Re: segmentation fault when cassert enabled

At Fri, 25 Oct 2019 12:28:38 -0400, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote in
> Jehan-Guillaume de Rorthais <jgdr(at)dalibo(dot)com> writes:
> > When investigating for the bug reported in thread "logical replication -
> > negative bitmapset member not allowed", I found a way to seg fault postgresql
> > only when cassert is enabled.
> > ...
> > I hadn't time to digg further yet. However, I don't understand why this crash
> > is triggered when cassert is enabled.
>
> Most likely, it's not so much assertions that provoke the crash as
> CLOBBER_FREED_MEMORY, ie the actual problem here is use of already-freed
> memory.

Agreed.

By the way I didn't get a crash by Jehan's script with the
--enable-cassert build of the master HEAD of a few days ago.

FWIW I sometimes got SEGVish crashes or mysterious misbehavor when
some structs were changed and I didn't do "make clean". Rarely I
needed "make distclean". (Yeah, I didn't ususally turn on
--enable-depend..)

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center