Subject: Re: readdir is incorrectly implemented at Windows
To: pgsql-hackers@lists.postgresql.org
References: <2cad7829-8d66-e39c-b937-ac825db5203d@postgrespro.ru>
From: Grigory Smolkin <g.smolkin@postgrespro.ru>
Message-ID: <591b93df-3d05-c88e-54bd-29c6a94d2a2d@postgrespro.ru>
Date: Wed, 27 Feb 2019 17:00:52 +0300
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Originally bug was reported by Yuri Kurenkov:
https://github.com/postgrespro/pg_probackup/issues/48

As pg_probackup rely on readdir() for listing files to backup, wrong 
permissions could lead to a broken backup.

On 02/25/2019 06:38 PM, Konstantin Knizhnik wrote:
> Hi hackers,
>
> Small issue with readir implementation for Windows.
> Right now it returns ENOENT in case of any error returned by 
> FindFirstFile.
> So all places in Postgres where opendir/listdir are used will assume 
> that directory is empty and
> do nothing without reporting any error.
> It is not so good if directory is actually not empty but there are not 
> enough permissions for accessing the directory and FindFirstFile
> returns ERROR_ACCESS_DENIED:
>
> struct dirent *
> readdir(DIR *d)
> {
>     WIN32_FIND_DATA fd;
>
>     if (d->handle == INVALID_HANDLE_VALUE)
>     {
>         d->handle = FindFirstFile(d->dirname, &fd);
>         if (d->handle == INVALID_HANDLE_VALUE)
>         {
>             errno = ENOENT;
>             return NULL;
>         }
>     }
>
>
> Attached please find small patch fixing the problem.
>

-- 
Grigory Smolkin
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company