malloc(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       malloc — a memory allocator

SYNOPSIS         top

       #include <stdlib.h>

       void *malloc(size_t size);

DESCRIPTION         top

       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.

RETURN VALUE         top

       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.

ERRORS         top

       The malloc() function shall fail if:

       ENOMEM Insufficient storage space is available.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       calloc(3p), free(3p), getrlimit(3p), posix_memalign(3p),
       realloc(3p)

       The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)

COPYRIGHT         top

       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)