Memory

Files
file	stdlib.h

Functions
void *	malloc (size_t size)
	Allocate memory. More...
void	free (void *ptr)
	Free allocated memory. More...

Detailed Description

With malloc() (memory allocation) a program can request memory from the operating system. The allocated memory is usable until it is free()'d again. It is important, that programs always check if a malloc() call was successful and free their memory after usage, otherwise a so-called memory leak exists.

// allocate memory
char *s = malloc(strlen("Hello World\n") + 1);
if (s == NULL) {
    perror("malloc");
    exit(EXIT_FAILURE);
}
 
// use allocated memory
strcpy(s, "Hello World\n");
printf("%s", s);
 
// free allocated memory
free(s);

Function Documentation

malloc()

void* malloc

(

size_t

size

)

The malloc() function allocates size bytes at the heap and returns a pointer to the allocated memory or NULL if an error has been occurred. Be aware, that the memory is not initialized after a successful call to malloc().

Parameters

size	number of bytes to be allocated

Return values

NULL	on error, errno is set
!=NULL	pointer to allocated memory

free()

void free

(

void *

ptr

)

The free() function frees the memory pointed to by ptr, which must have been returned by a previous call to malloc(). Otherwise, or if free(ptr) has already been called before, undefined behavior occurs. If ptr is NULL, no operation is performed.

Parameters

ptr	pointer to buffer