Bug 1232224 - Streamline setting of compile warnings in configure.in. r=glandium,cpeterson.

The main changes are to the warnings, which are as follows.

- Kept -Wall.

- Part of -Wall or on by default; remove all mentions:
  * -Waddress
  * -Wchar-subscripts
  * -Wcomment
  * -Wconversion-null
  * -Wendif-labels
  * -Wenum-compare
  * -Wimplicit-function-declaration
  * -Wint-to-pointer-cast
  * -Wmissing-braces
  * -Wmultichar
  * -Wnonnull
  * -Wparentheses
  * -Wpointer-sign
  * -Wpointer-to-int-cast (C only)
  * -Wreorder
  * -Wreturn-type
  * -Wsequence-point
  * -Wsign-compare (C++ only)
  * -Wswitch
  * -Wtrigraphs
  * -Wuninitialized
  * -Wunknown-pragmas
  * -Wunused-label
  * -Wunused-value
  * -Wwrite-strings (C++ only)

- Part of -Wextra; kept where present, added where missing:
  * -Wempty-body
  * -Wignored-qualifiers (not added for C++ code; many fixes needed to enable)
  * -Wtype-limits

- Part of -pedantic; kept where present, added where missing:
  * -pointer-arith

- C++ only, kept:
  * -Wno-invalid-offsetof
  * -Woverloaded-virtual

- Clang-only, kept:
  * -Wnon-literal-null-conversion (affected by a clang bug; see the big comment
    in the code)
  * -Wrange-loop-analysis (C++ only)
  * -Wno-unused-local-typedef

- This no longer exists?  I kept it to be safe:
  * -Winline-new-delete

A consequence of this is that, when --enable-warnings-as-errors is on, in
directories which have ALLOW_COMPILER_WARNINGS specified we no longer have any
fatal warnings. (We previously did have all the explicitly-mentioned
-Werror=foo ones.) This is a sensible change; if we are going to allow warnings
in a directory we should allow all of them, not just some of them.

Other changes:

- Some C warnings incorrectly used the CXX macros. Fixes that.

- Moves comments about warnings closer to the lines where they are defined, to
  make it easier to keep the comments consistent with the code.

- Reorders things a little, e.g. so that all enabled warnings are before all
  disabled warnings.

The C and C++ warnings are now very similar, in both configure.in and
js/src/configure.in.

--HG--
extra : rebase_source : 6f8db0fecda1315504a29fbcafb6fdee3053d8a5

configure.in

@@ -1444,65 +1444,35 @@ if test "$GNU_CC"; then
     fi
 
     # Turn on gcc/clang warnings:
-    # https://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Warning-Options.html
+    # https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Warning-Options.html
-    #
+
-    # -Wall - turn on a lot of warnings
+    # -Wall - lots of useful warnings
-    # -Wchar-subscripts - catches array index using signed char
-    # -Wcomment - catches nested comments
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Wendif-labels - catches `#else FOO` and `#endif FOO` not in comment
-    # -Wenum-compare - catches comparison of different enum types
     # -Wignored-qualifiers - catches returns types with qualifiers like const
-    # -Wint-to-pointer-cast - catches cast to pointer from integer of different size
-    # -Wmultichar - catches multicharacter integer constants like 'THIS'
-    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
-    # -Wnonnull - catches NULL used with functions arguments marked as non-null
     # -Wpointer-arith - catches pointer arithmetic using NULL or sizeof(void)
-    # -Wpointer-sign - catches mixing pointers to signed and unsigned types
-    # -Wpointer-to-int-cast - catches casts from pointer to different sized int
-    # -Wreturn-type - catches missing returns, zero false positives
-    # -Wsequence-point - catches undefined order behavior like `a = a++`
-    # -Wsign-compare - catches comparison of signed and unsigned types
-    # -Wtrigraphs - catches unlikely use of trigraphs
     # -Wtype-limits - catches overflow bugs, few false positives
-    # -Wunknown-pragmas - catches unexpected #pragma directives
-    #
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall"
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wempty-body"
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wpointer-to-int-cast"
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wignored-qualifiers"
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wsign-compare"
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wpointer-arith"
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wtype-limits"
 
