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| .TH MALLOC_GET_STATE 3 2017-09-15 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| malloc_get_state, malloc_set_state \- record and restore state of malloc implementation |
| .SH SYNOPSIS |
| .nf |
| .B #include <malloc.h> |
| .PP |
| .BI "void* malloc_get_state(void);" |
| .PP |
| .BI "int malloc_set_state(void *" state ); |
| .fi |
| .SH DESCRIPTION |
| .IR Note : |
| these function are removed in glibc version 2.25. |
| .PP |
| The |
| .BR malloc_get_state () |
| function records the current state of all |
| .BR malloc (3) |
| internal bookkeeping variables |
| (but not the actual contents of the heap |
| or the state of |
| .BR malloc_hook (3) |
| functions pointers). |
| The state is recorded in a system-dependent opaque data structure |
| dynamically allocated via |
| .BR malloc (3), |
| and a pointer to that data structure is returned as the function result. |
| (It is the caller's responsibility to |
| .BR free (3) |
| this memory.) |
| .PP |
| The |
| .BR malloc_set_state () |
| function restores the state of all |
| .BR malloc (3) |
| internal bookkeeping variables to the values recorded in |
| the opaque data structure pointed to by |
| .IR state . |
| .SH RETURN VALUE |
| On success, |
| .BR 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), |
| .BR malloc_get_state () |
| returns NULL. |
| .PP |
| On success, |
| .BR malloc_set_state () |
| returns 0. |
| If the implementation detects that |
| .I state |
| does not point to a correctly formed data structure, |
| .\" if(ms->magic != MALLOC_STATE_MAGIC) return -1; |
| .BR malloc_set_state () |
| returns \-1. |
| If the implementation detects that |
| the version of the data structure referred to by |
| .I state |
| is a more recent version than this implementation knows about, |
| .\" /* Must fail if the major version is too high. */ |
| .\" if((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl)) return -2; |
| .BR malloc_set_state () |
| returns \-2. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lbw19 lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR malloc_get_state (), |
| .BR malloc_set_state () |
| T} Thread safety MT-Safe |
| .TE |
| .sp 1 |
| .SH CONFORMING TO |
| These functions are GNU extensions. |
| .SH NOTES |
| These functions are useful when using this |
| .BR 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. |
| .PP |
| Hook function pointers are never saved or restored by these |
| functions, with two exceptions: |
| if malloc checking (see |
| .BR mallopt (3)) |
| was in use when |
| .BR malloc_get_state () |
| was called, then |
| .BR malloc_set_state () |
| resets malloc checking hooks |
| .\" i.e., calls __malloc_check_init() |
| if possible; |
| .\" i.e., malloc checking is not already in use |
| .\" and the caller requested malloc checking |
| 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. |
| .SH SEE ALSO |
| .BR malloc (3), |
| .BR mallopt (3) |