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, 44 insertions, 46 deletions

diff --git a/Python/getargs.c b/Python/getargs.c
index df60a86..16f156f 100644
--- a/Python/getargs.c
+++ b/Python/getargs.c
@@ -6,33 +6,33 @@
 #include <ctype.h>
 
 
-int PyArg_Parse(PyObject *, char *, ...);
-int PyArg_ParseTuple(PyObject *, char *, ...);
-int PyArg_VaParse(PyObject *, char *, va_list);
+int PyArg_Parse(PyObject *, const char *, ...);
+int PyArg_ParseTuple(PyObject *, const char *, ...);
+int PyArg_VaParse(PyObject *, const char *, va_list);
 
 int PyArg_ParseTupleAndKeywords(PyObject *, PyObject *,
-				char *, char **, ...);
+				const char *, const char **, ...);
 int PyArg_VaParseTupleAndKeywords(PyObject *, PyObject *,
-				char *, char **, va_list);
+				const char *, const char **, va_list);
 
 
 /* Forward */
-static int vgetargs1(PyObject *, char *, va_list *, int);
-static void seterror(int, char *, int *, char *, char *);
-static char *convertitem(PyObject *, char **, va_list *, int *, char *, 
+static int vgetargs1(PyObject *, const char *, va_list *, int);
+static void seterror(int, const char *, int *, const char *, const char *);
+static char *convertitem(PyObject *, const char **, va_list *, int *, char *, 
 			 size_t, PyObject **);
-static char *converttuple(PyObject *, char **, va_list *,
+static char *converttuple(PyObject *, const char **, va_list *,
 			  int *, char *, size_t, int, PyObject **);
-static char *convertsimple(PyObject *, char **, va_list *, char *,
+static char *convertsimple(PyObject *, const char **, va_list *, char *,
 			   size_t, PyObject **);
 static int convertbuffer(PyObject *, void **p, char **);
 
 static int vgetargskeywords(PyObject *, PyObject *,
-			    char *, char **, va_list *);
-static char *skipitem(char **, va_list *);
+			    const char *, const char **, va_list *);
+static char *skipitem(const char **, va_list *);
 
 int
-PyArg_Parse(PyObject *args, char *format, ...)
+PyArg_Parse(PyObject *args, const char *format, ...)
 {
 	int retval;
 	va_list va;
@@ -45,7 +45,7 @@ PyArg_Parse(PyObject *args, char *format, ...)
 
 
 int
-PyArg_ParseTuple(PyObject *args, char *format, ...)
+PyArg_ParseTuple(PyObject *args, const char *format, ...)
 {
 	int retval;
 	va_list va;
@@ -58,7 +58,7 @@ PyArg_ParseTuple(PyObject *args, char *format, ...)
 
 
 int
-PyArg_VaParse(PyObject *args, char *format, va_list va)
+PyArg_VaParse(PyObject *args, const char *format, va_list va)
 {
 	va_list lva;
 
@@ -120,17 +120,17 @@ cleanreturn(int retval, PyObject *freelist)
 
 
 static int
-vgetargs1(PyObject *args, char *format, va_list *p_va, int compat)
+vgetargs1(PyObject *args, const char *format, va_list *p_va, int compat)
 {
 	char msgbuf[256];
 	int levels[32];
-	char *fname = NULL;
-	char *message = NULL;
+	const char *fname = NULL;
+	const char *message = NULL;
 	int min = -1;
 	int max = 0;
 	int level = 0;
 	int endfmt = 0;
-	char *formatsave = format;
+	const char *formatsave = format;
 	int i, len;
 	char *msg;
 	PyObject *freelist = NULL;
@@ -269,7 +269,8 @@ vgetargs1(PyObject *args, char *format, va_list *p_va, int compat)
 
 
 static void
-seterror(int iarg, char *msg, int *levels, char *fname, char *message)
+seterror(int iarg, const char *msg, int *levels, const char *fname,
+         const char *message)
 {
 	char buf[512];
 	int i;
@@ -324,12 +325,12 @@ seterror(int iarg, char *msg, int *levels, char *fname, char *message)
 */
 
 static char *
-converttuple(PyObject *arg, char **p_format, va_list *p_va, int *levels,
+converttuple(PyObject *arg, const char **p_format, va_list *p_va, int *levels,
 	     char *msgbuf, size_t bufsize, int toplevel, PyObject **freelist)
 {
 	int level = 0;
 	int n = 0;
-	char *format = *p_format;
+	const char *format = *p_format;
 	int i;
 	
 	for (;;) {
@@ -392,11 +393,11 @@ converttuple(PyObject *arg, char **p_format, va_list *p_va, int *levels,
 /* Convert a single item. */
 
