compiler: -Werror=shift-overflow=2 hardening

Warn about left shift overflows. This warning is enabled by default in
C99 and C++11 modes (and newer).

-Wshift-overflow=2
This warning level also warns about left-shifting 1 into the sign bit,
unless C++14 mode (or newer) is active.

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

diff --git a/configure.ac b/configure.ac
index 729f262c0d9a35677a290a80dc7c94a87b353fa5..c59b7664d979bd5fa7bd35268dac4b1bd1208538 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -716,6 +716,7 @@ AX_CHECK_COMPILE_FLAG([-Wendif-labels], [CFLAGS="$CFLAGS -Wendif-labels"],,[-Wer
 AX_CHECK_COMPILE_FLAG([-Werror=overflow], [CFLAGS="$CFLAGS -Werror=overflow"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-fdiagnostics-show-option], [CFLAGS="$CFLAGS -fdiagnostics-show-option"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Werror=shift-count-overflow], [CFLAGS="$CFLAGS -Werror=shift-count-overflow"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-Werror=shift-overflow=2], [CFLAGS="$CFLAGS -Werror=shift-overflow=2"],,[-Werror])
 
 AX_CHECK_LINK_FLAG([-z relro], [LDLAGS="$LDLAGS -z relro"],,[])
 AX_CHECK_LINK_FLAG([-z now], [LDLAGS="$LDLAGS -z now"],,[])