C goto Statement

In this page:

What is goto?
Syntax and Labels
Breaking Out of Deep Nesting
Backward Jumps
Best Practices with goto

What is goto?

goto transfers execution directly to a labeled line elsewhere in the same function, bypassing the normal sequential flow of the code entirely, which makes it powerful but also the control-flow tool most likely to make a program's logic hard to follow if used carelessly.

Example: What is goto?

#include <stdio.h>
int main() {
	goto skip;
	printf("never runs");
	skip:
	printf("Jumped past the printf");
	return 0;
}

Syntax and Labels

A label is simply an identifier followed by a colon placed in front of a statement, marking that line as a valid jump target, and it can be positioned anywhere within the same function that a goto elsewhere in that function wants to reach.

Example: Syntax and Labels

#include <stdio.h>
int main() {
	int x = 5;
	if (x > 0) goto positive;
	printf("not positive");
	return 0;
	positive:
	printf("Positive");
	return 0;
}

Breaking Out of Deep Nesting

When an error condition is detected deep inside several nested loops, a single goto cleanup; can exit all of them in one step, whereas a plain break only escapes the single innermost loop, leaving you to manually break out of each remaining level.

Example: Breaking Out of Deep Nesting

#include <stdio.h>
int main() {
	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 3; j++) {
			if (i == 1 && j == 1) {
				goto cleanup;
			}
		}
	}
	cleanup:
	printf("Exited both loops");
	return 0;
}

Backward Jumps

Because goto can jump to a label that appears earlier in the code, it's possible to build a loop by jumping backward to a label — but you must make sure the surrounding condition eventually evaluates false, or that backward jump repeats forever exactly like a runaway while loop.

Example: Backward Jumps

#include <stdio.h>
int main() {
	int i = 0;
	loopStart:
	if (i < 3) {
		printf("%d ", i);
		i++;
		goto loopStart;
	}
	return 0;
}

Best Practices with goto

Most C style guides restrict goto to a narrow set of legitimate uses, chiefly escaping deeply nested loops and centralizing cleanup code (like closing several open resources before returning), while steering clear of using it as a general substitute for structured loops and conditionals.

Example: Best Practices with goto

#include <stdio.h>
int main() {
	int success = 0;
	if (!success) {
		goto cleanup;
	}
	printf("never runs");
	cleanup:
	printf("Centralized cleanup reached");
	return 0;
}

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