 static char *
-convertitem(PyObject *arg, char **p_format, va_list *p_va, int *levels,
+convertitem(PyObject *arg, const char **p_format, va_list *p_va, int *levels,
 	    char *msgbuf, size_t bufsize, PyObject **freelist)
 {
 	char *msg;
-	char *format = *p_format;
+	const char *format = *p_format;
 	
 	if (*format == '(' /* ')' */) {
 		format++;
@@ -424,7 +425,7 @@ convertitem(PyObject *arg, char **p_format, va_list *p_va, int *levels,
 /* Format an error message generated by convertsimple(). */
 
 static char *
-converterr(char *expected, PyObject *arg, char *msgbuf, size_t bufsize)
+converterr(const char *expected, PyObject *arg, char *msgbuf, size_t bufsize)
 {
 	assert(expected != NULL);
 	assert(arg != NULL); 
@@ -459,10 +460,10 @@ float_argument_error(PyObject *arg)
 */
 
 static char *
-convertsimple(PyObject *arg, char **p_format, va_list *p_va, char *msgbuf,
-	      size_t bufsize, PyObject **freelist)
+convertsimple(PyObject *arg, const char **p_format, va_list *p_va,
+              char *msgbuf, size_t bufsize, PyObject **freelist)
 {
-	char *format = *p_format;
+	const char *format = *p_format;
 	char c = *format++;
 #ifdef Py_USING_UNICODE
 	PyObject *uarg;
@@ -1134,8 +1135,8 @@ convertbuffer(PyObject *arg, void **p, char **errmsg)
 int
 PyArg_ParseTupleAndKeywords(PyObject *args,
 			    PyObject *keywords,
-			    char *format, 
-			    char **kwlist, ...)
+			    const char *format, 
+			    const char **kwlist, ...)
 {
 	int retval;
 	va_list va;
@@ -1158,9 +1159,9 @@ PyArg_ParseTupleAndKeywords(PyObject *args,
 
 int
 PyArg_VaParseTupleAndKeywords(PyObject *args,
-			    PyObject *keywords,
-			    char *format, 
-			    char **kwlist, va_list va)
+                              PyObject *keywords,
+                              const char *format, 
+                              const char **kwlist, va_list va)
 {
 	int retval;
 	va_list lva;
@@ -1190,16 +1191,16 @@ PyArg_VaParseTupleAndKeywords(PyObject *args,
 
 
 static int
-vgetargskeywords(PyObject *args, PyObject *keywords, char *format,
-	         char **kwlist, va_list *p_va)
+vgetargskeywords(PyObject *args, PyObject *keywords, const char *format,
+	         const char **kwlist, va_list *p_va)
 {
 	char msgbuf[512];
 	int levels[32];
-	char *fname, *message;
+	const char *fname, *message;
 	int min, max;
-	char *formatsave;
+	const char *formatsave;
 	int i, len, nargs, nkeywords;
-	char *msg, **p;
+	const char *msg, **p;
 	PyObject *freelist = NULL;
 
 	assert(args != NULL && PyTuple_Check(args));
@@ -1269,7 +1270,7 @@ vgetargskeywords(PyObject *args, PyObject *keywords, char *format,
 	   keyword parameter in messages */
 	if (nkeywords > 0) {
 		for (i = 0; i < nargs; i++) {
-			char *thiskw = kwlist[i];
+			const char *thiskw = kwlist[i];
 			if (thiskw == NULL)
 				break;
 			if (PyDict_GetItemString(keywords, thiskw)) {
@@ -1402,9 +1403,9 @@ vgetargskeywords(PyObject *args, PyObject *keywords, char *format,
 
 
 static char *
-skipitem(char **p_format, va_list *p_va)
+skipitem(const char **p_format, va_list *p_va)
 {
-	char *format = *p_format;
+        const char *format = *p_format;
 	char c = *format++;
 	
 	switch (c) {
@@ -1518,7 +1519,7 @@ err:
 
 
 int
-PyArg_UnpackTuple(PyObject *args, char *name, int min, int max, ...)
+PyArg_UnpackTuple(PyObject *args, const char *name, int min, int max, ...)
 {
 	int i, l;
 	PyObject **o;
@@ -1583,7 +1584,7 @@ PyArg_UnpackTuple(PyObject *args, char *name, int min, int max, ...)
  * not emtpy, returns 1 otherwise
  */
 int
-_PyArg_NoKeywords(char *funcname, PyObject *kw)
+_PyArg_NoKeywords(const char *funcname, PyObject *kw)
 {
 	if (kw == NULL)
 		return 1;
@@ -1598,6 +1599,3 @@ _PyArg_NoKeywords(char *funcname, PyObject *kw)
 			funcname);
 	return 0;
 }
-
-
-