Match MSVC's handling of commas during macro argument expansion

This allows clang to parse the type_traits header in Visual Studio 2012,
which is included widely in practice.

This is a rework of r163022 by João Matos.  The original patch broke
preprocessing of gtest headers, which this patch addresses.

Patch by Will Wilson!

llvm-svn: 184968

1 files changed, 12 insertions, 0 deletions

diff --git a/clang/test/Preprocessor/microsoft-ext.c b/clang/test/Preprocessor/microsoft-ext.c
index ec10374a1d6..b03f6775429 100644
--- a/clang/test/Preprocessor/microsoft-ext.c
+++ b/clang/test/Preprocessor/microsoft-ext.c
@@ -22,3 +22,15 @@ class GMOCK_ACTION_CLASS_(name, value_params) {\
 ACTION_TEMPLATE(InvokeArgument,
                 HAS_1_TEMPLATE_PARAMS(int, k),
                 AND_2_VALUE_PARAMS(p0, p1));
+
+// This tests compatibility with behaviour needed for type_traits in VS2012
+// Test based on _VARIADIC_EXPAND_0X macros in xstddef of VS2012
+#define _COMMA ,
+
+#define MAKER(_arg1, _comma, _arg2)                                            \
+  void func(_arg1 _comma _arg2) {}
+#define MAKE_FUNC(_makerP1, _makerP2, _arg1, _comma, _arg2)                    \
+  _makerP1##_makerP2(_arg1, _comma, _arg2)
+
+MAKE_FUNC(MAK, ER, int a, _COMMA, int b);
+// CHECK: void func(int a , int b) {}