I'm looking for the whole source code of all the C standard libraries. That said, I'm looking for the source code of stdio.h, stdlib.h, string.h, math.h, etc... I would like to see how they were created. I think that it depends from platform to platform, but Linux or Windows one will be welcomed.
PJ Plauger wrote a book about the standard C library. Includes references from the (now dated) standard, and source code.