comparison: handle preops like "if (++a == b)"
[smatch.git] / smatch_implied.c
blob3e6afad90c5340ccac347884d0314a9d255460c0
1 /*
2 * Copyright (C) 2008 Dan Carpenter.
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
19 * Imagine we have this code:
20 * foo = 1;
21 * if (bar)
22 * foo = 99;
23 * else
24 * frob();
25 * // <-- point #1
26 * if (foo == 99) // <-- point #2
27 * bar->baz; // <-- point #3
30 * At point #3 bar is non null and can be dereferenced.
32 * It's smatch_implied.c which sets bar to non null at point #2.
34 * At point #1 merge_slist() stores the list of states from both
35 * the true and false paths. On the true path foo == 99 and on
36 * the false path foo == 1. merge_slist() sets their pool
37 * list to show the other states which were there when foo == 99.
39 * When it comes to the if (foo == 99) the smatch implied hook
40 * looks for all the pools where foo was not 99. It makes a list
41 * of those.
43 * Then for bar (and all the other states) it says, ok bar is a
44 * merged state that came from these previous states. We'll
45 * chop out all the states where it came from a pool where
46 * foo != 99 and merge it all back together.
48 * That is the implied state of bar.
50 * merge_slist() sets up ->pool. An sm_state only has one ->pool and
51 * that is the pool where it was first set. The my pool gets set when
52 * code paths merge. States that have been set since the last merge do
53 * not have a ->pool.
54 * merge_sm_state() sets ->left and ->right. (These are the states which were
55 * merged to form the current state.)
56 * a pool: a pool is an slist that has been merged with another slist.
59 #include <sys/time.h>
60 #include <time.h>
61 #include "smatch.h"
62 #include "smatch_slist.h"
63 #include "smatch_extra.h"
65 char *implied_debug_msg;
66 #define DIMPLIED(msg...) do { if (option_debug_implied) printf(msg); } while (0)
68 int option_debug_implied = 0;
69 int option_no_implied = 0;
71 #define RIGHT 0
72 #define LEFT 1
75 * tmp_range_list():
76 * It messes things up to free range list allocations. This helper fuction
77 * lets us reuse memory instead of doing new allocations.
79 static struct range_list *tmp_range_list(long long num)
81 static struct range_list *my_list = NULL;
82 static struct data_range *my_range;
84 __free_ptr_list((struct ptr_list **)&my_list);
85 my_range = alloc_range(ll_to_sval(num), ll_to_sval(num));
86 add_ptr_list(&my_list, my_range);
87 return my_list;
90 static void print_debug_tf(struct sm_state *s, int istrue, int isfalse)
92 if (!option_debug_implied && !option_debug)
93 return;
95 if (istrue && isfalse) {
96 printf("'%s = %s' from %d does not exist.\n", s->name,
97 show_state(s->state), s->line);
98 } else if (istrue) {
99 printf("'%s = %s' from %d is true. [stree %d]\n", s->name, show_state(s->state),
100 s->line, get_stree_id(s->pool));
101 } else if (isfalse) {
102 printf("'%s = %s' from %d is false. [stree %d]\n", s->name, show_state(s->state),
103 s->line, get_stree_id(s->pool));
104 } else {
105 printf("'%s = %s' from %d could be true or false. [stree %d]\n", s->name,
106 show_state(s->state), s->line, get_stree_id(s->pool));
111 * add_pool() adds a slist to *pools. If the slist has already been
112 * added earlier then it doesn't get added a second time.
114 static void add_pool(struct stree_stack **pools, struct stree *new)
116 struct stree *tmp;
118 FOR_EACH_PTR(*pools, tmp) {
119 if (tmp < new)
120 continue;
121 else if (tmp == new) {
122 return;
123 } else {
124 INSERT_CURRENT(new, tmp);
125 return;
127 } END_FOR_EACH_PTR(tmp);
128 add_ptr_list(pools, new);
132 * If 'foo' == 99 add it that pool to the true pools. If it's false, add it to
133 * the false pools. If we're not sure, then we don't add it to either.
