[PATCH] Add renameat2 function [BZ #17662]

[Andreas Schwab]

On Jul 03 2018, Paul Eggert <eggert@cs.ucla.edu> wrote:

> Florian Weimer wrote:
>> Surely that's a gnulib bug because the main reason for the
>> RENAME_NOREPLACE variant renameat2 was to avoid exactly that race (or
>> the other race where the file exists under both the old and new path).
>
> No, it's intended behavior, not a bug. GNU mv uses renameat2 with
> RENAME_NOREPLACE. mv wants the noreplace semantics on platforms that
> support it (currently only recent Linux and macOS kernels); otherwise it
> wants exactly that race because that's the best that can be done on other
> platforms. If Gnulib renameat2 simply failed with EINVAL because
> RENAME_NOREPLACE was not supported, GNU mv would simply use the same racy
> fallback that Gnulib renameat2 already uses.
>
> Other GNU applications are similar to GNU mv in this respect.

IMHO we should not repeat the pselect error.  Glibc should provide the
race-free guarantee that RENAME_NOREPLACE gives, so that programs that
need it can use it without fear.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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