Re: Using XLogFileNameP in critical section

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Using XLogFileNameP in critical section
Date: 2019-12-02 15:56:08
Message-ID: 20191202155608.GA7029@alvherre.pgsql
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On 2019-Dec-02, Michael Paquier wrote:

> I think that we had better just get rid of XLogFileNameP() (on HEAD)
> and just change those code paths so as they use a buffer of size
> MAXFNAMELEN, with XLogFileName() generating the file name. This leads
> actually to some simplifications, see for example XLogWalRcvWrite..

+1, that function is a footgun and there's no possible way to fix it so
that it's never misused(*). Also, put a comment atop XLogFileName
indicating never to create such a "helper" function again.

(*) unless there was a way to have a StaticAssert() that the function is
not called in a critical section -- have the compiler work for us. I
don't think it's possible to write such a thing.

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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