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

[Timo Rothenpieler <timo@rothenpieler.org>]

On 06/09/2023 01:26, Kacper Michajłow wrote:
> 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
> +)

Can't say I'm a fan of maintaining a random list in the middle of 
configure, which manually contains all libs we think need libstdc++.

This could for one change any time. But also, those dependenies might 
have other dependencies, which when linking statically might need libstdc++.

But in general, this seems extremely brittle and a maintenance nightmare.

> +for l in ${cxx_deps[@]}; do
> +    enabled $l && ld_default=$cxx
> +done
> +
>   : ${as_default:=$cc}
>   : ${objcc_default:=$cc}
>   : ${dep_cc_default:=$cc}
> @@ -6706,12 +6716,12 @@ enabled libfribidi        && require_pkg_config libfribidi fribidi fribidi.h fri
>   enabled libharfbuzz       && require_pkg_config libharfbuzz harfbuzz hb.h hb_buffer_create
>   enabled libglslang && { check_lib spirv_compiler glslang/Include/glslang_c_interface.h glslang_initialize_process \
>                               -lglslang -lMachineIndependent -lOSDependent -lHLSL -lOGLCompiler -lGenericCodeGen \
> -                            -lSPVRemapper -lSPIRV -lSPIRV-Tools-opt -lSPIRV-Tools -lpthread -lstdc++ -lm ||
> +                            -lSPVRemapper -lSPIRV -lSPIRV-Tools-opt -lSPIRV-Tools -lpthread -lm ||
>                           require spirv_compiler glslang/Include/glslang_c_interface.h glslang_initialize_process \
>                               -lglslang -lOSDependent -lHLSL -lOGLCompiler \
> -                            -lSPVRemapper -lSPIRV -lSPIRV-Tools-opt -lSPIRV-Tools -lpthread -lstdc++ -lm; }
> +                            -lSPVRemapper -lSPIRV -lSPIRV-Tools-opt -lSPIRV-Tools -lpthread -lm; }
>   enabled libgme            && { check_pkg_config libgme libgme gme/gme.h gme_new_emu ||
> -                               require libgme gme/gme.h gme_new_emu -lgme -lstdc++; }
> +                               require libgme gme/gme.h gme_new_emu -lgme; }
>   enabled libgsm            && { for gsm_hdr in "gsm.h" "gsm/gsm.h"; do
>                                      check_lib libgsm "${gsm_hdr}" gsm_create -lgsm && break;
>                                  done || die "ERROR: libgsm not found"; }
> @@ -6770,7 +6780,7 @@ enabled libopencv         && { check_headers opencv2/core/core_c.h &&
>   enabled libopenh264       && require_pkg_config libopenh264 openh264 wels/codec_api.h WelsGetCodecVersion
>   enabled libopenjpeg       && { check_pkg_config libopenjpeg "libopenjp2 >= 2.1.0" openjpeg.h opj_version ||
>                                  { require_pkg_config libopenjpeg "libopenjp2 >= 2.1.0" openjpeg.h opj_version -DOPJ_STATIC && add_cppflags -DOPJ_STATIC; } }
> -enabled libopenmpt        && require_pkg_config libopenmpt "libopenmpt >= 0.2.6557" libopenmpt/libopenmpt.h openmpt_module_create -lstdc++ && append libopenmpt_extralibs "-lstdc++"
> +enabled libopenmpt        && require_pkg_config libopenmpt "libopenmpt >= 0.2.6557" libopenmpt/libopenmpt.h openmpt_module_create
>   enabled libopenvino       && { { check_pkg_config libopenvino openvino openvino/c/openvino.h ov_core_create && enable openvino2; } ||
>                                   { check_pkg_config libopenvino openvino c_api/ie_c_api.h ie_c_api_version ||
>                                     require libopenvino c_api/ie_c_api.h ie_c_api_version -linference_engine_c_api; } }
> @@ -6789,12 +6799,12 @@ enabled librav1e          && require_pkg_config librav1e "rav1e >= 0.5.0" rav1e.
>   enabled librist           && require_pkg_config librist "librist >= 0.2.7" librist/librist.h rist_receiver_create
>   enabled librsvg           && require_pkg_config librsvg librsvg-2.0 librsvg-2.0/librsvg/rsvg.h rsvg_handle_render_cairo
>   enabled librtmp           && require_pkg_config librtmp librtmp librtmp/rtmp.h RTMP_Socket
> -enabled librubberband     && require_pkg_config librubberband "rubberband >= 1.8.1" rubberband/rubberband-c.h rubberband_new -lstdc++ && append librubberband_extralibs "-lstdc++"
> +enabled librubberband     && require_pkg_config librubberband "rubberband >= 1.8.1" rubberband/rubberband-c.h rubberband_new
>   enabled libshaderc        && require_pkg_config spirv_compiler "shaderc >= 2019.1" shaderc/shaderc.h shaderc_compiler_initialize
>   enabled libshine          && require_pkg_config libshine shine shine/layer3.h shine_encode_buffer
>   enabled libsmbclient      && { check_pkg_config libsmbclient smbclient libsmbclient.h smbc_init ||
>                                  require libsmbclient libsmbclient.h smbc_init -lsmbclient; }
> -enabled libsnappy         && require libsnappy snappy-c.h snappy_compress -lsnappy -lstdc++
> +enabled libsnappy         && require libsnappy snappy-c.h snappy_compress -lsnappy
>   enabled libsoxr           && require libsoxr soxr.h soxr_create -lsoxr
>   enabled libssh            && require_pkg_config libssh libssh libssh/sftp.h sftp_init
>   enabled libspeex          && require_pkg_config libspeex speex speex/speex.h speex_decoder_init

The only correct way I see to deal with this would be to fully rely on 
pkg-config to contain the correct library.
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