malloc_get_state(3)

1malloc_get_state(3)        Library Functions 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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LIBRARY

10       Standard C library (libc, -lc)
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SYNOPSIS

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

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

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

46       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
47       tributes(7).
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49       ┌────────────────────────────────────────────┬───────────────┬─────────┐
50       │Interface                                   │ Attribute     │ Value   │
51       ├────────────────────────────────────────────┼───────────────┼─────────┤
52       │malloc_get_state(), malloc_set_state()      │ Thread safety │ MT-Safe │
53       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

56       GNU.
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NOTES

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