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;
| ^~~
--
Kees Cook
