Linux libc-Doku

Files | Functions
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);
printf
int printf(const char *format,...)
Print formatted data to stdout
perror
void perror(const char *s)
Print an error message.
malloc
void * malloc(size_t size)
Allocate memory.
free
void free(void *ptr)
Free allocated memory.
exit
void exit(int status)
Terminate process.
strcpy
char * strcpy(char *dest, const char *src)
Copy a string.
strlen
size_t strlen(const char *s)
Calculate the length of a string.

Function Documentation

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
sizenumber of bytes to be allocated
Return values
NULLon error, errno is set
!=NULLpointer to allocated memory
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
ptrpointer to buffer