-    # Treat some warnings as errors if --enable-warnings-as-errors:
+    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
-    if test "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
+    # -Wsometimes-initialized - catches some uninitialized values
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=char-subscripts"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=comment"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=endif-labels"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=enum-compare"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=ignored-qualifiers"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=int-to-pointer-cast"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=multichar"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=nonnull"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=pointer-arith"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=pointer-sign"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=return-type"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=sequence-point"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=trigraphs"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=uninitialized"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=unknown-pragmas"
-
-        MOZ_C_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_c_has_werror_non_literal_null_conversion)
-        MOZ_C_SUPPORTS_WARNING(-Werror=, sometimes-uninitialized, ac_c_has_sometimes_uninitialized)
-    fi
-
-    # Turn off the following warnings that -Wall turns on:
-    # -Wno-unused - lots of violations in third-party code
-    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
     #
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wno-unused"
+    # XXX: at the time of writing, the version of clang used on the OS X test
-
+    # machines has a bug that causes it to reject some valid files if both
-    MOZ_CXX_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_cxx_has_wno_unused_local_typedef)
+    # -Wnon-literal-null-conversion and -Wsometimes-uninitialized are
+    # specified. We work around this by instead using
+    # -Werror=non-literal-null-conversion, but we only do that when
+    # --enable-warnings-as-errors is specified so that no unexpected fatal
+    # warnings are produced.
+    if test "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
+        MOZ_C_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_c_has_non_literal_null_conversion)
+    fi
+    MOZ_C_SUPPORTS_WARNING(-W, sometimes-uninitialized, ac_c_has_sometimes_uninitialized)
 
+    # -Wcast-align - catches problems with cast alignment
     if test -z "$INTEL_CC" -a -z "$CLANG_CC"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
@@ -1515,8 +1485,17 @@ if test "$GNU_CC"; then
        esac
     fi
 
+    # Turn off some non-useful warnings that -Wall turns on.
+
+    # -Wno-unused - lots of violations in third-party code
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wno-unused"
+
+    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
+    MOZ_C_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_c_has_wno_unused_local_typedef)
+
     _DEFINES_CFLAGS='-include $(topobjdir)/mozilla-config.h -DMOZILLA_CLIENT'
     _USE_CPP_INCLUDE_FLAG=1
+
     ASFLAGS="$ASFLAGS $_DEFINES_CFLAGS"
 
 elif test "$SOLARIS_SUNPRO_CC"; then
@@ -1548,65 +1527,37 @@ if test "$GNU_CXX"; then
     CXXFLAGS="$CXXFLAGS -fno-exceptions -fno-strict-aliasing"
 
     # Turn on gcc/clang warnings:
-    # https://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Warning-Options.html
+    # https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Warning-Options.html
-    #
+
-    # -Wall - turn on a lot of warnings
+    # -Wall - lots of useful warnings
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Wendif-labels - catches `#else FOO` and `#endif FOO` not in comment
-    # -Wint-to-pointer-cast - catches cast to pointer from integer of different size
-    # -Wmissing-braces - catches aggregate initializers missing nested braces
-    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
     # -Woverloaded-virtual - function declaration hides virtual function from base class
-    # -Wparentheses - catches `if (a=b)` and operator precedence bugs
     # -Wpointer-arith - catches pointer arithmetic using NULL or sizeof(void)
-    # -Wrange-loop-analysis - catches copies during range-based for loops.
-    # -Wreturn-type - catches missing returns, zero false positives
-    # -Wsequence-point - catches undefined order behavior like `a = a++`
-    # -Wsign-compare - catches comparison of signed and unsigned types
-    # -Wswitch - catches switches without all enum cases or default case
-    # -Wtrigraphs - catches unlikely use of trigraphs
     # -Wtype-limits - catches overflow bugs, few false positives
-    # -Wunused-label - catches unused goto labels
-    # -Wwrite-strings - catches non-const char* pointers to string literals
-    #
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall"
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wempty-body"
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Woverloaded-virtual"
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wsign-compare"
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wpointer-arith"
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wwrite-strings"
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wtype-limits"
 
