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.
free — free allocated memory
void free(void *ptr);
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
The free() function shall not return a value.
No errors are defined.
The following sections are informative.
There is now no requirement for the implementation to support the inclusion of
calloc(), malloc(), posix_memalign(),
The Base Definitions volume of POSIX.1‐2017,
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 .
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