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

["Rémi Denis-Courmont" <remi@remlab.net>]

Le keskiviikkona 6. syyskuuta 2023, 2.26.29 EEST Kacper Michajłow a écrit :
> Other C++ standard libraries exist. Also, this is not a proper way to
> link the standard library anyway. Instead when a C++ dependency is
> detected, switch to the C++ compiler driver to properly link everything.
> 
> Signed-off-by: Kacper Michajłow <kasper93@gmail.com>
> ---
>  configure | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/configure b/configure
> index bd7f7697c8..f3ff48586a 100755
> --- a/configure
> +++ b/configure
> @@ -3584,11 +3584,9 @@ bktr_indev_deps_any="dev_bktr_ioctl_bt848_h
> machine_ioctl_bt848_h dev_video_bktr caca_outdev_deps="libcaca"
>  decklink_deps_any="libdl LoadLibrary"
>  decklink_indev_deps="decklink threads"
> -decklink_indev_extralibs="-lstdc++"
>  decklink_indev_suggest="libzvbi"
>  decklink_outdev_deps="decklink threads"
>  decklink_outdev_suggest="libklvanc"
> -decklink_outdev_extralibs="-lstdc++"
>  dshow_indev_deps="IBaseFilter"
>  dshow_indev_extralibs="-lpsapi -lole32 -lstrmiids -luuid -loleaut32
> -lshlwapi" fbdev_indev_deps="linux_fb_h"
> @@ -4984,6 +4982,18 @@ set_ccvars HOSTCC
>  test -n "$cc_type" && enable $cc_type ||
>      warn "Unknown C compiler $cc, unable to select optimal CFLAGS"
> 
> +cxx_deps=(
> +    decklink
> +    libglslang
> +    libgme
> +    libopenmpt
> +    librubberband
> +    libsnappy
> +)

Hard-coding "-lstdc++" is admittedly a brittle kludge. On some systems, the
C++ runtime has a different name for one.

But hard-coding the set of library that would require the C++ linker is just 
as much of a hack. I would argue it's even more of a kludge. If a certain 
runtime (C++ or other) is necessary for a library then it should be in 
Libs.static in the pkg-config manifest. From there, FFmpeg should pick it up if 
and *only* if the libarry is linked statically.

Indeed, there are no reasons to even force C++ linking to use a C++ *shared* 
library exposing a pure C interface. Thus, I don't think that forcing the C++ 
linker is correct.

(Also I more or less agree with Timo here.)

-- 
レミ・デニ-クールモン
http://www.remlab.net/



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