Re: random crashes on -HEAD for a few days now

Tom Lane wrote:
> Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> writes:
>> at least one of my buildfarm members (emu) is crashing on what seems
>> totally unrelated regression tests for a few days now:
>
> I was wondering about that ...
>
>> it took me about 10 tries to reproduce that manually and I'm getting the
>> following stacktrace:
>
>> #0 varbit_out (fcinfo=0x88c75000) at varbit.c:549
>> 549 x = *sp;
>
> Just eyeballing that code, it looks like it will try to fetch the byte
> immediately beyond the end of the bit array, when the number of bits is
> an exact multiple of 8. This is unlikely to cause a problem but it
> *could* happen that the input is right up against the end of memory.
> Could you check whether that is what happened here? (The important
> question is whether the input seems to be sane, ie, "len" isn't huge.)

"end of memory" sounds familiar to:

http://archives.postgresql.org/pgsql-hackers/2005-06/msg00819.php

which is how emu is (still) set up.

as for len it seems to be 0:

#0 varbit_out (fcinfo=0x88c75000) at varbit.c:549
s = (VarBit *) 0x88c75000
result = 0x84d33128 ""
r = 0x84d33128 ""
sp = (bits8 *) 0x88c75000 <Address 0x88c75000 out of bounds>
x = 0 '\0'
i = 0
k = 0
len = 0

Stefan