Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!uunet!taumet!steve
From: steve@taumet.com (Stephen Clamage)
Newsgroups: comp.lang.c++
Subject: Re: Question about C++ signal handling
Message-ID: <686@taumet.com>
Date: 23 Apr 91 15:34:41 GMT
References: <1991Apr22.194302.17795@watdragon.waterloo.edu>
Organization: Taumetric Corporation, San Diego
Lines: 33

fkho@watdragon.waterloo.edu (Frederick K. Ho) writes:

>Hi, I would like to know if anyone tried to register a signal inside a
>member function with the callback signal handler being another member
>function of the same class?

I don't believe you can do this.  The member function must be called
with a 'this' pointer, which the operating system will not be able to
supply.

>class A {
>	...
>	f();
>	timeout();
>};

>A::f()
>{
>	::signal(SIGALRM, timeout);
>	 ...
>}

The second paramater to signal() is of type "pointer to function taking
one int parameter, returning void".  The type of "timeout" is "pointer
to member function of A with no parameters, returning int".  This is a
type mismatch, and you should have gotten a compile-time error at the
call to signal().

It should be ok if timeout is a static member function of the right type:
	class A { ... static void timeout(int); ... };
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com