c - Legitimate uses of a goto

Question

Closed. This question is opinion-based. It is not currently accepting answers. question from:https://stackoverflow.com/questions/65893226/legitimate-uses-of-a-goto

Answer 1

While you can use goto in this way, it's generally considered bad style since the language has other constructs like while that do the same thing in a "cleaner" fashion.

Once place where it does make sense to use goto is to jump forward for error handling situations. For example, this:

void foo()
{
    char *p1 = NULL, *p2 = NULL, *p3 = NULL, *p4 = NULL;
    
    p1 = malloc(1000);
    if (!p1) {
        perror("malloc failed");
        return;
    }
    p2 = malloc(1000);
    if (!p2) {
        perror("malloc failed");
        free(p1);
        return;
    }
    p3 = malloc(1000);
    if (!p3) {
        perror("malloc failed");
        free(p2);
        free(p1);
        return;
    }
    p4 = malloc(1000);
    if (!p4) {
        perror("malloc failed");
        free(p3);
        free(p2);
        free(p1);
        return;
    }

    // Do something with p1, p2, p3, p4

    free(p4);
    free(p3);
    free(p2);
    free(p1);
}

Can be translated to this:

void foo()
{
    char *p1 = NULL, *p2 = NULL, *p3 = NULL, *p4 = NULL;
    
    p1 = malloc(1000);
    if (!p1) {
        perror("malloc failed");
        goto err0;
    }
    p2 = malloc(1000);
    if (!p2) {
        perror("malloc failed");
        goto err1;
    }
    p3 = malloc(1000);
    if (!p3) {
        perror("malloc failed");
        goto err2;
    }
    p4 = malloc(1000);
    if (!p4) {
        perror("malloc failed");
        goto err3;
    }

    // Do something with p1, p2, p3, p4

    free(p4);
err3:
    free(p3);
err2:
    free(p2);
err1:
    free(p1);
err0:
    return;
}

This puts all of the cleanup code in one place.