Delphi FreeLibrary freezes when using TTask in DLL - delphi

Question

Here is my code in DLL:
procedure TTaskTest;
begin
TTask.Run(
procedure
begin
Sleep(300);
end);
end;
exports TTaskTest;
After calling this method in host app, then call FreeLibrary will freeze host app.
After debug , I found that the program freezes at if TMonitor.Wait(FLock, Timeout) then in TLightweightEvent.WaitFor , but the debugger cannot step into TMonitor.Wait.
How to solve?

Answer 1

This issue was reported (RSP-13742 Problem with ITask, IFuture inside DLL).
It was closed "Works as Expected" with a remark:
To prevent this failure using ITask or IFuture from a DLL, the DLL will need to be using its own instance of TThreadPool in place of the default instance of TThreadPool.
Here is an example from Embarcadero how to handle it:
library TestLib;
uses
System.SysUtils,
System.Classes,
System.Threading;
{$R *.res}
VAR
tpool: TThreadPool;
procedure TestDelay;
begin
tpool := TThreadPool.Create;
try
TTask.Run(
procedure begin
Sleep(300);
end,
tpool
);
finally
FreeAndNil(tpool);
end;
end;
exports
TestDelay;
begin
end.
Another way is to create the threadpool when the library is loaded, and add a release procedure, which you call before calling FreeLibrary.
// In dll
procedure TestDelay;
begin
TTask.Run(
procedure begin
Sleep(300);
end,
tpool
);
end;
procedure ReleaseThreadPool;
begin
FreeAndNil(tpool);
end;
exports
TestDelay,ReleaseThreadPool;
begin
tpool := TThreadPool.Create;
end.