[thirdparty/man-pages.git] / man3 / malloc_get_state.3

.\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.TH MALLOC_GET_STATE 3 2012-05-04 "GNU" "Linux Programmer's Manual"
.SH NAME
malloc_get_state, malloc_set_state \- record and restore state of malloc implementation
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
.sp
.BI "void* malloc_get_state(void);"

.BI "int malloc_set_state(void *" state );
.fi
.SH DESCRIPTION
The
.BR malloc_get_state ()
function records the current state of all
.BR malloc (3)
internal bookkeeping variables
(but not the actual contents of the heap
or the state of
.BR malloc_hook (3)
functions pointers).
The state is recorded in a system-dependent opaque data structure
dynamically allocated via
.BR malloc (3),
and a pointer to that data structure is returned as the function result.
(It is the caller's responsibility to
.BR free (3)
this memory.)

The
.BR malloc_set_state ()
function restores the state of all
.BR malloc (3)
internal bookkeeping variables to the values recorded in
the opaque data structure pointed to by
.IR state .
.SH RETURN VALUE
On success,
.BR malloc_get_state ()
returns a pointer to a newly allocated opaque data structure.
On error (for example, memory could not be allocated for the data structure),
.BR malloc_get_state ()
returns NULL.

On success,
.BR malloc_set_state ()
returns 0.
If the implementation detects that
.I state
does not point to a correctly formed data structure,
.\" if(ms->magic != MALLOC_STATE_MAGIC) return -1;
.BR malloc_set_state ()
returns \-1.
If the implementation detects that
the version of the data structure referred to by
.I state
is a more recent version than this implementation knows about,
.\" /* Must fail if the major version is too high. */
.\" if((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl)) return -2;
.BR malloc_set_state ()
returns \-2.
.SH CONFORMING TO
These functions are GNU extensions.
.SH NOTES
These functions are especially useful when using this
.BR malloc (3)
implementation as part of a shared library,
and the heap contents are saved/restored via some other method.
This technique is used by the GNU Emacs to implement its "dumping" function.

Hook function pointers are never saved or restored by these
functions, with two exceptions:
if malloc checking (see
.BR mallopt (3))
was in use when
.BR malloc_get_state ()
was called, then
.BR malloc_set_state ()
resets malloc checking hooks
.\" i.e., calls __malloc_check_init()
if possible;
.\" i.e., malloc checking is not already in use
.\" and the caller requested malloc checking
if malloc checking was not in use in the recorded state,
but the caller has requested malloc checking,
then the hooks are reset to 0.
.SH SEE ALSO
.BR malloc (3),
.BR mallopt (3)
Commit	Line	Data
0669cc5f MK	1	.\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com>
0669cc5f MK	2	.\"
93015253	3	.\" %%%LICENSE_START(VERBATIM)
0669cc5f MK	4	.\" Permission is granted to make and distribute verbatim copies of this
	5	.\" manual provided the copyright notice and this permission notice are
	6	.\" preserved on all copies.
	7	.\"
	8	.\" Permission is granted to copy and distribute modified versions of this
	9	.\" manual under the conditions for verbatim copying, provided that the
	10	.\" entire resulting derived work is distributed under the terms of a
	11	.\" permission notice identical to this one.
	12	.\"
	13	.\" Since the Linux kernel and libraries are constantly changing, this
	14	.\" manual page may be incorrect or out-of-date. The author(s) assume no
	15	.\" responsibility for errors or omissions, or for damages resulting from
	16	.\" the use of the information contained herein. The author(s) may not
	17	.\" have taken the same level of care in the production of this manual,
	18	.\" which is licensed free of charge, as they might when working
	19	.\" professionally.
	20	.\"
	21	.\" Formatted or processed versions of this manual, if unaccompanied by
	22	.\" the source, must acknowledge the copyright and authors of this work.
4b72fb64	23	.\" %%%LICENSE_END
0669cc5f	24	.\"
092af13a	25	.TH MALLOC_GET_STATE 3 2012-05-04 "GNU" "Linux Programmer's Manual"
0669cc5f	26	.SH NAME
092af13a	27	malloc_get_state, malloc_set_state \- record and restore state of malloc implementation
0669cc5f MK	28	.SH SYNOPSIS
	29	.nf
	30	.B #include <stdlib.h>
	31	.sp
	32	.BI "void* malloc_get_state(void);"
	33
	34	.BI "int malloc_set_state(void *" state );
	35	.fi
	36	.SH DESCRIPTION
	37	The
	38	.BR malloc_get_state ()
	39	function records the current state of all
	40	.BR malloc (3)
	41	internal bookkeeping variables
	42	(but not the actual contents of the heap
	43	or the state of
	44	.BR malloc_hook (3)
	45	functions pointers).
	46	The state is recorded in a system-dependent opaque data structure
	47	dynamically allocated via
	48	.BR malloc (3),
	49	and a pointer to that data structure is returned as the function result.
	50	(It is the caller's responsibility to
	51	.BR free (3)
	52	this memory.)
	53
	54	The
	55	.BR malloc_set_state ()
	56	function restores the state of all
	57	.BR malloc (3)
	58	internal bookkeeping variables to the values recorded in
	59	the opaque data structure pointed to by
	60	.IR state .
	61	.SH RETURN VALUE
	62	On success,
	63	.BR malloc_get_state ()
	64	returns a pointer to a newly allocated opaque data structure.
	65	On error (for example, memory could not be allocated for the data structure),
	66	.BR malloc_get_state ()
	67	returns NULL.
	68
	69	On success,
	70	.BR malloc_set_state ()
	71	returns 0.
	72	If the implementation detects that
	73	.I state
	74	does not point to a correctly formed data structure,
	75	.\" if(ms->magic != MALLOC_STATE_MAGIC) return -1;
	76	.BR malloc_set_state ()
	77	returns \-1.
	78	If the implementation detects that
	79	the version of the data structure referred to by
	80	.I state
	81	is a more recent version than this implementation knows about,
	82	.\" /* Must fail if the major version is too high. */
	83	.\" if((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl)) return -2;
	84	.BR malloc_set_state ()
	85	returns \-2.
	86	.SH CONFORMING TO
	87	These functions are GNU extensions.
	88	.SH NOTES
	89	These functions are especially useful when using this
	90	.BR malloc (3)
	91	implementation as part of a shared library,
92	and the heap contents are saved/restored via some other method.
93	This technique is used by the GNU Emacs to implement its "dumping" function.
94
95	Hook function pointers are never saved or restored by these
96	functions, with two exceptions:
97	if malloc checking (see
98	.BR mallopt (3))
99	was in use when
100	.BR malloc_get_state ()
101	was called, then
102	.BR malloc_set_state ()
103	resets malloc checking hooks
104	.\" i.e., calls __malloc_check_init()
105	if possible;
106	.\" i.e., malloc checking is not already in use
107	.\" and the caller requested malloc checking
108	if malloc checking was not in use in the recorded state,
109	but the caller has requested malloc checking,
110	then the hooks are reset to 0.
111	.SH SEE ALSO
112	.BR malloc (3),
113	.BR mallopt (3)