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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Terminate threads during application or not?

Posted by jpluimers on 2019/10/02

I got an interesting question a while ago: should an application terminate (anonymous) threads or not?

A problem is that a thread might not execute unless you call WaitFor before Terminate is called. The reason is that the internal function ThreadProc does not start Execute if the thread is already terminated.

The ThreadProc in the System.Classes unit is an ideal place to set breakpoints in order to see which threads might start.

Other useful places to set breakpoints:

  • TAnonymousThread.Execute
  • TExternalThread.Execute

Execute not being called by ThreadProc is a bug, but it is not documented because QC is gone (taking the below entry with it), it is not in QP and the docwiki never got updated.

Given QC has so much information, I am still baffled that Embarcadero took it down.

Sergey Kasandrov (a.k.a. serg or sergworks) wrote in [WayBack] Sleep sort and TThread corner case | The Programming Works about this bug and refers to WayBack: QualityCentral 35451 – TThread implementation doesn’t guarantee that thread’s Execute method will be called at all .

The really bad thing are the WayBack: QualityCentral Resolution Entries for Report #35451 Resolution “As Designed” implying the design is wrong.

In his post, sergworks implemented the Sleep sorting in Delphi. Related:

Note that application shutdown is a much debated topic. Best is to do as little cleanup as possible: your process is going to terminate soon anyway. No need to close handles or free memory: Windows will do that for you anyway. See for instance:

 

Related to waiting:

Related to executing:

–jeroen

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