Add Base.hash() method to sidestep python's hash()

claripy/ast/base.py

@@ -491,6 +491,14 @@ def _arg_serialize(arg: ArgType | Annotation) -> bytes:
     def __hash__(self) -> int:
         return self._hash
 
+    def hash(self) -> int:
+        """Python's built in hash function is not collision resistant, so we use our own.
+        When you call `hash(ast)`, the value is derived from the claripy hash, but it gets
+        passed through python's non-resistent hash function first. This skips that step,
+        allowing the claripy hash to be used directly, eg as a cache key.
+        """
+        return self._hash
+
     @property
     def cache_key(self: Self) -> ASTCacheKey[Self]:
         """
@@ -834,7 +842,7 @@ def children_asts(self) -> Iterator[Base]:
             if isinstance(ast, Base):
                 ast_queue.append(iter(ast.args))
 
-                l.debug("Yielding AST %s with hash %s with %d children", ast, hash(ast), len(ast.args))
+                l.debug("Yielding AST %s with hash %s with %d children", ast, ast.hash(), len(ast.args))
                 yield ast
 
     def leaf_asts(self) -> Iterator[Base]:
@@ -862,14 +870,14 @@ def is_leaf(self) -> bool:
         """
         return self.depth == 1
 
-    def dbg_is_looped(self) -> bool:
-        l.debug("Checking AST with hash %s for looping", hash(self))
+    def dbg_is_looped(self) -> Base | bool:  # TODO: this return type is bad
+        l.debug("Checking AST with hash %s for looping", self.hash())
 
         seen = set()
         for child_ast in self.children_asts():
-            if hash(child_ast) in seen:
+            if child_ast.hash() in seen:
                 return child_ast
-            seen.add(hash(child_ast))
+            seen.add(child_ast.hash())
 
         return False
 

claripy/frontend_mixins/constraint_deduplicator_mixin.py

@@ -26,14 +26,14 @@ def simplify(self):
         # we only add to the constraint hashes because we want to
         # prevent previous (now simplified) constraints from
         # being re-added
-        self._constraint_hashes.update(map(hash, added))
+        self._constraint_hashes.update(c.hash() for c in added)
         return added
 
     def _add(self, constraints, invalidate_cache=True):
-        filtered = tuple(c for c in constraints if hash(c) not in self._constraint_hashes)
+        filtered = tuple(c for c in constraints if c.hash() not in self._constraint_hashes)
         if len(filtered) == 0:
             return filtered
 
         added = super()._add(filtered, invalidate_cache=invalidate_cache)
-        self._constraint_hashes.update(map(hash, added))
+        self._constraint_hashes.update(c.hash() for c in added)
         return added

tests/test_expression.py

@@ -119,9 +119,9 @@ def test_expression(self):
         new_formula = old_formula.replace(old, new)
         ooo_formula = new_formula.replace(new, ooo)
 
-        self.assertNotEqual(hash(old_formula), hash(new_formula))
-        self.assertNotEqual(hash(old_formula), hash(ooo_formula))
-        self.assertNotEqual(hash(new_formula), hash(ooo_formula))
+        self.assertNotEqual(old_formula.hash(), new_formula.hash())
+        self.assertNotEqual(old_formula.hash(), ooo_formula.hash())
+        self.assertNotEqual(new_formula.hash(), ooo_formula.hash())
 
         self.assertEqual(old_formula.variables, frozenset(("old",)))
         self.assertEqual(new_formula.variables, frozenset(("new",)))

tests/test_serial.py

@@ -67,8 +67,8 @@ def test_identity(self):
         s.add(x == 3)
         s.finalize()
         ss = pickle.loads(pickle.dumps(s))
-        old_constraint_sets = [[hash(j) for j in k.constraints] for k in s._solver_list]
-        new_constraint_sets = [[hash(j) for j in k.constraints] for k in ss._solver_list]
+        old_constraint_sets = [[j.hash() for j in k.constraints] for k in s._solver_list]
+        new_constraint_sets = [[j.hash() for j in k.constraints] for k in ss._solver_list]
         assert old_constraint_sets == new_constraint_sets
         assert str(s.variables) == str(ss.variables)