[fpc-pascal] TProcess does not work in Windows XP
Pierre Free Pascal
pierre at freepascal.org
Wed Mar 25 10:47:30 CET 2015
> -----Message d'origine-----
> De : fpc-pascal-bounces at lists.freepascal.org [mailto:fpc-pascal-
> bounces at lists.freepascal.org] De la part de Michael Van Canneyt
> Envoyé : mercredi 25 mars 2015 09:54
> À : FPC-Pascal users discussions
> Objet : Re: [fpc-pascal] TProcess does not work in Windows XP
> On Wed, 25 Mar 2015, Antonio Sanguigni wrote:
> > 2015-03-25 8:41 GMT+01:00 Michael Van Canneyt
> <michael at freepascal.org>:
> >>> ---------------------- code ---------------
> >>> procedure TBurpClient.Run;
> >>> begin
> >>> fOurProcess.Options := [poUsePipes] + [poNoConsole];
> >>> fOurProcess.Execute;
> >>> while True do
> >>> begin
> >>> // make sure we have room
> >>> fMemStream.SetSize(fBytesRead + READ_BYTES);
> >>> // try reading it
> >>> fNumBytes := fOurProcess.Output.Read((fMemStream.Memory +
> >>> fBytesRead)^, READ_BYTES);
> >>> if fNumBytes > 0 then // All read() calls will block, except the
> >>> one.
> >> I am not sure this is always correct. Various versions of windows
> >> differently in this regard;
> >> zero (0) may be a valid return value. I suggest you check
> >> fOurProcess.IsRunning to break the loop.
> > Thank you, I will try it. But debugging I can see the problem is not
> > in the loop. In Windows XP fNumBytes is always zero:
> > fNumBytes := fOurProcess.Output.Read((fMemStream.Memory +
> > fBytesRead)^, READ_BYTES);
> > so it seems the Read of fOurProcess.Output is not giving the expected
> Read translates directly to a kernel call.
> > In Windows 7 it's ok.
> Once more:
> Zero is a valid return value for read from a pipe.
> So it can perfectly be that read attempts 50 times returns 0, and only
> read attempt 51 you get a positive result.
> That is why you must check isRunning, and not rely on the return value
> of readbytes.
It could also be due to the problem we detected in fpmkunit:
If the stderr is a separate pipe and that pipe is full,
the inferior will stop until that pipe is read.
See this patch:
Could the difference between Windows 7 and Windows XP
be related to different amount to stderr pipe?
Or maybe the internal pipe size is different?
In the hope this could be useful,
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