Bug 1264482 - Move adding -std=gnu99 and -std=gnu++11 to moz.configure. r=ted

We were unconditionally adding them, now actually check what the
compilers default to and add the flags if they are necessary.
This will, in the future, allow finer grained policy changes, where
we can decide that C++11 and C++14 are fine, downgrading compilers
that do C++17, etc.

build/autoconf/toolchain.m4

@@ -140,9 +140,6 @@ dnl Updates to the test below should be duplicated further below for the
 dnl cross-compiling case.
 AC_LANG_CPLUSPLUS
 if test "$GNU_CXX"; then
-    CXXFLAGS="$CXXFLAGS -std=gnu++11"
-    _ADDED_CXXFLAGS="-std=gnu++11"
-
     if test -n "$CLANG_CC"; then
         dnl We'd normally just check for the version from CC_VERSION (fed
         dnl from __clang_major__ and __clang_minor__), but the clang that
@@ -201,8 +198,6 @@ if test -n "$CROSS_COMPILE"; then
 	fi
     fi
 
-    HOST_CXXFLAGS="$HOST_CXXFLAGS -std=gnu++11"
-
     _SAVE_CXXFLAGS="$CXXFLAGS"
     _SAVE_CPPFLAGS="$CPPFLAGS"
     _SAVE_CXX="$CXX"
@@ -218,8 +213,6 @@ if test -n "$CROSS_COMPILE"; then
     CXXFLAGS="$_SAVE_CXXFLAGS"
     CPPFLAGS="$_SAVE_CPPFLAGS"
     CXX="$_SAVE_CXX"
-elif test "$GNU_CXX"; then
-    HOST_CXXFLAGS="$HOST_CXXFLAGS $_ADDED_CXXFLAGS"
 fi
 AC_LANG_C
 ])

build/moz.configure/toolchain.configure

@@ -191,29 +191,109 @@ def try_preprocess(compiler, language, source):
 
 @imports(_from='mozbuild.configure.constants', _import='CompilerType')
 @imports(_from='textwrap', _import='dedent')
-def check_compiler(compiler, language):
+def get_compiler_info(compiler, language):
+    '''Returns information about the given `compiler` (command line in the
+    form of a list or tuple), in the given `language`.
+
+    The returned information includes:
+    - the compiler type (msvc, clang-cl, clang or gcc)
+    - the compiler version
+    - the compiler supported language
+    - the compiler supported language version
+    '''
+    # Note: MSVC doesn't expose __STDC_VERSION__. It does expose __STDC__,
+    # but only when given the -Za option, which disables compiler
+    # extensions.
     check = dedent('''\
         #if defined(_MSC_VER)
         #if defined(__clang__)
-        COMPILER clang-cl _MSC_VER
+        %COMPILER clang-cl
+        %VERSION _MSC_VER
         #else
-        COMPILER msvc _MSC_FULL_VER
+        %COMPILER msvc
+        %VERSION _MSC_FULL_VER
         #endif
         #elif defined(__clang__)
-        COMPILER clang __clang_major__.__clang_minor__.__clang_patchlevel__
+        %COMPILER clang
+        %VERSION __clang_major__.__clang_minor__.__clang_patchlevel__
         #elif defined(__GNUC__)
-        COMPILER gcc __GNUC__.__GNUC_MINOR__.__GNUC_PATCHLEVEL__
+        %COMPILER gcc
+        %VERSION __GNUC__.__GNUC_MINOR__.__GNUC_PATCHLEVEL__
+        #endif
+
+        #if __cplusplus
+        %cplusplus __cplusplus
+        #elif __STDC_VERSION__
+        %STDC_VERSION __STDC_VERSION__
+        #elif __STDC__
+        %STDC_VERSION 198900L
         #endif
     ''')
 
     result = try_preprocess(compiler, language, check)
 
