Add const to several API functions that take char *. In C++, it's an error to pass a string literal to a char* function without a const_cast(). Rather than require every C++ extension module to put a cast around string literals, fix the API to state the const-ness. I focused on parts of the API where people usually pass literals: PyArg_ParseTuple() and friends, Py_BuildValue(), PyMethodDef, the type slots, etc. Predictably, there were a large set of functions that needed to be fixed as a result of these changes. The most pervasive change was to make the keyword args list passed to PyArg_ParseTupleAndKewords() to be a const char *kwlist[]. One cast was required as a result of the changes: A type object mallocs the memory for its tp_doc slot and later frees it. PyTypeObject says that tp_doc is const char *; but if the type was created by type_new(), we know it is safe to cast to char *.

--- a/Modules/itertoolsmodule.c	Sat Dec 10 17:44:27 2005 +0000
+++ b/Modules/itertoolsmodule.c	Sat Dec 10 18:50:16 2005 +0000
@@ -26,7 +26,7 @@
 static PyObject *
 groupby_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 {
-	static char *kwargs[] = {"iterable", "key", NULL};
+	static const char *kwargs[] = {"iterable", "key", NULL};
 	groupbyobject *gbo;
  	PyObject *it, *keyfunc = Py_None;