Condition occurs with no signal handler present

The following three figures illustrate how a condition such as a divide-by-zero is handled in a C routine in Language Environment if you do not use any Language Environment callable services, or don't have any user-written condition handlers registered.

There is no user-written condition handler or signal handler registered for C370C or any of the other C routines, so the condition is percolated through all of the stack frames on the stack. At this point, C default actions take place of percolating the condition to Language Environment. Language Environment takes its default action for an unhandled severity 3 condition and terminates the application. A message, trace, Language Environment dump, or a user address space dump could be generated depending on the setting of TERMTHDACT (see z/OS Language Environment Programming Reference).

Figure 1 is a C main routine that calls C370B, a subroutine that passes data to another subroutine, C370C.

Figure 1. C370A routine

/*Module/File Name:  EDCMLTA  */
/*******************************************************************/
/* Demonstrate a failing C/370 program                             */
/* with multiple active routines                                   */
/* on the stack.  The call sequence is as follows:                 */
/*  C370A ---> C370B ---> C370C (which does a divide-by-zero)      */
/*******************************************************************/

#include <stdio.h>

int y = 0;
void C370B(void);

int main(void) {

  printf("In Program C370A\n");
  C370B();
}

Figure 2 is a C subroutine that calls C370C, and passes data to it.

Figure 2. C370B routine

/*Module/File Name:  EDCMLTB  */
/**********************************************************************/
/* This routine is called to pass data forward to C370C.              */
/* C370C will then cause a zero divide.                               */
/**********************************************************************/

#include <stdio.h>

extern int y;
void C370C(int);

void C370B(void) {

  int x;
  printf("In Program C370B\n");
  x = y;
  C370C(x);
}

Figure 3 generates a divide-by-zero. The divide-by-zero condition is percolated back to C370B, to C370A, and to Language Environment default behavior.

Figure 3. C370C routine

/*Module/File Name:  EDCMLTC  */
/**********************************************************************/
/* This routine is called by C370B to generate a zero divide.         */
/**********************************************************************/

#include <stdio.h>


void C370C(int y) {

  printf("In Program C370C\n");
  y = 1/y;
}