On 07/20/2018 03:11 PM, Bernd Edlinger wrote:
I think I have found a valid test case where the latest patch
does generate invalid code:
This is due to another bug in string_constant() that's latent
on trunk but that's exposed by the patch. Trunk only "works"
because of a bug/limitation in c_strlen() that the patch fixes
or removes.
The underlying root cause is the handling of POINTER_PLUS
expressions in string_constant(). The original code (before
the handling of aggregates was added) just dealt with string
constants. The new code does much more but doesn't get it
quite right in these cases.
It shouldn't be too difficult to fix, but as valuable as
the testing you are doing is, I'd really prefer to focus
on one problem at a time and make incremental progress.
It will make it easier to track down and fix regressions
than lumping multiple fixes into a larger patch.
Martin
$ cat part.c
static const char a[3][8] = { "1234", "12345", "123456" };
int main ()
{
volatile int i = 1;
int n = __builtin_strlen (*(&a[1]+i));
if (n != 6)
__builtin_abort ();
}
$ gcc part.c -fdump-tree-original
$ ./a.out
Aborted (core dumped)
$ cat part.c.004t.original
;; Function main (null)
;; enabled by -tree-original
{
volatile int i = 1;
int n = (ssizetype) (SAVE_EXPR <(long unsigned int) i * 8>) <= 5 ? (int) (5 -
(unsigned int) (SAVE_EXPR <(long unsigned int) i * 8>)) : 0;
volatile int i = 1;
int n = (ssizetype) (SAVE_EXPR <(long unsigned int) i * 8>) <= 5 ? (int) (5 -
(unsigned int) (SAVE_EXPR <(long unsigned int) i * 8>)) : 0;
if (n != 6)
{
__builtin_abort ();
}
}
return 0;
string_constant is called with arg = (const char *) (&a[1] + (sizetype) ((long
unsigned int) i * 8))
