#4942: GHC.ConsoleHandler does not call back application when Close button is
pressed
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Reporter: Amatic | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 7.4.1
Component: GHC API | Version: 6.12.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Windows | Blocking:
Architecture: x86 | Failure: Incorrect result at runtime
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Comment(by fryguybob):
It looks like this behavior is by design, looking in
rts/win32/ConsoleHandler.c:
{{{
#!C
static BOOL WINAPI generic_handler(DWORD dwCtrlType)
{
/* Ultra-simple -- up the counter + signal a switch. */
switch(dwCtrlType) {
case CTRL_CLOSE_EVENT:
/* Don't support the delivery of this event; if we
* indicate that we've handled it here and the Haskell handler
* doesn't take proper action (e.g., terminate the OS process),
* the user of the app will be unable to kill/close it. Not
* good, so disable the delivery for now.
*/
return FALSE;
default:
if (!deliver_event) return TRUE;
#if defined(THREADED_RTS)
sendIOManagerEvent((StgWord8) ((dwCtrlType<<1) | 1));
#else
if ( stg_pending_events < N_PENDING_EVENTS ) {
stg_pending_buf[stg_pending_events] = dwCtrlType;
stg_pending_events++;
}
// we need to wake up awaitEvent()
abandonRequestWait();
#endif
return TRUE;
}
}
}}}
To get the behavior desired `CTRL_CLOSE_EVENT` would have to be handled
before `generic_handler` returns and have it return `FALSE` to which
windows responds by terminating the process or never return and ensure
that `rts_ConsoleHandlerDone` terminates the process in the cases of
`CTRL_CLOSE_EVENT`, `CTRL_LOGOFF_EVENT`, or `CTRL_SHUTDOWN_EVENT`. I
suppose there could be situations where returning `TRUE` could be desired
but the API given in `GHC.ConsoleHandler` doesn't provide for that and I'm
not sure it is particularly friendly to users (see remarks in the
[http://msdn.microsoft.com/en-us/library/ms683242(VS.85).aspx MSDN docs]).
I don't know enough about the implications of not returning from
`generic_handler` and having `rts_ConsoleHandlerDone` terminate the
process, but I think I will experiment a little and see what happens.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4942#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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