-    # Treat some warnings as errors if --enable-warnings-as-errors:
+    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
-    if test "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
+    # -Wrange-loop-analysis - catches copies during range-based for loops.
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=endif-labels"
+    # -Wsometimes-initialized - catches some uninitialized values
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=int-to-pointer-cast"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=missing-braces"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=parentheses"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=pointer-arith"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=return-type"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=sequence-point"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=switch"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=trigraphs"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=type-limits"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=uninitialized"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=unused-label"
-
-        MOZ_CXX_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_cxx_has_werror_non_literal_null_conversion)
-        MOZ_CXX_SUPPORTS_WARNING(-Werror=, range-loop-analysis, ac_cxx_has_range_loop_analysis)
-        MOZ_CXX_SUPPORTS_WARNING(-Werror=, sometimes-uninitialized, ac_cxx_has_sometimes_uninitialized)
-    fi
-
-    # Turn off the following warnings that -Wall turns on:
-    # -Wno-invalid-offsetof - we use offsetof on non-POD types frequently
-    # -Wno-inline-new-delete - we inline 'new' and 'delete' in mozalloc
-    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
-    #   for performance reasons, and because GCC and clang accept it (though
-    #   clang warns about it).
     #
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-invalid-offsetof"
+    # XXX: at the time of writing, the version of clang used on the OS X test
-
+    # machines has a bug that causes it to reject some valid files if both
-    MOZ_CXX_SUPPORTS_WARNING(-Wno-, inline-new-delete, ac_cxx_has_wno_inline_new_delete)
+    # -Wnon-literal-null-conversion and -Wsometimes-uninitialized are
-    MOZ_CXX_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_cxx_has_wno_unused_local_typedef)
+    # specified. We work around this by instead using
+    # -Werror=non-literal-null-conversion, but we only do that when
+    # --enable-warnings-as-errors is specified so that no unexpected fatal
+    # warnings are produced.
+    if test "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
+        MOZ_CXX_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_cxx_has_non_literal_null_conversion)
+    fi
+    MOZ_CXX_SUPPORTS_WARNING(-W, range-loop-analysis, ac_cxx_has_range_loop_analysis)
+    MOZ_CXX_SUPPORTS_WARNING(-W, sometimes-uninitialized, ac_cxx_has_sometimes_uninitialized)
 
+    # -Wcast-align - catches problems with cast alignment
     if test -z "$INTEL_CXX" -a -z "$CLANG_CXX"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
@@ -1619,8 +1570,15 @@ if test "$GNU_CXX"; then
        esac
     fi
 
-    _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -include $(topobjdir)/mozilla-config.h'
+    # Turn off some non-useful warnings that -Wall turns on.
-    _USE_CPP_INCLUDE_FLAG=1
+
+    # -Wno-invalid-offsetof - we use offsetof on non-POD types frequently
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-invalid-offsetof"
+
+    # -Wno-inline-new-delete - we inline 'new' and 'delete' in mozalloc
+    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
+    MOZ_CXX_SUPPORTS_WARNING(-Wno-, inline-new-delete, ac_cxx_has_wno_inline_new_delete)
+    MOZ_CXX_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_cxx_has_wno_unused_local_typedef)
 
