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MALLOC_GET_STATE(3) Linux Programmer's Manual MALLOC_GET_STATE(3)
NAME
malloc_get_state, malloc_set_state - record and restore state of malloc implementation
SYNOPSIS
#include <malloc.h>
void *malloc_get_state(void);
int malloc_set_state(void *state);
DESCRIPTION
Note: these function are removed in glibc version 2.25.
The malloc_get_state() function records the current state of all malloc(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 allocated 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) internal 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 allocated for the data
structure), malloc_get_state() returns NULL.
On success, malloc_set_state() returns 0. If the implementation detects that state does not point to a correctly formed data structure, malloc_set_state() re‐
turns -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() returns -2.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
│malloc_get_state(), malloc_set_state() │ Thread safety │ MT-Safe │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘
CONFORMING TO
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 mal‐
loc_get_state() was called, then malloc_set_state() resets malloc 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)
GNU 2021-03-22 MALLOC_GET_STATE(3)