform.config}-ar";
-    LD_FOR_TARGET = "${targetPlatform.config}-ld";
-    CC_FOR_TARGET = "${targetPlatform.config}-gcc";
-    NM_FOR_TARGET = "${targetPlatform.config}-nm";
-    CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
-    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
+  /* For cross-built gcc (build != host == target) */
+  crossAttrs = {
     dontStrip = true;
-    configureFlags = ''
-      ${if enableMultilib then "" else "--disable-multilib"}
-      ${if enableShared then "" else "--disable-shared"}
-      ${if langJava then "--with-ecj-jar=${javaEcj.crossDrv}" else ""}
-      ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-      ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr.crossDrv}" else ""}
-      --with-gmp=${gmp.crossDrv}
-      --with-mpfr=${mpfr.crossDrv}
-      --with-mpc=${libmpc.crossDrv}
-      --disable-libstdcxx-pch
-      --without-included-gettext
-      --with-system-zlib
-      --enable-languages=${
-        concatStrings (intersperse ","
-          (  optional langC        "c"
-          ++ optional langCC       "c++"
-          ++ optional langFortran  "fortran"
-          ++ optional langJava     "java"
-          ++ optional langAda      "ada"
-          ++ optional langVhdl     "vhdl"
-          ++ optional langGo       "go"
-          )
-        )
-      }
-      ${if langAda then " --enable-libada" else ""}
-      ${xwithArch}
-      ${xwithCpu}
-      ${xwithAbi}
-      ${xwithFpu}
-      ${xwithFloat}
-    '';
     buildFlags = "";
   };
 
-
-  # Needed for the cross compilation to work
-  AR = "ar";
-  LD = "ld";
   # http://gcc.gnu.org/install/specific.html#x86-64-x-solaris210
-  CC = if stdenv.system == "x86_64-solaris" then "gcc -m64" else "gcc";
-
-  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find
-  # the library headers and binaries, regarless of the language being
-  # compiled.
+  ${if hostPlatform.system == "x86_64-solaris" then "CC" else null} = "gcc -m64";
 
-  # Note: When building the Java AWT GTK+ peer, the build system doesn't
-  # honor `--with-gmp' et al., e.g., when building
-  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just
-  # add them to $CPATH and $LIBRARY_PATH in this case.
+  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
+  # library headers and binaries, regarless of the language being compiled.
+  #
+  # Note: When building the Java AWT GTK+ peer, the build system doesn't honor
+  # `--with-gmp' et al., e.g., when building
+  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just add
+  # them to $CPATH and $LIBRARY_PATH in this case.
   #
   # Likewise, the LTO code doesn't find zlib.
+  #
+  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
+  # compiler (after the specs for the cross-gcc are created). Having
+  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.
 
-  CPATH = makeSearchPathOutput "dev" "include" ([]
+  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
@@ -488,39 +439,38 @@ stdenv.mkDerivation ({
     # On GNU/Hurd glibc refers to Mach & Hurd
     # headers.
     ++ optionals (libcCross != null && libcCross ? propagatedBuildInputs)
-                 libcCross.propagatedBuildInputs);
+                 libcCross.propagatedBuildInputs
+  ));
 
-  LIBRARY_PATH = makeLibraryPath ([]
+  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
-    ++ optional (libpthread != null) libpthread);
-
-  EXTRA_TARGET_CFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-idirafter ${getDev libcCross}/include"
-      ]
-      ++ optionals (! crossStageStatic) [
-        "-B${libcCross.out}/lib"
-      ]
-    else null;
-
-  EXTRA_TARGET_LDFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-Wl,-L${libcCross.out}/lib"
-      ]
-      ++ (if crossStageStatic then [
+    ++ optional (libpthread != null) libpthread)
+  );
+
+  EXTRA_TARGET_FLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-idirafter ${getDev libcCross}/include"
+    ] ++ optionals (! crossStageStatic) [
+      "-B${libcCross.out}/lib"
+    ]);
+
+  EXTRA_TARGET_LDFLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-Wl,-L${libcCross.out}/lib"
+    ] ++ (if crossStageStatic then [
         "-B${libcCross.out}/lib"
       ] else [
         "-Wl,-rpath,${libcCross.out}/lib"
         "-Wl,-rpath-link,${libcCross.out}/lib"
-      ])
-      ++ optionals (libpthreadCross != null) [
-        "-L${libpthreadCross}/lib"
-        "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
-      ]
-    else null;
+    ]) ++ optionals (libpthreadCross != null) [
+      "-L${libpthreadCross}/lib"
+      "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
+    ]);
 
   passthru =
     { inherit langC langCC langObjC langObjCpp langAda langFortran langVhdl langGo version; isGNU = true; };
@@ -561,7 +511,7 @@ stdenv.mkDerivation ({
 }
 
 # Strip kills static libs of other archs (hence targetPlatform != hostPlatform)
-// optionalAttrs (!stripped || targetPlatform != hostPlatform) { dontStrip = true; }
+// optionalAttrs (!stripped || targetPlatform != hostPlatform) { dontStrip = true; NIX_STRIP_DEBUG = 0; }
 
 // optionalAttrs (enableMultilib) { dontMoveLib64 = true; }
 )
diff --git a/pkgs/development/compilers/gcc/builder.sh b/pkgs/development/compilers/gcc/builder.sh
index ee56425f00b4..1796c83385e5 100644
--- a/pkgs/development/compilers/gcc/builder.sh
+++ b/pkgs/development/compilers/gcc/builder.sh
@@ -1,153 +1,156 @@
 source $stdenv/setup
 
 
-export NIX_FIXINC_DUMMY=$NIX_BUILD_TOP/dummy
-mkdir $NIX_FIXINC_DUMMY
+oldOpts="$(shopt -po nounset)" || true
+set -euo pipefail
+
+
+export NIX_FIXINC_DUMMY="$NIX_BUILD_TOP/dummy"
+mkdir "$NIX_FIXINC_DUMMY"
 
 
 if test "$staticCompiler" = "1"; then
     EXTRA_LDFLAGS="-static"
 else
-    EXTRA_LDFLAGS="-Wl,-rpath,$lib/lib"
+    EXTRA_LDFLAGS="-Wl,-rpath,${!outputLib}/lib"
 fi
 
 
 # GCC interprets empty paths as ".", which we don't want.
-if test -z "$CPATH"; then unset CPATH; fi
-if test -z "$LIBRARY_PATH"; then unset LIBRARY_PATH; fi
-echo "\$CPATH is \`$CPATH'"
-echo "\$LIBRARY_PATH is \`$LIBRARY_PATH'"
+if test -z "${CPATH-}"; then unset CPATH; fi
+if test -z "${LIBRARY_PATH-}"; then unset LIBRARY_PATH; fi
+echo "\$CPATH is \`${CPATH-}'"
+echo "\$LIBRARY_PATH is \`${LIBRARY_PATH-}'"
 
 if test "$noSysDirs" = "1"; then
 
-    if test -e $NIX_CC/nix-support/orig-libc; then
+    declare \
+        EXTRA_BUILD_FLAGS EXTRA_FLAGS EXTRA_TARGET_FLAGS \
+        EXTRA_BUILD_LDFLAGS EXTRA_TARGET_LDFLAGS
 
-        # Figure out what extra flags to pass to the gcc compilers
-        # being generated to make sure that they use our glibc.
-        extraFlags="$(cat $NIX_CC/nix-support/libc-cflags)"
-        extraLDFlags="$(cat $NIX_CC/nix-support/libc-ldflags) $(cat $NIX_CC/nix-support/libc-ldflags-before || true)"
+    # Extract flags from Bintools Wrappers
+    for pre in 'BUILD_' ''; do
+        curBintools="NIX_${pre}BINTOOLS"
 
-        # Use *real* header files, otherwise a limits.h is generated
-        # that does not include Glibc's limits.h (notably missing
-        # SSIZE_MAX, which breaks the build).
-        export NIX_FIXINC_DUMMY=$libc_dev/include
+        declare -a extraLDFlags=()
+        if [[ -e "${!curBintools}/nix-support/orig-libc" ]]; then
+            # Figure out what extra flags when linking to pass to the gcc
+            # compilers being generated to make sure that they use our libc.
+            extraLDFlags=($(< "${!curBintools}/nix-support/libc-ldflags") $(< "${!curBintools}/nix-support/libc-ldflags-before" || true))
 
-        # The path to the Glibc binaries such as `crti.o'.
-        glibc_libdir="$(cat $NIX_CC/nix-support/orig-libc)/lib"
+            # The path to the Libc binaries such as `crti.o'.
+            libc_libdir="$(< "${!curBintools}/nix-support/orig-libc")/lib"
+        else
+            # Hack: support impure environments.
+            extraLDFlags=("-L/usr/lib64" "-L/usr/lib")
+            libc_libdir="/usr/lib"
+        fi
+        extraLDFlags=("-L$libc_libdir" "-rpath" "$libc_libdir"
+                      "${extraLDFlags[@]}")
+        for i in "${extraLDFlags[@]}"; do
+            declare EXTRA_${pre}LDFLAGS+=" -Wl,$i"
+        done
+    done
 
-    else
-        # Hack: support impure environments.
-        extraFlags="-isystem /usr/include"
-        extraLDFlags="-L/usr/lib64 -L/usr/lib"
-        glibc_libdir="/usr/lib"
-        export NIX_FIXINC_DUMMY=/usr/include
-    fi
+    # Extract flags from CC Wrappers
+    for pre in 'BUILD_' ''; do
+        curCC="NIX_${pre}CC"
+        curFIXINC="NIX_${pre}FIXINC_DUMMY"
 
-    extraFlags="-I$NIX_FIXINC_DUMMY $extraFlags"
-    extraLDFlags="-L$glibc_libdir -rpath $glibc_libdir $extraLDFlags"
+        declare -a extraFlags=()
+        if [[ -e "${!curCC}/nix-support/orig-libc" ]]; then
+            # Figure out what extra compiling flags to pass to the gcc compilers
+            # being generated to make sure that they use our libc.
+            extraFlags=($(< "${!curCC}/nix-support/libc-cflags"))
 
-    # BOOT_CFLAGS defaults to `-g -O2'; since we override it below,
-    # make sure to explictly add them so that files compiled with the
-    # bootstrap compiler are optimized and (optionally) contain
-    # debugging information (info "(gccinstall) Building").
-    if test -n "$dontStrip"; then
-        extraFlags="-O2 -g $extraFlags"
-    else
-        # Don't pass `-g' at all; this saves space while building.
-        extraFlags="-O2 $extraFlags"
-    fi
+            # The path to the Libc headers
+            libc_devdir="$(< "${!curCC}/nix-support/orig-libc-dev")"
 
