libnggui.so: undefined reference to ffmpeg functions

[siegLoesch]

During build of netgen v6.2.2304 the link operation for ng/netgen failed (using cmake option: -DUSE_MPEG:BOOL=YES):
/usr/bin/ld: libnggui.so: undefined reference to avcodec_find_encoder' /usr/bin/ld: libnggui.so: undefined reference to avformat_write_header'
/usr/bin/ld: libnggui.so: undefined reference to av_frame_free' /usr/bin/ld: libnggui.so: undefined reference to avcodec_open2'
/usr/bin/ld: libnggui.so: undefined reference to av_interleaved_write_frame' /usr/bin/ld: libnggui.so: undefined reference to avformat_alloc_output_context2'
/usr/bin/ld: libnggui.so: undefined reference to av_frame_make_writable' /usr/bin/ld: libnggui.so: undefined reference to avcodec_send_frame'
/usr/bin/ld: libnggui.so: undefined reference to sws_freeContext' /usr/bin/ld: libnggui.so: undefined reference to av_init_packet'
/usr/bin/ld: libnggui.so: undefined reference to av_dict_free' /usr/bin/ld: libnggui.so: undefined reference to av_packet_rescale_ts'
/usr/bin/ld: libnggui.so: undefined reference to avcodec_get_name' /usr/bin/ld: libnggui.so: undefined reference to sws_scale'
/usr/bin/ld: libnggui.so: undefined reference to avcodec_parameters_from_context' /usr/bin/ld: libnggui.so: undefined reference to av_dump_format'
/usr/bin/ld: libnggui.so: undefined reference to av_write_trailer' /usr/bin/ld: libnggui.so: undefined reference to avformat_new_stream'
/usr/bin/ld: libnggui.so: undefined reference to avcodec_receive_packet' /usr/bin/ld: libnggui.so: undefined reference to av_frame_alloc'
/usr/bin/ld: libnggui.so: undefined reference to av_image_fill_arrays' /usr/bin/ld: libnggui.so: undefined reference to av_frame_get_buffer'
/usr/bin/ld: libnggui.so: undefined reference to avcodec_alloc_context3' /usr/bin/ld: libnggui.so: undefined reference to avcodec_free_context'
/usr/bin/ld: libnggui.so: undefined reference to sws_getContext' /usr/bin/ld: libnggui.so: undefined reference to avformat_free_context'
/usr/bin/ld: libnggui.so: undefined reference to avio_closep' /usr/bin/ld: libnggui.so: undefined reference to avio_open'
collect2: error: ld returned 1 exit status

My solution / workaround was to add ${FFMPEG_LIBRARIES} to the target_link_libraries command inside the CMakeLists.txt at ng directory. I have created a patch for that which is attached here: cmListsNg-ffmpegLibraries.zip. Using that it compiles fine without error.

If there is time please let us know if you agree with that.

Best regards
Siegfried

[drew-parsons]

The undefined references are in libnggui.so not netgen directly. Other optional libraries are processed in the toplevel CMakeLists.txt . Using them as an example, this patch works

Index: netgen/CMakeLists.txt
===================================================================
--- netgen.orig/CMakeLists.txt  2023-11-10 10:33:08.124132623 +0100
+++ netgen/CMakeLists.txt       2023-11-10 10:35:43.421445839 +0100
@@ -438,6 +438,9 @@
     find_package(FFMPEG REQUIRED)
     add_definitions(-DFFMPEG -D__STDC_CONSTANT_MACROS)
     include_directories(${FFMPEG_INCLUDE_DIR})
+    if(USE_GUI)
+        target_link_libraries(nggui INTERFACE ${FFMPEG_LIBRARIES})
+    endif(USE_GUI)
 endif (USE_MPEG)

 #######################################################################

[luzpaz]

@mhochsteger 👆