On Fri, 2 Feb 2024 at 11:41, Kees Cook <[email protected]> wrote: > > On Fri, Feb 02, 2024 at 10:57:11AM +0100, Marco Elver wrote: > > On Fri, 2 Feb 2024 at 10:46, Kees Cook <[email protected]> wrote: > > > > > > 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? > > 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; > | ^~~
Then I'd just combine the compiler flag with switching most of these variables to volatile so the tests keep working if the compiler decides to optimize too much.
