The exp10 function is a GNU extension, as the man page acknowledges. The exp10(3) man page (available if you install the "cygwin-doc" package) doesn't mention that you need to compile with "-D_GNU_SOURCE" to use it. It seems to be inordinately difficult to find this information.
The corresponding GNU man page, for example exp10(3) on Ubuntu, says: SYNOPSIS #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <math.h> I suggest adding similar wording to the Cygwin/newlib man pages for functions that require it. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple