At least, let's get it archived on GCC mailing lists.
On Fri, Apr 17, 2009 at 11:25 AM, Torbjorn Granlund <t...@gmplib.org> wrote:
> Vincent Lefevre <vinc...@vinc17.org> writes:
>
> FYI, here's a simple testcase:
>
> /* With GCC 4.3.2 and -O2 option: output value is 1 instead of 0.
> * If -fno-strict-aliasing is added, this bug disappears.
> */
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int test (int n)
> {
> unsigned long *p, *q;
> int i;
>
> q = p = malloc (n * sizeof (unsigned long));
> if (p == NULL)
> return 2;
> for (i = 0; i < n - 1; i++)
> p[i] = 0;
> p[n - 1] = 1;
> while ((*(q++))-- == 0) ;
> return p[n - 1] == 1;
> }
>
> int main (void)
> {
> int r;
>
> r = test (17);
> printf ("%d\n", r);
> return r;
> }
>
> You may want to use it in configure to detect the bug there (as not
> all users run "make check"). Possibly add -fno-strict-aliasing if
> the bug is detected.
>
> Nice. I think that test should go onto the GCC testsuite.
>
> I suppose a problem is that the code wrt GMP need to be *executed*;
> configure feature tests should work also when cross-compiling, I think.
>
> --
> Torbjörn
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