I wasn't aware that Windows has a process (message) queue. So far, I was under the impression that for a message queue you always needed a window handle.
Um. I get a little fuzzy with my terminology. Threads can(*) have message queues, not processes. Of course, in a single threaded process, the two are (roughly) equivalent.
(*)From PostThreadMessage(): "The system creates a thread's message queue when the thread makes its first call to one of the User or GDI functions.".
In Perl, this (probably) occurs when Win32_create_message_window() is called:
## win32.c
HWND
win32_create_message_window()
{
/* "message-only" windows have been implemented in Windows 2000 an
+d later.
* On earlier versions we'll continue to post messages to a specif
+ic
* thread and use hwnd==NULL. This is brittle when either an embe
+dding
* application or an XS module is also posting messages to hwnd=NU
+LL
* because once removed from the queue they cannot be delivered to
+ the
* "right" place with DispatchMessage() anymore, as there is no Wi
+ndowProc
* if there is no window handle.
*/
if (!IsWin2000())
return NULL;
return CreateWindow("Static", "", 0, 0, 0, 0, 0, HWND_MESSAGE, 0,
+0, NULL);
}
See also win32_kill() in the same file.
If you use the fork emulation, to start a non-perl, child process, then a thread is spawned to act as a 'placeholder' for the actual process. This then waits for the alien process to terminate and so can (could?) post (raise) a SIGCHLD to the main or spawning thread. The problem is that signals sent to the child pseudo-process' pseudo-pid do not necessarially reflect the state of, or affect, the real alien process. And that's where the emulation falls down.
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In the absence of evidence, opinion is indistinguishable from prejudice.
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