Re: Bad bug in fopen() wrapper code

From: "Claudio Natoli" <claudio(dot)natoli(at)memetrics(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Magnus Hagander" <mha(at)sollentuna(dot)net>
Cc: <pgsql-hackers(at)postgresql(dot)org>, <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Bad bug in fopen() wrapper code
Date: 2006-09-25 00:04:29
Message-ID: C9A33A2803C7F3479A02A333328A174756CAB2@ewell.memetrics.local
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Hello guys,

it's been a while, but...

> What's bugging me is that 0 and O_EXCL give the same answer, and
> O_TRUNC and O_TRUNC | O_EXCL give the same answer,

This is ok, as (iirc) O_EXCL only has effect in the presence of O_CREAT.
(a comment to this effect would help here, as well as perhaps links to the CreateFile and open specs)

> but O_CREAT and O_CREAT | O_EXCL give different answers,
> as do O_CREAT | O_TRUNC and O_CREAT | O_TRUNC | O_EXCL.

See above.

> I'm also pretty suspicious of both O_CREAT | O_EXCL and
> O_CREAT | O_TRUNC | O_EXCL giving the same answer.

O_CREAT | O_EXCL is effectively "create, but fail if the file exists", which is the behaviour specified by CREATE_NEW. Adding O_TRUNC to this combination, which can only apply to a successfully opened existent file, can have no impact afaics.

Cheers,
Claudio

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