Re: BUG #16837: Invalid memory access on \h in psql

At Tue, 26 Jan 2021 11:11:22 -0500, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote in
> Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> writes:
> > At Tue, 26 Jan 2021 07:00:00 +0000, PG Bug reporting form <noreply(at)postgresql(dot)org> wrote in
> >> When executing in psql (under valgrind):
> >> \h\
> >> valgrind detects the following error:
> >> ==00:00:00:00.000 3226182==
> >> ==00:00:00:04.045 3226182== Conditional jump or move depends on
> >> uninitialised value(s)
>
> > This is reproducible on master HEAD. helpSQL assumes that the first
> > word is longer than two characters and the second word exists. It also
> > doesn't care overruns. Addition to those issues, it miscounts the
> > length of the first two words if the third word exists.
>
> Weirdly, valgrind isn't whining about this for me. But I agree that
> that loop is unsafe. There are other problems too I think: neither
> the initialization of "output" nor the calculation of nl_count seem
> to be done sanely. This function really needs thoroughgoing review :-(

It looks far better now. Thanks!

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center