g++ Linking Error on Mac while compiling FFMPEG
- by Saptarshi Biswas
g++ on Snow Leopard is throwing linking errors on the following piece of code
test.cpp
#include <iostream>
using namespace std;
#include <libavcodec/avcodec.h> // required headers
#include <libavformat/avformat.h>
int main(int argc, char**argv) {
av_register_all(); // offending library call
return 0;
}
When I try to compile this using the following command
g++ test.cpp -I/usr/local/include -L/usr/local/lib \
-lavcodec -lavformat -lavutil -lz -lm -o test
I get the error
Undefined symbols:
"av_register_all()", referenced from:
_main in ccUD1ueX.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
Interestingly, if I have an equivalent c code,
test.c
#include <stdio.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
int main(int argc, char**argv) {
av_register_all();
return 0;
}
gcc compiles it just fine
gcc test.c -I/usr/local/include -L/usr/local/lib \
-lavcodec -lavformat -lavutil -lz -lm -o test
I am using Mac OS X 10.6.5
$ g++ --version
i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664)
$ gcc --version
i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664)
FFMPEG's libavcodec, libavformat etc. are C libraries and I have built them on my machine like thus:
./configure --enable-gpl --enable-pthreads --enable-shared \
--disable-doc --enable-libx264
make && sudo make install
As one would expect, libavformat indeed contains the symbol av_register_all
$ nm /usr/local/lib/libavformat.a | grep av_register_all
0000000000000000 T _av_register_all
00000000000089b0 S _av_register_all.eh
I am inclined to believe g++ and gcc have different views of the libraries on my machine. g++ is not able to pick up the right libraries. Any clue?
