Step by Step solution about How to resolve the algorithm Detect division by zero step by step in the C programming language

This code demonstrates how to handle floating-point exceptions (FPE) in C, specifically focusing on division by zero. It uses the sigsetjmp() and siglongjmp() functions to create a non-local exit point that can be used to jump out of a function when an FPE occurs.

Let's go through the code step by step:

1. Header Includes: The code includes several standard C library headers, including <limits.h> for accessing integer limits, <setjmp.h> for non-local jumps, <stdio.h> for input/output functions, <stdlib.h> for program exit, and <signal.h> for signal handling.

2. SIGFPE Handler (fpe_handler): This function serves as the handler for the SIGFPE signal (floating-point exception). When a SIGFPE is raised due to an FPE, this handler is invoked. Its job is to execute a non-local jump back to the point where sigsetjmp() was called in the main program.

3. try_division Function: This function attempts to perform a division of two integers, x and y. It starts by setting up a signal handler for SIGFPE using sigaction. This handler will jump to the fpe_env buffer if a SIGFPE occurs.

4. sigsetjmp and Division: The function uses sigsetjmp to save the current program state in the fpe_env buffer. This is the point where the program will resume after handling the SIGFPE. After saving the state, it performs the division of x by y and stores the result in result.

5. Restoring the Signal Handler: Once the division is complete, the function restores the old signal handler for SIGFPE using sigaction. This is necessary to prevent any subsequent SIGFPEs from interrupting the program flow.

6. Printing the Result: If the division was successful, the function prints the result using printf.

7. SIGFPE Handling: If a SIGFPE occurred during the division, the program jumps back to the sigsetjmp call within the fpe_handler function. The code parameter passed to siglongjmp indicates the type of FPE that occurred. The handler prints an appropriate message based on the error code and restores the old signal handler.

8. Main Function: The main function calls the try_division function with various pairs of integers to demonstrate the division by zero handling. It tests both successful and unsuccessful divisions, including division by zero and overflow cases.

Summary: This code uses non-local jumps to handle floating-point exceptions, particularly division by zero. It demonstrates how to catch SIGFPE, determine the type of FPE, and handle it gracefully without crashing the program. This technique is useful in situations where it's critical to prevent undefined behavior or unexpected program termination due to FPEs.

#include <limits.h>	/* INT_MIN */
#include <setjmp.h>	/* siglongjmp(), sigsetjmp() */
#include <stdio.h>	/* perror(), printf() */
#include <stdlib.h>	/* exit() */
#include <signal.h>	/* sigaction(), sigemptyset() */

static sigjmp_buf fpe_env;

/*
 * This SIGFPE handler jumps to fpe_env.
 *
 * A SIGFPE handler must not return, because the program might retry
 * the division, which might cause an infinite loop. The only safe
 * options are to _exit() the program or to siglongjmp() out.
 */
static void
fpe_handler(int signal, siginfo_t *w, void *a)
{
	siglongjmp(fpe_env, w->si_code);
	/* NOTREACHED */
}

/*
 * Try to do x / y, but catch attempts to divide by zero.
 */
void
try_division(int x, int y)
{
	struct sigaction act, old;
	int code;
	/*
	 * The result must be volatile, else C compiler might delay
	 * division until after sigaction() restores old handler.
	 */
	volatile int result;

	/*
	 * Save fpe_env so that fpe_handler() can jump back here.
	 * sigsetjmp() returns zero.
	 */
	code = sigsetjmp(fpe_env, 1);
	if (code == 0) {
		/* Install fpe_handler() to trap SIGFPE. */
		act.sa_sigaction = fpe_handler;
		sigemptyset(&act.sa_mask);
		act.sa_flags = SA_SIGINFO;
		if (sigaction(SIGFPE, &act, &old) < 0) {
			perror("sigaction");
			exit(1);
		}

		/* Do division. */
		result = x / y;

		/*
		 * Restore old hander, so that SIGFPE cannot jump out
		 * of a call to printf(), which might cause trouble.
		 */
		if (sigaction(SIGFPE, &old, NULL) < 0) {
			perror("sigaction");
			exit(1);
		}

		printf("%d / %d is %d\n", x, y, result);
	} else {
		/*
		 * We caught SIGFPE. Our fpe_handler() jumped to our
		 * sigsetjmp() and passes a nonzero code.
		 *
		 * But first, restore old handler.
		 */
		if (sigaction(SIGFPE, &old, NULL) < 0) {
			perror("sigaction");
			exit(1);
		}

		/* FPE_FLTDIV should never happen with integers. */
		switch (code) {
		case FPE_INTDIV: /* integer division by zero */
		case FPE_FLTDIV: /* float division by zero */
			printf("%d / %d: caught division by zero!\n", x, y);
			break;
		default:
			printf("%d / %d: caught mysterious error!\n", x, y);
			break;
		}
	}
}

/* Try some division. */
int
main()
{
	try_division(-44, 0);
	try_division(-44, 5);
	try_division(0, 5);
	try_division(0, 0);
	try_division(INT_MIN, -1);
	return 0;
}