-    EXTRA_FLAGS="$extraFlags"
-    for i in $extraLDFlags; do
-        EXTRA_LDFLAGS="$EXTRA_LDFLAGS -Wl,$i"
-    done
+            # Use *real* header files, otherwise a limits.h is generated that
+            # does not include Libc's limits.h (notably missing SSIZE_MAX,
+            # which breaks the build).
+            declare NIX_${pre}FIXINC_DUMMY="$libc_devdir/include"
+        else
+            # Hack: support impure environments.
+            extraFlags=("-isystem" "/usr/include")
+            declare NIX_${pre}FIXINC_DUMMY=/usr/include
+        fi
 
-    if test -n "$targetConfig"; then
-        # Cross-compiling, we need gcc not to read ./specs in order to build
-        # the g++ compiler (after the specs for the cross-gcc are created).
-        # Having LIBRARY_PATH= makes gcc read the specs from ., and the build
-        # breaks. Having this variable comes from the default.nix code to bring
-        # gcj in.
-        unset LIBRARY_PATH
-        unset CPATH
-    else
-        if test -z "$NIX_CC_CROSS"; then
-            EXTRA_TARGET_CFLAGS="$EXTRA_FLAGS"
-            EXTRA_TARGET_CXXFLAGS="$EXTRA_FLAGS"
-            EXTRA_TARGET_LDFLAGS="$EXTRA_LDFLAGS"
+        extraFlags=("-I${!curFIXINC}" "${extraFlags[@]}")
+
+        # BOOT_CFLAGS defaults to `-g -O2'; since we override it below, make
+        # sure to explictly add them so that files compiled with the bootstrap
+        # compiler are optimized and (optionally) contain debugging information
+        # (info "(gccinstall) Building").
+        if test -n "${dontStrip-}"; then
+            extraFlags=("-O2" "-g" "${extraFlags[@]}")
         else
-            # This the case of cross-building the gcc.
-            # We need special flags for the target, different than those of the build
-            # Assertion:
-            test -e $NIX_CC_CROSS/nix-support/orig-libc
-
-            # Figure out what extra flags to pass to the gcc compilers
-            # being generated to make sure that they use our glibc.
-            extraFlags="$(cat $NIX_CC_CROSS/nix-support/libc-cflags)"
-            extraLDFlags="$(cat $NIX_CC_CROSS/nix-support/libc-ldflags) $(cat $NIX_CC_CROSS/nix-support/libc-ldflags-before)"
-
-            # The path to the Glibc binaries such as `crti.o'.
-            glibc_dir="$(cat $NIX_CC_CROSS/nix-support/orig-libc)"
-            glibc_libdir="$glibc_dir/lib"
-            glibc_devdir="$(cat $NIX_CC_CROSS/nix-support/orig-libc-dev)"
-            configureFlags="$configureFlags --with-native-system-header-dir=$glibc_devdir/include"
-
-            # Use *real* header files, otherwise a limits.h is generated
-            # that does not include Glibc's limits.h (notably missing
-            # SSIZE_MAX, which breaks the build).
-            NIX_FIXINC_DUMMY_CROSS="$glibc_devdir/include"
-
-            extraFlags="-I$NIX_FIXINC_DUMMY_CROSS $extraFlags"
-            extraLDFlags="-L$glibc_libdir -rpath $glibc_libdir $extraLDFlags"
-
-            EXTRA_TARGET_CFLAGS="$extraFlags"
-            for i in $extraLDFlags; do
-                EXTRA_TARGET_LDFLAGS="$EXTRA_TARGET_LDFLAGS -Wl,$i"
-            done
+            # Don't pass `-g' at all; this saves space while building.
+            extraFlags=("-O2" "${extraFlags[@]}")
         fi
+
+        declare EXTRA_${pre}FLAGS="${extraFlags[*]}"
+    done
+
+    if test -z "${targetConfig-}"; then
+        # host = target, so the flags are the same
+        EXTRA_TARGET_FLAGS="$EXTRA_FLAGS"
+        EXTRA_TARGET_LDFLAGS="$EXTRA_LDFLAGS"
     fi
 
