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free(3p)

IEEE/The Open Group
2013

man-pages

Linux kernel and C library user-space interface documentation

man-pages-posix

POSIX Manual Pages

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.1-2008 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.1-2008, <stdlib.h>

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .
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