Created: 2023-08-21 12:50
Status: #concept
Subject: Programming
Tags: C Library Dynamic Memory Allocation

stdlib.h

Process Control

• void exit(int signal)
  • Allows us to return from the int main() function of the program anywhere in our code.
  • EXIT_SUCCESS and EXIT_FAILURE are Macro Definitions bound to 0 and 1 respectively.
• int system(const char *cmd)
  • executes a cmd string in the CLI, can run Bash commands on a Linux system.

Memory Allocation Functions

• void *malloc(size_t bytes)
  • allocates bytes of memory and returns a void * which can be type casted into other type Pointer Variables.
• void *calloc(size_t items, size_t bytes)
  • allocates items * bytes of memory like malloc(), but sets all the bits in the byte to 0, clearing any data in the Memory Addresses.

struct point { int x, y; } *p;

p = malloc(sizeof(struct point));
// initializes a 'point' struct with random values inside their members

p = calloc(1, sizeof(struct point));
// initializes a 'point' struct with 0 in all members

• void free(void *ptr)
  • frees allocated memory pointed by ptr.

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

int main () {
   char *str;

   /* Initial memory allocation */
   str = (char *) malloc(15);
   strcpy(str, "tutorialspoint");
   printf("String = %s,  Address = %u\n", str, str);

   /* Reallocating memory */
   str = (char *) realloc(str, 25);
   strcat(str, ".com");
   printf("String = %s,  Address = %u\n", str, str);

   /* Deallocate allocated memory */
   free(str);
   
   return(0);
}

String Conversion Functions

• int atoi(const char *str) C String to Integer
• double atof(const char *str) to Double.

References

• WikiBooks Entry