[LIP] Timing out blocking system calls

I have this silly little program I use for small-time monitoring called
tcpping. It uses TCP and hence works in cases where ICMP is blocked
at firewalls.

It has a timer mechanism implemented using SIGALRM and
sigsetjmp/siglongjmp. Something like:

void alarm_handler (int s) {
   siglongjmp (env);
}

And in the main program:

signal (SIGALRM, alarm_handler);
alarm (timeout);
if (sigsetjmp(env, 0) == 0) {
   /* Normal code path */
} else {
   /* Timer expired */
}

Now, this ran fine for years on Linux. Until today, when I tried to build
it in Solaris 9, where it segfaulted every single time. I ultimately
traced the bug (in my code) - which is even documented in the Solaris
man page for sigsetjmp:

     The values of register and  automatic  variables  are  unde-
     fined.  Register  or automatic variables whose value must be
     relied upon must be declared as volatile.

The temporary fix I applied was to move ALL my variables to global scope :)

So, the question really is: What is the best way to implement a portable
timeout? I want to have a mechanism by which I can timeout any blocking
system call.

TIA,

Binand

-- 
Hanlon's Razor: Never attribute to malice that which can be adequately
explained by stupidity.
Bruce's Razor: Never attribute to stupidity that which can be adequately
explained by Microsoft funding.


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