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

[Martin Storsjö]

On Sat, 21 Jun 2025, Kacper Michajlow wrote:

> On Sat, 21 Jun 2025 at 12:34, Martin Storsjö <martin at martin.st> wrote:
>>
>> On Sat, 21 Jun 2025, Kacper Michajlow wrote:
>>
>> > On Fri, 20 Jun 2025 at 22:26, Hendrik Leppkes
>> > <h.leppkes-at-gmail.com at ffmpeg.org> wrote:
>> >>
>> >> On Fri, Jun 20, 2025 at 9:25 PM Timo Rothenpieler <timo at rothenpieler.org> wrote:
>> >> >
>> >> > On 19.06.2025 22:21, Martin Storsjö wrote:
>> >> > > On Fri, 13 Jun 2025, Martin Storsjö wrote:
>> >> > >
>> >> > >> When running plain "cl", to get the MSVC version, it prints the
>> >> > >> version header on stderr, while the usage instructions are printed
>> >> > >> on stdout. Usually, the version on stderr gets flushed first,
>> >> > >> so "head -n1" gets the line it expects, but some times (in particular
>> >> > >> when running MSVC wrapped in wine), it can get the usage line
>> >> > >> first.
>> >> > >>
>> >> > >> Redirect stdout to /dev/null, so we only grab the version among
>> >> > >> the lines printed to stderr. This should make the version number
>> >> > >> grabbing more robust.
>> >> > >>
>> >> > >> At least all relevant versions of MSVC seem to print this specifically
>> >> > >> to stderr, not stdout (so we don't risk to miss it); checked down
>> >> > >> to MSVC 2010.
>> >> > >> ---
>> >> > >> This should avoid the occasionally misdetected version number lines
>> >> > >> as seen at https://fate.ffmpeg.org/history.cgi?slot=x86_64-msvc2022-wine.
>> >> > >> ---
>> >> > >> configure | 5 ++++-
>> >> > >> 1 file changed, 4 insertions(+), 1 deletion(-)
>> >> > >
>> >> > > Will push.
>> >> >
>> >> > 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)
>>
>> Sorry about the breakage, and thanks for figuring out what's wrong!
>>
>> It's odd that this issue didn't appear for me; perhaps it's related to
>> running the MSVC tools on Linux wrapped in wine somehow?
>
> I also didn't see an issue. I was running on a server with redirected
> output, so it probably also disabled paganination then. Maybe when
> there is no console, dunno. I could repro when running interactively
> locally.

Interesting, thanks!

Can you confirm that Alexander's patch fixes the issue?

// Martin