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).
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>.
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.
