Re: [FFmpeg-devel] [PATCH v2 1/2] configure: don't force specific C++ standard library linking

From: Kacper Michajlow <kasper93@gmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Cc: Timo Rothenpieler <timo@rothenpieler.org>
Subject: Re: [FFmpeg-devel] [PATCH v2 1/2] configure: don't force specific C++ standard library linking
Date: Fri, 8 Sep 2023 20:55:39 +0200
Message-ID: <CABPLASQN52UTb56KkTcXcY=QVxKeK3-kbv7UBKHV0HyTt1dT-w@mail.gmail.com> (raw)
In-Reply-To: <2f980e77-31cb-64ae-d172-28f5cc498b3d@rothenpieler.org>

On Fri, 8 Sept 2023 at 01:35, Timo Rothenpieler via ffmpeg-devel
<ffmpeg-devel@ffmpeg.org> wrote:
>
> On 07.09.2023 23:38, Kacper Michajlow wrote:
> > On Thu, 7 Sept 2023 at 15:12, Derek Buitenhuis
> > <derek.buitenhuis@gmail.com> wrote:
> >>
> >> On 9/6/2023 6:31 PM, Kacper Michajlow wrote:
> >>> What would be a downside of preferring CXX always if it exists?
> >>
> >> FFmpeg runs in a multitude of environments with a multitude of portability
> >> requirements. Needlessly linking a C++ runtime is not OK.
> >
> > This does not answer my question. Let me rephrase. Do we know the case
> > where using C++ compiler driver rather than C would degrade the
> > quality of the resulting build?
> >
> > Using C++ driver would indeed append the (correct) runtime library to
> > the linker command, but if nothing references any symbols from it it
> > would not be linked. It is also why the current way of forcing
> > `lstdc++` kinda works, because it is silently ignored when not needed.
> >
> > Implementing logic to use C++ only when necessary is possible, but I'm
> > not a big fan of such automation. And in practice not sure how well it
> > would work, because it would require trying to link twice every
> > dependency in configure.
> >
> > Also the fact that "FFmpeg runs in a multitude of environment" is
> > precisely why I really don't like the current unconditional including
> > `-lstdc++`.
>
> Couldn't you just check if stdc++ is in the ldflags/extralibs, and if
> so, remove it, and use g++ to link?

Well, I'm lost now. Are you suggesting building on top of existing
hacks is a better solution than the proposed patch?

I refuse supporting any kind of random `-lstdc++` adding in configure
and then removing it in the end.

- Kacper
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