1 /* Copyright (c) 2007-2014. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
10 #include "simgrid_config.h"
16 #include <elfutils/libdw.h>
19 #include "mc/datatypes.h"
21 #include "xbt/config.h"
22 #include "xbt/function_types.h"
23 #include "xbt/mmalloc.h"
24 #include "../simix/smx_private.h"
25 #include "../xbt/mmalloc/mmprivate.h"
26 #include "xbt/automaton.h"
29 #include "msg/datatypes.h"
30 #include "xbt/strbuff.h"
31 #include "xbt/parmap.h"
34 typedef struct s_dw_frame s_dw_frame_t, *dw_frame_t;
35 typedef struct s_mc_function_index_item s_mc_function_index_item_t, *mc_function_index_item_t;
37 /****************************** Snapshots ***********************************/
39 #define NB_REGIONS 3 /* binary data (data + BSS) (type = 2), libsimgrid data (data + BSS) (type = 1), std_heap (type = 0)*/
41 typedef struct s_mc_mem_region{
46 // Size of the data region:
48 // For per-page snapshots, this is an array to the number of
50 } s_mc_mem_region_t, *mc_mem_region_t;
52 static inline __attribute__ ((always_inline))
53 bool mc_region_contain(mc_mem_region_t region, void* p)
55 return p >= region->start_addr &&
56 p < (void*)((char*) region->start_addr + region->size);
61 * Some parts of the snapshot are ignored by zeroing them out: the real
62 * values is stored here.
64 typedef struct s_mc_snapshot_ignored_data {
68 } s_mc_snapshot_ignored_data_t, *mc_snapshot_ignored_data_t;
70 typedef struct s_mc_snapshot{
71 size_t heap_bytes_used;
72 mc_mem_region_t regions[NB_REGIONS];
73 xbt_dynar_t enabled_processes;
74 mc_mem_region_t* privatization_regions;
75 int privatization_index;
78 xbt_dynar_t to_ignore;
80 xbt_dynar_t ignored_data;
81 } s_mc_snapshot_t, *mc_snapshot_t;
83 mc_mem_region_t mc_get_snapshot_region(void* addr, mc_snapshot_t snapshot);
85 static inline __attribute__ ((always_inline))
86 mc_mem_region_t mc_get_region_hinted(void* addr, mc_snapshot_t snapshot, mc_mem_region_t region)
88 if (mc_region_contain(region, addr))
91 return mc_get_snapshot_region(addr, snapshot);
94 /** Information about a given stack frame
97 typedef struct s_mc_stack_frame {
98 /** Instruction pointer */
102 unw_word_t frame_base;
105 unw_cursor_t unw_cursor;
106 } s_mc_stack_frame_t, *mc_stack_frame_t;
108 typedef struct s_mc_snapshot_stack{
109 xbt_dynar_t local_variables;
110 xbt_dynar_t stack_frames; // mc_stack_frame_t
111 }s_mc_snapshot_stack_t, *mc_snapshot_stack_t;
113 typedef struct s_mc_global_t{
114 mc_snapshot_t snapshot;
118 int initial_communications_pattern_done;
119 int comm_deterministic;
120 int send_deterministic;
121 }s_mc_global_t, *mc_global_t;
123 typedef struct s_mc_checkpoint_ignore_region{
126 }s_mc_checkpoint_ignore_region_t, *mc_checkpoint_ignore_region_t;
130 static void* mc_snapshot_get_heap_end(mc_snapshot_t snapshot);
132 mc_snapshot_t SIMIX_pre_mc_snapshot(smx_simcall_t simcall);
133 mc_snapshot_t MC_take_snapshot(int num_state);
134 void MC_restore_snapshot(mc_snapshot_t);
135 void MC_free_snapshot(mc_snapshot_t);
137 int mc_important_snapshot(mc_snapshot_t snapshot);
139 size_t* mc_take_page_snapshot_region(void* data, size_t page_count, uint64_t* pagemap, size_t* reference_pages);
140 void mc_free_page_snapshot_region(size_t* pagenos, size_t page_count);
141 void mc_restore_page_snapshot_region(mc_mem_region_t region, size_t page_count, uint64_t* pagemap, mc_mem_region_t reference_region);
143 mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc_mem_region_t ref_reg);
144 void mc_region_restore_sparse(mc_mem_region_t reg, mc_mem_region_t ref_reg);
145 void mc_softdirty_reset();
147 typedef struct s_mc_pages_store s_mc_pages_store_t, * mc_pages_store_t;
148 mc_pages_store_t mc_pages_store_new();
149 const void* mc_page_store_get_page(mc_pages_store_t page_store, size_t pageno);
151 static inline __attribute__((always_inline))
152 bool mc_snapshot_region_linear(mc_mem_region_t region) {
