{{keywords>wiki library source code example reference}}
====== free ======
<code c>
    #include <stdlib.h>
    void free(void *ptr);
</code> 

=== description ===
The free() function shall cause the space pointed to by ptr to be deallocated; that is, made available for further allocation.\\
If ptr is a null pointer, no action shall occur. Otherwise, if the argument does not match a pointer earlier returned by \\
the calloc(), malloc(), posix_memalign(), realloc(), or strdup() function, or if the space has been deallocated by a call\\
to free() or realloc(), the behavior is undefined.\\
\\
Any use of a pointer that refers to freed space results in undefined behavior.\\

=== return value ===
The free() function shall not return a value.

===== free c Sourcecode Example =====    
<code c>
/* 
 * free example code
 * http://code-reference.com/c/stdlib.h/free
 */
#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */

#include <stdlib.h>

int testit ( int *x )
{
     if (x != NULL) {
         printf("allocation of memory was successfully.\n");
     }
     else {
          printf("allocation of memory failed.\n");
     }
return 0;
}
int main ( void )
{
  int *buffer;
  printf("set buffer to 100 * sizeof(int)\n");
  buffer = (int*) malloc (100*sizeof(int));
  testit(buffer); 
  
  printf("set buffer to 1000 * sizeof(int)\n");
  buffer = (int*) calloc (1000,sizeof(int));
  testit(buffer);

  printf("set buffer to 10 * sizeof(int)\n");
  buffer = (int*) realloc (buffer,10*sizeof(int));
  testit(buffer);

  printf("try to free the buffer\n");
  free (buffer);
  return 0;
}

</code>

==== Output ====
    user@host:~$  ./free 
    set buffer to 100 * sizeof(int)
    allocation of memory was successfully.
    set buffer to 1000 * sizeof(int)
    allocation of memory was successfully.
    set buffer to 10 * sizeof(int)
    allocation of memory was successfully.
    try to free the buffer