Deallocate a memory block.
| #include <stdlib.h> | For ANSI compatibility (free only) | |
| #include <malloc.h> | Required only for function declarations |
void free( void *memblock );
void _bfree( __segment seg, void __based( void ) *memblock );
void _ffree( void __far *memblock );
void _nfree( void __near *memblock );
| memblock | Allocated memory block | |
| seg | Based-heap segment selector |
The free family of functions deallocates a memory block. The argument memblock points to a memory block previously allocated through a call to calloc, malloc, or realloc. The number of bytes freed is the number of bytes specified when the block was allocated (or reallocated, in the case of realloc). After the call, the freed block is available for allocation.
The seg argument specifies the based heap containing the memory block to be freed by the _bfree function.
Attempting to free an invalid pointer may affect subsequent allocation and cause errors. An invalid pointer is one not allocated with the appropriate call.
The following restrictions apply to use of the free, _bfree, _ffree, and _nfree functions:
| Blocks allocated with: | Should be freed with: |
| calloc, malloc, realloc | free |
| _bcalloc, _bmalloc, _brealloc | _bfree |
| _fcalloc, _fmalloc, _frealloc | _ffree |
| _ncalloc, _nmalloc, _nrealloc | _nfree |
A NULL pointer argument is ignored.
In large data models (compact-, large-, and huge-model programs), free maps to _ffree. In small data models (tiny-, small-, and medium-model programs), free maps to _nfree.
The various free functions deallocate a memory block in the segments shown in the list below:
| Function | Data Segment |
| free | Depends on data model of program |
| _bfree | Based heap specified by seg value |
| _ffree | Far heap (outside default data segment) |
| _nfree | Near heap (inside default data segment) |
None.
free
Standards:ANSI, UNIX
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:DOS32X
_bfree, _ffree, _nfree
Standards:None
16-Bit:DOS, WIN, WIN DLL
32-Bit:None
calloc functions, malloc functions, realloc functions
/* MALLOC.C: This program allocates memory with malloc, then frees
* the memory with free.
*/
#include <stdlib.h> /* Definition of _MAX_PATH */
#include <stdio.h>
#include <malloc.h>
void main( void )
{
char *string;
/* Allocate space for a path name */
string = malloc( _MAX_PATH );
if( string == NULL )
printf( “Insufficient memory available\n” );
else
printf( “Memory space allocated for path name\n” );
free( string );
printf( “Memory freed\n” );
}
Memory space allocated for path name
Memory freed