# Re: Just-in-time debugging on Linux

[Michael Veksler <veksler at il dot ibm dot com>]

/References/: <007a01c20e82$daf93e20$0301a8c0@rowboat 
<http://sources.redhat.com/ml/gdb/2002-06/msg00063.html>> 
<20020608172614.GA16912@redhat.com 
<http://sources.redhat.com/ml/gdb/2002-06/msg00064.html>>

> Christopher,
>
> > On windows you'd do:
> >
> > set cygwin=error_start=x:/path/to/gdb.exe
>
> Thanks lots, but I meant Linux. Does anyone know the trick to launch gdb
> automatically there?
>
> Robin

Try the following code:

#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <signal.h>
#include <stdio.h>

static char* exec_name="";

static void crash_handler(int sig)
{
  int status=0;
  int pid;
  char * gdb_array[]={"gdb", exec_name, "PID", NULL};
  char pid_str[40];

  sprintf(pid_str, "%d%c", getpid(), '\0');
  gdb_array[2]= pid_str;

  pid= fork();

  if (pid < 0)    /* error */
    abort();
  else if (pid)   /* parent */
  {
    sleep(60);   /* Give GDB time to attach */
    _exit(1);     /* you can skip this line by telling gdb to "return" */
  }
  else            /* child */
    execvp("gdb", gdb_array);
}
void register_gdb()
{
  signal(SIGQUIT, crash_handler);  /* Normally got from Ctrl-\ */
  signal(SIGILL,  crash_handler);
  signal(SIGTRAP, crash_handler);
  signal(SIGABRT, crash_handler);
  signal(SIGFPE,  crash_handler);
  signal(SIGBUS,  crash_handler);
  signal(SIGSEGV, crash_handler);  /* This is the most common crash */
  signal(SIGSYS,  crash_handler);
}

void crash_segv()
{
  int *p=0;
  *p=1;
}

int main(int argc, char *argv[])
{
  exec_name=argv[0];
  register_gdb();
  crash_segv();
  return 0;
}