Re: SIGALRM in a class member?

James Kanze <>
Wed, 13 Aug 2008 02:22:20 -0700 (PDT)
On Aug 13, 1:57 am, R Samuel Klatchko <> wrote:

Ron Eggler wrote:

signal( SIGALRM, sendHeartbeat );
but the problem is signal wouldn't allow me to have a function pointer =

to a

member method like INITSource::sendHeartbeat. If I need to do it this w=

ay I

would end up in crazy static declarations and linker conflicts - I have
gone there already and apparently didn't solve it...

You can do this with a forwarding function that is a static
member (you can also do it with a non-member function).

Not according to the standard. "All signal handlers shall have C
linkage" (=A718.7/5). And "A C language linkage is ignored for the
names of class members and the member function type of class
member functions" (=A77.5/4). A compiler is required to diagnose
this error (and some do).

Because signal does not give you a way to attach some caller
defined data, you will also need a static member variable to
hold a pointer to the instance of the class you want to use:

Note, however, that it is implementation defined whether you can
access said variable. Typically, if it is a pointer, you can,
but calling a member function on it, etc., is less sure.

Since you can only deal with one instance this way (and since at
least under Unix, SIGALRM only manages a single timer), the best
solution is to declare a sig_atomic_t with static lifetime, and
test it. (Except that most systems, or at least Unix and
Windows, offer even better facilities for managing time.)

James Kanze (GABI Software)
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