Is there a specification on how the FILE macro will be expanded if it is in a .h? So if I #define MYFILE __FILE__ in foo.h and foo.c #includes "foo.h" void main(){ printf("%s",MYFILE); .... does this output foo.h or foo.c? (Yes I realize this is a stupid example) Sorry for what should be a simple question. The documentation on the web seems conflicting. For what it is worth VS2008 comes back as foo.c which is what I would expect....I think. I am just trying to confirm if this is defined behavior.