I was in the process of building(using make) a tetris game when I got the error message, “unable to initialize SDL_mixer” (error handling message defined in the main.c of this program). Further digging pointed to the error, “Mixer not built with MP3 support” (from the Mix_GetError function). Google search led me here, where someone else had encountered this error while using the SDL2_Mixer in Ubuntu 14.04 LTS x86_64 and had submitted a patch.
I didn’t try using the patch, since I didn’t understand the bug, so I dug a little deeper by taking a look at the SDL_Mixer 1.2 source.
A bit more research and it turns out that this bug was fixed in SDL_mixer 2.0.0 so I stopped here and just used it instead of SDL_mixer 1.2.
I’d like to get back to understanding this bug sometime, for learning purposes.