[llvm-commits] [llvm-gcc] Potential bug in iasm_extra_clobbers ??

[Reid Spencer]

Applites,

While I've been perusing c-common.c, I have found a warning that you
might not be seeing because of compiler differences:

../../src-2/gcc/c-common.c: In function ‘iasm_extra_clobbers’:
../../src-2/gcc/c-common.c:7017: warning: comparison of unsigned expression < 0 is always false

This comes from this function:

> static void
> iasm_extra_clobbers (const char *opcode, tree *clobbersp)
> {
>   struct iasm_op_clobber db[] = { IASM_EXTRA_CLOBBERS };

Note number of elements of db is 1.

>   struct iasm_op_clobber key;
>   struct iasm_op_clobber *r;
>   const char **clobbers;
>   int num;
> 
> /* APPLE LOCAL LLVM */
> #if defined(TARGET_IASM_EXTRA_CLOBBERS) && defined(ENABLE_CHECKING)
>   /* Ensure that the table is sorted. */
>   static int once;
>   if (once == 0)
>     {
>       size_t i;
>       once = 1;
>       for (i=0; i < sizeof (db) / sizeof(db[0]) - 1; ++i)

Are you sure you want to subtract one from the size computation? Perhaps
at one time this was null terminated? In any event (sizeof(db) /
sizeof(db[0])) == 1, which if you subtract 1 from it is causing the
unsigned range warning on the comparison with i.

Not sure if this matters, but thought I'd point it out.

>         gcc_assert (iasm_op_clobber_comp (&db[i+1], &db[i]) >= 0);
>     }
> #endif
>