     # CFLAGS_FOR_TARGET are needed for the libstdc++ configure script to find
     # the startfiles.
     # FLAGS_FOR_TARGET are needed for the target libraries to receive the -Bxxx
     # for the startfiles.
-    makeFlagsArray+=( \
-        NATIVE_SYSTEM_HEADER_DIR="$NIX_FIXINC_DUMMY" \
-        SYSTEM_HEADER_DIR="$NIX_FIXINC_DUMMY" \
-        CFLAGS_FOR_BUILD="$EXTRA_FLAGS $EXTRA_LDFLAGS" \
-        CXXFLAGS_FOR_BUILD="$EXTRA_FLAGS $EXTRA_LDFLAGS" \
-        CFLAGS_FOR_TARGET="$EXTRA_TARGET_CFLAGS $EXTRA_TARGET_LDFLAGS" \
-        CXXFLAGS_FOR_TARGET="$EXTRA_TARGET_CFLAGS $EXTRA_TARGET_LDFLAGS" \
-        FLAGS_FOR_TARGET="$EXTRA_TARGET_CFLAGS $EXTRA_TARGET_LDFLAGS" \
-        LDFLAGS_FOR_BUILD="$EXTRA_FLAGS $EXTRA_LDFLAGS" \
-        LDFLAGS_FOR_TARGET="$EXTRA_TARGET_LDFLAGS $EXTRA_TARGET_LDFLAGS" \
+    makeFlagsArray+=(
+        "BUILD_SYSTEM_HEADER_DIR=$NIX_BUILD_FIXINC_DUMMY"
+        "SYSTEM_HEADER_DIR=$NIX_BUILD_FIXINC_DUMMY"
+        "NATIVE_SYSTEM_HEADER_DIR=$NIX_FIXINC_DUMMY"
+
+        "LDFLAGS_FOR_BUILD=$EXTRA_BUILD_LDFLAGS"
+        #"LDFLAGS=$EXTRA_LDFLAGS"
+        "LDFLAGS_FOR_TARGET=$EXTRA_TARGET_LDFLAGS"
+
+        "CFLAGS_FOR_BUILD=$EXTRA_BUILD_FLAGS $EXTRA_BUILD_LDFLAGS"
+        "CXXFLAGS_FOR_BUILD=$EXTRA_BUILD_FLAGS $EXTRA_BUILD_LDFLAGS"
+        "FLAGS_FOR_BUILD=$EXTRA_BUILD_FLAGS $EXTRA_BUILD_LDFLAGS"
+
+        # It seems there is a bug in GCC 5
+        #"CFLAGS=$EXTRA_FLAGS $EXTRA_LDFLAGS"
+        #"CXXFLAGS=$EXTRA_FLAGS $EXTRA_LDFLAGS"
+
+        "CFLAGS_FOR_TARGET=$EXTRA_TARGET_FLAGS $EXTRA_TARGET_LDFLAGS"
+        "CXXFLAGS_FOR_TARGET=$EXTRA_TARGET_FLAGS $EXTRA_TARGET_LDFLAGS"
+        "FLAGS_FOR_TARGET=$EXTRA_TARGET_FLAGS $EXTRA_TARGET_LDFLAGS"
+    )
+
+    if test -z "${targetConfig-}"; then
+        makeFlagsArray+=(
+            "BOOT_CFLAGS=$EXTRA_FLAGS $EXTRA_LDFLAGS"
+            "BOOT_LDFLAGS=$EXTRA_TARGET_FLAGS $EXTRA_TARGET_LDFLAGS"
         )
-
-    if test -z "$targetConfig"; then
-        makeFlagsArray+=( \
-            BOOT_CFLAGS="$EXTRA_FLAGS $EXTRA_LDFLAGS" \
-            BOOT_LDFLAGS="$EXTRA_TARGET_CFLAGS $EXTRA_TARGET_LDFLAGS" \
-            )
     fi
 
-    if test -n "$targetConfig" -a "$crossStageStatic" == 1; then
+    if test -n "${targetConfig-}" -a "$crossStageStatic" == 1; then
         # We don't want the gcc build to assume there will be a libc providing
         # limits.h in this stagae
-        makeFlagsArray+=( \
-            LIMITS_H_TEST=false \
-            )
+        makeFlagsArray+=(
+            'LIMITS_H_TEST=false'
+        )
     else
-        makeFlagsArray+=( \
-            LIMITS_H_TEST=true \
-            )
+        makeFlagsArray+=(
+            'LIMITS_H_TEST=true'
+        )
     fi
 fi
 
-if test -n "$targetConfig"; then
+if test -n "${targetConfig-}"; then
     # The host strip will destroy some important details of the objects
     dontStrip=1
 fi
 
+eval "$oldOpts"
+
 providedPreConfigure="$preConfigure";
 preConfigure() {
     if test -n "$newlibSrc"; then
diff --git a/pkgs/development/compilers/gcc/snapshot/default.nix b/pkgs/development/compilers/gcc/snapshot/default.nix
index e235be639c6e..c1306d374d5d 100644
--- a/pkgs/development/compilers/gcc/snapshot/default.nix
+++ b/pkgs/development/compilers/gcc/snapshot/default.nix
@@ -23,7 +23,7 @@
 , x11Support ? langJava
 , gnatboot ? null
 , enableMultilib ? false
-, enablePlugin ? true             # whether to support user-supplied plug-ins
+, enablePlugin ? hostPlatform == buildPlatform # Whether to support user-supplied plug-ins
 , name ? "gcc"
 , libcCross ? null
 , crossStageStatic ? false
@@ -35,6 +35,7 @@
 , darwin ? null
 , flex ? null
 , buildPlatform, hostPlatform, targetPlatform
+, buildPackages
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -49,9 +50,6 @@ assert libelf != null -> zlib != null;
 # Make sure we get GNU sed.
 assert hostPlatform.isDarwin -> gnused != null;
 
-# Need c++filt on darwin
-assert hostPlatform.isDarwin -> targetPackages.stdenv.cc.bintools or null != null;
-
 # The go frontend is written in c++
 assert langGo -> langCC;
 
@@ -99,107 +97,81 @@ let version = "7-20170409";
 
