NAME

free - free allocated memory

SYNOPSIS

#include <stdlib.h>

void free(void *ptr);


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C standard.

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 a function in POSIX.1-2017 that allocates memory as if by malloc(), 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.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

There is now no requirement for the implementation to support the inclusion of <malloc.h>.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

calloc, malloc, posix_memalign, realloc

XBD <stdlib.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

Reference to the valloc() function is removed.

Issue 7

The DESCRIPTION is updated to clarify that if the pointer returned is not by a function that allocates memory as if by malloc(), then the behavior is undefined.