     # Recent clang and gcc support C++11 deleted functions without warnings if
     # compiling with -std=c++0x or -std=gnu++0x (or c++11 or gnu++11 in very new
@@ -1633,6 +1591,9 @@ if test "$GNU_CXX"; then
         MOZ_CXX_SUPPORTS_WARNING(-Wno-, extended-offsetof, ac_cxx_has_wno_extended_offsetof)
     fi
 
+    _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -include $(topobjdir)/mozilla-config.h'
+    _USE_CPP_INCLUDE_FLAG=1
+
 else
     _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -D_MOZILLA_CONFIG_H_ $(ACDEFINES)'
 fi

js/src/configure.in

@@ -1187,79 +1187,35 @@ if test "$GNU_CC"; then
                   LDFLAGS=$_SAVE_LDFLAGS)
 
     # Turn on gcc/clang warnings:
-    # https://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Warning-Options.html
+    # https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Warning-Options.html
-    #
+
-    # -Wall - turn on a lot of warnings
+    # -Wall - lots of useful warnings
-    # -Waddress - catches suspicious uses of memory addresses
-    # -Wchar-subscripts - catches array index using signed char
-    # -Wcomment - catches nested comments
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Wendif-labels - catches `#else FOO` and `#endif FOO` not in comment
-    # -Wenum-compare - catches comparison of different enum types
     # -Wignored-qualifiers - catches returns types with qualifiers like const
-    # -Wimplicit-function-declaration - catches missing C function prototypes
-    # -Wint-to-pointer-cast - catches cast to pointer from integer of different size
-    # -Wmissing-braces - catches aggregate initializers missing nested braces
-    # -Wmultichar - catches multicharacter integer constants like 'THIS'
-    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
-    # -Wnonnull - catches NULL used with functions arguments marked as non-null
-    # -Wparentheses - catches `if (a=b)` and operator precedence bugs
     # -Wpointer-arith - catches pointer arithmetic using NULL or sizeof(void)
-    # -Wpointer-sign - catches mixing pointers to signed and unsigned types
-    # -Wpointer-to-int-cast - catches casts from pointer to different sized int
-    # -Wreturn-type - catches missing returns, zero false positives
-    # -Wsequence-point - catches undefined order behavior like `a = a++`
-    # -Wsign-compare - catches comparison of signed and unsigned types
-    # -Wswitch - catches switches without all enum cases or default case
-    # -Wtrigraphs - catches unlikely use of trigraphs
     # -Wtype-limits - catches overflow bugs, few false positives
-    # -Wunknown-pragmas - catches unexpected #pragma directives
-    # -Wwrite-strings - catches non-const char* pointers to string literals
-    #
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall"
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wsign-compare"
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wempty-body"
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wignored-qualifiers"
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wpointer-arith"
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wtype-limits"
 
-    # Treat some warnings as errors if --enable-warnings-as-errors:
+    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
-    if test "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
+    # -Wsometimes-initialized - catches some uninitialized values
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=address"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=char-subscripts"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=comment"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=empty-body"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=endif-labels"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=enum-compare"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=ignored-qualifiers"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=implicit-function-declaration"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=int-to-pointer-cast"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=missing-braces"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=multichar"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=nonnull"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=parentheses"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=pointer-arith"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=pointer-sign"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=pointer-to-int-cast"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=return-type"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=sequence-point"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=switch"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=trigraphs"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=uninitialized"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=unknown-pragmas"
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Werror=write-strings"
-
-        MOZ_C_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_c_has_werror_non_literal_null_conversion)
-        MOZ_C_SUPPORTS_WARNING(-Werror=, sometimes-uninitialized, ac_c_has_sometimes_uninitialized)
-    fi
-
-    # Turn off the following warnings that -Wall turns on:
-    # -Wno-unused - lots of violations in third-party code
-    # -Wno-inline-new-delete - we inline 'new' and 'delete' in mozalloc
-    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
     #
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wno-unused"
+    # XXX: at the time of writing, the version of clang used on the OS X test
-
+    # machines has a bug that causes it to reject some valid files if both
-    MOZ_CXX_SUPPORTS_WARNING(-Wno-, inline-new-delete, ac_cxx_has_wno_inline_new_delete)
+    # -Wnon-literal-null-conversion and -Wsometimes-uninitialized are
-    MOZ_CXX_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_cxx_has_wno_unused_local_typedef)
+    # specified. We work around this by instead using
+    # -Werror=non-literal-null-conversion, but we only do that when
+    # --enable-warnings-as-errors is specified so that no unexpected fatal
+    # warnings are produced.
+    if test "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
+        MOZ_C_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_c_has_non_literal_null_conversion)
+    fi
+    MOZ_C_SUPPORTS_WARNING(-W, sometimes-uninitialized, ac_c_has_sometimes_uninitialized)
 
