When compiling mplayer svn (r27917) on cygwin compilation fails with the following error: stream/cache2.o:cache2.c:(.text+0x572): undefined reference to `__beginthread' stream/cache2.o:cache2.c:(.text+0xf23): undefined reference to `__endthread' I've tracked this down to r27804 where the use of these funtions was introduced. But it seems they don't exist on cygwin... After reverting the changes from r27804 the compilation succeeds.