lib{std,}c++: Fix setup hooks for cross

1 files changed, 13 insertions, 2 deletions

diff --git a/pkgs/development/compilers/llvm/4/libc++/setup-hook.sh b/pkgs/development/compilers/llvm/4/libc++/setup-hook.sh
index 9022fced6ecf..bcd93cf486ff 100644
--- a/pkgs/development/compilers/llvm/4/libc++/setup-hook.sh
+++ b/pkgs/development/compilers/llvm/4/libc++/setup-hook.sh
@@ -1,3 +1,14 @@
+# The `hostOffset` describes how the host platform of the dependencies
+# relative to the depending package. It is brought into scope of the setup hook
+# defined as the role of the dependency whose hooks is being run.
+case $hostOffset in
+    -1) local role='BUILD_' ;;
+    0)  local role='' ;;
+    1)  local role='TARGET_' ;;
+    *)  echo "cc-wrapper: Error: Cannot be used with $hostOffset-offset deps" >2;
+        return 1 ;;
+esac
+
 linkCxxAbi="@linkCxxAbi@"
-export NIX_CXXSTDLIB_COMPILE+=" -isystem @out@/include/c++/v1"
-export NIX_CXXSTDLIB_LINK=" -stdlib=libc++${linkCxxAbi:+" -lc++abi"}"
+export NIX_${role}CXXSTDLIB_COMPILE+=" -isystem @out@/include/c++/v1"
+export NIX_${role}CXXSTDLIB_LINK=" -stdlib=libc++${linkCxxAbi:+" -lc++abi"}"