135 static void do_compare(struct sm_state *sm_state, int comparison, struct range_list *vals,
136 int lr,
137 struct stree_stack **true_stack,
138 struct stree_stack **false_stack)
140 struct sm_state *s;
141 int istrue;
142 int isfalse;
144 if (!sm_state->pool)
145 return;
147 if (is_implied(sm_state)) {
148 s = get_sm_state_stree(sm_state->pool,
149 sm_state->owner, sm_state->name,
150 sm_state->sym);
151 } else {
152 s = sm_state;
155 if (!s) {
156 if (option_debug_implied || option_debug)
157 sm_msg("%s from %d, has borrowed implications.",
158 sm_state->name, sm_state->line);
159 return;
162 if (lr == LEFT) {
163 istrue = !possibly_false_rl(estate_rl(s->state), comparison, vals);
164 isfalse = !possibly_true_rl(estate_rl(s->state), comparison, vals);
165 } else {
166 istrue = !possibly_false_rl(vals, comparison, estate_rl(s->state));
167 isfalse = !possibly_true_rl(vals, comparison, estate_rl(s->state));
170 print_debug_tf(s, istrue, isfalse);
172 if (istrue)
173 add_pool(true_stack, s->pool);
175 if (isfalse)
176 add_pool(false_stack, s->pool);
179 static int pool_in_pools(struct stree *pool,
180 struct stree_stack *pools)
182 struct stree *tmp;
184 FOR_EACH_PTR(pools, tmp) {
185 if (tmp == pool)
186 return 1;
187 if (tmp > pool)
188 return 0;
189 } END_FOR_EACH_PTR(tmp);
190 return 0;
193 static int is_checked(struct state_list *checked, struct sm_state *sm)
195 struct sm_state *tmp;
197 FOR_EACH_PTR(checked, tmp) {
198 if (tmp == sm)
199 return 1;
200 } END_FOR_EACH_PTR(tmp);
201 return 0;
205 * separate_pools():
206 * Example code: if (foo == 99) {
208 * Say 'foo' is a merged state that has many possible values. It is the combination
209 * of merges. separate_pools() iterates through the pools recursively and calls
210 * do_compare() for each time 'foo' was set.
212 static void separate_pools(struct sm_state *sm_state, int comparison, struct range_list *vals,
213 int lr,
214 struct stree_stack **true_stack,
215 struct stree_stack **false_stack,
216 struct state_list **checked)
218 int free_checked = 0;
219 struct state_list *checked_states = NULL;
221 if (!sm_state)
222 return;
225 Sometimes the implications are just too big to deal with
226 so we bail. Theoretically, bailing out here can cause more false
227 positives but won't hide actual bugs.
229 if (sm_state->nr_children > 4000) {
230 static char buf[1028];
231 snprintf(buf, sizeof(buf), "debug: separate_pools: nr_children over 4000 (%d). (%s %s)",
232 sm_state->nr_children, sm_state->name, show_state(sm_state->state));
233 implied_debug_msg = buf;
234 return;
237 if (checked == NULL) {
238 checked = &checked_states;
239 free_checked = 1;
241 if (is_checked(*checked, sm_state))
242 return;
243 add_ptr_list(checked, sm_state);
245 do_compare(sm_state, comparison, vals, lr, true_stack, false_stack);
247 separate_pools(sm_state->left, comparison, vals, lr, true_stack, false_stack, checked);
248 separate_pools(sm_state->right, comparison, vals, lr, true_stack, false_stack, checked);
249 if (free_checked)
250 free_slist(checked);
253 struct sm_state *filter_pools(struct sm_state *sm,
254 struct stree_stack *remove_stack,
255 struct stree_stack *keep_stack,
256 int *modified)
258 struct sm_state *ret = NULL;
259 struct sm_state *left;
260 struct sm_state *right;
261 int removed = 0;
263 if (!sm)
264 return NULL;
266 if (sm->nr_children > 4000) {
267 static char buf[1028];
268 snprintf(buf, sizeof(buf), "debug: %s: nr_children over 4000 (%d). (%s %s)",
269 __func__, sm->nr_children, sm->name, show_state(sm->state));
270 implied_debug_msg = buf;
271 return NULL;
274 if (pool_in_pools(sm->pool, remove_stack)) {
275 DIMPLIED("removed %s from %d [stree %d]\n", show_sm(sm), sm->line, get_stree_id(sm->pool));