153 return !region || !region->data;
156 void* mc_snapshot_read_region(void* addr, mc_mem_region_t region, void* target, size_t size);
157 void* mc_snapshot_read(void* addr, mc_snapshot_t snapshot, void* target, size_t size);
158 int mc_snapshot_region_memcp(
159 void* addr1, mc_mem_region_t region1,
160 void* addr2, mc_mem_region_t region2, size_t size);
161 int mc_snapshot_memcp(
162 void* addr1, mc_snapshot_t snapshot1,
163 void* addr2, mc_snapshot_t snapshot2, size_t size);
165 static void* mc_snapshot_read_pointer(void* addr, mc_snapshot_t snapshot);
167 /** @brief State of the model-checker (global variables for the model checker)
169 * Each part of the state of the model chercker represented as a global
170 * variable prevents some sharing between snapshots and must be ignored.
171 * By moving as much state as possible in this structure allocated
172 * on the model-chercker heap, we avoid those issues.
174 typedef struct s_mc_model_checker {
175 // This is the parent snapshot of the current state:
176 mc_snapshot_t parent_snapshot;
177 mc_pages_store_t pages;
180 } s_mc_model_checker_t, *mc_model_checker_t;
182 extern mc_model_checker_t mc_model_checker;
184 void* mc_translate_address_region(uintptr_t addr, mc_mem_region_t region);
186 /** \brief Translate a pointer from process address space to snapshot address space
188 * The address space contains snapshot of the main/application memory:
189 * this function finds the address in a given snaphot for a given
190 * real/application address.
192 * For read only memory regions and other regions which are not int the
193 * snapshot, the address is not changed.
195 * \param addr Application address
196 * \param snapshot The snapshot of interest (if NULL no translation is done)
197 * \return Translated address in the snapshot address space
199 void* mc_translate_address(uintptr_t addr, mc_snapshot_t snapshot);
201 extern xbt_dynar_t mc_checkpoint_ignore;
203 /********************************* MC Global **********************************/
205 extern double *mc_time;
206 extern FILE *dot_output;
207 extern const char* colors[13];
208 extern xbt_parmap_t parmap;
210 extern int user_max_depth_reached;
212 int MC_deadlock_check(void);
213 void MC_replay(xbt_fifo_t stack, int start);
214 void MC_replay_liveness(xbt_fifo_t stack, int all_stack);
215 void MC_wait_for_requests(void);
216 void MC_show_deadlock(smx_simcall_t req);
217 void MC_show_stack_safety(xbt_fifo_t stack);
218 void MC_dump_stack_safety(xbt_fifo_t stack);
219 int SIMIX_pre_mc_random(smx_simcall_t simcall, int min, int max);
221 extern xbt_fifo_t mc_stack;
222 int get_search_interval(xbt_dynar_t list, void *ref, int *min, int *max);
225 /********************************* Requests ***********************************/
227 int MC_request_depend(smx_simcall_t req1, smx_simcall_t req2);
228 char* MC_request_to_string(smx_simcall_t req, int value);
229 unsigned int MC_request_testany_fail(smx_simcall_t req);
230 /*int MC_waitany_is_enabled_by_comm(smx_req_t req, unsigned int comm);*/
231 int MC_request_is_visible(smx_simcall_t req);
232 int MC_request_is_enabled(smx_simcall_t req);
233 int MC_request_is_enabled_by_idx(smx_simcall_t req, unsigned int idx);
234 int MC_process_is_enabled(smx_process_t process);
235 char *MC_request_get_dot_output(smx_simcall_t req, int value);
238 /******************************** States **************************************/
240 extern mc_global_t initial_global_state;
242 /* Possible exploration status of a process in a state */
244 MC_NOT_INTERLEAVE=0, /* Do not interleave (do not execute) */
245 MC_INTERLEAVE, /* Interleave the process (one or more request) */
246 MC_MORE_INTERLEAVE, /* Interleave twice the process (for mc_random simcall) */
247 MC_DONE /* Already interleaved */
248 } e_mc_process_state_t;
