C

malloc in c

#include <stdlib.h>

void *malloc(size_t size);

void exemple(void)
{
  char *string;
  
  string = malloc(sizeof(char) * 5);
  if (string == NULL)
    return;
  string[0] = 'H';
  string[1] = 'e';
  string[2] = 'y';
  string[3] = '!';
  string[4] = '';
  printf("%s
", string);
  free(string);
}

/// output : "Hey!"

what does malloc do

adds specified amount of memory but there could be more writable memory ahead, so you have to decide how much you access

how to use malloc in c

int* a =(int*)malloc(sizeof(int))

malloc basics

// Program to calculate the sum of n numbers entered by the user

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

int main() {
  int n, i, *ptr, sum = 0;

  printf("Enter number of elements: ");
  scanf("%d", &n);

  ptr = (int*) malloc(n * sizeof(int));
 
  // if memory cannot be allocated
  if(ptr == NULL) {
    printf("Error! memory not allocated.");
    exit(0);
  }

  printf("Enter elements: ");
  for(i = 0; i < n; ++i) {
    scanf("%d", ptr + i);
    sum += *(ptr + i);
  }

  printf("Sum = %d", sum);
  
  // deallocating the memory
  free(ptr);

  return 0;
}

malloc

// if you initialize a pointer and want to use it like an array, 
// you have to claim the space you use, 
// that is what the memory-allocation-funtion (malloc) does;

// exaple for that: str(0) belongs to you, but str(1), str(2), ... do not
// if you do not use the malloc funtion; 
// you can access it, but it could be used by another programm;

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

void func(void)
{
    char *str = malloc(sizeof(char) * 5); // sizeof --> char needs 
    // a specific space per value saved;
    // *5 --> 5 is the number of values in the array;

    char *str1 = malloc( 5 * sizeof *str1 );//      |
    char *str2 = malloc( sizeof(char[5]) );//       | other syntaxes

    if(str == NULL) { exit(1); } // malloc returns NULL 
    // if it could not allocate the memory;
    str[0] = 'H';
    *(str+1) = 'e';	// used like pointer
    str[2] = 'y';	// used like array
    *(str+3) = '!';
    str[4] = '';

    printf("%s
", str);

    free(str); // frees the memory allocated to str;
    // if you free the memory too early and try to access str later
    // that is called a memory leak;
}

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

// shell: Hey!

// improved version of Thurger's

malloc in c

// Let's allocate enough space on the heap for an array storing 4 ints

intArray = (int *) malloc(4 * sizeof(int)); // A pointer to an array of ints

intArray[0] = 10;
intArray[1] = 20;
intArray[2] = 25;
intArray[3] = 35;

malloc

/*
 *Dynamic memory creation using malloc
 *Language: C
 */

#include<stdio.h>
//To use malloc function in our program
#include<stdlib.h>

int main()
{
    int *ptr;

    //allocating memory for 1 integer
    ptr = malloc(sizeof(int));

    if(ptr != NULL)
           printf("Memory created successfully
");

    return 0;
}

what is the use of malloc in c

In C, the library function malloc is used to allocate a block of memory on the heap. The program accesses this block of memory via a pointer that malloc returns. When the memory is no longer needed, the pointer is passed to free which deallocates the memory so that it can be used for other purposes.

malloc

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

char *create_array(unsigned int, char);

/**
 * main - check the code .
 *
 * Return: Always 0.
 */
int main(void)
{
	char *buffer;
	unsigned int size;

	size = 0;
	buffer = create_array(size, 'H');
	if (buffer == NULL)
	{
		printf("failed to allocate memory
");
		return (1);
	}
	free(buffer);
	return (0);
}

Malloc

ptr = malloc(size); //You dont need to cast

malloc

char *ptr;
ptr = malloc(10);