Linker errors when building a simple c++ program with ffmpeg - c++

Question

I have this c++ program:
#include <iostream>
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
}
namespace hrean::ffmpeg
{
namespace detail
{
}//namespace detail
void testFFmpeg()
{
AVFormatContext *avFormatContext = avformat_alloc_context();
//I can comment out the rest of the function, the error is the same
} //testFFmpeg()
} //namespace hrean::ffmpeg
int main(int argc, char **argv)
{
try
{
hrean::ffmpeg::testFFmpeg();
}
catch(const std::runtime_error& e)
{
std::cerr << "Error! " << e.what() << '\n';
return -1;
}
catch(...)
{
std::cerr << "Unknown error\n";
return -1;
}
return 0;
}
The CMakeLists.txt for this is:
cmake_minimum_required(VERSION 3.13)
project(hrean)
add_subdirectory(lib/ffmpeg-module)
message("[temp] FFMPEG_INCLUDE_DIRS = ${FFMPEG_INCLUDE_DIRS}")
message("[temp] FFMPEG_LIBRARIES = ${FFMPEG_LIBRARIES}")
add_executable(hrean-app src/main.cpp)
target_include_directories(hrean-app PUBLIC ${FFMPEG_INCLUDE_DIRS})
target_link_libraries(hrean-app PUBLIC ${FFMPEG_LIBRARIES})
The CMakeLists.txt for lib/ffmpeg-module contains only
find_package(FFmpeg REQUIRED MODULE)
The CMake output is:
-- The C compiler identification is GNU 11.3.0
-- The CXX compiler identification is GNU 11.3.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PkgConfig: /usr/bin/pkg-config (found version "0.29.2")
-- Checking for module 'libavcodec'
-- Found libavcodec, version 60.2.100
-- Checking for module 'libavformat'
-- Found libavformat, version 60.2.100
-- Checking for module 'libavdevice'
-- Found libavdevice, version 60.0.100
-- Checking for module 'libavutil'
-- Found libavutil, version 58.1.100
-- Checking for module 'libavfilter'
-- Found libavfilter, version 9.1.100
-- Checking for module 'libswscale'
-- Found libswscale, version 7.0.100
-- Checking for module 'libpostproc'
-- Found libpostproc, version 57.0.100
-- Checking for module 'libswresample'
-- Found libswresample, version 4.9.100
-- Found FFmpeg: /home/serban/ffmpeg_build/lib/libavcodec.a;/home/serban/ffmpeg_build/lib/libavformat.a;/home/serban/ffmpeg_build/lib/libavutil.a
[temp] FFMPEG_INCLUDE_DIRS = /home/serban/ffmpeg_build/include
[temp] FFMPEG_LIBRARIES = /home/serban/ffmpeg_build/lib/libavcodec.a;/home/serban/ffmpeg_build/lib/libavformat.a;/home/serban/ffmpeg_build/lib/libavutil.a
-- Configuring done
-- Generating done
-- Build files have been written to: /home/serban/Work/hrean/build
When I run make, I get the following errors. The problem is, this worked perfectly yesterday and I changed nothing. I create a new Ubuntu virtual machine, everything fresh and I still get the same problem. The output is 1000+ lines long, here is some of it:
[ 50%] Building CXX object CMakeFiles/hrean-app.dir/src/main.cpp.o
[100%] Linking CXX executable hrean-app
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(amvenc.o): in function `amv_write_packet':
/home/serban/ffmpeg/libavformat/amvenc.c:356: undefined reference to `av_packet_unref'
/usr/bin/ld: /home/serban/ffmpeg/libavformat/amvenc.c:357: undefined reference to `av_packet_ref'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(amvenc.o): in function `amv_deinit':
/home/serban/ffmpeg/libavformat/amvenc.c:209: undefined reference to `av_packet_free'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(amvenc.o): in function `amv_init':
/home/serban/ffmpeg/libavformat/amvenc.c:111: undefined reference to `avcodec_get_name'
/usr/bin/ld: /home/serban/ffmpeg/libavformat/amvenc.c:117: undefined reference to `avcodec_get_name'
/usr/bin/ld: /home/serban/ffmpeg/libavformat/amvenc.c:188: undefined reference to `av_new_packet'
/usr/bin/ld: /home/serban/ffmpeg/libavformat/amvenc.c:196: undefined reference to `av_packet_alloc'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `asf_read_close':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1413: undefined reference to `av_packet_free'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `asf_read_single_payload':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1119: undefined reference to `av_new_packet'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `asf_read_packet':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1388: undefined reference to `av_packet_move_ref'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `reset_packet':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1030: undefined reference to `av_packet_unref'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `asf_deinterleave':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1313: undefined reference to `av_packet_unref'
/usr/bin/ld: /home/serban/ffmpeg/libavformat/asfdec_o.c:1314: undefined reference to `av_packet_from_data'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `asf_read_replicated_data':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1043: undefined reference to `av_new_packet'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `asf_read_timestamp':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1463: undefined reference to `av_packet_alloc'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `reset_packet':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1030: undefined reference to `av_packet_unref'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(asfdec_o.o): in function `asf_read_timestamp':
/home/serban/ffmpeg/libavformat/asfdec_o.c:1512: undefined reference to `av_packet_unref'
Any idea how to debug this?
Later edit:
This is the find script I am using: FindFFmpeg.cmake
I changed the way I link to the libraries, this way causes the least amount of errors:
set(ORDERED_FFMPEG_LIBRARIES ${AVFORMAT_LIBRARIES} ${AVCODEC_LIBRARIES} ${AVUTIL_LIBRARIES})
message("[temp] ORDERED_FFMPEG_LIBRARIES=${ORDERED_FFMPEG_LIBRARIES}")
add_executable(hrean-app src/main.cpp)
target_include_directories(hrean-app PUBLIC ${FFMPEG_INCLUDE_DIRS})
target_link_libraries(hrean-app PUBLIC ${ORDERED_FFMPEG_LIBRARIES})
The errors are similar, but they seem to point to other locations:
[100%] Linking CXX executable hrean-app
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(mov.o): in function `mov_read_cmov':
/home/serban/ffmpeg/libavformat/mov.c:5578: undefined reference to `uncompress'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(swfdec.o): in function `swf_read_packet':
/home/serban/ffmpeg/libavformat/swfdec.c:393: undefined reference to `uncompress'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(swfdec.o): in function `swf_read_header':
/home/serban/ffmpeg/libavformat/swfdec.c:161: undefined reference to `inflateInit_'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(swfdec.o): in function `zlib_refill':
/home/serban/ffmpeg/libavformat/swfdec.c:134: undefined reference to `inflate'
/usr/bin/ld: /home/serban/ffmpeg_build/lib/libavformat.a(swfdec.o): in function `swf_read_close':
/home/serban/ffmpeg/libavformat/swfdec.c:557: undefined reference to `inflateEnd'
Do I have to link to anything else?
Regards,
Serban

Answer 1

Not far ago ffmpeg became depended off zlib.
See this include.
You may build ffmpeg without zlib
Or you may install zlib and link with it:
find_library(ZLIB NAMES z zlib REQUIRED)
target_link_libraries(hrean-app PRIVATE ${ZLIB})