+    # -Wcast-align - catches problems with cast alignment
     if test -z "$INTEL_CC" -a -z "$CLANG_CC"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
@@ -1272,6 +1228,14 @@ if test "$GNU_CC"; then
        esac
     fi
 
+    # Turn off some non-useful warnings that -Wall turns on.
+
+    # -Wno-unused - lots of violations in third-party code
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wno-unused"
+
+    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
+    MOZ_C_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_c_has_wno_unused_local_typedef)
+
     _DEFINES_CFLAGS='-include $(topobjdir)/js/src/js-confdefs.h -DMOZILLA_CLIENT'
     _USE_CPP_INCLUDE_FLAG=1
 
@@ -1301,77 +1265,40 @@ fi
 
 if test "$GNU_CXX"; then
     # Turn on gcc/clang warnings:
-    # https://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Warning-Options.html
+    # https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Warning-Options.html
-    #
+
-    # -Wall - turn on a lot of warnings
+    # -Wall - lots of useful warnings
-    # -Wchar-subscripts - catches array index using signed char
-    # -Wcomment - catches nested comments
-    # -Wconversion-null - catches conversions between NULL and non-pointer types
     # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    # -Wendif-labels - catches `#else FOO` and `#endif FOO` not in comment
-    # -Wignored-qualifiers - catches returns types with qualifiers like const
-    # -Wint-to-pointer-cast - catches cast to pointer from integer of different size
-    # -Wmissing-braces - catches aggregate initializers missing nested braces
-    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
     # -Woverloaded-virtual - function declaration hides virtual function from base class
-    # -Wparentheses - catches `if (a=b)` and operator precedence bugs
     # -Wpointer-arith - catches pointer arithmetic using NULL or sizeof(void)
-    # -Wpointer-to-int-cast - catches casts from pointer to different sized int
-    # -Wrange-loop-analysis - catches copies during range-based for loops.
-    # -Wreorder - catches ctor initializer list not matching class definition order
-    # -Wreturn-type - catches missing returns, zero false positives
-    # -Wsequence-point - catches undefined order behavior like `a = a++`
-    # -Wsign-compare - catches comparison of signed and unsigned types
-    # -Wswitch - catches switches without all enum cases or default case
-    # -Wtrigraphs - catches unlikely use of trigraphs
     # -Wtype-limits - catches overflow bugs, few false positives
-    # -Wunknown-pragmas - catches unexpected #pragma directives
-    # -Wunused-label - catches unused goto labels
-    # -Wunused-value - catches unused expression results
-    # -Wwrite-strings - catches non-const char* pointers to string literals
-    #
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall"
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wsign-compare"
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wempty-body"
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Woverloaded-virtual"
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wpointer-arith"
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wtype-limits"
 
