Re: [FFmpeg-devel] [PATCH] configure: Make MSVC version grabbing more robust

[Kacper Michajlow <kasper93-at-gmail.com@ffmpeg.org>]

On Sat, 21 Jun 2025 at 19:18, Alexander Strasser via ffmpeg-devel
<ffmpeg-devel@ffmpeg.org> wrote:
>
>
>
>
> ---------- Forwarded message ----------
> From: Alexander Strasser <eclipse7@gmx.net>
> To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> Cc:
> Bcc:
> Date: Sat, 21 Jun 2025 19:18:03 +0200
> Subject: Re: [FFmpeg-devel] [PATCH] configure: Make MSVC version grabbing more robust
> Hi Martin!
>
> On 2025-06-21 13:37 +0300, Martin Storsjö wrote:
> > > On 21. Jun 2025, at 12.20, Alexander Strasser via ffmpeg-devel <ffmpeg-devel@ffmpeg.org> wrote:
> > >
> > >
> > > On 2025-06-21 00:03 +0200, Kacper Michajlow wrote:
> > >> On Fri, 20 Jun 2025 at 22:26, Hendrik Leppkes
> > >> <h.leppkes-at-gmail.com@ffmpeg.org> wrote:
> > >>>
> > >>> On Fri, Jun 20, 2025 at 9:25 PM Timo Rothenpieler <timo@rothenpieler.org> wrote:
> > >>>>
> > >>>> Likely this patch broke multiple fate runners in a silent way.
> > >>>> On mine, configure simply never returns, and just sits there
> > >>>> indefinitely, with no CPU usage or any activity whatsoever.
> > >>>>
> > >>>> nevcairiel confirmed seeing the same behaviour on IRC.
> > >>>>
> > >>>> The msys+clang builds from within the same environment work fine.
> > >>>>
> > >>>>
> > >>>> Didn't verify completely if it's caused by this patch, but nothing else
> > >>>> happened with configure since the last successful run.
> > >>>
> > >>> I did some digging, and it happens when probe_cc probes link.exe
> > >>>
> > >>> link.exe has an interactive help output (its paginated) - previously
> > >>> piping stdout disabled the pagination automatically - but redirecting
> > >>> it to devnull does not, and it gets stuck waiting for input.
> > >>> Additionally, link.exe outputs the ident on stdout, so there is no
> > >>> result on stderr (not super bad, as LD_IDENT is never used - yet)
> > >>
> > >> Instead of redirecting to devnull, we could use the same condition as
> > >> in if. We already look for specific ident line, so no need to head.
> > >> _ident=$($_cc -nologo- 2>&1 | grep ^Microsoft | tr -d '\r')
> > >> should work, no? I would be happy to see a better solution, though.
> > >
> > > I think making sure to only use the first line that starts with
> > > Microsoft is more robust; there could be (in the future) more lines
> > > that start with Microsoft.
> > >
> > >> btw. running cl.exe 3 times to just get its name is interesting :)
> > >
> > > Yes, so that as well. Could be optimized, but is probably not so
> > > relevant in total.
> > >
> > > I propose the attached patch.
> > >
> > >
> > >  Alexander
> > > <0001-configure-Fix-a-regression-when-probing-link.exe.patch>
> >
> > Thanks, this patch looks good to me, feel free to push! (And I can push it later today if nobody else does it before that.)
> >
> > If you want to, one can also extend the commit message further to say more explicitly, that 45a30e03613a3c63d74a40f7ac86ce28dce14ff8 caused configure to hang in some configurations, which this fixes.
>
> I have attached an updated version. Hope you like the commit message
> better.
>
> I can push it tomorrow or you can do earlier.

LGTM. I tested locally for link.exe and cl.exe. As for server/fate
testing, I think we can push and monitor if runners are unblocked.
People have things automated, so it probably takes "effort" to just do
manual patch testing out-of-tree.

- Kacper
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