On 09/06/2012 03:42 PM, Eric Blake wrote: > Some versions of gcc (at least 4.2.1) noisily warn if > -Wuninitialized is given without -O; in isolation, configure > learns that the warning option is supported, but when later > compiling with -Werror, this makes builds fail. If the > option will have no effect for the configured choice of > $CFLAGS, then it is not worth including in the set. > > * m4/manywarnings.m4 (gl_MANYWARN_ALL_GCC): Add test for > -Wuninitialized without -O.
No comments, so I pushed this.
> +++ b/m4/manywarnings.m4
> @@ -1,4 +1,4 @@
> -# manywarnings.m4 serial 4
> +# manywarnings.m4 serial 5
> dnl Copyright (C) 2008-2012 Free Software Foundation, Inc.
> dnl This file is free software; the Free Software Foundation
> dnl gives unlimited permission to copy and/or distribute it,
> @@ -35,14 +35,12 @@ AC_DEFUN([gl_MANYWARN_COMPLEMENT],
> # make sure your gcc understands it.
> AC_DEFUN([gl_MANYWARN_ALL_GCC],
> [
> - dnl First, check if -Wno-missing-field-initializers is needed.
> - dnl -Wmissing-field-initializers is implied by -W, but that issues
> - dnl warnings with GCC version before 4.7, for the common idiom
> - dnl of initializing types on the stack to zero, using { 0, }
> + dnl First, check for some issues that only occur when combining multiple
> + dnl gcc warning categories.
> AC_REQUIRE([AC_PROG_CC])
> if test -n "$GCC"; then
>
> - dnl First, check -W -Werror -Wno-missing-field-initializers is supported
> + dnl Check if -W -Werror -Wno-missing-field-initializers is supported
> dnl with the current $CC $CFLAGS $CPPFLAGS.
> AC_MSG_CHECKING([whether -Wno-missing-field-initializers is supported])
> AC_CACHE_VAL([gl_cv_cc_nomfi_supported], [
> @@ -77,8 +75,24 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
> ])
> AC_MSG_RESULT([$gl_cv_cc_nomfi_needed])
> fi
> +
> + dnl Next, check if -Werror -Wuninitialized is useful with the
> + dnl user's choice of $CFLAGS; some versions of gcc warn that it
> + dnl has no effect if -O is not also used
> + AC_MSG_CHECKING([whether -Wuninitialized is supported])
> + AC_CACHE_VAL([gl_cv_cc_uninitialized_supported], [
> + gl_save_CFLAGS="$CFLAGS"
> + CFLAGS="$CFLAGS -Werror -Wuninitialized"
> + AC_COMPILE_IFELSE(
> + [AC_LANG_PROGRAM([[]], [[]])],
> + [gl_cv_cc_uninitialized_supported=yes],
> + [gl_cv_cc_uninitialized_supported=no])
> + CFLAGS="$gl_save_CFLAGS"])
> + AC_MSG_RESULT([$gl_cv_cc_uninitialized_supported])
> +
> fi
>
> + # List all gcc warning categories.
> gl_manywarn_set=
> for gl_manywarn_item in \
> -W \
> @@ -197,10 +211,14 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC],
> gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
> done
>
> - # Disable the missing-field-initializers warning if needed
> + # Disable specific options as needed.
> if test "$gl_cv_cc_nomfi_needed" = yes; then
> gl_manywarn_set="$gl_manywarn_set -Wno-missing-field-initializers"
> fi
>
> + if test "$gl_cv_cc_uninitialized_supported" = no; then
> + gl_manywarn_set="$gl_manywarn_set -Wno-uninitialized"
> + fi
> +
> $1=$gl_manywarn_set
> ])
>
--
Eric Blake ebl...@redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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