Always use -Wl,-Bsymbolic flag in shared build #460
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Without this, when I was building ffms2 and ffmpeg in a shared library AND ffmpeg wasn't installed on the system on ubuntu (in /usr/lib) (it was installed to a path I specified with --prefix), ffms2 was failing to build. I was getting this error: ``` libtool: link: g++ -std=c++11 -fvisibility=hidden -Werror -Wno-error=deprecated-declarations -o src/index/.libs/ffmsindex src/index/ffmsindex.o -lavutil src/core/.libs/libffms2.so -Wl,-rpath -Wl,/home/runner/work/ffms2/ffms2/ffmpeg-8.0/ffmpeg_build/lib /usr/bin/ld: cannot find -lavutil: No such file or directory ``` After this change, it works fine and this is now how the libtool logs looks: ``` libtool: link: g++ -std=c++11 -fvisibility=hidden -Werror -Wno-error=deprecated-declarations -o src/index/.libs/ffmsindex src/index/ffmsindex.o -L/home/runner/work/ffms2/ffms2/ffmpeg-8.0/ffmpeg_build/lib -lavutil src/core/.libs/libffms2.so -Wl,-rpath -Wl,/home/runner/work/ffms2/ffms2/ffmpeg-8.0/ffmpeg_build/lib ```
The file m4/ax_check_link_flag.m4 is a copy of https://www.gnu.org/software/autoconf-archive/ax_check_link_flag.html Fix FFMS#458 and also fix when building ffms2 as a shared library and link with a static ffmpeg on ubuntu (it was building properly on macOS + windows (msys2)).
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@dwbuiten What do you think about this PR? |
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One comment on the first commit.
For the second commit: This is not a supported use case of the *nix configure as far as I am concerned.
| AC_SUBST(pkgconfigdir) | ||
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| PKG_CHECK_MODULES(FFMPEG, [libavformat >= 61.7.0 libavcodec >= 61.19.0 libswscale >= 8.3.0 libavutil >= 59.39.0 libswresample >= 5.3.0]) | ||
| PKG_CHECK_MODULES([AVUTIL], [libavutil >= 59.39.0]) |
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Where did this version come from?
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It's from the precedent line.
I guess you are referring to But, as we can see in this pr that test the build (moi15moi#3), on ubuntu, without this fix, when ffmpeg is shared and ffms2 is static, without this fix, the build fail. |
No, I'm talking about building a shared library linking a static ffmpeg. I don't consider this something autotools should support, or any distro should support. It's not a done thing. If people insist on using msys+mingw instead of msvc or clang, they should just pass extra cflags. |
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In this case, why this code is present? As specified in the doc (https://ffmpeg.org/platform.html#Advanced-linking-configuration), If you don't want to support this case, this should just be removed. |
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That is FFmpeg documentation, not FFMS2's. |
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Yes, it is ffmpeg doc. It explain the reason when we need to use the linking flag |
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Fix #458
I created another PR to test all the possibility (ex: ffmpeg static with ffms2 shared, ffmpeg shared with ffms2 shared, etc) to properly test this PR.
See: moi15moi#3
As we can see, without this PR, we couldn't even build ffms2 as a shared library on ubuntu when ffmpeg was installed with a specific prefix (thought it was working properly on macOS and Windows (msys2)).