man3/malloc_get_state.3

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  25 .TH MALLOC_GET_STATE 3 2016-12-12 "GNU" "Linux Programmer's Manual"
  26 .SH NAME
  27 malloc_get_state, malloc_set_state \- record and restore state of malloc implementation
  28 .SH SYNOPSIS
  29 .nf
  30 .B #include <malloc.h>
  31 .PP
  32 .BI "void* malloc_get_state(void);"
  33
  34 .BI "int malloc_set_state(void *" state );
  35 .fi
  36 .SH DESCRIPTION
  37 .IR Note :
  38 these function are removed in glibc version 2.25.
  39
  40 The
  41 .BR malloc_get_state ()
  42 function records the current state of all
  43 .BR malloc (3)
  44 internal bookkeeping variables
  45 (but not the actual contents of the heap
  46 or the state of
  47 .BR malloc_hook (3)
  48 functions pointers).
  49 The state is recorded in a system-dependent opaque data structure
  50 dynamically allocated via
  51 .BR malloc (3),
  52 and a pointer to that data structure is returned as the function result.
  53 (It is the caller's responsibility to
  54 .BR free (3)
  55 this memory.)
  56
  57 The
  58 .BR malloc_set_state ()
  59 function restores the state of all
  60 .BR malloc (3)
  61 internal bookkeeping variables to the values recorded in
  62 the opaque data structure pointed to by
  63 .IR state .
  64 .SH RETURN VALUE
  65 On success,
  66 .BR malloc_get_state ()
  67 returns a pointer to a newly allocated opaque data structure.
  68 On error (for example, memory could not be allocated for the data structure),
  69 .BR malloc_get_state ()
  70 returns NULL.
  71
  72 On success,
  73 .BR malloc_set_state ()
  74 returns 0.
  75 If the implementation detects that
  76 .I state
  77 does not point to a correctly formed data structure,
  78 .\" if(ms->magic != MALLOC_STATE_MAGIC) return -1;
  79 .BR malloc_set_state ()
  80 returns \-1.
  81 If the implementation detects that
  82 the version of the data structure referred to by
  83 .I state
  84 is a more recent version than this implementation knows about,
  85 .\" /* Must fail if the major version is too high. */
  86 .\" if((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl)) return -2;
  87 .BR malloc_set_state ()
  88 returns \-2.
  89 .SH ATTRIBUTES
  90 For an explanation of the terms used in this section, see
  91 .BR attributes (7).
  92 .TS
  93 allbox;
  94 lbw19 lb lb
  95 l l l.
  96 Interface       Attribute       Value
  97 T{
  98 .BR malloc_get_state (),
  99 .BR malloc_set_state ()
 100 T}      Thread safety   MT-Safe
 101 .TE
 102
 103 .SH CONFORMING TO
 104 These functions are GNU extensions.
 105 .SH NOTES
 106 These functions are useful when using this
 107 .BR malloc (3)
 108 implementation as part of a shared library,
 109 and the heap contents are saved/restored via some other method.
 110 This technique is used by GNU Emacs to implement its "dumping" function.
 111
 112 Hook function pointers are never saved or restored by these
 113 functions, with two exceptions:
 114 if malloc checking (see
 115 .BR mallopt (3))
 116 was in use when
 117 .BR malloc_get_state ()
 118 was called, then
 119 .BR malloc_set_state ()
 120 resets malloc checking hooks
 121 .\" i.e., calls __malloc_check_init()
 122 if possible;
 123 .\" i.e., malloc checking is not already in use
 124 .\" and the caller requested malloc checking
 125 if malloc checking was not in use in the recorded state,
 126 but the caller has requested malloc checking,
 127 then the hooks are reset to 0.
 128 .SH SEE ALSO
 129 .BR malloc (3),
 130 .BR mallopt (3)