Hey,

The proposed changes to fopen 'a' seem reasonable for us to implement. We're mostly concerned with preserving backwards compatibility, and I don't see any major impact from ensuring the file access is atomic.

I want to note though that the UCRT does implement fopen 'x' (the paper claims it isn't implemented). This hasn't always been the case, but support was added in 2017 and backported to all our UCRT versions. Other Microsoft CRTs, however, do not have this feature.

Thanks,
Steve

From: Casey Carter <cartec69_at_[hidden]>
Sent: Monday, October 11, 2021 2:54 PM
To: liaison_at_[hidden]; Steve Wishnousky <stwish_at_[hidden]>
Cc: Niall Douglas <s_sourceforge_at_[hidden]>
Subject: Re: [wg14/wg21 liaison] WG14 N2830 fopen('x') and fopen('a')

+Steve for UCRT feedback

On Mon, Oct 11, 2021 at 6:13 AM Niall Douglas via Liaison <liaison_at_[hidden]<mailto:liaison_at_[hidden]>> wrote:
CC: Mr. Wakely

To our WG21 colleagues, please find attached for your information WG14
N2830 fopen('x') and fopen('a') which proposes strengthened wording for
those two operations, which in turn may affect C++ iostreams.

I would once again ask that a maintainer of Microsoft's UCRT get in
touch, as theirs is the only implementation of fopen('a') which I
reviewed which is not atomic (and for no good reason, as Win32
implements it perfectly well).

Niall
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