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Fix GH-14361: Deep recursion in zend_cfg.c causes segfault instead of error #14432

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Fix GH-14361: Deep recursion in zend_cfg.c causes segfault instead of error #14432

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62ebccc
Indent current code
nielsdos Jun 3, 2024
d2b79af
Change CFG reachability algorithm to an iterative algorithm
nielsdos Jun 3, 2024
1943c2d
Remove tail call optimization
nielsdos Jun 4, 2024
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29 changes: 14 additions & 15 deletions Zend/Optimizer/zend_cfg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,13 +28,20 @@ static void zend_mark_reachable(zend_op *opcodes, zend_cfg *cfg, zend_basic_bloc
{
zend_basic_block *blocks = cfg->blocks;

while (1) {
zend_worklist work;
ALLOCA_FLAG(list_use_heap)
ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);

zend_worklist_push(&work, b - cfg->blocks);

while (zend_worklist_len(&work)) {
int i;
b = cfg->blocks + zend_worklist_pop(&work);

b->flags |= ZEND_BB_REACHABLE;
if (b->successors_count == 0) {
b->flags |= ZEND_BB_EXIT;
return;
continue;
}

for (i = 0; i < b->successors_count; i++) {
Expand Down Expand Up @@ -86,22 +93,14 @@ static void zend_mark_reachable(zend_op *opcodes, zend_cfg *cfg, zend_basic_bloc
succ->flags |= ZEND_BB_FOLLOW;
}

if (i == b->successors_count - 1) {
/* Tail call optimization */
if (succ->flags & ZEND_BB_REACHABLE) {
return;
}

b = succ;
break;
} else {
/* Recursively check reachability */
if (!(succ->flags & ZEND_BB_REACHABLE)) {
zend_mark_reachable(opcodes, cfg, succ);
}
/* Check reachability of successor */
if (!(succ->flags & ZEND_BB_REACHABLE)) {
zend_worklist_push(&work, succ - cfg->blocks);
}
}
}

ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
}
/* }}} */

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