276 *modified = 1;
277 return NULL;
280 if (!is_merged(sm) || pool_in_pools(sm->pool, keep_stack)) {
281 DIMPLIED("kept %s from %d [stree %d]\n", show_sm(sm), sm->line, get_stree_id(sm->pool));
282 return sm;
285 DIMPLIED("checking %s from %d (%d) [stree %d] left = %s [stree %d] right = %s [stree %d]\n",
286 show_sm(sm), sm->line, sm->nr_children, get_stree_id(sm->pool),
287 sm->left ? show_sm(sm->left) : "<none>", sm->left ? get_stree_id(sm->left->pool) : -1,
288 sm->right ? show_sm(sm->right) : "<none>", sm->right ? get_stree_id(sm->right->pool) : -1);
289 left = filter_pools(sm->left, remove_stack, keep_stack, &removed);
290 right = filter_pools(sm->right, remove_stack, keep_stack, &removed);
291 if (!removed) {
292 DIMPLIED("kept %s from %d [stree %d]\n", show_sm(sm), sm->line, get_stree_id(sm->pool));
293 return sm;
295 *modified = 1;
296 if (!left && !right) {
297 DIMPLIED("removed %s from %d <none> [stree %d]\n", show_sm(sm), sm->line, get_stree_id(sm->pool));
298 return NULL;
301 if (!left) {
302 ret = clone_sm(right);
303 ret->merged = 1;
304 ret->right = right;
305 ret->left = NULL;
306 ret->pool = sm->pool;
307 } else if (!right) {
308 ret = clone_sm(left);
309 ret->merged = 1;
310 ret->left = left;
311 ret->right = NULL;
312 ret->pool = sm->pool;
313 } else {
314 ret = merge_sm_states(left, right);
315 ret->pool = sm->pool;
317 ret->implied = 1;
318 DIMPLIED("partial %s => ", show_sm(sm));
319 DIMPLIED("%s from %d [stree %d]\n", show_sm(ret), sm->line, get_stree_id(sm->pool));
320 return ret;
323 static int highest_stree_id(struct sm_state *sm)
325 int left = 0;
326 int right = 0;
328 if (!sm->left && !sm->right)
329 return 0;
331 if (sm->left)
332 left = get_stree_id(sm->left->pool);
333 if (sm->right)
334 right = get_stree_id(sm->right->pool);
336 if (right > left)
337 return right;
338 return left;
341 static struct stree *filter_stack(struct sm_state *gate_sm,
342 struct stree *pre_stree,
343 struct stree_stack *remove_stack,
344 struct stree_stack *keep_stack)
346 struct stree *ret = NULL;
347 struct sm_state *tmp;
348 struct sm_state *filtered_sm;
349 int modified;
351 if (!remove_stack)
352 return NULL;
354 FOR_EACH_SM(pre_stree, tmp) {
355 if (highest_stree_id(tmp) < highest_stree_id(gate_sm)) {
356 DIMPLIED("skipping %s. set before. %d vs %d\n",
357 tmp->name, highest_stree_id(tmp),
358 highest_stree_id(gate_sm));
359 continue;
361 modified = 0;
362 filtered_sm = filter_pools(tmp, remove_stack, keep_stack, &modified);
363 if (filtered_sm && modified) {
364 /* the assignments here are for borrowed implications */
365 filtered_sm->name = tmp->name;
366 filtered_sm->sym = tmp->sym;
367 avl_insert(&ret, filtered_sm);
368 if (out_of_memory())
369 return NULL;
372 } END_FOR_EACH_SM(tmp);
373 return ret;
376 static void separate_and_filter(struct sm_state *sm_state, int comparison, struct range_list *vals,
377 int lr,
378 struct stree *pre_stree,
379 struct stree **true_states,
380 struct stree **false_states)
382 struct stree_stack *true_stack = NULL;
383 struct stree_stack *false_stack = NULL;
384 struct timeval time_before;
385 struct timeval time_after;
387 gettimeofday(&time_before, NULL);
389 if (!is_merged(sm_state)) {
390 DIMPLIED("%d '%s' is not merged.\n", get_lineno(), sm_state->name);
391 return;
394 if (option_debug_implied || option_debug) {
395 if (lr == LEFT)
396 sm_msg("checking implications: (%s %s %s)",
397 sm_state->name, show_special(comparison), show_rl(vals));
398 else
399 sm_msg("checking implications: (%s %s %s)",
400 show_rl(vals), show_special(comparison), sm_state->name);
403 separate_pools(sm_state, comparison, vals, lr, &true_stack, &false_stack, NULL);
405 DIMPLIED("filtering true stack.\n");
