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From: Andreas Schwab <schwab@suse.de>
To: Joe Simmons-Talbott <josimmon@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH] nss: Get rid of alloca usage in makedb's write_output.
In-Reply-To: <20230928131432.GB4098455@oak> (Joe Simmons-Talbott's message of
	"Thu, 28 Sep 2023 09:14:32 -0400")
References: <20230926135528.3517253-1-josimmon@redhat.com>
	<mvmv8bupmz3.fsf@suse.de> <20230928131432.GB4098455@oak>
X-Yow: Is there something I should be DOING with a GLAZED DONUT??
Date: Thu, 28 Sep 2023 15:32:31 +0200
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On Sep 28 2023, Joe Simmons-Talbott wrote:

> On Thu, Sep 28, 2023 at 01:16:00PM +0200, Andreas Schwab wrote:
>> On Sep 26 2023, Joe Simmons-Talbott wrote:
>> 
>> > @@ -802,6 +812,7 @@ write_output (int fd)
>> >    assert (iov_nelts <= INT_MAX);
>> >    if (writev (fd, iov, iov_nelts) != keydataoffset)
>> >      {
>> > +      scratch_buffer_free (&sbuf);
>> >        error (0, errno, gettext ("failed to write new database file"));
>> >        return EXIT_FAILURE;
>> 
>> Does scratch_buffer_free guarantee that errno is not changed?
>
> scratch_buffer_free doesn't do anything other than call free when the
> buffer has been heap-allocated.  IIUC free preserves errno since 2.33 in
> the default free.  So I guess if there is a non-default free that
> doesn't preserve errno then there is no explicit guarantee.  Should I
> adjust scratch_buffer_free to explicitly preserve errno (in a separate
> patch) or just preserve errno around this one call to
> scratch_buffer_free?

You could just move the call down.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."