C - Go to Statement

Overview

goto performs an unconditional jump to a labeled statement. Use sparingly; structured control flow is usually clearer.

Learning Objectives

• Recognize when goto may be acceptable (e.g., error cleanup).

Prerequisites

• C - Looping Statements

Example

#include <stdio.h>

int main(void) {
  int i = 0;
loop:
  if (i < 3) { printf("%d\n", i++); goto loop; }
}

Checks for Understanding

1. Why is goto discouraged in most cases?

Practical Example: Error handling and cleanup

#include <stdio.h>
#include <stdlib.h>

int main(void) {
  FILE *f = fopen("data.txt", "r");
  char *buf = NULL;
  if (!f) goto cleanup;
  buf = malloc(1024);
  if (!buf) goto cleanup;
  // ... work with f and buf ...
cleanup:
  if (buf) free(buf);
  if (f) fclose(f);
  return 0;
}

Expected Output: No output; resources are safely released on any path.

Common Pitfalls

• Jumping into a block can skip initializations (undefined behavior); only jump forward to labels in the same function.
• Overuse of goto harms readability—prefer structured control flow.

Exercises

1. Open a file and allocate a buffer; ensure both are freed/closed using a single cleanup label.
2. Simulate an error path and verify cleanup still occurs.