------- Comment #21 from david dot kirkby at onetel dot net 2009-07-18 01:18
-------
(In reply to comment #20)
> (In reply to comment #19)
> > (In reply to comment #18)
> > > I've compiled and linked that code. It does not abort.
> >
> > Bad point for this theory :-(
> > The result could still depend on the alignment of the pointer, so you could
> > try
> > replacing buf[0] by buf[4] and calling memset(buf+4,...) (try several small
> > values instead of 4).
> >
>
> I tried this in a loop. It still works, with no abort.
>
>
> typedef __SIZE_TYPE__ size_t;
> extern void *memset (void *, const void *, size_t);
> extern void abort (void);
> volatile size_t i = 0x80000000U, j = 0x80000000U;
> char buf[16];
>
> int main (void)
> {
> int n;
>
> for (n=0 ; n <=64;++n) {
> if (sizeof (size_t) != 4)
> return 0;
> buf[n] = 6;
> memset (buf+n, 0, i + j);
> if (buf[0] != 6)
> abort ();
> }
> return 0;
> }
>
> I extended 'n' to larger values and find it does abort when it is 5592, but
> not
> exactly the 'small' value you were looking for.
>
Looking closely, you only declared allocated 16 bytes for the buffer, so it was
hardly surprising it aborted at large n. When I increased the buffer size, so
it worked as expected, even for n as large as 10000
dave
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40757
