ubsan: Silence W=1 warnings in self-test

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 <[email protected]>

Closes https://lore.kernel.org/oe-kbuild-all/[email protected]/ open here

Signed-off-by Kees Cook <[email protected]>

---
 lib/Makefile | 1 +
 1 file changed, 1 insertion(+)

lib/Makefile +1 -1

index 6b09731d8e61..bc36a5c167db 100644
@@ -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
--

2.34.1

Quoted 7 lines · Kees Cook

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;
         |             ^

This is the shift_out_of_bounds test? It looks like the neg and wrap variables are volatile but the written-to variables aren't. Technically the compiler just has to emit the reads to neg and wrap, and can entirely omit the writes to val1 and val2.

Does making it volatile fix the warning?

Quoted 9 lines · Marco Elver

Quoted 7 lines · Kees Cook

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;
         |             ^

Quoted 6 lines

This is the shift_out_of_bounds test? It looks like the neg and wrap variables are volatile but the written-to variables aren't. Technically the compiler just has to emit the reads to neg and wrap, and can entirely omit the writes to val1 and val2.

Does making it volatile fix the warning?

It does for some, but not all:

../lib/test_ubsan.c: In function 'test_ubsan_out_of_bounds':
../lib/test_ubsan.c:115:22: warning: variable 'arr' set but not used [-Wunused-but-set-variable]
115 | volatile int arr[4];
| ^~~
../lib/test_ubsan.c:114:23: warning: variable 'above' set but not used [-Wunused-but-set-variable]
114 | volatile char above[4] = { }; /* Protect surrounding memory. */
| ^~~~~
../lib/test_ubsan.c: In function 'test_ubsan_load_invalid_value':
../lib/test_ubsan.c:137:44: warning: variable 'eptr' set but not used [-Wunused-but-set-variable]
137 | enum ubsan_test_enum eval, eval2, *eptr;
| ^~~~
../lib/test_ubsan.c:136:26: warning: variable 'ptr' set but not used [-Wunused-but-set-variable]
136 | bool val, val2, *ptr;
| ^~~