On Sat, Nov 02, 2013 at 01:09:25AM +0200, Martin Storsjö wrote:
> On Fri, 1 Nov 2013, Diego Biurrun wrote:
> >
> >configure: Properly check for availability of -Wno-foo warning flags
> >
> >For some weird reason gcc does not check if the -Wno disabling variants
> >of warning flags match existing warning flags. Instead it swallows them
> >silently. That is, unless other warning or error messages are generated,
> >because then - for some even more bizarre reason - a complaint about the
> >unknown disable warning flag is issued along with the error or warning
> >message.
> >
> >Thus to check for the availability of a warning disabling option, one
> >needs to check for the enabling variant instead and then add the
> >disabling variant to CFLAGS.
> >
> >--- a/configure
> >+++ b/configure
> >@@ -3903,13 +3903,9 @@ enabled debug && add_cflags -g"$debuglevel" &&
> >add_asflags -g"$debuglevel"
> ># add some useful compiler flags if supported
> >check_cflags -Wdeclaration-after-statement
> >check_cflags -Wall
> >-check_cflags -Wno-parentheses
> >-check_cflags -Wno-switch
> >-check_cflags -Wno-format-zero-length
> >check_cflags -Wdisabled-optimization
> >check_cflags -Wpointer-arith
> >check_cflags -Wredundant-decls
> >-check_cflags -Wno-pointer-sign
> >check_cflags -Wcast-qual
> >check_cflags -Wwrite-strings
> >@@ -3918,6 +3914,17 @@ check_cflags -Wmissing-prototypes
> >check_cflags -Wstrict-prototypes
> >enabled extra_warnings && check_cflags -Winline
> >
> >+check_disable_warning(){
> >+ warning_flag=-W${1#-Wno-}
> >+ test_cflags $warning_flag && add_cflags $1
> >+}
> >+
> >+check_disable_warning -Wno-parentheses
> >+check_disable_warning -Wno-switch
> >+check_disable_warning -Wno-format-zero-length
> >+check_disable_warning -Wno-pointer-sign
> >+enabled extra_warnings || check_disable_warning -Wno-maybe-uninitialized
> >+
> >@@ -4008,7 +4015,6 @@ elif enabled gcc; then
> > check_cflags -Werror=declaration-after-statement
> > check_cflags -Werror=vla
> >- enabled extra_warnings || check_cflags -Wno-maybe-uninitialized
> >elif enabled llvm_gcc; then
> > check_cflags -mllvm -stack-alignment=16
> >elif enabled clang; then
>
> The maybe-uninitialized check still needs to be moved back into a
> gcc specific block, since this now spews warnings with clang:
> https://fate.libav.org/x86_64-linux-clang
Wait, clang groks -Wmaybe-uninitialized, but not -Wno-maybe-uninitialized?
WTF?
Diego
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