[boost] Re: Child processes

From: Jonathan Biggar (jon_at_[hidden])
Date: 2004-06-22 17:26:48

Angus Leeming wrote:
> namespace {
> 
> std::map<pid_t, int> completed_children;
> 
> int status;
> sig_atomic_t pid;
> 
> }
> 
> extern "C"
> void child_handler(int)
> {
>         pid = wait(&status);
>         std::map<pid_t, int>::iterator it = completed_children.find(pid);
>         if (it != completed_children.end())
>                 it->second = status;
> }
> 
> I'm pretty sure that the above is safe code. It does the absolute minimum
> in the handler routine. wait() is guaranteed to be async-safe. Moreover,
> the handler receives only SIGCHLD signals and so cannot receive multiple
> calls simultaneaously. However, I'm unsure whether it Ok to search the
> map like this. Any advice?

That's not safe code, since the child_handler() function could be called 
at any time, interrupting other code that is modifying the 
completed_children map.

-- 
Jon Biggar
Floorboard Software
jon_at_[hidden]
jon_at_[hidden]