Add support for building with clang-cl

README

@@ -146,12 +146,17 @@ It's also possible to build libffi on Windows platforms with
 Microsoft's Visual C++ compiler.  In this case, use the msvcc.sh
 wrapper script during configuration like so:
 
-path/to/configure CC=path/to/msvcc.sh CXX=path/to/msvcc.sh LD=link CPP=\"cl -nologo -EP\"
+path/to/configure CC=path/to/msvcc.sh CXX=path/to/msvcc.sh LD=link CPP="cl -nologo -EP"
 
 For 64-bit Windows builds, use CC="path/to/msvcc.sh -m64" and
 CXX="path/to/msvcc.sh -m64".  You may also need to specify --build
 appropriately.
 
+It is also possible to build libffi on Windows platforms with the LLVM
+project's clang-cl compiler, like below:
+
+path/to/configure CC="path/to/msvcc.sh -clang-cl" CXX="path/to/msvcc.sh -clang-cl" LD=link CPP="clang-cl -EP"
+
 When building with MSVC under a MingW environment, you may need to
 remove the line in configure that sets 'fix_srcfile_path' to a 'cygpath'
 command.  ('cygpath' is not present in MingW, and is not required when

include/ffi.h.in

@@ -68,7 +68,7 @@ extern "C" {
 
 #ifndef LIBFFI_ASM
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) && !defined(__clang__)
 #define __attribute__(X)
 #endif
 

msvcc.sh

@@ -63,11 +63,15 @@ do
       shift 1
     ;;
     -m64)
-      cl="cl"   # "$MSVC/x86_amd64/cl"
       ml="ml64" # "$MSVC/x86_amd64/ml64"
       safeseh=
       shift 1
     ;;
+    -clang-cl)
+      cl="clang-cl"
+      safeseh=
+      shift 1
+    ;;
     -O0)
       args="$args -Od"
       shift 1