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I am trying to compile a c program for windows and ubuntu to do that i am using mingw but it seems that it cant find the required libraries that gcc can find when i execute this command 

gcc decode_video.c -o dv -lavcodec -lavutil

Everything compiles normally but when i use this 

x86_64-w64-mingw32-gcc decode_video.c -o dv.exe -lavcodec -lavutil

it says that header files arent found

after changing the build command to 

x86_64-w64-mingw32-gcc decode_video.c -o dv.exe -I /usr/include/x86_64-linux-gnu -L /usr/lib/x86_64-linux-gnu -l avcodec -l avutil

it know gives me this error even though the libraries are linked 

/tmp/ccgn1NTi.o:decode_video.c:(.text+0x138): undefined reference to `avcodec_send_packet'

/tmp/ccgn1NTi.o:decode_video.c:(.text+0x192): undefined reference to avcodec_receive_frame' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x33f): undefined reference toav_packet_alloc' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x37d): undefined reference to avcodec_find_decoder' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x3d0): undefined reference toav_parser_init' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x421): undefined reference to avcodec_alloc_context3' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x481): undefined reference toavcodec_open2' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x512): undefined reference to av_frame_alloc' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x5fc): undefined reference toav_parser_parse2' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x6f8): undefined reference to av_parser_close' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x707): undefined reference toavcodec_free_context' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x716): undefined reference to av_frame_free' /tmp/ccgn1NTi.o:decode_video.c:(.text+0x722): undefined reference toav_packet_free' collect2: error: ld returned 1 exit status

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  • What header files? Commented Mar 6, 2020 at 10:06
  • decode_video.c:34:10: fatal error: libavcodec/avcodec.h: No such file or directory #include <libavcodec/avcodec.h> ^~~~~~~~~~~~~~~~~~~~~~ compilation terminated. Commented Mar 6, 2020 at 10:10

1 Answer 1

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Finally, it turned that you tried to link against libraries for an incompatible architecture:

Why can't mingw find libraries that gcc can find?

  • Either compiler are using different default options for the linker.

  • Even with same -L <path> and same LD_LIBRARY_PATH etc., the linker will skip incompatible libraries. In your case, gcc is presumably hosted by x86_64-linux-gnu, whereas x86_64-w64-mingw32-gcc is obviously hosted by x86_64-w64-mingw32. Both are incompatible.

  1. Try adding -I <path> to the compilation where <path> contains libavcodec/avcodec.h. Add more -I if you need more paths. Use -isystem <path> if it's supposed to be system headers. Add -v -H to the compilation to see what include paths are in use. gcc prints: 
    #include "..." search starts here: #include <...> search starts here:

  2. Try adding -L <path> to the link stage where <path> contains the libraries like lib*.a / lib*.so to be linked against. Add -Wl,-v to see which options the compiler driver passes to the GNU linker ld.

  3. Make sure the symbols are in the libraries, e.g. using tools like nm or x86_64-w64-mingw32-nm.

  4. Make sure you are using libraries cross-compiled using the x86_64-w64-mingw32 toolchain.

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7 Comments

this is exactly what i did you can see it in the edited command these directories are for headers and and lib.a locations and it generated that aeerror
pastebin.com/w18A1tsf this is a link to verbose output
Are the symbols in that said libraries?
yes i have checked them and if they werent how would it compile with gcc
@Wajdi Muhtadi : Your aren't trying to use the same libraries, do you? See 4. in my answer. You need libs cross-compiled with x86_64-w64-mingw32 toolchain.
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