malloc_get_state(3) Library Functions Manual malloc_get_state(3)
NAME
malloc_get_state, malloc_set_state - record and restore state of malloc
implementation
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <malloc.h>
void *malloc_get_state(void);
int malloc_set_state(void *state);
DESCRIPTION
Note: these function are removed in glibc 2.25.
The malloc_get_state() function records the current state of all mal-
loc(3) internal bookkeeping variables (but not the actual contents of
the heap or the state of malloc_hook(3) functions pointers). The state
is recorded in a system-dependent opaque data structure dynamically al-
located via malloc(3), and a pointer to that data structure is returned
as the function result. (It is the caller's responsibility to free(3)
this memory.)
The malloc_set_state() function restores the state of all malloc(3) in-
ternal bookkeeping variables to the values recorded in the opaque data
structure pointed to by state.
RETURN VALUE
On success, malloc_get_state() returns a pointer to a newly allocated
opaque data structure. On error (for example, memory could not be al-
located for the data structure), malloc_get_state() returns NULL.
On success, malloc_set_state() returns 0. If the implementation de-
tects that state does not point to a correctly formed data structure,
malloc_set_state() returns -1. If the implementation detects that the
version of the data structure referred to by state is a more recent
version than this implementation knows about, malloc_set_state() re-
turns -2.
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│malloc_get_state(), malloc_set_state() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
These functions are GNU extensions.
NOTES
These functions are useful when using this 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 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 mallopt(3)) was in use
when malloc_get_state() was called, then malloc_set_state() resets mal-
loc checking hooks if possible; 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.
SEE ALSO
malloc(3), mallopt(3)
Linux man-pages 6.03 2022-12-15 malloc_get_state(3)
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