406 *true_states = filter_stack(sm_state, pre_stree, false_stack, true_stack);
407 DIMPLIED("filtering false stack.\n");
408 *false_states = filter_stack(sm_state, pre_stree, true_stack, false_stack);
409 free_stree_stack(&true_stack);
410 free_stree_stack(&false_stack);
411 if (option_debug_implied || option_debug) {
412 printf("These are the implied states for the true path:\n");
413 __print_stree(*true_states);
414 printf("These are the implied states for the false path:\n");
415 __print_stree(*false_states);
418 gettimeofday(&time_after, NULL);
419 if (time_after.tv_sec - time_before.tv_sec > 7)
420 __bail_on_rest_of_function = 1;
423 static struct expression *get_left_most_expr(struct expression *expr)
425 expr = strip_expr(expr);
426 if (expr->type == EXPR_ASSIGNMENT)
427 return get_left_most_expr(expr->left);
428 return expr;
431 static int is_merged_expr(struct expression *expr)
433 struct sm_state *sm;
434 sval_t dummy;
436 if (get_value(expr, &dummy))
437 return 0;
438 sm = get_sm_state_expr(SMATCH_EXTRA, expr);
439 if (!sm)
440 return 0;
441 if (is_merged(sm))
442 return 1;
443 return 0;
446 static void delete_equiv_stree(struct stree **stree, const char *name, struct symbol *sym)
448 struct smatch_state *state;
449 struct relation *rel;
451 state = get_state(SMATCH_EXTRA, name, sym);
452 if (!estate_related(state)) {
453 delete_state_stree(stree, SMATCH_EXTRA, name, sym);
454 return;
457 FOR_EACH_PTR(estate_related(state), rel) {
458 delete_state_stree(stree, SMATCH_EXTRA, rel->name, rel->sym);
459 } END_FOR_EACH_PTR(rel);
462 static void handle_comparison(struct expression *expr,
463 struct stree **implied_true,
464 struct stree **implied_false)
466 struct sm_state *sm = NULL;
467 struct range_list *ranges = NULL;
468 struct expression *left;
469 struct expression *right;
470 int lr;
472 left = get_left_most_expr(expr->left);
473 right = get_left_most_expr(expr->right);
475 if (is_merged_expr(left)) {
476 lr = LEFT;
477 sm = get_sm_state_expr(SMATCH_EXTRA, left);
478 get_implied_rl(right, &ranges);
479 } else if (is_merged_expr(right)) {
480 lr = RIGHT;
481 sm = get_sm_state_expr(SMATCH_EXTRA, right);
482 get_implied_rl(left, &ranges);
485 if (!ranges || !sm) {
486 free_rl(&ranges);
487 return;
490 separate_and_filter(sm, expr->op, ranges, lr, __get_cur_stree(), implied_true, implied_false);
491 free_rl(&ranges);
492 delete_equiv_stree(implied_true, sm->name, sm->sym);
493 delete_equiv_stree(implied_false, sm->name, sm->sym);
496 static void handle_zero_comparison(struct expression *expr,
497 struct stree **implied_true,
498 struct stree **implied_false)
500 struct symbol *sym;
501 char *name;
502 struct sm_state *sm;
504 if (expr->type == EXPR_POSTOP)
505 expr = strip_expr(expr->unop);
507 if (expr->type == EXPR_ASSIGNMENT) {
508 /* most of the time ->pools will be empty here because we
509 just set the state, but if have assigned a conditional
510 function there are implications. */
511 expr = expr->left;
514 name = expr_to_var_sym(expr, &sym);
515 if (!name || !sym)
516 goto free;
517 sm = get_sm_state(SMATCH_EXTRA, name, sym);
518 if (!sm)
519 goto free;
521 separate_and_filter(sm, SPECIAL_NOTEQUAL, tmp_range_list(0), LEFT, __get_cur_stree(), implied_true, implied_false);
522 delete_equiv_stree(implied_true, name, sym);
523 delete_equiv_stree(implied_false, name, sym);
524 free:
525 free_string(name);
528 static void get_tf_states(struct expression *expr,
529 struct stree **implied_true,
530 struct stree **implied_false)
532 if (expr->type == EXPR_COMPARE)
533 handle_comparison(expr, implied_true, implied_false);
534 else
535 handle_zero_comparison(expr, implied_true, implied_false);
