Am 13.10.2010 09:39, schrieb Michael Van Canneyt:
On Wed, 13 Oct 2010, Luca Olivetti wrote:
En/na Michael Van Canneyt ha escrit:
and in "WaitFor" it says:
"Call WaitFor to obtain the value of ReturnValue when the
thread finishes executing. WaitFor doesn't return until the thread
terminates, so the thread must exit either by finishing the Execute
method
or by exiting when the Terminated property is true."
There you have it. Nowhere does it say that if the main thread is
blocked,
your synchronize() method will be executed nonetheless. Indeed, both
specs
explicitly say that the calling thread is suspended or blocked (!)
till the call returns.
And in older versions of the documentation (delphi 2) it explicitly says
"Don't call WaitFor in the context of the main VCL thread if your
thread uses Synchronize. Doing so will either cause a deadlock, making
it appear that your application has hung, or cause an EThread
exception to be raised. (Synchronize waits for the main VCL thread to
enter the message loop before allowing the method it is trying to
synchronize to execute. If the main VCL thread has called WaitFor, it
won't enter the message loop and Synchronize will never return.
TThread detects that case and will raise an EThread exception in the
thread, causing it to terminate and, if not caught in the Execute
method, the application will terminate as well. If Synchronize is
already waiting on the main VCL thread when WaitFor is called, TThread
can't intervene, and your application will deadlock.)"
They probably changed the implementation later on to avoid this, but
old farts like me still avoid to mix synchronize and waitfor.
... And Delphi 7 help explicitly mentions that Synchronize() does not work
in console applications (VCL and CLX), since it uses the message system.
Seems to me that there is plenty of cause for complaints :)
Well... then the person who implemented WaitFor on Windows thought about
all those problems and circumvented them...
Regards,
Sven
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