Add clang multilib variants (x64_64-only, 64/32bit), basic multilib tests

pkgs/development/compilers/llvm/multi.nix

@@ -0,0 +1,44 @@
+{ runCommand,
+clang,
+gcc64,
+gcc32,
+glibc_multi
+}:
+
+let
+  combine = basegcc: runCommand "combine-gcc-libc" {} ''
+    mkdir -p $out
+    cp -r ${basegcc.cc}/lib $out/lib
+
+    chmod u+rw -R $out/lib
+    cp -r ${basegcc.libc}/lib/* $(ls -d $out/lib/gcc/*/*)
+  '';
+  gcc_multi_sysroot = runCommand "gcc-multi-sysroot" {} ''
+    mkdir -p $out/lib/gcc
+
+    ln -s ${combine gcc64}/lib/gcc/* $out/lib/gcc/
+    ln -s ${combine gcc32}/lib/gcc/* $out/lib/gcc/
+    # XXX: This shouldn't be needed, clang just doesn't look for "i686-unknown"
+    ln -s $out/lib/gcc/i686-unknown-linux-gnu $out/lib/gcc/i686-pc-linux-gnu
+
+
+    # includes
+    ln -s ${glibc_multi.dev}/include $out/
+
+    # dynamic linkers
+    mkdir -p $out/lib/32
+    ln -s ${glibc_multi.out}/lib/ld-linux* $out/lib
+    ln -s ${glibc_multi.out}/lib/32/ld-linux* $out/lib/32/
+  '';
+
+  clangMulti = clang.override {
+    # Only used for providing expected structure re:dynamic linkers, AFAIK
+    # Most of the magic is done by setting the --gcc-toolchain option below
+    libc = gcc_multi_sysroot;
+
+    extraBuildCommands = ''
+      sed -e '$a --gcc-toolchain=${gcc_multi_sysroot}' -i $out/nix-support/libc-cflags
+    '';
+  };
+
+in clangMulti

pkgs/test/cc-wrapper/multilib.nix

@@ -0,0 +1,37 @@
+{ stdenv }:
+
+stdenv.mkDerivation {
+  name = "cc-multilib-test";
+
+  # XXX: "depend" on cc-wrapper test?
+
+  # TODO: Have tests report pointer size or something; ensure they are what we asked for
+  buildCommand = ''
+    NIX_DEBUG=1 $CC -v
+    NIX_DEBUG=1 $CXX -v
+
+    printf "checking whether compiler builds valid C binaries... " >&2
+    $CC -o cc-check ${./cc-main.c}
+    ./cc-check
+
+    printf "checking whether compiler builds valid 32bit C binaries... " >&2
+    $CC -m32 -o c32-check ${./cc-main.c}
+    ./c32-check
+
+    printf "checking whether compiler builds valid 64bit C binaries... " >&2
+    $CC -m64 -o c64-check ${./cc-main.c}
+    ./c64-check
+
+    printf "checking whether compiler builds valid 32bit C++ binaries... " >&2
+    $CXX -m32 -o cxx32-check ${./cxx-main.cc}
+    ./cxx32-check
+
+    printf "checking whether compiler builds valid 64bit C++ binaries... " >&2
+    $CXX -m64 -o cxx64-check ${./cxx-main.cc}
+    ./cxx64-check
+
+    touch $out
+  '';
+
+  meta.platforms = stdenv.lib.platforms.x86_64;
+}

pkgs/top-level/all-packages.nix

@@ -5579,7 +5579,20 @@ with pkgs;
       '';
   }) else throw "Multilib ${cc.name} not supported on ‘${system}’";
 
+  wrapClangMulti = clang:
+    if system == "x86_64-linux" then
+      callPackages ../development/compilers/llvm/multi.nix {
+        inherit clang;
+        gcc32 = pkgsi686Linux.gcc;
+        gcc64 = pkgs.gcc;
+      }
+    else throw "Multilib ${clang.cc.name} not supported on '${system}'";
+
   gcc_multi = wrapCCMulti gcc;
+  clang_multi = wrapClangMulti clang;
+
+  gccMultiStdenv = overrideCC stdenv gcc_multi;
+  clangMultiStdenv = overrideCC stdenv clang_multi;
 
   gcc_debug = lowPrio (wrapCC (gcc.cc.override {
     stripped = false;
@@ -20040,6 +20053,9 @@ with pkgs;
     cc-wrapper-libcxx-5 = callPackage ../test/cc-wrapper { stdenv = llvmPackages_5.libcxxStdenv; };
     stdenv-inputs = callPackage ../test/stdenv-inputs { };
 
+    cc-multilib-gcc = callPackage ../test/cc-wrapper/multilib.nix { stdenv = gccMultiStdenv; };
+    cc-multilib-clang = callPackage ../test/cc-wrapper/multilib.nix { stdenv = clangMultiStdenv; };
+
     macOSSierraShared = callPackage ../test/macos-sierra-shared {};
   };
 

pkgs/top-level/release.nix

@@ -112,6 +112,8 @@ let
               jobs.tests.cc-wrapper-clang-39.x86_64-darwin
               jobs.tests.cc-wrapper-libcxx-39.x86_64-linux
               jobs.tests.cc-wrapper-libcxx-39.x86_64-darwin
+              jobs.tests.cc-multilib-gcc.x86_64-linux
+              jobs.tests.cc-multilib-clang.x86_64-linux
               jobs.tests.stdenv-inputs.x86_64-linux
               jobs.tests.stdenv-inputs.x86_64-darwin
               jobs.tests.macOSSierraShared.x86_64-darwin