MS Compat: interpose vadefs.h to fix definitions of _crt_va_{start,end,arg} (PR21247)

[hans]

Summary

Please take a look.

[rnk]

lib/Headers/vadefs.h

24 ↗

(On Diff #14889)

I'd wordsmith this to "Only include this if we're aiming for MSVC compatibility."

32 ↗

(On Diff #14889)

Should we only do this if __has_include(<vadefs.h>) ?

34 ↗

(On Diff #14889)

I think we should do "#ifndef _crt_va_start #undef _crt_va_start" to avoid warnings with -Wsystem-headers.

[hans]

lib/Headers/vadefs.h

24 ↗

(On Diff #14889)

Done.

32 ↗

(On Diff #14889)

I think we should always do it. If the user is including vadefs.h, she's expecting to get the system one, and we should just always try to forward to it.

34 ↗

(On Diff #14889)

Done.

[hans]

Addressing rnk's comments.

I tried this on a small program with -Wsystem-headers, and it was clean.

[rnk]

lgtm

[hans]

Closed by commit rL219740 (authored by @hans).

cfe/trunk/lib/Headers/CMakeLists.txt

set(files
   stddef.h
   __stddef_max_align_t.h
   stdint.h
   stdnoreturn.h
   tbmintrin.h
   tgmath.h
   tmmintrin.h
   varargs.h
+  vadefs.h
   wmmintrin.h
   __wmmintrin_aes.h
   __wmmintrin_pclmul.h
   x86intrin.h
   xmmintrin.h
   xopintrin.h
   cpuid.h
   unwind.h

cfe/trunk/lib/Headers/vadefs.h

+/* ===-------- vadefs.h ---------------------------------------------------===
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ *===-----------------------------------------------------------------------===
+ */
+
+/* Only include this if we are aiming for MSVC compatibility. */
+#ifndef _MSC_VER
+#include_next <vadefs.h>
+#else
+
+#ifndef __clang_vadefs_h
+#define __clang_vadefs_h
+
+#include_next <vadefs.h>
+
+/* Override macros from vadefs.h with definitions that work with Clang. */
+#ifdef _crt_va_start
+#undef _crt_va_start
+#endif
+#ifdef _crt_va_end
+#undef _crt_va_end
+#endif
+#ifdef _crt_va_arg
+#undef _crt_va_arg
+#endif
+
+#define _crt_va_start(ap, param) __builtin_va_start(ap, param)
+#define _crt_va_end(ap)          __builtin_va_end(ap)
+#define _crt_va_arg(ap, type)    __builtin_va_arg(ap, type)
+
+#endif
+#endif