mem_alloc_demo.c

#include <stdlib.h>
#include <stdio.h>
#include <memory.h>

void main() {
	int **data = NULL;
	size_t rows = 4, columns = 5;
	size_t alloc_size = rows * sizeof(int*) + rows * columns * sizeof(int);
	data = (int **)malloc(alloc_size);
	if (!data) {
		perror("Cannot allocate memory");
		exit(1);
	}

	printf("data = %p\n", data);

	for (int i = 0; i < rows; i++) {
		data[i] = (int*)((char *)data + sizeof(int *) * rows + i * columns * sizeof(int));
		printf("&data[%d] = %p\n", i, &data[i]);
		printf("data[%d] = %p\n", i, data[i]);
	}

	for (int i = 0; i < rows; i++) {
		for (int j = 0; j < columns; j++) {
			data[i][j] = 'A' + i * columns + j;
		}
	}

	char * data2 = (char *) data;
	char * end = data2 + alloc_size;
	while(data2 < end) {
		printf("%c ", *data2);
		data2++;
	}
	free(data);
	printf("\n");
}