Hi again, As a follow up to my last posting, I have found a not very elegant workaround which consists in modifying the appropriate compiler flags in the compiler's compiler_so list. These ultimately come from Python's make and include files via the function "customize_compiler" in "distutils.sysconfig". Is there any convenient way of altering these flags between calls to "setup" which would avoid having to change or extend the distutils code? Any help would be appreciated. Martin.