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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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MALLOC(3P) POSIX Programmer's Manual MALLOC(3P)
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.
malloc — a memory allocator
#include <stdlib.h>
void *malloc(size_t size);
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 malloc() function shall allocate unused space for an object
whose size in bytes is specified by size and whose value is
unspecified.
The order and contiguity of storage allocated by successive calls
to malloc() is unspecified. The pointer returned if the
allocation succeeds shall be suitably aligned so that it may be
assigned to a pointer to any type of object and then used to
access such an object in the space allocated (until the space is
explicitly freed or reallocated). Each such allocation shall
yield a pointer to an object disjoint from any other object. The
pointer returned points to the start (lowest byte address) of the
allocated space. If the space cannot be allocated, a null pointer
shall be returned. If the size of the space requested is 0, the
behavior is implementation-defined: either a null pointer shall
be returned, or the behavior shall be as if the size were some
non-zero value, except that the behavior is undefined if the
returned pointer is used to access an object.
Upon successful completion with size not equal to 0, malloc()
shall return a pointer to the allocated space. If size is 0,
either:
* A null pointer shall be returned and errno may be set to an
implementation-defined value, or
* A pointer to the allocated space shall be returned. The
application shall ensure that the pointer is not used to
access an object.
Otherwise, it shall return a null pointer and set errno to
indicate the error.
The malloc() function shall fail if:
ENOMEM Insufficient storage space is available.
The following sections are informative.
None.
None.
None.
None.
calloc(3p), free(3p), getrlimit(3p), posix_memalign(3p),
realloc(3p)
The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)
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 .
IEEE/The Open Group 2017 MALLOC(3P)
Pages that refer to this page: stdlib.h(0p), calloc(3p), fmemopen(3p), free(3p), getcwd(3p), getdelim(3p), getrlimit(3p), hcreate(3p), posix_memalign(3p), putenv(3p), realloc(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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