malloc_get_state(3)

1MALLOC_GET_STATE(3)        Linux Programmer's Manual       MALLOC_GET_STATE(3)
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NAME

6       malloc_get_state, malloc_set_state - record and restore state of malloc
7       implementation
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SYNOPSIS

10       #include <malloc.h>
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12       void *malloc_get_state(void);
13       int malloc_set_state(void *state);
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DESCRIPTION

16       Note: these function are removed in glibc version 2.25.
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18       The malloc_get_state() function records the current state of  all  mal‐
19       loc(3)  internal  bookkeeping variables (but not the actual contents of
20       the heap or the state of malloc_hook(3) functions pointers).  The state
21       is recorded in a system-dependent opaque data structure dynamically al‐
22       located via malloc(3), and a pointer to that data structure is returned
23       as  the function result.  (It is the caller's responsibility to free(3)
24       this memory.)
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26       The malloc_set_state() function restores the state of all malloc(3) in‐
27       ternal  bookkeeping variables to the values recorded in the opaque data
28       structure pointed to by state.
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RETURN VALUE

31       On success, malloc_get_state() returns a pointer to a  newly  allocated
32       opaque  data structure.  On error (for example, memory could not be al‐
33       located for the data structure), malloc_get_state() returns NULL.
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35       On success, malloc_set_state() returns 0.  If  the  implementation  de‐
36       tects  that  state does not point to a correctly formed data structure,
37       malloc_set_state() returns -1.  If the implementation detects that  the
38       version  of  the  data  structure referred to by state is a more recent
39       version than this implementation knows  about,  malloc_set_state()  re‐
40       turns -2.
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ATTRIBUTES

43       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
44       tributes(7).
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46       ┌────────────────────────────────────────────┬───────────────┬─────────┐
47       │Interface                                   │ Attribute     │ Value   │
48       ├────────────────────────────────────────────┼───────────────┼─────────┤
49       │malloc_get_state(), malloc_set_state()      │ Thread safety │ MT-Safe │
50       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

53       These functions are GNU extensions.
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NOTES

56       These functions are useful when using this malloc(3) implementation  as
57       part  of a shared library, and the heap contents are saved/restored via
58       some other method.  This technique is used by GNU  Emacs  to  implement
59       its "dumping" function.
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61       Hook  function pointers are never saved or restored by these functions,
62       with two exceptions: if malloc checking (see  mallopt(3))  was  in  use
63       when malloc_get_state() was called, then malloc_set_state() resets mal‐
64       loc checking hooks if possible; if malloc checking was not  in  use  in
65       the  recorded state, but the caller has requested malloc checking, then
66       the hooks are reset to 0.
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COLOPHON

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73       description  of  the project, information about reporting bugs, and the
74       latest    version    of    this    page,    can     be     found     at
75       https://www.kernel.org/doc/man-pages/.
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79GNU                               2021-03-22               MALLOC_GET_STATE(3)