/*WBL 11 Nov 2020  */

/*Modifications:
WBL 13 Nov 2020 Fix for stack overflow SIGSEGV too
WBL 11 Nov 2020 Try Dan Blackwell's SIGSEGV handler. Cf:
   https://stackoverflow.com/questions/77005/how-to-automatically-generate-a-stacktrace-when-my-program-crashes
 */

/*compile with -g and link with -rdynamic. Eg: gcc -g -rdynamic segv.c */

/*run (various) eg: 
  ./a.out
  gdb -batch -ex=run -ex=bt ./a.out 
*/

#include <stdio.h>
#include <string.h>
#include <execinfo.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>

/*Alternative stack so can hangle stack overflow*/
/*https://www.gnu.org/software/libc/manual/html_node/Signal-Stack.html */
/*https://stackoverflow.com/questions/5785746/how-to-use-sigaltstack-in-signal-handler-program*/

/*https://www.gnu.org/software/libc/manual/html_node/Backtraces.html*/
void handler(int sig) {
  const int bt_size = 20;
  void *array[bt_size];
  size_t size;

  /*use write as stream IO fails when stack is trashed*/
  char buf[80];
  sprintf(buf,"signal handler(%d)\n",sig);
  write(STDERR_FILENO,buf,strlen(buf));

  /* get void*'s for all entries on the stack
   * NB backtrace may sometimes return 0,
   * eg in cluster when all memory is used up */
  size = backtrace(array, bt_size);

  sprintf(buf,"backtrace(array,%d) gives %d pointers\n",bt_size,size);
  write(STDERR_FILENO,buf,strlen(buf));

  // print out all the frames to stderr
  //fprintf(stderr, "Error: signal %d:\n", sig);

  backtrace_symbols_fd(array, size, STDERR_FILENO);
  exit(128+sig);
}

void A();

void C(const int c, const char* text) {
  printf("C(%d,%s) called\n",c,text);
  //A(); //recurse until exhaust stack
  int* bad = 0;
  bad[1] = 999;
}
void B(const int b) {
  printf("B(%d) called\n",b);
  C(b,"c");
}
void A() {
  printf("A called\n");
  B(1);
}

char stack[SIGSTKSZ];
stack_t signal_stack_info = {
  .ss_size = SIGSTKSZ,
  .ss_sp = stack,
};
struct sigaction signal_action_info = {
  .sa_handler = handler,
  .sa_flags = SA_ONSTACK
};

int main(int argc, char * argv[]){
  int i;
  printf("$Revision: 1.4 $\n");
  for(i=0; i<argc; i++) {
    printf("argv[%d]=%s\n",i,argv[i]); 
  }
  {const int e = sigaltstack(&signal_stack_info, 0);
  if(e!=0){fprintf(stderr,"ERROR sigaltstack failed %d\n",e);return 1;}}
  sigfillset(&signal_action_info.sa_mask);
  {const int e = sigaction(SIGSEGV, &signal_action_info, 0);
  if(e!=0){fprintf(stderr,"ERROR sigaction failed %d\n",e);return 1;}}
  //signal(SIGSEGV, handler);   // install our handler

  A();
  printf("done 0\n");
  return 0;
}