This blog post was about Compiling Sean Eddy’s COVE suite on Mac OS X > 10.7
For the basic problem and solution refer here:
http://stackoverflow.com/questions/7376566/can-an-ansi-c-compliant-implementation-include-additional-functions-in-its-stand
To fix the problem and compile the suite, add this in the COVE Makefile:
MDEFS = -D_POSIX_C_SOURCE=200112L