anchor.diff:      NIX_LDFLAGS="-L$NIX_BUILD_TOP/foo/lib -rpath $NIX_BUILD_TOP/foo/lib" $CC -lfoo -o ldflags-check ${./ldflags-main.c}
       ./ldflags-check
   
  -    $CC -o sanitizers -fsanitize=address,undefined ${./sanitizers.c}
  -    ./sanitizers
  +    ${optionalString (!sanitizersBroken) ''
  +      printf "checking whether sanitizers are fully functional... ">&2
  +      $CC -o sanitizers -fsanitize=address,undefined ${./sanitizers.c}
  +      ./sanitizers
  +    ''}
   
       touch $out
     '';
   
  -  meta.platforms = stdenv.lib.platforms.all;
  +  meta.platforms = platforms.all;
   }
  
positive.code:     $CXX -o cxx-check ${./cxx-main.cc}
      ./cxx-check
  
      ${stdenv.lib.optionalString (stdenv.isDarwin && stdenv.cc.isClang) ''
        printf "checking whether compiler can build with CoreFoundation.framework... " >&2
        mkdir -p foo/lib
        $CC -framework CoreFoundation -o core-foundation-check ${./core-foundation-main.c}
  
negative.code:     printf "checking whether compiler uses NIX_LDFLAGS... " >&2
      mkdir -p foo/lib
      $CC -shared \
        ${optionalString stdenv.isDarwin "-Wl,-install_name,@rpath/libfoo.dylib"} \
        -DVALUE=42 \
        -o foo/lib/libfoo${stdenv.hostPlatform.extensions.sharedLibrary} \
        ${./foo.c}
  