realloc.3

早期freebsd实现

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.\"     @(#)realloc.3	8.2 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt REALLOC 3
.Os
.Sh NAME
.Nm realloc
.Nd reallocation of memory function
.Sh SYNOPSIS
.Fd #include <stdlib.h>
.Ft void *
.Fn realloc "void *ptr" "size_t size"
.Sh DESCRIPTION
The
.Fn realloc
function changes the size of the object pointed to by
.Fa ptr
to the size specified by
.Fa size .
The contents of the object are unchanged up to the lesser
of the new and old sizes.
If the new size is larger, the value of the newly allocated portion
of the object is indeterminate.
If
.Fa ptr
is a null pointer, the
.Fn realloc
function behaves like the
.Xr malloc 3
function for the specified size.
Otherwise, if
.Fa ptr
does not match a pointer earlier returned by the
.Xr calloc 3 ,
.Xr malloc 3 ,
or 
.Fn realloc
function, or if the space has been deallocated
by a call to the
.Xr free
or
.Fn realloc
function, unpredictable and usually detrimental
behavior will occur.
If the space cannot be allocated, the object 
pointed to by
.Fa ptr
is unchanged.
If
.Fa size
is zero and
.Fa ptr
is not a null pointer, the object it points to is freed.
.Pp
The
.Fn realloc
function returns either a null pointer or a pointer
to the possibly moved allocated space.
.Sh SEE ALSO
.Xr alloca 3 ,
.Xr calloc 3 ,
.Xr free 3 ,
.Xr malloc 3 ,
.Sh STANDARDS
The
.Fn realloc
function conforms to
.St -ansiC .