I emailed you code - for libx.c, hello.c, test_x11.c and test_lib2d_x11.c; I also placed code for these four files in ~mcbryan/5229/hw4 in the lab. I am not certain that these are exactly the same.
The files in the lab are compiled successfully and work - so I suggest that you use those over the ones I emailed. Since email changes spacing, tabs, line breaks etc it is hard to diff the files to see if they are identical. So if you are having problems and are using the emailed files, then you might look at using the online files.