g++ and signal handlers that use sigcontext

[David L]

I found some example code regarding how to use backtrace from signal 
handlers at: http://www.linuxjournal.com/article.php?sid=6391 .  That 
example code compiled with warnings but no errors using old versions of g++ 
(eg: egcs-2.91), but now has an error:

foo.cc: In function `void bt_sighandler(int, sigcontext)':
foo.cc:26: `exit' undeclared (first use this function)
foo.cc:26: (Each undeclared identifier is reported only once for each 
function
   it appears in.)
foo.cc: In function `int main()':
foo.cc:56: invalid conversion from `void*' to `void (*)(int)'

What is the proper way to set up a signal handler with a 2nd argument 
(sigcontext )?

Thanks...   David

PS - Here is the example code:

#include <stdio.h>
#include <signal.h>
#include <execinfo.h>

void bt_sighandler(int sig, struct sigcontext ctx) {

  void *trace[16];
  char **messages = (char **)NULL;
  int i, trace_size = 0;

  if (sig == SIGSEGV)
	printf("Got signal %d, faulty address is %p, "
		   "from %p\n", sig, ctx.cr2, ctx.eip);
  else
	printf("Got signal %d\n", sig);

  trace_size = backtrace(trace, 16);
  /* overwrite sigaction with caller's address */
  trace[1] = (void *)ctx.eip;
  messages = backtrace_symbols(trace, trace_size);
  /* skip first stack frame (points here) */
  printf("[bt] Execution path:\n");
  for (i=1; i<trace_size; ++i)
	printf("[bt] %s\n", messages[i]);

  exit(0);
}


int func_a(int a, char b) {

  char *p = (char *)0xdeadbeef;

  a = a + b;
  *p = 10;	/* CRASH here!! */

  return 2*a;
}


int func_b() {

  int res, a = 5;

  res = 5 + func_a(a, 't');

  return res;
}


int main() {

  /* Install our signal handler */
  struct sigaction sa;

  sa.sa_handler = (void *)bt_sighandler;
  sigemptyset(&sa.sa_mask);
  sa.sa_flags = SA_RESTART;

  sigaction(SIGSEGV, &sa, NULL);
  sigaction(SIGUSR1, &sa, NULL);
  /* ... add any other signal here */

  /* Do something */
  printf("%d\n", func_b());


}

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