250 /* On every state, each process has an entry of the following type */
251 typedef struct mc_procstate{
252 e_mc_process_state_t state; /* Exploration control information */
253 unsigned int interleave_count; /* Number of times that the process was
255 } s_mc_procstate_t, *mc_procstate_t;
257 /* An exploration state is composed of: */
258 typedef struct mc_state {
259 unsigned long max_pid; /* Maximum pid at state's creation time */
260 mc_procstate_t proc_status; /* State's exploration status by process */
261 s_smx_action_t internal_comm; /* To be referenced by the internal_req */
262 s_smx_simcall_t internal_req; /* Internal translation of request */
263 s_smx_simcall_t executed_req; /* The executed request of the state */
264 int req_num; /* The request number (in the case of a
265 multi-request like waitany ) */
266 mc_snapshot_t system_state; /* Snapshot of system state */
268 } s_mc_state_t, *mc_state_t;
270 mc_state_t MC_state_new(void);
271 void MC_state_delete(mc_state_t state);
272 void MC_state_interleave_process(mc_state_t state, smx_process_t process);
273 unsigned int MC_state_interleave_size(mc_state_t state);
274 int MC_state_process_is_done(mc_state_t state, smx_process_t process);
275 void MC_state_set_executed_request(mc_state_t state, smx_simcall_t req, int value);
276 smx_simcall_t MC_state_get_executed_request(mc_state_t state, int *value);
277 smx_simcall_t MC_state_get_internal_request(mc_state_t state);
278 smx_simcall_t MC_state_get_request(mc_state_t state, int *value);
279 void MC_state_remove_interleave_process(mc_state_t state, smx_process_t process);
282 /****************************** Statistics ************************************/
284 typedef struct mc_stats {
285 unsigned long state_size;
286 unsigned long visited_states;
287 unsigned long visited_pairs;
288 unsigned long expanded_states;
289 unsigned long expanded_pairs;
290 unsigned long executed_transitions;
291 } s_mc_stats_t, *mc_stats_t;
293 extern mc_stats_t mc_stats;
295 void MC_print_statistics(mc_stats_t);
298 /********************************** MEMORY ******************************/
299 /* The possible memory modes for the modelchecker are standard and raw. */
300 /* Normally the system should operate in std, for switching to raw mode */
301 /* you must wrap the code between MC_SET_RAW_MODE and MC_UNSET_RAW_MODE */
303 extern void *std_heap;
304 extern void *mc_heap;
307 /* FIXME: Horrible hack! because the mmalloc library doesn't provide yet of */
308 /* an API to query about the status of a heap, we simply call mmstats and */
309 /* because I now how does structure looks like, then I redefine it here */
311 /* struct mstats { */
312 /* size_t bytes_total; /\* Total size of the heap. *\/ */
313 /* size_t chunks_used; /\* Chunks allocated by the user. *\/ */
314 /* size_t bytes_used; /\* Byte total of user-allocated chunks. *\/ */
315 /* size_t chunks_free; /\* Chunks in the free list. *\/ */
316 /* size_t bytes_free; /\* Byte total of chunks in the free list. *\/ */
319 #define MC_SET_MC_HEAP mmalloc_set_current_heap(mc_heap)
320 #define MC_SET_STD_HEAP mmalloc_set_current_heap(std_heap)
323 /******************************* MEMORY MAPPINGS ***************************/
324 /* These functions and data structures implements a binary interface for */
325 /* the proc maps ascii interface */
327 /* Each field is defined as documented in proc's manual page */
328 typedef struct s_map_region {
330 void *start_addr; /* Start address of the map */
331 void *end_addr; /* End address of the map */
332 int prot; /* Memory protection */
333 int flags; /* Additional memory flags */
334 void *offset; /* Offset in the file/whatever */
335 char dev_major; /* Major of the device */
336 char dev_minor; /* Minor of the device */
337 unsigned long inode; /* Inode in the device */
338 char *pathname; /* Path name of the mapped file */
