malloc_get_state(3)	    Library Functions Manual	     malloc_get_state(3)

NAME
     malloc_get_state, malloc_set_state - record and restore state of malloc im-
     plementation

LIBRARY
     Standard C library (libc, -lc)

SYNOPSIS
     #include <malloc.h>

     void *malloc_get_state(void);
     int malloc_set_state(void *state);

DESCRIPTION
     Note: these functions are removed in glibc 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  mal-
     loc(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)  inter-
     nal  bookkeeping variables to the values recorded in the opaque data struc-
     ture 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 allo-
     cated 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, mal-
     loc_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() returns -2.

ATTRIBUTES
     For  an  explanation  of the terms used in this section, see attributes(7).
     allbox; lbx lb lb l l l.  Interface Attribute Value T{ malloc_get_state(),
     malloc_set_state() T}   Thread safety  MT-Safe

STANDARDS
     GNU.

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 "dump-
     ing" 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)

Linux man-pages 6.18		   2026-02-08		     malloc_get_state(3)