Potential resource leak in TThread on Unix - no EndThread called

[abouchez]

I've observed a weird behavior with FPC 3.1.1 trunk and Linux.
Using htop + user threads showing on a server program, a lot of threads are listed, even if they are not active any more.

Looking in details, I discovered that in rtl/unix/tthread.inc, ThreadFunc() doesn't call EndThread if FreeOnTerminate=false.

Code: Pascal  [Select][+][-]

1. function ThreadFunc(parameter: Pointer): ptrint;
2. var
3. ....
4.   LFreeOnTerminate := LThread.FreeOnTerminate;
5.   LThread.DoTerminate;
6.   LThread.FFinished := True;
7.   if LFreeOnTerminate then
8.     begin
9.       WRITE_DEBUG('Thread ',ptruint(lthread),' should be freed');
10.       LThread.Free;
11.       WRITE_DEBUG('Thread freed');
12.       WRITE_DEBUG('thread func calling EndThread');
13.       // we can never come here if the thread has already been joined, because
14.       // this function is the thread's main function (so it would have terminated
15.       // already in case it was joined)
16.       EndThread(Result);
17.     end;
18. end;
19.  

So no pthread_detach/pthread_exit() seems to be called.

What did I miss?
I can't find the source of this resource leak, which could be very difficult with serious multithreaded process on a Linux server...

[abouchez]

I missed something for sure.

There is no resource leak if I look closer with strace, but I can't say honnestly why it works!
Any idea?

[engkin]

You are looking at OS specific code. Try the common code ThreadProc that is the real proc used when BeginThread is called:

Code: Pascal  [Select][+][-]

1. //\rtl\objpas\classes\classes.inc
2. function ThreadProc(ThreadObjPtr: Pointer): PtrInt;
3.   var
4.     FreeThread: Boolean;
5.     Thread: TThread absolute ThreadObjPtr;
6.   begin
7. ....
8.     FreeThread := Thread.FFreeOnTerminate;
9.     Result := Thread.FReturnValue;
10.     Thread.FFinished := True;
11.     Thread.DoTerminate;
12.     if FreeThread then
13.       Thread.Free;
14.     EndThread(Result);
15.   end;

1^st Edit:
Spoke to soon, Unix does not use ThreadProc.

2^nd Edit:
Using cthreads:
calls CBeginThread and passes ThreadMain:

Code: Pascal  [Select][+][-]

1. //\rtl\unix\cthreads.pp
2.     function ThreadMain(param : pointer) : pointer;cdecl;
3. ...
4.         pthread_exit(ThreadMain);
5.       end;

[abouchez]

Sounds fair enough.

This code is difficult to follow, with at least TjreadProc/ThreadFunc/ThreadMain involved...

Thanks for the input!