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, 6 insertions, 4 deletions

diff --git a/Include/ceval.h b/Include/ceval.h
index 9481506..6db0818 100644
--- a/Include/ceval.h
+++ b/Include/ceval.h
@@ -18,9 +18,11 @@ PyAPI_FUNC(PyObject *) PyEval_CallObject(PyObject *, PyObject *);
 #define PyEval_CallObject(func,arg) \
         PyEval_CallObjectWithKeywords(func, arg, (PyObject *)NULL)
 
-PyAPI_FUNC(PyObject *) PyEval_CallFunction(PyObject *obj, char *format, ...);
+PyAPI_FUNC(PyObject *) PyEval_CallFunction(PyObject *obj,
+                                           const char *format, ...);
 PyAPI_FUNC(PyObject *) PyEval_CallMethod(PyObject *obj,
-                                        char *methodname, char *format, ...);
+                                         const char *methodname,
+                                         const char *format, ...);
 
 PyAPI_FUNC(void) PyEval_SetProfile(Py_tracefunc, PyObject *);
 PyAPI_FUNC(void) PyEval_SetTrace(Py_tracefunc, PyObject *);
@@ -60,8 +62,8 @@ PyAPI_DATA(int) _Py_CheckRecursionLimit;
 #  define _Py_MakeRecCheck(x)  (++(x) > _Py_CheckRecursionLimit)
 #endif
 
-PyAPI_FUNC(char *) PyEval_GetFuncName(PyObject *);
-PyAPI_FUNC(char *) PyEval_GetFuncDesc(PyObject *);
+PyAPI_FUNC(const char *) PyEval_GetFuncName(PyObject *);
+PyAPI_FUNC(const char *) PyEval_GetFuncDesc(PyObject *);
 
 PyAPI_FUNC(PyObject *) PyEval_GetCallStats(PyObject *);
 PyAPI_FUNC(PyObject *) PyEval_EvalFrame(struct _frame *);