[fpc-devel] SimpleIPC and TWinMsgServerComm.PeekMessage
pascaldragon at googlemail.com
Wed Oct 9 17:10:43 CEST 2013
Am 09.10.2013 10:40, schrieb Juha Manninen:
> I am testing SimpleIPC with components/chmhelp/lhelp
> The latter works as a master application, sending a file name to lhelp
> and starting it if not running already.
> On Linux this works perfectly. The return message status is always "Success".
> On Windows there is a bug when lhelp is not yet running and it must be started.
> In TWinMsgServerComm.PeekMessage() (part of SimpleIPC),
> if Windows.PeekMessage() failed, the idea is to wait a given TimeOut
> and then try again:
> The caller gives 50 ms as timeout but also uses a loop for 5 seconds
> total timeout.
> It should be enough for even slowly starting processes.
> However, when the process does not exist yet,
> MsgWaitForMultipleObjects returns WAIT_FAILED instead of WAIT_TIMEOUT,
> and it does NOT wait. It returns immediately.
> I was able to fix it like this:
> if R=WAIT_FAILED then
> B:=(R<>WAIT_TIMEOUT) and (R<>WAIT_FAILED);
> The fix can be tested with lhelpconnectiondemo1.
> Currently the first reply status is NoAnswer, after the fix it is Success.
> If you think the fix is OK, I can make a patch.
I've looked at the code a bit more and the problem must be something
else. MsgWaitForMultipleObjects waits on a FHWND which it created itself
and additionally waits for the reception of a message through
SendMessage. So this should not fail except maybe the creation of the
window failed. Could you print the error message returned by
"SysErrorMessage(GetLastOSError)" if put at the then-part of "if
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