Issue #21523: Fix over-pessimistic computation of the stack effect of some opcodes in the compiler.
This also fixes a quadratic compilation time issue noticeable when compiling
code with a large number of "and" and "or" operators.
diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index 4bcb438..ec2709d 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -1,3 +1,4 @@
+import math
import unittest
import sys
import _ast
@@ -519,8 +520,46 @@
self.assertRaises(TypeError, compile, ast, '<ast>', 'exec')
+class TestStackSize(unittest.TestCase):
+ # These tests check that the computed stack size for a code object
+ # stays within reasonable bounds (see issue #21523 for an example
+ # dysfunction).
+ N = 100
+
+ def check_stack_size(self, code):
+ # To assert that the alleged stack size is not O(N), we
+ # check that it is smaller than log(N).
+ if isinstance(code, str):
+ code = compile(code, "<foo>", "single")
+ max_size = math.ceil(math.log(len(code.co_code)))
+ self.assertLessEqual(code.co_stacksize, max_size)
+
+ def test_and(self):
+ self.check_stack_size("x and " * self.N + "x")
+
+ def test_or(self):
+ self.check_stack_size("x or " * self.N + "x")
+
+ def test_and_or(self):
+ self.check_stack_size("x and x or " * self.N + "x")
+
+ def test_chained_comparison(self):
+ self.check_stack_size("x < " * self.N + "x")
+
+ def test_if_else(self):
+ self.check_stack_size("x if x else " * self.N + "x")
+
+ def test_binop(self):
+ self.check_stack_size("x + " * self.N + "x")
+
+ def test_func_and(self):
+ code = "def f(x):\n"
+ code += " x and x\n" * self.N
+ self.check_stack_size(code)
+
+
def test_main():
- test_support.run_unittest(TestSpecifics)
+ test_support.run_unittest(__name__)
if __name__ == "__main__":
- test_main()
+ unittest.main()