[Python-Dev] buildin vs. shared modules

[Thomas Heller]

Alex Martelli <aleaxit at yahoo.com> writes:

> On Tuesday 21 October 2003 06:26 pm, Thomas Heller wrote:
>    ...
>> Yet another approach would be to use the delay_load feature of MSVC, it
>> allows dynamic loading of the dlls at runtime, ideally without changing
>> the source code.
>>
>> So far I have never tried that, does anyone know if this really works?
>
> Yes, back when I was in think3 we experimented extensively as soon as
> it was available (still in a beta of -- I don't recall if it was the SDK or 
> VStudio 6), and except for a few specific libraries that gave some trouble
> (MSVCRT.DLL and the MFC one, only -- I think because they did
> something to the memory allocation mechanisms, MSVCRT having it
> and MFC changing it -- perhaps it was because we were ALSO using
> other memory-related tools in DLL's, e.g. leak-detectors), it always worked 
> smoothly and "spread" the load, making the app startup faster.  So we
> set the two DLL's that gave us trouble for load and startup and the rest
> for delayed load and lived happily ever after (I don't even recall exactly
> HOW we did that, it WAS years ago...).

After installing MSVC6 on a win98 machine, where I could rename
wsock32.dll away (which was not possible on XP due to file system
protection), I was able to change socketmodule.c to use delay loading of
the winsock dll.  I had to wrap up the WSAStartup() call inside a 
__try {} __except {} block to catch the exception thrown.

With this change, _socket (and maybe also select) could then also be
converted into builtin modules.

Guido, what do you think?

Thomas

PS: Here's the exception raised when loading of wsock32.dll fails:
>>> import _socket
Traceback (most recent call last):
  File "<stdin>", line1m in ?
ImportError: WSAStartup failed: error code -1066598274

and here's the tiny patch:

Index: socketmodule.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Modules/socketmodule.c,v
retrieving revision 1.271.6.5
diff -c -r1.271.6.5 socketmodule.c
*** socketmodule.c	20 Oct 2003 14:34:47 -0000	1.271.6.5
--- socketmodule.c	21 Oct 2003 18:21:39 -0000
***************
*** 3381,3387 ****
  	WSADATA WSAData;
  	int ret;
  	char buf[100];
! 	ret = WSAStartup(0x0101, &WSAData);
  	switch (ret) {
  	case 0:	/* No error */
  		Py_AtExit(os_cleanup);
--- 3381,3391 ----
  	WSADATA WSAData;
  	int ret;
  	char buf[100];
! 	__try {
! 		ret = WSAStartup(0x0101, &WSAData);
! 	} __except (ret = GetExceptionCode(), EXCEPTION_EXECUTE_HANDLER) {
! 		;
! 	}
  	switch (ret) {
  	case 0:	/* No error */
  		Py_AtExit(os_cleanup);