Re: Fixing code that ignores failure of XLogRecGetBlockTag

From: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Fixing code that ignores failure of XLogRecGetBlockTag
Date: 2022-04-11 21:16:12
Message-ID: CA+hUKG+4Xsn+b8tcXFizVy-mAHe0bR1qbCeHgq7ZnxMDzfSdvA@mail.gmail.com
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On Tue, Apr 12, 2022 at 8:58 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Mon, Apr 11, 2022 at 2:20 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Currently, XLogRecGetBlockTag has 41 callers, of which only four
> > bother to check the function's result. The remainder take it on
> > faith that they got valid data back, and many of them will
> > misbehave in seriously nasty ways if they didn't. (This point
> > was drawn to my attention by a Coverity complaint.)
> >
> > I think we should make this a little less fragile. Since we
> > already have XLogRecGetBlockTagExtended, I propose that callers
> > that need to handle the case of no-such-block must use that,
> > while XLogRecGetBlockTag throws an error. The attached patch
> > fixes that up, and also cleans up some random inconsistency
> > about use of XLogRecHasBlockRef().
>
> Looks reasonable.

+1

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