Date: Thu, 18 Jun 2020 17:20:27 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: pgsql-hackers@postgresql.org,
	Kunshchikov Vladimir <Vladimir.Kunshchikov@infotecs.ru>
Subject: Re: pg_dump, gzwrite, and errno
Message-ID: <20200618212027.GA17103@alvherre.pgsql>
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On 2020-Jun-11, Justin Pryzby wrote:

> --- a/src/bin/pg_dump/pg_backup_directory.c
> +++ b/src/bin/pg_dump/pg_backup_directory.c
> @@ -347,8 +347,12 @@ _WriteData(ArchiveHandle *AH, const void *data, size_t dLen)
>         lclContext *ctx = (lclContext *) AH->formatData;
>  
>         if (dLen > 0 && cfwrite(data, dLen, ctx->dataFH) != dLen)
> +       {
> +               if (errno == 0)
> +                       errno = ENOSPC;
>                 fatal("could not write to output file: %s",
>                           get_cfp_error(ctx->dataFH));
> +       }
>  }

This seems correct to me.  (I spent a long time looking at zlib sources
to convince myself that it does work with compressed files too).  There
are more calls to cfwrite in pg_backup_directory.c though -- we should
patch them all.

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