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I am trying to build osg v 3.4 following the github readme, however i get the following compilation error after on the make VERBOSE=1 step:

[ 94%] Linking CXX shared module ../../../lib/osgPlugins-3.4.0/osgdb_ffmpeg.so
cd /home/workdir/osg_tst/osg/build/src/osgPlugins/ffmpeg && /usr/local/bin/cmake -E cmake_link_script CMakeFiles/osgdb_ffmpeg.dir/link.txt --verbose=1
/usr/local/bin/c++ -fPIC  -Wall -Wparentheses -Wno-long-long -Wno-import -pedantic -Wreturn-type -Wmissing-braces -Wunknown-pragmas -Wunused -Wno-deprecated-declarations -O3 -DNDEBUG -shared  -o ../../../lib/osgPlugins-3.4.0/osgdb_ffmpeg.so CMakeFiles/osgdb_ffmpeg.dir/FFmpegClocks.o CMakeFiles/osgdb_ffmpeg.dir/FFmpegDecoderAudio.o CMakeFiles/osgdb_ffmpeg.dir/FFmpegDecoder.o CMakeFiles/osgdb_ffmpeg.dir/FFmpegDecoderVideo.o CMakeFiles/osgdb_ffmpeg.dir/FFmpegImageStream.o CMakeFiles/osgdb_ffmpeg.dir/FFmpegAudioStream.o CMakeFiles/osgdb_ffmpeg.dir/FFmpegParameters.o CMakeFiles/osgdb_ffmpeg.dir/ReaderWriterFFmpeg.o  -Wl,-rpath,/home/workdir/osg_tst/osg/build/lib: ../../../lib/libosgDB.so.3.4.0 ../../../lib/libosgUtil.so.3.4.0 -Wl,-Bstatic -lavformat -lavdevice -lavcodec -lavutil -lswscale -lswresample -Wl,-Bdynamic ../../../lib/libosg.so.3.4.0 ../../../lib/libOpenThreads.so.3.3.0 -lpthread -lm -lrt -ldl -lz -lGL 
/usr/bin/ld: /usr/local/lib/gcc/x86_64-linux-gnu/12.2.0/../../../libavformat.a(allformats.o): relocation R_X86_64_32 against symbol `ff_a64_muxer' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: /usr/local/lib/gcc/x86_64-linux-gnu/12.2.0/../../../libavformat.a(amr.o): relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: /usr/local/lib/gcc/x86_64-linux-gnu/12.2.0/../../../libavformat.a(anm.o): relocation R_X86_64_32 against `.rodata.str1.1' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: /usr/local/lib/gcc/x86_64-linux-gnu/12.2.0/../../../libavformat.a(apc.o): relocation R_X86_64_32 against `.rodata.str1.1' can not be used when making a shared object; recompile with -fPIC
.
.
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collect2: error: ld returned 1 exit status
make[2]: *** [src/osgPlugins/ffmpeg/CMakeFiles/osgdb_ffmpeg.dir/build.make:224: lib/osgPlugins-3.4.0/osgdb_ffmpeg.so] Error 1
make[2]: Leaving directory '/home/workdir/osg_tst/osg/build'
make[1]: *** [CMakeFiles/Makefile2:5205: src/osgPlugins/ffmpeg/CMakeFiles/osgdb_ffmpeg.dir/all] Error 2
make[1]: Leaving directory '/home/workdir/osg_tst/osg/build'
make: *** [Makefile:136: all] Error 2

The list of error goes on, but i am only showing the first three for clarity, as they all match the same error.

The error recommends using the -fPIC option, however it is clearly already in use in the command displayed.

From the gcc documentation It should have something to do with the architecture used, but the project is also already in 64 bit, as is my linux architecture in x86_64, so what am i missing here?

Corentin Salomon
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  • Why `-Wl,-Bstatic`? If it's something cmake generates by default, then it's a bug in the build script. Static libraries cannot be expected to be position-independent. – n. m. could be an AI Mar 22 '23 at 15:25

1 Answers1

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The -fPIC problem isn't with the project you're compiling, but with the ffmpeg binaries which you are linking against. Note that the compiler error references /usr/local/lib/gcc/x86_64-linux-gnu/12.2.0/../../../libavformat.a, which is your system installation of libavformat, part of the ffmpeg project.

I'd recommend building ffmpeg from source by following the instructions here. If you pass --enable-pic to the configure script, then it will be compiled with the -fPIC flag, enabling you to link against it without error.

TartanLlama
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  • Hello, thank you for your answer, it was indeed coming from my ffmpeg installation, i also add to use these flags on configure command before rebuildint it: --enable-pic --enable-shared – Corentin Salomon Mar 24 '23 at 10:36