When adding the -std=gnu99 flag, we set $wantwarn instead of appending to it. This meant all the compiler warnings were accidentally discarded. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- Pushed as a trivial fix for the previous commit m4/virt-compile-warnings.m4 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index 411d257465..26f231f97e 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -192,7 +192,7 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ # Request the gnu99 standard which is the best choice with # gcc 4.8.0. Not a warning flag, but the probing mechanism # is convenient - wantwarn="-std=gnu99" + wantwarn="$wantwarn -std=gnu99" # Check for $CC support of each warning for w in $wantwarn; do -- 2.21.0