Re: [patch] more bitmap obstacks

[Tobias Burnus <burnus at net-b dot de>]

Steven Bosscher wrote:
> On Sat, Aug 18, 2012 at 9:01 AM, Tobias Burnus <burnus@net-b.de> wrote:
> > I think it's your patch which breaks bootstrapping here:
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x00000000005bfa40 in bitmap_obstack_free (map=0x18693a0) at
> > /projects/tob/gcc-git/gcc/gcc/bitmap.c:388
> > 388           map->first = (bitmap_element *) map->obstack->heads;
> > (gdb) p map->obstack
> > $1 = (bitmap_obstack *) 0x9090909090909090
> >
> > Thus, your patch assumes that malloc returns nullified memory, but e.g. with
> > MALLOC_PERTURB_ set, that's not the case.
> If my patch broke this, it was broken before also. I only added a few
> more bitmap obstacks, but there were lots of existing ones before the
> patch.

Maybe, but MALLOC_PERTURB_ builds were successful since years – 
including my Friday morning build (though, I didn't do a bootstrap). My 
last full bootstrap was on 2012-08-15 and a FreeBSD jemalloc's junk 
filling build was done by Steve on the 10th.

Thus, either there is a fairly new bug or some change made an old bug 
surface. I also haven't bisected, thus it could also be some other patch.

> Can you file a big report with a test case and instructions to
> reproduce, so that I can have a look?

I filled a small bug report at 
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54313

I hope it is sufficient. If you need more, please tell me.

Tobias