342 typedef struct s_memory_map {
344 s_map_region_t *regions; /* Pointer to an array of regions */
345 int mapsize; /* Number of regions in the memory */
347 } s_memory_map_t, *memory_map_t;
350 void MC_init_memory_map_info(void);
351 memory_map_t MC_get_memory_map(void);
352 void MC_free_memory_map(memory_map_t map);
354 extern char *libsimgrid_path;
356 /********************************** Snapshot comparison **********************************/
358 typedef struct s_mc_comparison_times{
359 double nb_processes_comparison_time;
360 double bytes_used_comparison_time;
361 double stacks_sizes_comparison_time;
362 double binary_global_variables_comparison_time;
363 double libsimgrid_global_variables_comparison_time;
364 double heap_comparison_time;
365 double stacks_comparison_time;
366 }s_mc_comparison_times_t, *mc_comparison_times_t;
368 extern __thread mc_comparison_times_t mc_comp_times;
369 extern __thread double mc_snapshot_comparison_time;
371 int snapshot_compare(void *state1, void *state2);
372 int SIMIX_pre_mc_compare_snapshots(smx_simcall_t simcall, mc_snapshot_t s1, mc_snapshot_t s2);
373 void print_comparison_times(void);
378 /********************************** Safety verification **************************************/
386 extern e_mc_reduce_t mc_reduce_kind;
387 extern xbt_dict_t first_enabled_state;
389 void MC_pre_modelcheck_safety(void);
390 void MC_modelcheck_safety(void);
392 typedef struct s_mc_visited_state{
393 mc_snapshot_t system_state;
394 size_t heap_bytes_used;
397 int other_num; // dot_output for
398 }s_mc_visited_state_t, *mc_visited_state_t;
400 extern xbt_dynar_t visited_states;
401 int is_visited_state(void);
402 void visited_state_free(mc_visited_state_t state);
403 void visited_state_free_voidp(void *s);
405 /********************************** Liveness verification **************************************/
407 extern xbt_automaton_t _mc_property_automaton;
409 typedef struct s_mc_pair{
412 mc_state_t graph_state; /* System state included */
413 xbt_automaton_state_t automaton_state;
414 xbt_dynar_t atomic_propositions;
416 }s_mc_pair_t, *mc_pair_t;
418 typedef struct s_mc_visited_pair{
420 int other_num; /* Dot output for */
422 mc_state_t graph_state; /* System state included */
423 xbt_automaton_state_t automaton_state;
424 xbt_dynar_t atomic_propositions;
425 size_t heap_bytes_used;
427 int acceptance_removed;
429 }s_mc_visited_pair_t, *mc_visited_pair_t;
431 mc_pair_t MC_pair_new(void);
432 void MC_pair_delete(mc_pair_t);
433 void mc_pair_free_voidp(void *p);
434 mc_visited_pair_t MC_visited_pair_new(int pair_num, xbt_automaton_state_t automaton_state, xbt_dynar_t atomic_propositions);
435 void MC_visited_pair_delete(mc_visited_pair_t p);
437 void MC_pre_modelcheck_liveness(void);
438 void MC_modelcheck_liveness(void);
439 void MC_show_stack_liveness(xbt_fifo_t stack);
440 void MC_dump_stack_liveness(xbt_fifo_t stack);
442 extern xbt_dynar_t visited_pairs;
443 int is_visited_pair(mc_visited_pair_t pair, int pair_num, xbt_automaton_state_t automaton_state, xbt_dynar_t atomic_propositions);
446 /********************************** Variables with DWARF **********************************/
448 #define MC_OBJECT_INFO_EXECUTABLE 1
450 struct s_mc_object_info {
453 char *start_exec, *end_exec; // Executable segment
454 char *start_rw, *end_rw; // Read-write segment
455 char *start_ro, *end_ro; // read-only segment
456 xbt_dict_t subprograms; // xbt_dict_t<origin as hexadecimal string, dw_frame_t>
457 xbt_dynar_t global_variables; // xbt_dynar_t<dw_variable_t>
458 xbt_dict_t types; // xbt_dict_t<origin as hexadecimal string, dw_type_t>
459 xbt_dict_t full_types_by_name; // xbt_dict_t<name, dw_type_t> (full defined type only)
461 // Here we sort the minimal information for an efficient (and cache-efficient)
462 // lookup of a function given an instruction pointer.