     /* Platform flags */
     platformFlags = let
-        gccArch = stdenv.platform.gcc.arch or null;
-        gccCpu = stdenv.platform.gcc.cpu or null;
-        gccAbi = stdenv.platform.gcc.abi or null;
-        gccFpu = stdenv.platform.gcc.fpu or null;
-        gccFloat = stdenv.platform.gcc.float or null;
-        gccMode = stdenv.platform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
+        gccArch = targetPlatform.platform.gcc.arch or null;
+        gccCpu = targetPlatform.platform.gcc.cpu or null;
+        gccAbi = targetPlatform.platform.gcc.abi or null;
+        gccFpu = targetPlatform.platform.gcc.fpu or null;
+        gccFloat = targetPlatform.platform.gcc.float or null;
+        gccMode = targetPlatform.platform.gcc.mode or null;
       in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode;
-
-    /* Cross-gcc settings */
+        optional (gccArch != null) "--with-arch=${gccArch}" ++
+        optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
+        optional (gccAbi != null) "--with-abi=${gccAbi}" ++
+        optional (gccFpu != null) "--with-fpu=${gccFpu}" ++
+        optional (gccFloat != null) "--with-float=${gccFloat}" ++
+        optional (gccMode != null) "--with-mode=${gccMode}";
+
+    /* Cross-gcc settings (build == host != target) */
     crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";
     crossDarwin = targetPlatform != hostPlatform && targetPlatform.libc == "libSystem";
-    crossConfigureFlags = let
-        gccArch = targetPlatform.gcc.arch or null;
-        gccCpu = targetPlatform.gcc.cpu or null;
-        gccAbi = targetPlatform.gcc.abi or null;
-        gccFpu = targetPlatform.gcc.fpu or null;
-        gccFloat = targetPlatform.gcc.float or null;
-        gccMode = targetPlatform.gcc.mode or null;
-        withArch = if gccArch != null then " --with-arch=${gccArch}" else "";
-        withCpu = if gccCpu != null then " --with-cpu=${gccCpu}" else "";
-        withAbi = if gccAbi != null then " --with-abi=${gccAbi}" else "";
-        withFpu = if gccFpu != null then " --with-fpu=${gccFpu}" else "";
-        withFloat = if gccFloat != null then " --with-float=${gccFloat}" else "";
-        withMode = if gccMode != null then " --with-mode=${gccMode}" else "";
-      in
-        withArch +
-        withCpu +
-        withAbi +
-        withFpu +
-        withFloat +
-        withMode +
-        # Ensure that -print-prog-name is able to find the correct programs.
-        " --with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as" +
-        " --with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" +
-        (if crossMingw && crossStageStatic then
-          " --with-headers=${libcCross}/include" +
-          " --with-gcc" +
-          " --with-gnu-as" +
-          " --with-gnu-ld" +
-          " --with-gnu-ld" +
-          " --disable-shared" +
-          " --disable-nls" +
-          " --disable-debug" +
-          " --enable-sjlj-exceptions" +
-          " --enable-threads=win32" +
-          " --disable-win32-registry"
-          else if crossStageStatic then
-          " --disable-libssp --disable-nls" +
-          " --without-headers" +
-          " --disable-threads " +
-          " --disable-libgomp " +
-          " --disable-libquadmath" +
-          " --disable-shared" +
-          " --disable-libatomic " +  # libatomic requires libc
-          " --disable-decimal-float" # libdecnumber requires libc
-          else
-          (if crossDarwin then " --with-sysroot=${getLib libcCross}/share/sysroot"
-           else                " --with-headers=${getDev libcCross}/include") +
-          # Ensure that -print-prog-name is able to find the correct programs.
-          " --enable-__cxa_atexit" +
-          " --enable-long-long" +
-          (if crossMingw then
-            " --enable-threads=win32" +
-            " --enable-sjlj-exceptions" +
-            " --enable-hash-synchronization" +
-            " --disable-libssp" +
-            " --disable-nls" +
-            " --with-dwarf2" +
-            # I think noone uses shared gcc libs in mingw, so we better do the same.
-            # In any case, mingw32 g++ linking is broken by default with shared libs,
-            # unless adding "-lsupc++" to any linking command. I don't know why.
-            " --disable-shared" +
-            # To keep ABI compatibility with upstream mingw-w64
-            " --enable-fully-dynamic-string"
-            else (if targetPlatform.libc == "uclibc" then
-              # libsanitizer requires netrom/netrom.h which is not
-              # available in uclibc.
-              " --disable-libsanitizer" +
-              # In uclibc cases, libgomp needs an additional '-ldl'
-              # and as I don't know how to pass it, I disable libgomp.
-              " --disable-libgomp" else "") +
-            " --enable-threads=posix" +
-            " --enable-nls" +
-            " --disable-decimal-float") # No final libdecnumber (it may work only in 386)
-          );
+    crossConfigureFlags =
+      # Ensure that -print-prog-name is able to find the correct programs.
+      [ "--with-as=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-as"
+        "--with-ld=${targetPackages.stdenv.cc.bintools}/bin/${targetPlatform.config}-ld" ] ++
+      (if crossMingw && crossStageStatic then [
+        "--with-headers=${libcCross}/include"
+        "--with-gcc"
+        "--with-gnu-as"
+        "--with-gnu-ld"
+        "--with-gnu-ld"
+        "--disable-shared"
+        "--disable-nls"
+        "--disable-debug"
+        "--enable-sjlj-exceptions"
+        "--enable-threads=win32"
+        "--disable-win32-registry"
+      ] else if crossStageStatic then [
+        "--disable-libssp"
+        "--disable-nls"
+        "--without-headers"
+        "--disable-threads"
+        "--disable-libgomp"
+        "--disable-libquadmath"
+        "--disable-shared"
+        "--disable-libatomic"  # libatomic requires libc
+        "--disable-decimal-float" # libdecnumber requires libc
+      ] else [
+        (if crossDarwin then "--with-sysroot=${getLib libcCross}/share/sysroot"
+         else                "--with-headers=${getDev libcCross}/include")
+        "--enable-__cxa_atexit"
+        "--enable-long-long"
+      ] ++
+        (if crossMingw then [
+          "--enable-threads=win32"
+          "--enable-sjlj-exceptions"
+          "--enable-hash-synchronization"
+          "--enable-libssp"
+          "--disable-nls"
+          "--with-dwarf2"
+          # To keep ABI compatibility with upstream mingw-w64
+          "--enable-fully-dynamic-string"
+        ] else
+          optionals (targetPlatform.libc == "uclibc") [
+            # libsanitizer requires netrom/netrom.h which is not
+            # available in uclibc.
+            "--disable-libsanitizer"
+            # In uclibc cases, libgomp needs an additional '-ldl'
+            # and as I don't know how to pass it, I disable libgomp.
+            "--disable-libgomp"
+          ] ++ [
+          "--enable-threads=posix"
+          "--enable-nls"
+          "--disable-decimal-float" # No final libdecnumber (it may work only in 386)
+        ]));
     stageNameAddon = if crossStageStatic then "-stage-static" else "-stage-final";
     crossNameAddon = if targetPlatform != hostPlatform then "-${targetPlatform.config}" + stageNameAddon else "";
 
