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/Modules/bz2module.c b/Modules/bz2module.c
index af67ff1..db93675 100644
--- a/Modules/bz2module.c
+++ b/Modules/bz2module.c
@@ -1285,8 +1285,8 @@ static PyMemberDef BZ2File_members[] = {
 static int
 BZ2File_init(BZ2FileObject *self, PyObject *args, PyObject *kwargs)
 {
-	static char *kwlist[] = {"filename", "mode", "buffering",
-				 "compresslevel", 0};
+	static const char *kwlist[] = {"filename", "mode", "buffering",
+                                       "compresslevel", 0};
 	PyObject *name;
 	char *mode = "r";
 	int buffering = -1;
@@ -1674,7 +1674,7 @@ BZ2Comp_init(BZ2CompObject *self, PyObject *args, PyObject *kwargs)
 {
 	int compresslevel = 9;
 	int bzerror;
-	static char *kwlist[] = {"compresslevel", 0};
+	static const char *kwlist[] = {"compresslevel", 0};
 
 	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|i:BZ2Compressor",
 					 kwlist, &compresslevel))
@@ -2019,7 +2019,7 @@ bz2_compress(PyObject *self, PyObject *args, PyObject *kwargs)
 	bz_stream _bzs;
 	bz_stream *bzs = &_bzs;
 	int bzerror;
-	static char *kwlist[] = {"data", "compresslevel", 0};
+	static const char *kwlist[] = {"data", "compresslevel", 0};
 
 	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "s#|i",
 					 kwlist, &data, &datasize,