compiler: -Wold-style-definition hardening

Warn if an old-style function definition is used. A warning is given
even if there is a previous prototype.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/configure.ac b/configure.ac
index 5918bc5e487a0a24732439600cbfeeea4ce69ff0..2e220923903eac33f576760f4778825dd45773aa 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -703,6 +703,7 @@ AX_CHECK_COMPILE_FLAG([--mcet -fcf-protection], [CFLAGS="$CFLAGS --mcet -fcf-pro
 AX_CHECK_COMPILE_FLAG([-Werror=implicit-function-declaration], [CFLAGS="$CFLAGS -Werror=implicit-function-declaration"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wlogical-op], [CFLAGS="$CFLAGS -Wlogical-op"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wmissing-include-dirs], [CFLAGS="$CFLAGS -Wmissing-include-dirs"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-Wold-style-definition], [CFLAGS="$CFLAGS -Wold-style-definition"],,[-Werror])
 
 AX_CHECK_LINK_FLAG([-z relro], [LDLAGS="$LDLAGS -z relro"],,[])
 AX_CHECK_LINK_FLAG([-z now], [LDLAGS="$LDLAGS -z now"],,[])