C: Using calloc() For Dynamic Memory Allocation.
Video demonstration: https://youtu.be/xhnOzx4TzH4
https://github.com/pereiradaniel/c_programs/blob/master/dyn_mem/calloc/calloc.c
// Dynamic Memory Allocation - calloc
// ----------------------------------
// This program accepts user input to create a dynamic array of ints.
// calloc zeroes the space first!
#include <stdio.h>
#include <stdlib.h> // calloc!
int main(int argc, char* argv[])
{
// Prompt user for number of ints for dynamic memory allocation:
int num_ints = 0;
printf("This program will dynamically allocate memory for an array of ints.\nHow many ints would you like? ");
scanf(" %d", &num_ints);
// Create a dynamically allocated array of integers using user input:
int *a = calloc(num_ints, sizeof(int));
// Displays zeroed data first:
printf("Using calloc zeroes all the data first:\n");
for (int i=0; i<num_ints; ++i)
printf("a[%d] = %d\n", i, a[i]);
printf("\n"); // new line!
// Use for loop to assign values to the int array a.
for (int i=0; i<num_ints; ++i)
a[i] = i;
// Use for loop to print contents of array a.
printf("After the ints have been assigned:\n");
for (int i=0; i<num_ints; ++i)
printf("a[%d] = %d\n", i, a[i]);
printf("\n"); // new line!
printf("a: %p\n", a); // Prints memory location of a.
int *save = a; // Save memory location to ptr a!
free(a); // Deallocate memory!
// Display contents of memory locations that were free'd.
// free() does not delete data, it simply frees it for use again, therefore some data will remain.
printf("save: %p\n", save); // Prints memory location of save.
// Display memory after using free:
for (int i=0; i<num_ints; ++i)
printf("save[%d] = %d\n", i, save[i]);
printf("\n"); // new line!
return 0;
}==215== Memcheck, a memory error detector ==215== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==215== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==215== Command: ./calloc ==215== This program will dynamically allocate memory for an array of ints. How many ints would you like? 5 Using calloc zeroes all the data first: a[0] = 0 a[1] = 0 a[2] = 0 a[3] = 0 a[4] = 0 After the ints have been assigned: a[0] = 0 a[1] = 1 a[2] = 2 a[3] = 3 a[4] = 4 a: 0x4a4e8c0 save: 0x4a4e8c0 ==215== Invalid read of size 4 ==215== at 0x1093AE: main (in /mnt/c/Users/perei/source/repos/c_programs/dyn_mem/calloc/calloc) ==215== Address 0x4a4e8c0 is 0 bytes inside a block of size 20 free'd ==215== at 0x483CA3F: free (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==215== by 0x109378: main (in /mnt/c/Users/perei/source/repos/c_programs/dyn_mem/calloc/calloc) ==215== Block was alloc'd at ==215== at 0x483DD99: calloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==215== by 0x10926C: main (in /mnt/c/Users/perei/source/repos/c_programs/dyn_mem/calloc/calloc) ==215== save[0] = 0 save[1] = 1 save[2] = 2 save[3] = 3 save[4] = 4 ==215== ==215== HEAP SUMMARY: ==215== in use at exit: 0 bytes in 0 blocks ==215== total heap usage: 3 allocs, 3 frees, 2,068 bytes allocated ==215== ==215== All heap blocks were freed -- no leaks are possible ==215== ==215== For lists of detected and suppressed errors, rerun with: -s ==215== ERROR SUMMARY: 5 errors from 1 contexts (suppressed: 0 from 0)
