For ctypes to compile with the SUN's C compiler, there is quite a bit of 
tricky asm code which needs to be ported (and tested).  Most of that is 
in libffi and that library is only supported with gcc, it seems.  But 
that is not mentioned explicitly anywhere either, see 
<http://sources.redhat.com/libffi/>.

In any case, the _ctypes module does not compile with SUN C in the 
current situation.  And it is not obvious why.  Making that clear with 
some message that ctypes (rather _ctypes) requires gcc would help and 
might be sufficient.

However, leaving the _ctypes module out altogether would be better. Just 
like other modules which have environment-specific dependencies, for 
example _tkinter.  I'll take a look how that is handled.

/Jean