1 files changed, 62 insertions, 8 deletions
diff --git a/pkgs/build-support/cc-wrapper/add-flags.sh b/pkgs/build-support/cc-wrapper/add-flags.sh
index 5634c82aa285..39633fce69a8 100644
--- a/pkgs/build-support/cc-wrapper/add-flags.sh
+++ b/pkgs/build-support/cc-wrapper/add-flags.sh
@@ -1,28 +1,82 @@
+# N.B. It may be a surprise that the derivation-specific variables are exported,
+# since this is just sourced by the wrapped binaries---the end consumers. This
+# is because one wrapper binary may invoke another (e.g. cc invoking ld). In
+# that case, it is cheaper/better to not repeat this step and let the forked
+# wrapped binary just inherit the work of the forker's wrapper script.
+
+var_templates=(
+    NIX+CFLAGS_COMPILE
+    NIX+CFLAGS_LINK
+    NIX+CXXSTDLIB_COMPILE
+    NIX+CXXSTDLIB_LINK
+    NIX+GNATFLAGS_COMPILE
+    NIX+IGNORE_LD_THROUGH_GCC
+    NIX+LDFLAGS
+    NIX+LDFLAGS_BEFORE
+    NIX+LDFLAGS_AFTER
+
+    NIX+SET_BUILD_ID
+    NIX+DONT_SET_RPATH
+    NIX+ENFORCE_NO_NATIVE
+)
+
+# Accumulate infixes for taking in the right input parameters. See setup-hook
+# for details.
+declare -a role_infixes=()
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_BUILD:-}" ]; then
+    role_infixes+=(_BUILD_)
+fi
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_HOST:-}" ]; then
+    role_infixes+=(_)
+fi
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_TARGET:-}" ]; then
+    role_infixes+=(_TARGET_)
+fi
+
+# We need to mangle names for hygiene, but also take parameters/overrides
+# from the environment.
+for var in "${var_templates[@]}"; do
+    outputVar="${var/+/_@infixSalt@_}"
+    export ${outputVar}+=''
+    # For each role we serve, we accumulate the input parameters into our own
+    # cc-wrapper-derivation-specific environment variables.
+    for infix in "${role_infixes[@]}"; do
+        inputVar="${var/+/${infix}}"
+        if [ -v "$inputVar" ]; then
+            export ${outputVar}+="${!outputVar:+ }${!inputVar}"
+        fi
+    done
+done
+
 # `-B@out@/bin' forces cc to use ld-wrapper.sh when calling ld.
-export NIX_CFLAGS_COMPILE="-B@out@/bin/ $NIX_CFLAGS_COMPILE"
+NIX_@infixSalt@_CFLAGS_COMPILE="-B@out@/bin/ $NIX_@infixSalt@_CFLAGS_COMPILE"
+
+# Export and assign separately in order that a failing $(..) will fail
+# the script.
 
 if [ -e @out@/nix-support/libc-cflags ]; then
-    export NIX_CFLAGS_COMPILE="$(cat @out@/nix-support/libc-cflags) $NIX_CFLAGS_COMPILE"
+    NIX_@infixSalt@_CFLAGS_COMPILE="$(< @out@/nix-support/libc-cflags) $NIX_@infixSalt@_CFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/cc-cflags ]; then
-    export NIX_CFLAGS_COMPILE="$(cat @out@/nix-support/cc-cflags) $NIX_CFLAGS_COMPILE"
+    NIX_@infixSalt@_CFLAGS_COMPILE="$(< @out@/nix-support/cc-cflags) $NIX_@infixSalt@_CFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/gnat-cflags ]; then
-    export NIX_GNATFLAGS_COMPILE="$(cat @out@/nix-support/gnat-cflags) $NIX_GNATFLAGS_COMPILE"
+    NIX_@infixSalt@_GNATFLAGS_COMPILE="$(< @out@/nix-support/gnat-cflags) $NIX_@infixSalt@_GNATFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/libc-ldflags ]; then
-    export NIX_LDFLAGS+=" $(cat @out@/nix-support/libc-ldflags)"
+    NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/libc-ldflags)"
 fi
 
 if [ -e @out@/nix-support/cc-ldflags ]; then
-    export NIX_LDFLAGS+=" $(cat @out@/nix-support/cc-ldflags)"
+    NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/cc-ldflags)"
 fi
 
 if [ -e @out@/nix-support/libc-ldflags-before ]; then
-    export NIX_LDFLAGS_BEFORE="$(cat @out@/nix-support/libc-ldflags-before) $NIX_LDFLAGS_BEFORE"
+    NIX_@infixSalt@_LDFLAGS_BEFORE="$(< @out@/nix-support/libc-ldflags-before) $NIX_@infixSalt@_LDFLAGS_BEFORE"
 fi
 
-export NIX_CC_WRAPPER_FLAGS_SET=1
+# That way forked processes will not extend these environment variables again.
+export NIX_CC_WRAPPER_@infixSalt@_FLAGS_SET=1