Re: patch: prevent user from setting wal_buffers over 2GB bytes

On 2015-08-04 09:49:58 -0400, Tom Lane wrote:
> Takashi Horikawa <t-horikawa@aj.jp.nec.com> writes:
> >>>> Why does this cause a core dump?  We could consider fixing whatever
> >>>> the problem is rather than capping the value.
> 
> > As far as I experiment with my own evaluation environment using 
> > PostgreSQL-9.4.4 on a x86_64 Linux, this problem can be fixed with the patch 
> > attached.
> 
> I'm unsure whether this represents a complete fix ... but even if it does,
> it would be awfully easy to re-introduce similar bugs in future code
> changes, and who would notice?  Josh's approach of restricting the buffer
> size seems a lot more robust.
> 
> If there were any practical use-case for such large WAL buffers then it
> might be worth spending some effort/risk here.  But AFAICS, there is not.
> Indeed, capping wal_buffers might be argued to be a good thing in itself
> because it would prevent users from wasting shared memory foolishly.
> 
> So my vote is for the original approach.  (I've not read Josh's patch,
> so there might be something wrong with it in detail, but I like the
> basic approach.)

+1