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MALLOC_USABLE_SIZE(3) Linux Programmer's Manual MALLOC_USABLE_SIZE(3)

NAME

     malloc_usable_size - obtain size of block of memory allocated from heap

SYNOPSIS

     #include <malloc.h>

     size_t malloc_usable_size (void *ptr);

DESCRIPTION

     The malloc_usable_size() function returns the number of usable bytes in
     the  block  pointed to by ptr, a pointer to a block of memory allocated
     by malloc(3) or a related function.

RETURN VALUE

     malloc_usable_size() returns the number of usable bytes in the block of
     allocated memory pointed to by ptr.  If ptr is NULL, 0 is returned.

ATTRIBUTES

     For   an   explanation   of   the  terms  used  in  this  section,  see
     attributes(7).

     +---------------------+---------------+---------+
     |Interface            | Attribute     | Value   |
     +---------------------+---------------+---------+
     |malloc_usable_size() | Thread safety | MT-Safe |
     +---------------------+---------------+---------+

CONFORMING TO

     This function is a GNU extension.

NOTES

     The  value  returned  by  malloc_usable_size()  may be greater than the
     requested size of the allocation because of alignment and minimum  size
     constraints.   Although  the  excess  bytes  can  be overwritten by the
     application without ill effects, this is not good programming practice:
     the  number  of excess bytes in an allocation depends on the underlying
     implementation.

     The main use of this function is for debugging and introspection.

SEE ALSO

     malloc(3)

COLOPHON

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GNU 2017-09-15 MALLOC_USABLE_SIZE(3)