Q: Why are some ANSI/ISO Standard library functions showing up as undefined, even though I've got an ANSI compiler?
A: It's possible to have a compiler available which accepts ANSI syntax, but not to have ANSI-compatible header files or run-time libraries installed. (In fact, this situation is rather common when using a non-vendor-supplied compiler such as gcc.) See also questions 11.29a, 13.25, and 13.26.