Most of these can be backported.

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 *.

evaluating keyword arguments.

(fixes bug #1119418)

commit a yelp about a noted flaw the error messages for METH_KEYWORDS
functions under some circumstances.

numbers in PyLong_AsLongLong, and update test suite accordingly.
Backported to 2.4.

Backported to 2.4.

[ 991812 ] PyArg_ParseTuple can miss errors with warnings as exceptions

as suggested in the report.

This is definitely a 2.3 candidate (as are most of the checkins I've
made in the last month...)

PyArg_VaParse().

Closes patch #550732.  Thanks Greg Chapman.

changes stay.

New functions:
  unsigned long PyInt_AsUnsignedLongMask(PyObject *);
  unsigned PY_LONG_LONG) PyInt_AsUnsignedLongLongMask(PyObject *);
  unsigned long PyLong_AsUnsignedLongMask(PyObject *);
  unsigned PY_LONG_LONG) PyLong_AsUnsignedLongLongMask(PyObject *);

New and changed format codes:

b unsigned char 0..UCHAR_MAX
B unsigned char none **
h unsigned short 0..USHRT_MAX
H unsigned short none **
i int INT_MIN..INT_MAX
I * unsigned int 0..UINT_MAX
l long LONG_MIN..LONG_MAX
k * unsigned long none
L long long LLONG_MIN..LLONG_MAX
K * unsigned long long none

Notes:

* New format codes.

** Changed from previous "range-and-a-half" to "none"; the
range-and-a-half checking wasn't particularly useful.

New test test_getargs2.py, to verify all this.

instead of raising a TypeError.  Closes #660144 (again).

Calling PyInt_AsLong() on a float truncates it which is almost never
the desired behavior.  This closes SF bug #660144.

the --disable-unicode build doesn't complain about an
unused variable.

Bugfix candidate.

going through the buffer interface API.

Added tests for this to the _testcapi module and updated docs.

use wrappers on all platforms, to make this as consistent as possible x-
platform (in particular, make sure there's at least one \0 byte in
the output buffer).  Also document more of the truth about what these do.

getargs.c, seterror():  Three computations of remaining buffer size were
backwards, thus telling PyOS_snprintf the buffer is larger than it
actually is.  This matters a lot now that PyOS_snprintf ensures there's a
trailing \0 byte (because it didn't get the truth about the buffer size,
it was storing \0 beyond the true end of the buffer).

sysmodule.c, mywrite():  Simplify, now that PyOS_vsnprintf guarantees to
produce a \0 byte.

vgetargskeywords():  Now that this routine is checking for bad input
(rather than dump core in some cases), some bad calls are raising errors
that previously "worked".  This patch makes the error strings more
revealing, and changes the exceptions from SystemError to RuntimeError
(under the theory that SystemError is more of a "can't happen!" assert-
like thing, and so inappropriate for bad arguments to a public C API
function).

Also change all the helper functions to pass along the size of the
msgbuf and use PyOS_snprintf() when writing into the buffer.

seterror() uses a char array and a pointer to the current position in
that array.  Use snprintf() and compute the amount of space left in
the buffer based on the current pointer position.

+ Squash another potential buffer overrun.
+ Simplify the keyword-arg loop by decrementing the count of keywords
  remaining instead of incrementing Yet Another Variable; also break
  out early if the number of keyword args remaining hits 0.

Since I hit the function's closing curly brace with this patch, that's
enough of this for now <wink>.

we're ensuring that's true during the format parse, get rid of nkwlist.

the format, instead of waiting until after we can overindex it by
mistake.

this routine will report an error now when it didn't before, but, if so,
it's a legitimate error that should never have been suppressed.

dict API everywhere on it instead of sometimes using the slower mapping
API.

The "need" for this was probably removed by an earlier patch that stopped
the loop right before it from passing NULL to a dict lookup routine.
I still haven't convinced myself that the next loop is correct, so am
leaving the next mysterious PyErr_Clear() call in for now.

+ Generally test nkeywords against 0 instead of keywords against NULL
  (saves a little work if an empty keywords dict is passed, and is
  conceptually more on-target regardless).
+ When a call erroneously specifies a keyword argument both by position
  and by keyword name:
    - It was easy to provoke this routine into an internal buffer overrun
      by using a long argument name.  Now uses PyErr_format instead (which
      computes a safe buffer size).
    - Improved the error msg.

+ Got rid of now-redundant dict typecheck.
+ Renamed nkwds to nkwlist.  Now all the "counting" vrbls have names
  related to the things they're counting in an obvious way.

+ Renamed argslen to nargs.
+ Renamed kwlen to nkeywords.  This one was especially confusing because
  kwlen wasn't the length of the kwlist argument, but of the keywords
  argument.

+ Removed now-redundant tuple typecheck.
+ Renamed "tplen" local to "argslen" (it's the length of the "args"
  argument; I suppose "tp" was for "Tim Peters should rename me
  someday <wink>).

introduced this bug just a little while ago, when *adding* internal error
checks).

vgetargskeywords:  Rewrote the section that crawls over the format string.
+ Added block comment so it won't take the next person 15 minutes to
  reverse-engineer what it's doing.
+ Lined up the "else" clauses.
+ Rearranged the ifs in decreasing order of likelihood (for speed).

and raise an error if they're insane.
vgetargskeywords:  the same, except that since this is an internal routine,
just assert that the arguments are sane.

the kwlist vector whenever there was a mix of positional and keyword
arguments, and the number of positional arguments exceeded the length
of the kwlist vector.  If there was just one more positional arg than
keyword, the kwlist-terminating NULL got passed to PyMapping_HasKeyString,
which set an internal error that vgetargskeywords() then squashed (but
it's impossible to say whether it knew it was masking an error).  If
more than one more positional argument, it went on to pass random trash
to PyMapping_HasKeyString, which is why the example at the start
happened to kill the process.

Pure bugfix candidate.

removing useless obfuscation.