463 // The entries are sorted by low_pc and a binary search can be used to look them up.
464 xbt_dynar_t functions_index;
467 mc_object_info_t MC_new_object_info(void);
468 mc_object_info_t MC_find_object_info(memory_map_t maps, char* name, int executable);
469 void MC_free_object_info(mc_object_info_t* p);
471 void MC_dwarf_get_variables(mc_object_info_t info);
472 void MC_dwarf_get_variables_libdw(mc_object_info_t info);
473 const char* MC_dwarf_attrname(int attr);
474 const char* MC_dwarf_tagname(int tag);
476 dw_frame_t MC_find_function_by_ip(void* ip);
477 mc_object_info_t MC_ip_find_object_info(void* ip);
479 extern mc_object_info_t mc_libsimgrid_info;
480 extern mc_object_info_t mc_binary_info;
481 extern mc_object_info_t mc_object_infos[2];
482 extern size_t mc_object_infos_size;
484 void MC_find_object_address(memory_map_t maps, mc_object_info_t result);
485 void MC_post_process_types(mc_object_info_t info);
486 void MC_post_process_object_info(mc_object_info_t info);
490 /** \brief a DWARF expression with optional validity contraints */
491 typedef struct s_mc_expression {
494 // Optional validity:
495 void* lowpc, *highpc;
496 } s_mc_expression_t, *mc_expression_t;
498 /** A location list (list of location expressions) */
499 typedef struct s_mc_location_list {
501 mc_expression_t locations;
502 } s_mc_location_list_t, *mc_location_list_t;
504 uintptr_t mc_dwarf_resolve_location(mc_expression_t expression, mc_object_info_t object_info, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot);
505 uintptr_t mc_dwarf_resolve_locations(mc_location_list_t locations, mc_object_info_t object_info, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot);
507 void mc_dwarf_expression_clear(mc_expression_t expression);
508 void mc_dwarf_expression_init(mc_expression_t expression, size_t len, Dwarf_Op* ops);
510 void mc_dwarf_location_list_clear(mc_location_list_t list);
512 void mc_dwarf_location_list_init_from_expression(mc_location_list_t target, size_t len, Dwarf_Op* ops);
513 void mc_dwarf_location_list_init(mc_location_list_t target, mc_object_info_t info, Dwarf_Die* die, Dwarf_Attribute* attr);
515 // ***** Variables and functions
519 Dwarf_Off id; /* Offset in the section (in hexadecimal form) */
520 char *name; /* Name of the type */
521 int byte_size; /* Size in bytes */
522 int element_count; /* Number of elements for array type */
523 char *dw_type_id; /* DW_AT_type id */
524 xbt_dynar_t members; /* if DW_TAG_structure_type, DW_TAG_class_type, DW_TAG_union_type*/
527 // Location (for members) is either of:
528 struct s_mc_expression location;
531 dw_type_t subtype; // DW_AT_type
532 dw_type_t full_type; // The same (but more complete) type
535 void* mc_member_resolve(const void* base, dw_type_t type, dw_type_t member, mc_snapshot_t snapshot);
537 typedef struct s_dw_variable{
538 Dwarf_Off dwarf_offset; /* Global offset of the field. */
545 s_mc_location_list_t locations;
549 mc_object_info_t object_info;
551 }s_dw_variable_t, *dw_variable_t;
558 s_mc_location_list_t frame_base;
559 xbt_dynar_t /* <dw_variable_t> */ variables; /* Cannot use dict, there may be several variables with the same name (in different lexical blocks)*/
560 unsigned long int id; /* DWARF offset of the subprogram */
561 xbt_dynar_t /* <dw_frame_t> */ scopes;
562 Dwarf_Off abstract_origin_id;
563 mc_object_info_t object_info;
566 struct s_mc_function_index_item {
567 void* low_pc, *high_pc;
571 void mc_frame_free(dw_frame_t freme);
573 void dw_type_free(dw_type_t t);
574 void dw_variable_free(dw_variable_t v);
575 void dw_variable_free_voidp(void *t);
577 void MC_dwarf_register_global_variable(mc_object_info_t info, dw_variable_t variable);
