From 8c328bb09d8366dc9d2bfe5b77026e6cd2b434cd Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Mon, 2 Jun 2025 16:30:44 +0200
Subject: [PATCH] gh-135028: Increase parser MAXSTACK for nested parenthesis

---
 Lib/test/test_grammar.py                 | 14 +++++++++++++-
 Parser/parser.c                          |  2 +-
 Tools/peg_generator/pegen/c_generator.py |  2 +-
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index c39565144bf7f4..7f5d48b9c63ab7 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -1,7 +1,7 @@
 # Python test set -- part 1, grammar.
 # This just tests whether the parser accepts them all.
 
-from test.support import check_syntax_error
+from test.support import check_syntax_error, skip_wasi_stack_overflow
 from test.support import import_helper
 import annotationlib
 import inspect
@@ -249,6 +249,18 @@ def test_eof_error(self):
                 compile(s, "<test>", "exec")
             self.assertIn("was never closed", str(cm.exception))
 
+    @skip_wasi_stack_overflow()
+    def test_max_level(self):
+        # Macro defined in Parser/lexer/state.h
+        MAXLEVEL = 200
+
+        result = eval("(" * MAXLEVEL + ")" * MAXLEVEL)
+        self.assertEqual(result, ())
+
+        with self.assertRaises(SyntaxError) as cm:
+            eval("(" * (MAXLEVEL + 1) + ")" * (MAXLEVEL + 1))
+        self.assertStartsWith(str(cm.exception), 'too many nested parentheses')
+
 var_annot_global: int # a global annotated is necessary for test_var_annot
 
 
diff --git a/Parser/parser.c b/Parser/parser.c
index 84a293cddffde6..d5aafef826ed3a 100644
--- a/Parser/parser.c
+++ b/Parser/parser.c
@@ -14,7 +14,7 @@
 #    define MAXSTACK 4000
 #  endif
 #else
-#  define MAXSTACK 4000
+#  define MAXSTACK 6000
 #endif
 static const int n_keyword_lists = 9;
 static KeywordToken *reserved_keywords[] = {
diff --git a/Tools/peg_generator/pegen/c_generator.py b/Tools/peg_generator/pegen/c_generator.py
index 2be85a163b4043..09c5651f24a3bb 100644
--- a/Tools/peg_generator/pegen/c_generator.py
+++ b/Tools/peg_generator/pegen/c_generator.py
@@ -44,7 +44,7 @@
 #    define MAXSTACK 4000
 #  endif
 #else
-#  define MAXSTACK 4000
+#  define MAXSTACK 6000
 #endif
 
 """