[PATCH v2] ubsan: Silence W=1 warnings in self-test

[Kees Cook <keescook@chromium.org>]

Silence a handful of W=1 warnings in the UBSan selftest, which set
variables without using them. For example:

   lib/test_ubsan.c:101:6: warning: variable 'val1' set but not used [-Wunused-but-set-variable]
     101 |         int val1 = 10;
         |             ^

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202401310423.XpCIk6KO-lkp@intel.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v2:
 - add additional "volatile" annotations for potential future proofing (marco)
v1: https://lore.kernel.org/all/20240202094550.work.205-kees@kernel.org/
---
 lib/Makefile     | 1 +
 lib/test_ubsan.c | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/Makefile b/lib/Makefile
index 6b09731d8e61..bc36a5c167db 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_HASH_KUNIT_TEST) += test_hash.o
 obj-$(CONFIG_TEST_IDA) += test_ida.o
 obj-$(CONFIG_TEST_UBSAN) += test_ubsan.o
 CFLAGS_test_ubsan.o += $(call cc-disable-warning, vla)
+CFLAGS_test_ubsan.o += $(call cc-disable-warning, unused-but-set-variable)
 UBSAN_SANITIZE_test_ubsan.o := y
 obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
 obj-$(CONFIG_TEST_LIST_SORT) += test_list_sort.o
diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c
index 2062be1f2e80..f4ee2484d4b5 100644
--- a/lib/test_ubsan.c
+++ b/lib/test_ubsan.c
@@ -23,8 +23,8 @@ static void test_ubsan_divrem_overflow(void)
 static void test_ubsan_shift_out_of_bounds(void)
 {
 	volatile int neg = -1, wrap = 4;
-	int val1 = 10;
-	int val2 = INT_MAX;
+	volatile int val1 = 10;
+	volatile int val2 = INT_MAX;
 
 	UBSAN_TEST(CONFIG_UBSAN_SHIFT, "negative exponent");
 	val1 <<= neg;
-- 
2.34.1