malloc and free in C

Allocating memory on the heap at run time.

#include <stdlib.h>

int *make_squares(int n) {
    int *items = malloc(n * sizeof(int));
    if (items == NULL)
        return NULL;
    for (int i = 0; i < n; i++)
        items[i] = i * i;
    return items;  /* caller must free() */
}

How it works

1. malloc(n * sizeof(int)) reserves an array.
2. A NULL return means allocation failed.
3. The caller owns the memory and must free it.

Keywords and builtins used here

• NULL
• for
• if
• int
• make_squares
• return
• sizeof

The run, in numbers

Lines

10

Characters to type

205

Tokens

64

Three-star pace

95 tpm

At the three-star pace of 95 tokens a minute, this run takes about 40 seconds.

Type this snippet

Step 1 of 5 in Dynamic memory, step 10 of 25 in Pointers & memory.

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