-  bootstrap = targetPlatform == hostPlatform;
+    bootstrap = targetPlatform == hostPlatform;
 
 in
 
@@ -285,12 +257,23 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler langJava
     libcCross crossMingw;
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
   nativeBuildInputs = [ texinfo which gettext ]
     ++ (optional (perl != null) perl)
     ++ (optional javaAwtGtk pkgconfig);
 
-  buildInputs = [ gmp mpfr libmpc libelf flex ]
-    ++ (optional (isl != null) isl)
+  # For building runtime libs
+  depsBuildTarget =
+    if hostPlatform == buildPlatform then [
+      targetPackages.stdenv.cc.bintools # newly-built gcc will be used
+    ] else assert targetPlatform == hostPlatform; [ # build != host == target
+      stdenv.cc
+    ];
+
+  buildInputs = [
+    gmp mpfr libmpc libelf flex
+    targetPackages.stdenv.cc.bintools # For linking code at run-time
+  ] ++ (optional (isl != null) isl)
     ++ (optional (zlib != null) zlib)
     ++ (optionals langJava [ boehmgc zip unzip ])
     ++ (optionals javaAwtGtk ([ gtk2 libart_lgpl ] ++ xlibs))
@@ -318,66 +301,85 @@ stdenv.mkDerivation ({
   # TODO(@Ericson2314): Always pass "--target" and always prefix.
   configurePlatforms =
     # TODO(@Ericson2314): Figure out what's going wrong with Arm
-    if hostPlatform == targetPlatform && targetPlatform.isArm
+    if buildPlatform == hostPlatform && hostPlatform == targetPlatform && targetPlatform.isArm
     then []
     else [ "build" "host" ] ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
 
-  configureFlags = "
-    ${if hostPlatform.isSunOS then
-      " --enable-long-long --enable-libssp --enable-threads=posix --disable-nls --enable-__cxa_atexit " +
-      # On Illumos/Solaris GNU as is preferred
-      " --with-gnu-as --without-gnu-ld "
-      else ""}
-    --enable-lto
-    ${if enableMultilib then "--enable-multilib --disable-libquadmath" else "--disable-multilib"}
-    ${if enableShared then "" else "--disable-shared"}
-    ${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
-    ${optionalString (isl != null) "--with-isl=${isl}"}
-    ${if langJava then
-      "--with-ecj-jar=${javaEcj} " +
+  configureFlags =
+    # Basic dependencies
+    [
+      "--with-gmp-include=${gmp.dev}/include"
+      "--with-gmp-lib=${gmp.out}/lib"
+      "--with-mpfr-include=${mpfr.dev}/include"
+      "--with-mpfr-lib=${mpfr.out}/lib"
+      "--with-mpc=${libmpc}"
+    ] ++
+    optional (libelf != null) "--with-libelf=${libelf}" ++
+    optional (!(crossMingw && crossStageStatic))
+      "--with-native-system-header-dir=${getDev stdenv.cc.libc}/include" ++
+
+    # Basic configuration
+    [
+      "--enable-lto"
+      "--disable-libstdcxx-pch"
+      "--without-included-gettext"
+      "--with-system-zlib"
+      "--enable-static"
+      "--enable-languages=${
+        concatStrings (intersperse ","
+          (  optional langC        "c"
+          ++ optional langCC       "c++"
+          ++ optional langFortran  "fortran"
+          ++ optional langJava     "java"
+          ++ optional langAda      "ada"
+          ++ optional langVhdl     "vhdl"
+          ++ optional langGo       "go"
+          ++ optional langObjC     "objc"
+          ++ optional langObjCpp   "obj-c++"
+          ++ optionals crossDarwin [ "objc" "obj-c++" ]
+          )
+        )
+      }"
+    ] ++
+
+    (if enableMultilib
+      then ["--enable-multilib" "--disable-libquadmath"]
+      else ["--disable-multilib"]) ++
+    optional (!enableShared) "--disable-shared" ++
+    (if enablePlugin
+      then ["--enable-plugin"]
+      else ["--disable-plugin"]) ++
+
+    # Optional features
+    optional (isl != null) "--with-isl=${isl}" ++
+
+    # Java options
+    optionals langJava [
+      "--with-ecj-jar=${javaEcj}"
 
