Commit c579d6b added a sledgehammer to silence spurious warnings from
gcc 4.2, but in the process, it also silenced useful warnings from
newer gcc (such as 4.4). As a result, a bug slipped in to commit 0caccb58.
Tested with FreeBSD (gcc 4.2.1), RHEL 6.3 (gcc 4.4), and F17 (gcc 4.7.2).
* m4/virt-compile-warnings.m4 (-Wno-format): Probe for the actual
spurious message, to once again allow gcc 4.4 to use -Wformat.
---
m4/virt-compile-warnings.m4 | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4
index d1173eb..f1b8f39 100644
--- a/m4/virt-compile-warnings.m4
+++ b/m4/virt-compile-warnings.m4
@@ -60,6 +60,23 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
# gcc 4.4.6 complains this is C++ only; gcc 4.7.0 implies this from -Wall
dontwarn="$dontwarn -Wenum-compare"
+ # gcc 4.2 treats attribute(format) as an implicit attribute(nonnull),
+ # which triggers spurious warnings for our usage
+ AC_CACHE_CHECK([whether gcc -Wformat allows NULL strings],
+ [lv_cv_gcc_wformat_null_works], [
+ save_CFLAGS=$CFLAGS
+ CFLAGS='-Wunknown-pragmas -Werror -Wformat'
+ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+ #include <stddef.h>
+ static __attribute__ ((__format__ (__printf__, 1, 2))) int
+ foo (const char *fmt, ...) { return !fmt; }
+ ]], [[
+ return foo(NULL);
+ ]])],
+ [lv_cv_gcc_wformat_null_works=yes],
+ [lv_cv_gcc_wformat_null_works=no])
+ CFLAGS=$save_CFLAGS])
+
# Gnulib uses '#pragma GCC diagnostic push' to silence some
# warnings, but older gcc doesn't support this.
AC_CACHE_CHECK([whether pragma GCC diagnostic push works],
@@ -117,7 +134,7 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
# ATTRIBUTE_FMT_PRINT, which causes -Wformat failure on our
# intentional use of virReportError(code, NULL).
gl_WARN_ADD([-Wno-format-nonliteral])
- if test $lv_cv_gcc_pragma_push_works = no; then
+ if test $lv_cv_gcc_wformat_null_works = no; then
gl_WARN_ADD([-Wno-format])
fi
--
1.7.11.4
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