[libcxx] r323490 - libcxx: Move #include_next <math.h> out of header guard in wrapper header.

[Peter Collingbourne via cfe-commits]

Author: pcc
Date: Thu Jan 25 17:19:23 2018
New Revision: 323490

URL: http://llvm.org/viewvc/llvm-project?rev=323490&view=rev
Log:
libcxx: Move #include_next <math.h> out of header guard in wrapper header.

Code on Windows expects to be able to do:

 #define _USE_MATH_DEFINES
 #include <math.h>

and receive the definitions of mathematical constants, even if <math.h>
has previously been included. To support this scenario, re-include
<math.h> every time the wrapper header is included.

Differential Revision: https://reviews.llvm.org/D42403

Added:
    libcxx/trunk/test/libcxx/depr/depr.c.headers/math_h.sh.cpp
Modified:
    libcxx/trunk/include/math.h

Modified: libcxx/trunk/include/math.h
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/math.h?rev=323490&r1=323489&r2=323490&view=diff
==============================================================================
--- libcxx/trunk/include/math.h (original)
+++ libcxx/trunk/include/math.h Thu Jan 25 17:19:23 2018
@@ -8,6 +8,16 @@
 //
 //===----------------------------------------------------------------------===//
 
+// This include lives outside the header guard in order to support an MSVC
+// extension which allows users to do:
+//
+// #define _USE_MATH_DEFINES
+// #include <math.h>
+//
+// and receive the definitions of mathematical constants, even if <math.h>
+// has previously been included.
+#include_next <math.h>
+
 #ifndef _LIBCPP_MATH_H
 #define _LIBCPP_MATH_H
 
@@ -298,8 +308,6 @@ long double    truncl(long double x);
 #pragma GCC system_header
 #endif
 
-#include_next <math.h>
-
 #ifdef __cplusplus
 
 // We support including .h headers inside 'extern "C"' contexts, so switch

Added: libcxx/trunk/test/libcxx/depr/depr.c.headers/math_h.sh.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/libcxx/depr/depr.c.headers/math_h.sh.cpp?rev=323490&view=auto
==============================================================================
--- libcxx/trunk/test/libcxx/depr/depr.c.headers/math_h.sh.cpp (added)
+++ libcxx/trunk/test/libcxx/depr/depr.c.headers/math_h.sh.cpp Thu Jan 25 17:19:23 2018
@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// RUN: %compile -fsyntax-only
+
+#ifdef _MSC_VER
+
+#include <math.h>
+
+#define _USE_MATH_DEFINES
+#include <math.h>
+
+#ifndef M_PI
+#error M_PI not defined
+#endif
+
+#endif