       # Follow Sun's layout for the convenience of IcedTea/OpenJDK.  See
       # <http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2010-April/008888.html>.
-      "--enable-java-home --with-java-home=\${prefix}/lib/jvm/jre "
-      else ""}
-    ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-    ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr}" else ""}
-    --with-gmp-include=${gmp.dev}/include
-    --with-gmp-lib=${gmp.out}/lib
-    --with-mpfr-include=${mpfr.dev}/include
-    --with-mpfr-lib=${mpfr.out}/lib
-    --with-mpc=${libmpc}
-    ${if libelf != null then "--with-libelf=${libelf}" else ""}
-    --disable-libstdcxx-pch
-    --without-included-gettext
-    --with-system-zlib
-    --enable-static
-    --enable-languages=${
-      concatStrings (intersperse ","
-        (  optional langC        "c"
-        ++ optional langCC       "c++"
-        ++ optional langFortran  "fortran"
-        ++ optional langJava     "java"
-        ++ optional langAda      "ada"
-        ++ optional langVhdl     "vhdl"
-        ++ optional langGo       "go"
-        ++ optional langObjC     "objc"
-        ++ optional langObjCpp   "obj-c++"
-        ++ optionals crossDarwin [ "objc" "obj-c++" ]
-        )
-      )
-    }
-    ${if targetPlatform == hostPlatform
-      then if hostPlatform.isDarwin
-        then " --with-native-system-header-dir=${darwin.usr-include}"
-        else " --with-native-system-header-dir=${getDev stdenv.cc.libc}/include"
-      else ""}
-    ${if langAda then " --enable-libada" else ""}
-    ${if targetPlatform == hostPlatform && targetPlatform.isi686 then "--with-arch=i686" else ""}
-    ${if targetPlatform != hostPlatform then crossConfigureFlags else ""}
-    ${if !bootstrap then "--disable-bootstrap" else ""}
-    ${if targetPlatform == hostPlatform then platformFlags else ""}
-  ";
+      "--enable-java-home"
+      "--with-java-home=\${prefix}/lib/jvm/jre"
+    ] ++
+    optional javaAwtGtk "--enable-java-awt=gtk" ++
+    optional (langJava && javaAntlr != null) "--with-antlr-jar=${javaAntlr}" ++
+
+    # Ada
+    optional langAda "--enable-libada" ++
+
+    platformFlags ++
+    optional (targetPlatform != hostPlatform) crossConfigureFlags ++
+    optional (!bootstrap) "--disable-bootstrap" ++
+
+    # Platform-specific flags
+    optional (targetPlatform == hostPlatform && targetPlatform.isi686) "--with-arch=i686" ++
+    optionals hostPlatform.isSunOS [
+      "--enable-long-long" "--enable-libssp" "--enable-threads=posix" "--disable-nls" "--enable-__cxa_atexit"
+      # On Illumos/Solaris GNU as is preferred
+      "--with-gnu-as" "--without-gnu-ld"
+    ]
+  ;
 
   targetConfig = if targetPlatform != hostPlatform then targetPlatform.config else null;
 
@@ -390,83 +392,30 @@ stdenv.mkDerivation ({
     then "install-strip"
     else "install";
 
-  crossAttrs = let
-    xgccArch = targetPlatform.gcc.arch or null;
-    xgccCpu = targetPlatform.gcc.cpu or null;
-    xgccAbi = targetPlatform.gcc.abi or null;
-    xgccFpu = targetPlatform.gcc.fpu or null;
-    xgccFloat = targetPlatform.gcc.float or null;
-    xwithArch = if xgccArch != null then " --with-arch=${xgccArch}" else "";
-    xwithCpu = if xgccCpu != null then " --with-cpu=${xgccCpu}" else "";
-    xwithAbi = if xgccAbi != null then " --with-abi=${xgccAbi}" else "";
-    xwithFpu = if xgccFpu != null then " --with-fpu=${xgccFpu}" else "";
-    xwithFloat = if xgccFloat != null then " --with-float=${xgccFloat}" else "";
-  in {
-    AR = "${targetPlatform.config}-ar";
-    LD = "${targetPlatform.config}-ld";
-    CC = "${targetPlatform.config}-gcc";
-    CXX = "${targetPlatform.config}-gcc";
-    AR_FOR_TARGET = "${targetPlatform.config}-ar";
-    LD_FOR_TARGET = "${targetPlatform.config}-ld";
-    CC_FOR_TARGET = "${targetPlatform.config}-gcc";
-    NM_FOR_TARGET = "${targetPlatform.config}-nm";
-    CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
-    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
+  /* For cross-built gcc (build != host == target) */
+  crossAttrs = {
     dontStrip = true;
-    configureFlags = ''
-      ${if enableMultilib then "" else "--disable-multilib"}
-      ${if enableShared then "" else "--disable-shared"}
-      ${if langJava then "--with-ecj-jar=${javaEcj.crossDrv}" else ""}
-      ${if javaAwtGtk then "--enable-java-awt=gtk" else ""}
-      ${if langJava && javaAntlr != null then "--with-antlr-jar=${javaAntlr.crossDrv}" else ""}
-      --with-gmp=${gmp.crossDrv}
-      --with-mpfr=${mpfr.crossDrv}
-      --with-mpc=${libmpc.crossDrv}
-      --disable-libstdcxx-pch
-      --without-included-gettext
-      --with-system-zlib
-      --enable-languages=${
-        concatStrings (intersperse ","
-          (  optional langC        "c"
-          ++ optional langCC       "c++"
-          ++ optional langFortran  "fortran"
-          ++ optional langJava     "java"
-          ++ optional langAda      "ada"
-          ++ optional langVhdl     "vhdl"
-          ++ optional langGo       "go"
-          )
-        )
-      }
-      ${if langAda then " --enable-libada" else ""}
-      ${xwithArch}
-      ${xwithCpu}
-      ${xwithAbi}
-      ${xwithFpu}
-      ${xwithFloat}
-    '';
     buildFlags = "";
   };
 
