On 31.05.2016 14:37, Stefan Schalk wrote:
> There is a memory consumption/leak using the TThread.Synchronize function.
>
> A callback function is called out of another ("external") thread (from an
> loaded DLL).
> Inside the callback function a synchronized call to a procedure has to be
> done.
> Every thing works without error, but there is a memory use increasement during
> the TThread.Synchronize call.
>
> procedure OnExternalThreadCallback(...); cdecl;
> begin
> ...
> TThread.Synchronize(nil, @MyMainClass.CallbachSyncedWithMainThread);
> ...
> end;
>
> The external thread are created/used/freed like discussed in the Lazarus
> mailing list:
> Mutlithreaded Dll Callback crashes my Application
> <http://lists.lazarus.freepascal.org/pipermail/lazarus/2010-August/054728.html>
>
>
> The memory leak problem arises with Lazarus 1.6.0 and FPC 3.0.0.
> Under the hood the processing of the TThread.Synchronize changed.
> Lazarus 1.4.4 with FPC 2.6.4 didn't have this problem.
> I don't have the versions between 1.4.4 and 1.6.0, therefore I cannot say
> something about them (if there are any).
I've committed a fix in FPC revision 33863 and if all goes well it
should be merged to 3.0.1 as well, thus becoming part of 3.0.2.
A check with Delphi has shown that the WakeMainThread event gets Nil as
Sender argument with an external thread, so I can avoid the use of
CurrentThread which triggered the memory usage.
Please note that this is however not a leak as CurrentThread will create
a TExternalThread instance for a thread that hasn't been created by
TThread (and for which no instance exists yet) and this instance must
(sadly) be kept around until the program terminates.
Regards,
Sven
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