Re: Thread-unsafe coding in ecpg

From: Michael Meskes <meskes(at)postgresql(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Thread-unsafe coding in ecpg
Date: 2019-01-19 19:15:37
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> So my conclusion is that this version of setlocale() has some
> thread-safety issues. I was all set to go file a bug report
> when I noticed this in the POSIX spec for setlocale:
> The setlocale() function need not be thread-safe.
> as well as this:
> The global locale established using setlocale() shall only be
> used
> in threads for which no current locale has been set using
> uselocale() or whose current locale has been set to the global
> locale using uselocale(LC_GLOBAL_LOCALE).

This one was new to me.

> IOW, not only is setlocale() not necessarily thread-safe itself,
> but using it to change locales in a multithread program is seriously
> unsafe because of concurrent effects on other threads.


> Therefore, it's plain crazy for ecpg to be calling setlocale() inside
> threaded code. It looks to me like what ecpg is doing is trying to
> defend
> itself against non-C LC_NUMERIC settings, which is laudable, but this
> implementation of that is totally unsafe.
> Don't know what's the best way out of this. The simplest thing would
> be to just remove that code and document that you'd better run ecpg
> in LC_NUMERIC locale, but it'd be nice if we could do better.

How about attached patch? According to my manpages it should only
affect the calling threat. I only tested it on my own system so far.
Could you please have a look and/or test on other systems?

Michael Meskes
Michael at Fam-Meskes dot De, Michael at Meskes dot (De|Com|Net|Org)
Meskes at (Debian|Postgresql) dot Org
Jabber: michael at xmpp dot meskes dot org
VfL Borussia! Força Barça! SF 49ers! Use Debian GNU/Linux, PostgreSQL

Attachment Content-Type Size
ecpg_locale.diff text/x-patch 1.8 KB

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