realloc

Reallocate memory and copy data in the old memory to the new memory.

void *realloc(void *old_pointer, size_t new_size);

Parameters

Parameter	Description	Value Range	Input/Output
old_pointer	Pointer to the old memory to be reallocated.	The value cannot be NULL.	Input
new_size	Number of bytes of the reallocated memory.	The value cannot be negative.	Input

Return Value

Success: A pointer to the reallocated memory is returned.
Failure: A null pointer is returned.

Example

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include "kqmalloc.h"

#define KQMALLOC_TEST_LEN 10

void ReallocExample()
{
    int8_t *old_pointer = (int8_t *)malloc(KQMALLOC_TEST_LEN * sizeof(int8_t));
    if (old_pointer == NULL) {
        printf("old_pointer is null\n");
        return;
    } else {
        printf("old_pointer address: %lx\n", old_pointer);
        for (int8_t i = 0; i < KQMALLOC_TEST_LEN; ++i) {
            old_pointer[i] = i;
        }
        printf("old_pointer test data:");
        for (int8_t i = 0; i < KQMALLOC_TEST_LEN; ++i) {
            printf(" %d", old_pointer[i]);
        }
        printf("\n");
    }

    int8_t *new_pointer = (int8_t *)realloc(old_pointer, 2 * KQMALLOC_TEST_LEN * sizeof(int8_t));
    if (new_pointer == NULL) {
        printf("new_pointer is null\n");
        free(old_pointer);
        return;
    } else {
        printf("new_pointer address: %lx\n", new_pointer);
        printf("new_pointer test data:");
        for (int8_t i = 0; i < KQMALLOC_TEST_LEN; ++i) {
            printf(" %d", new_pointer[i]);
        }
        printf("\n");
    }
    free(old_pointer);
    free(new_pointer);
}

int main(void) {
    ReallocExample();
    return 0;
}

Output:

old_pointer address: ffff921c8174
old_pointer test data: 0 1 2 3 4 5 6 7 8 9
new_pointer address: ffff921c87ec
new_pointer test data: 0 1 2 3 4 5 6 7 8 9

Parent topic: Function Syntax