[Python-checkins] r46642 - in python/trunk: Lib/socket.py Lib/struct.py Lib/test/test_socket.py Lib/test/test_struct.py Modules/_struct.c Modules/socketmodule.c

["Martin v. Löwis"]

Thomas Wouters wrote:
> Martin, any comments about the availability of ssize_t and the use of
> Py_ssize_t instead?

In general, return values should be stored in a variable of the same
type as the return type of the function being called. Single Unix 2
documents recv as

  ssize_t recv(int socket, void *buffer, size_t length, int flags);

so it is safe to use ssize_t on all systems conforming to Single
Unix. OTOH, WinSock declares recv as

  int recv(SOCKET s, char FAR* buf, int len, int flags);

So apparently, WinSock2 is limited to 2GiB of data per receive call.

socketmodule currently also limits the size of recv buffers to 2GiB
(the entire socket module isn't Py_ssize_t-clean). So the code was
actually correct before the patch.

If ssize_t variables are used, that must be conditional on the return
type of recv actually being ssize_t. That, in turn, might be difficult
to determine; HAVE_SSIZE_T is probably a good-enough approximation.

If the patch is reverted, a cast to (int) could be added, along with
a comment that this shouldn't truncate, as recv shouldn't return a
value larger than the length being passed in.

Regards,
Martin