1MALLOC(3P)                 POSIX Programmer's Manual                MALLOC(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       malloc — a memory allocator
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SYNOPSIS

15       #include <stdlib.h>
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17       void *malloc(size_t size);
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DESCRIPTION

20       The functionality described on this reference page is aligned with  the
21       ISO C  standard.  Any  conflict between the requirements described here
22       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
23       defers to the ISO C standard.
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25       The  malloc()  function shall allocate unused space for an object whose
26       size in bytes is specified by size and whose value is unspecified.
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28       The order and contiguity of storage allocated by  successive  calls  to
29       malloc()  is  unspecified.  The pointer returned if the allocation suc‐
30       ceeds shall be suitably aligned so that it may be assigned to a pointer
31       to  any  type  of  object and then used to access such an object in the
32       space allocated (until the space is explicitly freed  or  reallocated).
33       Each  such  allocation shall yield a pointer to an object disjoint from
34       any other object. The pointer returned points to the start (lowest byte
35       address)  of  the  allocated space. If the space cannot be allocated, a
36       null pointer shall be returned. If the size of the space  requested  is
37       0,  the behavior is implementation-defined: either a null pointer shall
38       be returned, or the behavior shall be as if the size were some non-zero
39       value, except that the behavior is undefined if the returned pointer is
40       used to access an object.
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RETURN VALUE

43       Upon successful completion with size not equal  to  0,  malloc()  shall
44       return a pointer to the allocated space. If size is 0, either:
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46        *  A  null pointer shall be returned and errno may be set to an imple‐
47           mentation-defined value, or
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49        *  A pointer to the allocated space shall be returned. The application
50           shall ensure that the pointer is not used to access an object.
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52       Otherwise, it shall return a null pointer and set errno to indicate the
53       error.
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ERRORS

56       The malloc() function shall fail if:
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58       ENOMEM Insufficient storage space is available.
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60       The following sections are informative.
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EXAMPLES

63       None.
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APPLICATION USAGE

66       None.
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RATIONALE

69       None.
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FUTURE DIRECTIONS

72       None.
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SEE ALSO

75       calloc(), free(), getrlimit(), posix_memalign(), realloc()
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77       The Base Definitions volume of POSIX.1‐2017, <stdlib.h>
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80       Portions of this text are reprinted and reproduced in  electronic  form
81       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
82       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
83       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
84       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
85       event of any discrepancy between this version and the original IEEE and
86       The Open Group Standard, the original IEEE and The Open Group  Standard
87       is  the  referee document. The original Standard can be obtained online
88       at http://www.opengroup.org/unix/online.html .
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90       Any typographical or formatting errors that appear  in  this  page  are
91       most likely to have been introduced during the conversion of the source
92       files to man page format. To report such errors,  see  https://www.ker‐
93       nel.org/doc/man-pages/reporting_bugs.html .
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97IEEE/The Open Group                  2017                           MALLOC(3P)
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