-
-  # Needed for the cross compilation to work
-  AR = "ar";
-  LD = "ld";
   # http://gcc.gnu.org/install/specific.html#x86-64-x-solaris210
-  CC = if stdenv.system == "x86_64-solaris" then "gcc -m64" else "gcc";
-
-  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find
-  # the library headers and binaries, regarless of the language being
-  # compiled.
+  ${if hostPlatform.system == "x86_64-solaris" then "CC" else null} = "gcc -m64";
 
-  # Note: When building the Java AWT GTK+ peer, the build system doesn't
-  # honor `--with-gmp' et al., e.g., when building
-  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just
-  # add them to $CPATH and $LIBRARY_PATH in this case.
+  # Setting $CPATH and $LIBRARY_PATH to make sure both `gcc' and `xgcc' find the
+  # library headers and binaries, regarless of the language being compiled.
+  #
+  # Note: When building the Java AWT GTK+ peer, the build system doesn't honor
+  # `--with-gmp' et al., e.g., when building
+  # `libjava/classpath/native/jni/java-math/gnu_java_math_GMP.c', so we just add
+  # them to $CPATH and $LIBRARY_PATH in this case.
   #
   # Likewise, the LTO code doesn't find zlib.
+  #
+  # Cross-compiling, we need gcc not to read ./specs in order to build the g++
+  # compiler (after the specs for the cross-gcc are created). Having
+  # LIBRARY_PATH= makes gcc read the specs from ., and the build breaks.
 
-  CPATH = makeSearchPathOutput "dev" "include" ([]
+  CPATH = optionals (targetPlatform == hostPlatform) (makeSearchPathOutput "dev" "include" ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
@@ -477,39 +426,38 @@ stdenv.mkDerivation ({
     # On GNU/Hurd glibc refers to Mach & Hurd
     # headers.
     ++ optionals (libcCross != null && libcCross ? propagatedBuildInputs)
-                 libcCross.propagatedBuildInputs);
+                 libcCross.propagatedBuildInputs
+  ));
 
-  LIBRARY_PATH = makeLibraryPath ([]
+  LIBRARY_PATH = optionals (targetPlatform == hostPlatform) (makeLibraryPath ([]
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
     ++ optionals javaAwtGtk [ gmp mpfr ]
-    ++ optional (libpthread != null) libpthread);
-
-  EXTRA_TARGET_CFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-idirafter ${getDev libcCross}/include"
-      ]
-      ++ optionals (! crossStageStatic) [
-        "-B${libcCross.out}/lib"
-      ]
-    else null;
-
-  EXTRA_TARGET_LDFLAGS =
-    if targetPlatform != hostPlatform && libcCross != null then [
-        "-Wl,-L${libcCross.out}/lib"
-      ]
-      ++ (if crossStageStatic then [
+    ++ optional (libpthread != null) libpthread)
+  );
+
+  EXTRA_TARGET_FLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-idirafter ${getDev libcCross}/include"
+    ] ++ optionals (! crossStageStatic) [
+      "-B${libcCross.out}/lib"
+    ]);
+
+  EXTRA_TARGET_LDFLAGS = optionals
+    (targetPlatform != hostPlatform && libcCross != null)
+    ([
+      "-Wl,-L${libcCross.out}/lib"
+    ] ++ (if crossStageStatic then [
         "-B${libcCross.out}/lib"
       ] else [
         "-Wl,-rpath,${libcCross.out}/lib"
         "-Wl,-rpath-link,${libcCross.out}/lib"
-      ])
-      ++ optionals (libpthreadCross != null) [
-        "-L${libpthreadCross}/lib"
-        "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
-      ]
-    else null;
+    ]) ++ optionals (libpthreadCross != null) [
+      "-L${libpthreadCross}/lib"
+      "-Wl,${libpthreadCross.TARGET_LDFLAGS}"
+    ]);
 
   passthru =
     { inherit langC langCC langObjC langObjCpp langAda langFortran langVhdl langGo version; isGNU = true; };
@@ -541,6 +489,8 @@ stdenv.mkDerivation ({
       stdenv.lib.platforms.linux ++
       stdenv.lib.platforms.freebsd ++
       optionals (langAda == false) stdenv.lib.platforms.darwin;
+
+    broken = true;
   };
 }