Bug 833254 - Fix MFBT's gcc version checks. r=waldo

mfbt/Assertions.h

@@ -9,6 +9,7 @@
 #define mozilla_Assertions_h_
 
 #include "mozilla/Attributes.h"
+#include "mozilla/Compiler.h"
 
 #include <stddef.h>
 #include <stdio.h>
@@ -312,7 +313,7 @@ MOZ_ReportAssertionFailure(const char* s, const char* file, int ln)
     * that, call a noreturn function; abort() will do nicely.  Qualify the call
     * in C++ in case there's another abort() visible in local scope.
     */
-#  if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
+#  if MOZ_GCC_VERSION_AT_LEAST(4, 5, 0)
 #    define MOZ_NOT_REACHED_MARKER() __builtin_unreachable()
 #  else
 #    ifdef __cplusplus

mfbt/Attributes.h

@@ -8,10 +8,7 @@
 #ifndef mozilla_Attributes_h_
 #define mozilla_Attributes_h_
 
-/*
+#include "mozilla/Compiler.h"
- * This header does not include any other headers so that it can be included by
- * code that is (only currently) mfbt-incompatible.
- */
 
 /*
  * MOZ_INLINE is a macro which expands to tell the compiler that the method
@@ -81,28 +78,18 @@
 #  endif
 #elif defined(__GNUC__)
 #  if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
-#    if __GNUC__ > 4
+#    if MOZ_GCC_VERSION_AT_LEAST(4, 7, 0)
-#      define MOZ_HAVE_CXX11_DELETE
 #      define MOZ_HAVE_CXX11_OVERRIDE
 #      define MOZ_HAVE_CXX11_FINAL       final
-#    elif __GNUC__ == 4
-#      if __GNUC_MINOR__ >= 7
-#        define MOZ_HAVE_CXX11_OVERRIDE
-#        define MOZ_HAVE_CXX11_FINAL     final
-#      endif
-#      if __GNUC_MINOR__ >= 6
-#        define MOZ_HAVE_CXX11_CONSTEXPR
-#      endif
-#      define MOZ_HAVE_CXX11_DELETE
 #    endif
+#    if MOZ_GCC_VERSION_AT_LEAST(4, 6, 0)
+#      define MOZ_HAVE_CXX11_CONSTEXPR
+#    endif
+#    define MOZ_HAVE_CXX11_DELETE
 #  else
      /* __final is a non-C++11 GCC synonym for 'final', per GCC r176655. */
-#    if __GNUC__ > 4
+#    if MOZ_GCC_VERSION_AT_LEAST(4, 7, 0)
 #      define MOZ_HAVE_CXX11_FINAL       __final
-#    elif __GNUC__ == 4
-#      if __GNUC_MINOR__ >= 7
-#        define MOZ_HAVE_CXX11_FINAL     __final
-#      endif
 #    endif
 #  endif
 #  define MOZ_HAVE_NEVER_INLINE          __attribute__((noinline))

mfbt/Compiler.h

@@ -0,0 +1,24 @@
+/* -*- 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/. */
+
+/* Various compiler checks. */
+
+#ifndef mozilla_Compiler_h_
+#define mozilla_Compiler_h_
+
+#if !defined(__clang__) && defined(__GNUC__)
+   /*
+    * This macro should simplify gcc version checking. For example, to check
+    * for gcc 4.5.1 or later, check `#ifdef MOZ_GCC_VERSION_AT_LEAST(4, 5, 1)`.
+    */
+#  define MOZ_GCC_VERSION_AT_LEAST(major, minor, patchlevel)          \
+     ((__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) \
+      >= ((major) * 10000 + (minor) * 100 + (patchlevel)))
+#if !MOZ_GCC_VERSION_AT_LEAST(4, 4, 0)
+#  error "mfbt (and Gecko) require at least gcc 4.4 to build."
+#endif
+#endif
+
+#endif  /* mozilla_Compiler_h_ */

mfbt/NullPtr.h

@@ -11,6 +11,8 @@
 #ifndef mozilla_NullPtr_h_
 #define mozilla_NullPtr_h_
 
+#include "mozilla/Compiler.h"
+
 #if defined(__clang__)
 #  ifndef __has_extension
 #    define __has_extension __has_feature
@@ -20,7 +22,7 @@
 #  endif
 #elif defined(__GNUC__)
 #  if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
-#    if (__GNUC__ * 1000 + __GNUC_MINOR__) >= 4006
+#    if MOZ_GCC_VERSION_AT_LEAST(4, 6, 0)
 #      define MOZ_HAVE_CXX11_NULLPTR
 #    endif
 #  endif

mfbt/TypedEnum.h

@@ -27,14 +27,9 @@
 #  endif
 #elif defined(__GNUC__)
 #  if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
-#    if __GNUC__ > 4
+#    if MOZ_GCC_VERSION_AT_LEAST(4, 5, 1)
 #      define MOZ_HAVE_CXX11_ENUM_TYPE
 #      define MOZ_HAVE_CXX11_STRONG_ENUMS
-#    elif __GNUC__ == 4
-#      if __GNUC_MINOR__ >= 5
-#        define MOZ_HAVE_CXX11_ENUM_TYPE
-#        define MOZ_HAVE_CXX11_STRONG_ENUMS
-#      endif
 #    endif
 #  endif
 #elif defined(_MSC_VER)

mfbt/exported_headers.mk

@@ -14,6 +14,7 @@ EXPORTS_mozilla += \
   BloomFilter.h \
   Char16.h \
   CheckedInt.h \
+  Compiler.h \
   Constants.h \
   DebugOnly.h \
   EnumSet.h \