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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
free — free allocated memory
SYNOPSIS
#include <stdlib.h> void free(void *ptr);
DESCRIPTION
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.1‐2008 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.
The following sections are informative.
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()
The Base Definitions volume of POSIX.1‐2017, <stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original
IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .