Edward Bartolo <edb...@gmail.com> writes:
> I am trying to reap zombies. The "while(fpwaitpid" pascal code is
> freezing my application.
>
> *********************************************************************************
> procedure handle_sigchld(sig: longint; info: psiginfo; context:
> psigcontext); cdecl;
> var
> Status: cint;
> a_pid: pid_t;
> begin
> Status := 0;
> a_pid := -1;
>
> // This is freezing my application
> while (fpwaitpid(a_pid, Status, WNOHANG) > 0) do
> begin
> backend_lives := backend_lives + 1;
> showmessage('hi strunz!!!');
> end;
> end;
>
>
> var sa: sigactionrec;
>
> initialization
> sa.sa_handler := @handle_sigchld;
> fpsigemptyset(&sa.sa_mask);
>
> sa.sa_flags := (SA_RESTART or SA_NOCLDSTOP);
> if (fpsigaction(SIGCHLD, @sa, nil) = -1) then
> begin
> // do nothing
> end;
> ******************************************************
>
> Any ideas?
As was already mentioned: The second argument to fpwaitpid must be a
pointer. As opposed to what was already mentioned, the loop condition is
generally correct: The loop must terminate if the return value is either
-1 (some kind of error occurred) or 0 (nothing more to do right now).
Caveat: The signal handler is asynchronously invoked by the kernel when
a SIGCHLD is posted and it will interrupt whatever else the application
was doing at the moment. This means it's as if it was running in a
separate thread (except even more complicated).
According to
http://www.freepascal.org/docs-html/rtl/baseunix/fpsigaction.html
Sa_Handler may be SIG_DFL for the default action or SIG_IGN to
ignore the signal.
For as long as you aren't using the exit status, using SIG_IGN instead
of a signal handler is to be preferred as the kernel will then just not
create zombies.
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