c - What is the best way to free memory after returning from an error?

Question

Suppose I have a function that allocates memory for the caller:

int func(void **mem1, void **mem2) {
    *mem1 = malloc(SIZE);
    if (!*mem1) return 1;

    *mem2 = malloc(SIZE);
    if (!*mem2) {
        /* ... */
        return 1;
    }

    return 0;
}

I'd like to hear your feedback on the best way to free() the allocated memory in case the second malloc() fails. You can imagine a more elaborate situation with more error exit points and more allocated memory.

Answer 1

I know people are loathe to use them, but this is the perfect situation for a goto in C.

int func( void** mem1, void** mem2 )
{
    int retval = 0;
    *mem1 = malloc(SIZE);
    if (!*mem1) {
        retval = 1;
        goto err;
    }

    *mem2 = malloc(SIZE);
    if (!*mem2) {
        retval = 1;
        goto err;
    }
// ...     
    goto out;
// ...
err:
    if( *mem1 ) free( *mem1 );
    if( *mem2 ) free( *mem2 );
out:
    return retval;
}