[Bug sanitizer/55309] gcc's address-sanitizer 66% slower than clang's

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55309



--- Comment #51 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-22 
15:01:08 UTC ---

Looks like a real SPEC bug to me.



PerlIO_funcs *

PerlIO_find_layer(pTHX_ const char *name, STRLEN len, int load)

{

    IV i;

    if ((SSize_t) len <= 0)

        len = strlen(name);

    for (i = 0; i < PL_known_layers->cur; i++) {

        PerlIO_funcs *f = PL_known_layers->array[i].funcs;

        if (memEQ(f->name, name, len) && f->name[len] == 0) {

            PerlIO_debug("%.*s => %p\n", (int) len, name, (void*)f);

            return f;

        }

    }



memEQ is memcmp, and my reading of ISO C99 or

http://pubs.opengroup.org/onlinepubs/9699919799/functions/memcmp.html is that

it is a bug to call memcmp ("abcdef", "defg", 6).  A valid memcmp

implementation could preread all bytes from both arrays (of the given length)

and only then compare.  And, at least some implementations (e.g. glibc

string/memcmp.c) does that if the two strings aren't starting at the same

address modulo size of word.