It looks like the defaults for ccompiler.executables that are set in compiler-specific sublcasses like UnixCCompiler are always overridden by customize_compiler in sysconfig.py. For example, in UnixCcompiler the value for executables['compiler'] is ["cc"], but this will never be used because comtomize_compiler invariably grabs the compiler value out of the Python Makefile and uses that. Should customize_compiler be reorganized a bit so that defaults are actually used if customize_compiler comes up empty-handed for certain values? Next, it looks like customize_compiler is really a method of UnixCcompiler disguised as an independent function. Would it make sense for Ccompiler to have an abstract method, "customize", and to move the current customize_compiler function into UnixCcompiler? On the topic of include directories, would it make sense to add a "sysinclude_dirs" option to the Extension class in order separate out the two different uses that include_dirs currently plays in setup.py scripts? -- Yorick