Who frees it? in C

C has no destructors, so ownership lives in the naming and the comments.

#include <stdlib.h>
#include <string.h>

/* Caller owns the result and must call name_free. */
char *name_new(const char *source) {
    size_t n = strlen(source);
    char *copy = malloc(n + 1);
    if (copy == NULL) {
        return NULL;
    }
    memcpy(copy, source, n + 1);
    return copy;
}

void name_free(char *name) {
    free(name);
}

/* Borrows only: nothing here is freed. */
size_t name_length(const char *name) {
    return strlen(name);
}

How it works

1. A function whose name creates something returns owned memory.
2. A matching destroy function is the other half of the contract.
3. Borrowed pointers are const and never freed by the callee.

Keywords and builtins used here

• NULL
• char
• const
• if
• name_free
• name_length
• name_new
• return
• size_t
• void

The run, in numbers

Lines

22

Characters to type

415

Tokens

94

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 56 seconds.

Type this snippet

Step 1 of 4 in Ownership & mistakes, step 15 of 25 in Pointers & memory.

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