538 static void implied_states_hook(struct expression *expr)
540 struct sm_state *sm;
541 struct stree *implied_true = NULL;
542 struct stree *implied_false = NULL;
544 if (option_no_implied)
545 return;
547 get_tf_states(expr, &implied_true, &implied_false);
549 FOR_EACH_SM(implied_true, sm) {
550 __set_true_false_sm(sm, NULL);
551 } END_FOR_EACH_SM(sm);
552 free_stree(&implied_true);
554 FOR_EACH_SM(implied_false, sm) {
555 __set_true_false_sm(NULL, sm);
556 } END_FOR_EACH_SM(sm);
557 free_stree(&implied_false);
560 struct range_list *__get_implied_values(struct expression *switch_expr)
562 char *name;
563 struct symbol *sym;
564 struct smatch_state *state;
565 struct range_list *ret = NULL;
567 name = expr_to_var_sym(switch_expr, &sym);
568 if (!name || !sym)
569 goto free;
570 state = get_state(SMATCH_EXTRA, name, sym);
571 if (!state)
572 goto free;
573 ret = clone_rl(estate_rl(state));
574 free:
575 free_string(name);
576 if (!ret) {
577 struct symbol *type;
579 type = get_type(switch_expr);
580 ret = alloc_rl(sval_type_min(type), sval_type_max(type));
582 return ret;
585 struct stree *__implied_case_stree(struct expression *switch_expr,
586 struct expression *case_expr,
587 struct range_list_stack **remaining_cases,
588 struct stree **raw_stree)
590 char *name = NULL;
591 struct symbol *sym;
592 struct sm_state *sm;
593 struct stree *true_states = NULL;
594 struct stree *false_states = NULL;
595 struct stree *extra_states = NULL;
596 struct stree *ret = clone_stree(*raw_stree);
597 sval_t sval;
598 struct range_list *vals = NULL;
600 name = expr_to_var_sym(switch_expr, &sym);
601 if (!name || !sym)
602 goto free;
603 sm = get_sm_state_stree(*raw_stree, SMATCH_EXTRA, name, sym);
605 if (case_expr) {
606 if (get_value(case_expr, &sval)) {
607 filter_top_rl(remaining_cases, sval);
608 add_range(&vals, sval, sval);
609 } else {
610 vals = clone_rl(top_rl(*remaining_cases));
612 } else {
613 vals = top_rl(*remaining_cases);
616 if (sm)
617 separate_and_filter(sm, SPECIAL_EQUAL, vals, LEFT, *raw_stree, &true_states, &false_states);
619 __push_fake_cur_stree();
620 __unnullify_path();
621 set_extra_nomod(name, sym, alloc_estate_rl(vals));
622 extra_states = __pop_fake_cur_stree();
623 overwrite_stree(extra_states, &true_states);
624 overwrite_stree(true_states, &ret);
625 free_stree(&extra_states);
626 free_stree(&true_states);
627 free_stree(&false_states);
628 free:
629 free_string(name);
630 return ret;
633 static void match_end_func(struct symbol *sym)
635 if (__inline_fn)
636 return;
637 implied_debug_msg = NULL;
640 static int sm_state_in_slist(struct sm_state *sm, struct state_list *slist)
642 struct sm_state *tmp;
644 FOR_EACH_PTR(slist, tmp) {
645 if (tmp == sm)
646 return 1;
647 } END_FOR_EACH_PTR(tmp);
648 return 0;
652 * The situation is we have a SMATCH_EXTRA state and we want to break it into
653 * each of the ->possible states and find the implications of each. The caller
654 * has to use __push_fake_cur_stree() to preserve the correct states so they
655 * can be restored later.
657 void overwrite_states_using_pool(struct sm_state *sm)
659 struct sm_state *old;
660 struct sm_state *new;
662 if (!sm->pool)
663 return;
665 FOR_EACH_SM(sm->pool, old) {
666 new = get_sm_state(old->owner, old->name, old->sym);
667 if (!new) /* the variable went out of scope */
668 continue;
669 if (sm_state_in_slist(old, new->possible))
670 set_state(old->owner, old->name, old->sym, old->state);
671 } END_FOR_EACH_SM(old);
674 void __extra_match_condition(struct expression *expr);
675 void register_implications(int id)
677 add_hook(&implied_states_hook, CONDITION_HOOK);
678 add_hook(&__extra_match_condition, CONDITION_HOOK);
679 add_hook(&match_end_func, END_FUNC_HOOK);