[fpc-devel] Possible bug in thread manager

Alexander Todorov alexx.todorov at gmail.com
Thu Jun 1 16:23:18 CEST 2006

I am sending you a sample which is not working as expected.
The sample contains 2 FPC projects compiled with Lazarus. They are
demonstrating a program that starts, goes in daemon mode, and creates
two threads that will do their job, as well as the demonized program
will do some job as well. This is shown with writelns.
classthreads.lpr - threads implementation using TThread descendants
systhreads.lpr - threads implementation using BeginThread functions
To run as daemon pass some parameter on command line.

The two FPC implementations are pretty much the same.
fork.c - a pthreads implementation in C. this is for reference only.

issue 1:
When demonising with LibC.Daemon(0, 0) the file handles to the
standard Input, Output and Error are closed properly and they are not
accessible to the created threads.
When the program is demonised using FpFork and closing the file hadles
with Close() this is not working as expected. Thread1/Thread2 CAN
write to the standard output and results get written in the console.
When forking file handles are copied to the child process and changes
are not visible to the parent or to the child. When creating threads
the changes should be visible to the new threads since they are in the
space of the process creating them. Am I right or not?

Issue 2:
When the program is compiled without {$DEFINE USE_DAEMON} it is being forked.
In this case the second thread is not created (IMO), the masted
program does not continue execution and all hangs up in the while loop
for thread 1.
If it is started with without any parameters, it is running in
non-daemon mode and the two threads are working fine.
If started with & in the end two threads are working fine again.

The C reference uses fork() to become a daemon.
When the file handles for stdin, stdout, stderr are closed the threads
don't print on the console.
If they are not closed the printed results are visible in console. In
both cases the two threads and the master process are running.

For more info please see the provided source code and the provided
listing of ps.
I am using FPC 2.0.2 on Linux.

Are these issues bugs in the thread manager?????
The projects are Linux (Unix) speciffic, can someone verify on Windows?
Can someone test this with newer FPC?
A long time ago I saw an e-mail that anouced another ThreadManager
implementation for FPC /something for real time threads IIRC/. Can
someone test with different thread manager?

If these are bugs, 2 as I see it, should I report them in mantis?

Thanks to all.
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