578 void MC_register_variable(mc_object_info_t info, dw_frame_t frame, dw_variable_t variable);
579 void MC_dwarf_register_non_global_variable(mc_object_info_t info, dw_frame_t frame, dw_variable_t variable);
580 void MC_dwarf_register_variable(mc_object_info_t info, dw_frame_t frame, dw_variable_t variable);
582 /** Find the DWARF offset for this ELF object
584 * An offset is applied to address found in DWARF:
587 * <li>for an executable obejct, addresses are virtual address
588 * (there is no offset) i.e. \f$\text{virtual address} = \{dwarf address}\f$;</li>
589 * <li>for a shared object, the addreses are offset from the begining
590 * of the shared object (the base address of the mapped shared
591 * object must be used as offset
592 * i.e. \f$\text{virtual address} = \text{shared object base address}
593 * + \text{dwarf address}\f$.</li>
596 void* MC_object_base_address(mc_object_info_t info);
598 /********************************** DWARF **********************************/
600 #define MC_EXPRESSION_STACK_SIZE 64
602 #define MC_EXPRESSION_OK 0
603 #define MC_EXPRESSION_E_UNSUPPORTED_OPERATION 1
604 #define MC_EXPRESSION_E_STACK_OVERFLOW 2
605 #define MC_EXPRESSION_E_STACK_UNDERFLOW 3
606 #define MC_EXPRESSION_E_MISSING_STACK_CONTEXT 4
607 #define MC_EXPRESSION_E_MISSING_FRAME_BASE 5
608 #define MC_EXPRESSION_E_NO_BASE_ADDRESS 6
610 typedef struct s_mc_expression_state {
611 uintptr_t stack[MC_EXPRESSION_STACK_SIZE];
614 unw_cursor_t* cursor;
616 mc_snapshot_t snapshot;
617 mc_object_info_t object_info;
618 } s_mc_expression_state_t, *mc_expression_state_t;
620 int mc_dwarf_execute_expression(size_t n, const Dwarf_Op* ops, mc_expression_state_t state);
622 void* mc_find_frame_base(dw_frame_t frame, mc_object_info_t object_info, unw_cursor_t* unw_cursor);
624 /********************************** Miscellaneous **********************************/
626 typedef struct s_local_variable{
627 dw_frame_t subprogram;
633 }s_local_variable_t, *local_variable_t;
635 /********************************* Communications pattern ***************************/
637 typedef struct s_mc_comm_pattern{
640 e_smx_comm_type_t type;
641 unsigned long src_proc;
642 unsigned long dst_proc;
643 const char *src_host;
644 const char *dst_host;
648 }s_mc_comm_pattern_t, *mc_comm_pattern_t;
650 extern xbt_dynar_t communications_pattern;
651 extern xbt_dynar_t incomplete_communications_pattern;
653 void get_comm_pattern(xbt_dynar_t communications_pattern, smx_simcall_t request, int call);
654 void complete_comm_pattern(xbt_dynar_t list, smx_action_t comm);
655 void MC_pre_modelcheck_comm_determinism(void);
656 void MC_modelcheck_comm_determinism(void);
658 /* *********** Sets *********** */
660 typedef struct s_mc_address_set *mc_address_set_t;
662 mc_address_set_t mc_address_set_new();
663 void mc_address_set_free(mc_address_set_t* p);
664 void mc_address_add(mc_address_set_t p, const void* value);
665 bool mc_address_test(mc_address_set_t p, const void* value);
667 /* *********** Hash *********** */
669 /** \brief Hash the current state
670 * \param num_state number of states
671 * \param stacks stacks (mc_snapshot_stak_t) used fot the stack unwinding informations
672 * \result resulting hash
674 uint64_t mc_hash_processes_state(int num_state, xbt_dynar_t stacks);
678 static inline __attribute__ ((always_inline))
679 void* mc_snapshot_get_heap_end(mc_snapshot_t snapshot) {
681 xbt_die("snapshot is NULL");
682 void** addr = &((xbt_mheap_t)std_heap)->breakval;
683 return mc_snapshot_read_pointer(addr, snapshot);
686 static inline __attribute__ ((always_inline))
687 void* mc_snapshot_read_pointer(void* addr, mc_snapshot_t snapshot)
690 return *(void**) mc_snapshot_read(addr, snapshot, &res, sizeof(void*));