-    if result:
+    if not result:
+        raise FatalCheckError(
+            'Unknown compiler or compiler not supported.')
+
+    data = {}
     for line in result.splitlines():
-            if line.startswith('COMPILER '):
-                _, type, version = line.split(None, 2)
-                version = version.replace(' ', '')
-                return CompilerType(type), version
+        if line.startswith('%'):
+            k, _, v = line.partition(' ')
+            k = k.lstrip('%')
+            data[k] = v.replace(' ', '')
+            log.debug('%s = %s', k, data[k])
+
+    type = data.get('COMPILER')
+    if not type:
+        raise FatalCheckError(
+            'Unknown compiler or compiler not supported.')
+
+    cplusplus = int(data.get('cplusplus', '0L').rstrip('L'))
+    stdc_version = int(data.get('STDC_VERSION', '0L').rstrip('L'))
+
+    return namespace(
+        type=CompilerType(type),
+        version=data['VERSION'],
+        language='C++' if cplusplus else 'C',
+        language_version=cplusplus if cplusplus else stdc_version,
+    )
+
+
+@imports(_from='mozbuild.shellutil', _import='quote')
+def check_compiler(compiler, language):
+    info = get_compiler_info(compiler, language)
+
+    flags = []
+
+    def append_flag(flag):
+        if flag not in flags:
+            if info.type == 'clang-cl':
+                flags.append('-Xclang')
+            flags.append(flag)
+
+    # Check language standards
+    # --------------------------------------------------------------------
+    if language != info.language:
+        raise FatalCheckError(
+            '`%s` is not a %s compiler.' % (quote(*compiler), language))
+
+    # Note: We do a strict version check because there sometimes are backwards
+    # incompatible changes in the standard, and not all code that compiles as
+    # C99 compiles as e.g. C11 (as of writing, this is true of libnestegg, for
+    # example)
+    if info.language == 'C' and info.language_version != 199901:
+        if info.type in ('clang-cl', 'clang', 'gcc'):
+            append_flag('-std=gnu99')
+
+    # Note: MSVC, while supporting C++11, still reports 199711L for __cplusplus.
+    # Note: this is a strict version check because we used to always add
+    # -std=gnu++11.
+    if info.language == 'C++' and info.language_version != 201103:
+        if info.type in ('clang-cl', 'clang', 'gcc'):
+            append_flag('-std=gnu++11')
+
+    return info.type, info.version, flags
 
 
 @template
@@ -342,7 +422,7 @@ def compiler(language, host_or_target, c_compiler=None, other_compiler=None):
                           input=delayed_getattr(provided_compiler, 'compiler'))
 
     @depends(compiler, provided_compiler, compiler_wrapper)
-    @checking('%s version' % what, lambda x: x.version if x else 'not found')
+    @checking('whether %s can be used' % what, lambda x: bool(x))
     @imports(_from='mozbuild.shellutil', _import='quote')
     def valid_compiler(compiler, provided_compiler, compiler_wrapper):
         wrapper = list(compiler_wrapper or ())
@@ -378,17 +458,20 @@ def compiler(language, host_or_target, c_compiler=None, other_compiler=None):
                     quote(os.path.dirname(found_compiler)),
                     quote(os.path.dirname(full_path)))
 
-        result = check_compiler(wrapper + [compiler] + flags, language)
-        if result:
-            type, version = result
+        type, version, more_flags = check_compiler(
+            wrapper + [compiler] + flags, language)
         return namespace(
             wrapper=wrapper,
             compiler=compiler,
-                flags=flags,
+            flags=flags + more_flags,
             type=type,
             version=version,
         )
-        die('Failed to get the compiler version')
+
+    @depends(valid_compiler)
+    @checking('%s version' % what)
+    def compiler_version(compiler):
+        return compiler.version
 
     if language == 'C++':
         @depends(valid_compiler, c_compiler)

js/src/old-configure.in

@@ -715,8 +715,6 @@ dnl ========================================================
 dnl GNU specific defaults
 dnl ========================================================
 if test "$GNU_CC"; then
-    # We use C99.
-    CFLAGS="$CFLAGS -std=gnu99"
     MKSHLIB='$(CXX) $(CXXFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -Wl,-h,$(DSO_SONAME) -o $@'
     MKCSHLIB='$(CC) $(CFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -Wl,-h,$(DSO_SONAME) -o $@'
     DSO_LDOPTS='-shared'

old-configure.in

@@ -900,8 +900,6 @@ if test "$GNU_CC"; then
     MMX_FLAGS="-mmmx"
     SSE_FLAGS="-msse"
     SSE2_FLAGS="-msse2"
-    # We use C99.
-    CFLAGS="$CFLAGS -std=gnu99"
     # FIXME: Let us build with strict aliasing. bug 414641.
     CFLAGS="$CFLAGS -fno-strict-aliasing"
     MKSHLIB='$(CXX) $(CXXFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -Wl,-h,$(DSO_SONAME) -o $@'