One of the plugins in Avidemux2 won't compile with clang-3.x on OSX at this point.
I made a short gist of the error, which might be an upstream problem.
But wait you say, it's upstream.
I know, but maybe it's an easy workaround for us.
Ok here is the error: Is it funny mangle? Is it the ASM_CONST=0 in
static long int FUNNY_MANGLE(_l_src_pitch) ASM_CONST =0;