C Malloc

programming C MOC

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Variables declared in code are saved to the heap, requiring limits, but data can be put into the heap for varying limits, like user input.

Bytes are allocated with malloc(<bytes>) and reallocated with realloc(<variable>, <bytes>).

Memory must be freed with free(<variable>) at the end of the program, but can exist outside of the context.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
int main () {
   char *msg;
 
   // Initial message added to memory using malloc and strcpy
   msg = (char *) malloc(12);
   strcpy(msg, "Hello there");
   printf("Message: %s\nAddress: %u\n\n", msg, *msg);
 
   // Updating message in memory using realloc and strcat
   msg = (char *) realloc(msg, 26);
   strcat(msg, " from SANS Foundations");
   printf("Message: %s\nAddress: %u\n\n", msg, *msg);
 
   // Free up the memory!
   free(msg);
 
   return(0);
}