At Tue, 19 Jul 2022 16:57:14 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in
> At Tue, 19 Jul 2022 16:02:26 +0900, Masahiko Sawada <sawada.mshk@gmail.com> wrote in
> > On Tue, Jul 19, 2022 at 1:47 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > > Good work. I wonder without comments this may create a problem in the
> > > future. OTOH, I don't see adding a check "catchange.xcnt > 0" before
> > > freeing the memory any less robust. Also, for consistency, we can use
> > > a similar check based on xcnt in the SnapBuildRestore to free the
> > > memory in the below code:
> > > + /* set catalog modifying transactions */
> > > + if (builder->catchange.xip)
> > > + pfree(builder->catchange.xip);
> >
> > I would hesitate to add comments about preventing the particular
> > optimization. I think we do null-pointer-check-then-pfree many place.
> > It seems to me that checking the array length before memcpy is more
> > natural than checking both the array length and the array existence
> > before pfree.
>
> Anyway according to commit message of 46ab07ffda, POSIX forbits
> memcpy(NULL, NULL, 0). It seems to me that it is the cause of the
> false (or over) optimization. So if we add some comment, it would be
> for memcpy, not pfree..
For clarilty, I meant that I don't think we need that comment.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center