calloc and zeroing in C

calloc takes a count and a size, and hands back memory already zeroed.

#include <stdlib.h>

int table_is_clean(size_t n) {
    int *table = calloc(n, sizeof(int));
    if (table == NULL) {
        return 0;
    }
    int clean = 1;
    for (size_t i = 0; i < n; i++) {
        if (table[i] != 0) {
            clean = 0;
        }
    }
    free(table);
    return clean;
}

How it works

1. It checks the multiplication for overflow, which malloc does not.
2. The block starts as all zero bytes.
3. free is the same either way.

Keywords and builtins used here

• NULL
• for
• if
• int
• return
• size_t
• sizeof
• table_is_clean

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Type this snippet

Step 2 of 5 in Dynamic memory, step 11 of 25 in Pointers & memory.

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