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 *.

1 files changed, 4 insertions, 4 deletions

diff --git a/Objects/methodobject.c b/Objects/methodobject.c
index 5818616..3a205f5 100644
--- a/Objects/methodobject.c
+++ b/Objects/methodobject.c
@@ -132,7 +132,7 @@ meth_dealloc(PyCFunctionObject *m)
 static PyObject *
 meth_get__doc__(PyCFunctionObject *m, void *closure)
 {
-	char *doc = m->m_ml->ml_doc;
+	const char *doc = m->m_ml->ml_doc;
 
 	if (doc != NULL)
 		return PyString_FromString(doc);
@@ -311,13 +311,13 @@ listmethodchain(PyMethodChain *chain)
 /* Find a method in a method chain */
 
 PyObject *
-Py_FindMethodInChain(PyMethodChain *chain, PyObject *self, char *name)
+Py_FindMethodInChain(PyMethodChain *chain, PyObject *self, const char *name)
 {
 	if (name[0] == '_' && name[1] == '_') {
 		if (strcmp(name, "__methods__") == 0)
 			return listmethodchain(chain);
 		if (strcmp(name, "__doc__") == 0) {
-			char *doc = self->ob_type->tp_doc;
+			const char *doc = self->ob_type->tp_doc;
 			if (doc != NULL)
 				return PyString_FromString(doc);
 		}
@@ -339,7 +339,7 @@ Py_FindMethodInChain(PyMethodChain *chain, PyObject *self, char *name)
 /* Find a method in a single method list */
 
 PyObject *
-Py_FindMethod(PyMethodDef *methods, PyObject *self, char *name)
+Py_FindMethod(PyMethodDef *methods, PyObject *self, const char *name)
 {
 	PyMethodChain chain;
 	chain.methods = methods;