+    # -Wclass-varargs - ???
+    # -Wnon-literal-null-conversion - catches expressions used as a null pointer constant
+    # -Wrange-loop-analysis - catches copies during range-based for loops.
+    # -Wsometimes-initialized - catches some uninitialized values
+    #
+    # XXX: at the time of writing, the version of clang used on the OS X test
+    # machines has a bug that causes it to reject some valid files if both
+    # -Wnon-literal-null-conversion and -Wsometimes-uninitialized are
+    # specified. We work around this by instead using
+    # -Werror=non-literal-null-conversion, but we only do that when
+    # --enable-warnings-as-errors is specified so that no unexpected fatal
+    # warnings are produced.
     MOZ_CXX_SUPPORTS_WARNING(-W, class-varargs, ac_cxx_has_wclass_varargs)
 
-    # Treat some warnings as errors if --enable-warnings-as-errors:
     if test "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=char-subscripts"
+        MOZ_CXX_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_cxx_has_non_literal_null_conversion)
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=comment"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=endif-labels"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=ignored-qualifiers"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=int-to-pointer-cast"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=missing-braces"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=overloaded-virtual"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=parentheses"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=pointer-arith"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=reorder"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=return-type"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=sequence-point"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=switch"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=trigraphs"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=uninitialized"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=unknown-pragmas"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=unused-label"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=unused-value"
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=write-strings"
-
-        MOZ_CXX_SUPPORTS_WARNING(-Werror=, conversion-null, ac_cxx_has_werror_conversion_null)
-        MOZ_CXX_SUPPORTS_WARNING(-Werror=, non-literal-null-conversion, ac_cxx_has_werror_non_literal_null_conversion)
-        MOZ_CXX_SUPPORTS_WARNING(-Werror=, range-loop-analysis, ac_cxx_has_range_loop_analysis)
-        MOZ_CXX_SUPPORTS_WARNING(-Werror=, sometimes-uninitialized, ac_cxx_has_sometimes_uninitialized)
     fi
+    MOZ_CXX_SUPPORTS_WARNING(-W, range-loop-analysis, ac_cxx_has_range_loop_analysis)
+    MOZ_CXX_SUPPORTS_WARNING(-W, sometimes-uninitialized, ac_cxx_has_sometimes_uninitialized)
 
-    # Turn off the following warnings that -Wall turns on:
+    # -Wcast-align - catches problems with cast alignment
-    # -Wno-invalid-offsetof - we use offsetof on non-POD types frequently
-    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
-    #
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-invalid-offsetof"
-
-    MOZ_CXX_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_cxx_has_wno_unused_local_typedef)
-
     if test -z "$INTEL_CXX" -a -z "$CLANG_CXX"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
@@ -1384,8 +1311,15 @@ if test "$GNU_CXX"; then
        esac
     fi
 
-    _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -include $(topobjdir)/js/src/js-confdefs.h'
+    # Turn off some non-useful warnings that -Wall turns on.
-    _USE_CPP_INCLUDE_FLAG=1
+
+    # -Wno-invalid-offsetof - we use offsetof on non-POD types frequently
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-invalid-offsetof"
+
+    # -Wno-inline-new-delete - we inline 'new' and 'delete' in mozalloc
+    # -Wno-unused-local-typedef - catches unused typedefs, which are commonly used in assertion macros
+    MOZ_CXX_SUPPORTS_WARNING(-Wno-, inline-new-delete, ac_cxx_has_wno_inline_new_delete)
+    MOZ_CXX_SUPPORTS_WARNING(-Wno-, unused-local-typedef, ac_cxx_has_wno_unused_local_typedef)
 
     # Recent clang and gcc support C++11 deleted functions without warnings if
     # compiling with -std=c++0x or -std=gnu++0x (or c++11 or gnu++11 in very new
@@ -1398,6 +1332,9 @@ if test "$GNU_CXX"; then
         MOZ_CXX_SUPPORTS_WARNING(-Wno-, extended-offsetof, ac_cxx_has_wno_extended_offsetof)
     fi
 
+    _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -include $(topobjdir)/js/src/js-confdefs.h'
+    _USE_CPP_INCLUDE_FLAG=1
+
 else
     _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -D_JS_CONFDEFS_H_ $(ACDEFINES)'
 fi