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• gcc "relocation R_X86_64_PC32 against symbol `ff_M24A'" error when linking statically against ffmpeg on linux

  22 janvier 2016, par YB_Evil

  I am trying to build a JNI shared library which statically links to ffmpeg.

  But at the linking stage, gcc fails with the following error :

  /usr/bin/ld: ./lib_lin64/libswscale.a(swscale.o): relocation R_X86_64_PC32 against symbol `ff_M24A' can not be used when making a shared object; recompile with -fPIC

  I am using the following commands to compile my jni library :

  gcc -I $JAVA_HOME/include -I $JAVA_HOME/include/linux -I ./include -fPIC -c *.c
  

  gcc -shared -Wl,--no-undefined -o libnv_avc_dec.so *.o -Wl,-Bstatic -L./lib_lin64 -lavcodec -lavutil -lswresample -lswscale -Wl,-Bdynamic -lm

  And I only use h264 decoding feature, so I am also building ffmpeg from source with the minimal required feature set. The ./configure command I use is :

  ./configure \
--enable-pic --prefix=ffmpeg-dist \
--disable-debug --enable-version3 --enable-gpl \
--disable-everything --enable-hwaccel=h264_vdpau --enable-hwaccel=h264_vaapi --enable-hwaccel=h264_qsv --enable-hwaccel=h264_mmal \
--enable-decoder=h264 --enable-decoder=h264_vdpau --enable-decoder=h264_crystalhd --enable-decoder=h264_mmal --enable-decoder=h264_qsv \
--disable-iconv --disable-securetransport --disable-xlib --disable-zlib --disable-lzma  --disable-bzlib  --disable-doc --disable-programs --disable-avformat --disable-avfilter --disable-postproc

  So, as I understand, the linker tells me that ffmpeg should be compiled with -fPIC flag in order to make a shared library. But I believe that I’ve already done so by specifying the —enable-pic configure flag. And I am pretty much stuck here because I am not very familiar with autotools, nor with ffmpeg build process in particular.

  If this is the issue of ffmpeg .a libs not being compiled with -fPIC flag, how can i force it ? And if this is not the case, what am i doing wrong and how can i fix this error ?

  Environment details : Ubuntu 14.04.3 64-bit in Virtualbox, gcc 4.8.5 and 5.3 (both give the same results), ffmpeg v.2.8.5

• Unresolved external symbol when linking ffmpeg/avcodec with Visual Studio 2015 ?

  2 décembre 2015, par Ragnar

  I’m trying to build ffmpeg/avcodec library with Visual Studio 2015 and it gives me following linking error :

  allcodecs.obj : error LNK2001: unresolved external symbol ff_h263_vaapi_hwaccel 
  
  allcodecs.obj : error LNK2001: unresolved external symbol ff_h263_vdpau_hwaccel
  
  allcodecs.obj : error LNK2001: unresolved external symbol ff_h263_videotoolbox_hwaccel
  
  ...

  The problem comes from this macro https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/allcodecs.c#L34

  #include "config.h"
  
  #include "avcodec.h"
  
  #include "version.h"
  
  
  
  ...
  
  
  
  #define REGISTER_HWACCEL(X, x)                                      \
  
      {                                                               \
  
          extern AVHWAccel ff_##x##_hwaccel;                          \
  
          if (CONFIG_##X##_HWACCEL)                                   \
  
              av_register_hwaccel(&ff_##x##_hwaccel);                 \
  
      }
  
  
  
  ...
  
  
  
  void avcodec_register_all(void)
  
  {
  
      static int initialized;
  
  
  
      if (initialized)
  
          return;
  
      initialized = 1;
  
  
  
      /* hardware accelerators */
  
      REGISTER_HWACCEL(H263_VAAPI,        h263_vaapi);
  
      REGISTER_HWACCEL(H263_VIDEOTOOLBOX, h263_videotoolbox);
  
      ...

  I don’t understand why do these methods even get declared when my config has them set to 0

  #define CONFIG_H263_VAAPI_HWACCEL 0
  
  #define CONFIG_H263_VDPAU_HWACCEL 0
  
  #define CONFIG_H263_VIDEOTOOLBOX_HWACCEL 0
  
  ...

  Btw it builds OK when I use msys/make tooling.

• build : add Solaris symbol versioning

  7 octobre 2015, par Sean McGovern

  build : add Solaris symbol versioning
  The versioning facility in the Solaris linker differs from Linux in 3 ways :
  1. It does not support globs in linker scripts for
  
  symbol versioning — this is a GNU extension.
  2. The linker argument is ’-M’, instead of ’—version-script’.
  3. It is picky about line endings.
  
  Each symbol or directive must be on a line of it’s own.
  Let’s use make_sunver.pl from GCC to generate a version script that works
  
  correctly with the Solaris linker. It’s function is to correctly expand the
  
  globs in the original generated version script.
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DBH] Makefile
  • [DBH] common.mak
  • [DBH] compat/solaris/make_sunver.pl
  • [DBH] configure