链接器链接正确的文件，但无法找到符号

Question

I'm playing around with libav*. I wrote a simple program to open a file and output how many streams it has in it, just something to get my feet wet. I link with avformat, avcodec and avutil. However, I get undefined reference errors from ld. The undefined references are all libav* functions. I took a look at the verbose linker output and see that it is linking with the correct libraries and I used objdump to confirm that the symbols are located in the library, but ld still throws undefined reference errors.

Answer 1

Are you programming in C++? If that's the case, you need to add 'extern "C" {...};'.

Take a look here: Why do we need extern "C"{ #include <foo.h> } in C++? and note that libav* is written in C.