Bug 782647. Move the nullptr workaround macros to MFBT so that it can be shared. r=waldo

This also changes the header to use compiler detection instead of a
configure test. This makes the header more portable because
it doesn't require the configure infrastructure.

configure.in

@@ -754,9 +754,6 @@ if test -n "$_WIN32_MSVC"; then
     AC_DEFINE(HAVE_IO_H)
     AC_DEFINE(HAVE_SETBUF)
     AC_DEFINE(HAVE_ISATTY)
-    if test $_MSC_VER -ge 1600; then
-        AC_DEFINE(HAVE_NULLPTR)
-    fi
 fi
 
 fi # COMPILE_ENVIRONMENT
@@ -2804,21 +2801,6 @@ dnl Note that we assume that mac & win32 have short wchar (see nscore.h)
     fi
 fi
 
-dnl Check for nullptr (bug 626472)
-AC_LANG_CPLUSPLUS
-AC_MSG_CHECKING(for nullptr)
-AC_CACHE_VAL(ac_cv_nullptr,
- [AC_TRY_COMPILE([],
-                 [int* foo = nullptr;],
-                 [ac_cv_nullptr=true],
-                 [ac_cv_nullptr=false])])
-if test "$ac_cv_nullptr" = true ; then
-  AC_DEFINE(HAVE_NULLPTR)
-  AC_MSG_RESULT(yes)
-else
-  AC_MSG_RESULT(no)
-fi
-
 AC_LANG_C
 
 dnl Check for .hidden assembler directive and visibility attribute.

gfx/2d/Types.h

@@ -6,24 +6,8 @@
 #ifndef MOZILLA_GFX_TYPES_H_
 #define MOZILLA_GFX_TYPES_H_
 
-/**
- * Use C++11 nullptr if available; otherwise use a C++ typesafe template; and
- * for C, fall back to longs.  See bugs 547964 and 626472.
- * Copy and paste job from nscore.h, see bug 781943
- */
-#if defined(MOZ_GFX) && !defined(HAVE_NULLPTR)
-#ifndef __cplusplus
-# define nullptr ((void*)0)
-#elif defined(__GNUC__)
-# define nullptr __null
-#elif defined(_WIN64)
-# define nullptr 0LL
-#else
-# define nullptr 0L
-#endif
-#endif /* defined(MOZ_GFX) && !defined(HAVE_NULLPTR) */
-
 #include "mozilla/StandardInteger.h"
+#include "mozilla/NullPtr.h"
 
 #include <stddef.h>
 

mfbt/NullPtr.h

@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Implements a workaround for compilers which do not support the C++11 nullptr
+ * constant.
+ */
+
+#ifndef mozilla_NullPtr_h_
+#define mozilla_NullPtr_h_
+
+#if defined(__clang__)
+#  ifndef __has_extension
+#    define __has_extension __has_feature
+#  endif
+#  if __has_extension(cxx_nullptr)
+#    define MOZ_HAVE_CXX11_NULLPTR
+#  endif
+#elif defined(__GNUC__)
+#  if defined(_GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
+#    if (__GNUC__ * 1000 + __GNU_MINOR__) >= 4006
+#      define MOZ_HAVE_CXX11_NULLPTR
+#    endif
+#  endif
+#elif _MSC_VER >= 1600
+# define MOZ_HAVE_CXX11_NULLPTR
+#endif
+
+/**
+ * Use C++11 nullptr if available; otherwise use __null for gcc, or a 0 literal
+ * with the correct size to match the size of a pointer on a given platform.
+ */
+
+#ifndef MOZ_HAVE_CXX11_NULLPTR
+#  if defined(__GNUC__)
+#    define nullptr __null
+#  elif defined(_WIN64)
+#    define nullptr 0LL
+#  else
+#    define nullptr 0L
+#  endif
+#endif
+
+#endif  /* mozilla_NullPtr_h_ */

mfbt/exported_headers.mk

@@ -21,6 +21,7 @@ EXPORTS_mozilla += \
   LinkedList.h \
   MathAlgorithms.h \
   MSStdInt.h \
+  NullPtr.h \
   RangedPtr.h \
   RefPtr.h \
   Scoped.h \

xpcom/base/nscore.h

@@ -26,6 +26,8 @@
 #include "mozilla/StandardInteger.h"
 #include "stddef.h"
 
+#include "mozilla/NullPtr.h"
+
 /*
  * This is for functions that are like malloc_usable_size.  Such functions are
  * used for measuring the size of data structures.
@@ -324,22 +326,6 @@ typedef unsigned long nsrefcnt;
 typedef uint32_t nsrefcnt;
 #endif
 
-/**
- * Use C++11 nullptr if available; otherwise use a C++ typesafe template; and
- * for C, fall back to longs.  See bugs 547964 and 626472.
- */
-#ifndef HAVE_NULLPTR
-#ifndef __cplusplus
-# define nullptr ((void*)0)
-#elif defined(__GNUC__)
-# define nullptr __null
-#elif defined(_WIN64)
-# define nullptr 0LL
-#else
-# define nullptr 0L
-#endif
-#endif /* defined(HAVE_NULLPTR) */
-
 #include "nsError.h"
 
 /* ------------------------------------------------------------------------ */