8000 bpo-41690: Use a loop to collect args in the parser instead of recurs… · python/cpython@4a97b15 · GitHub
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bpo-41690: Use a loop to collect args in the parser instead of recursion (GH-22053)
This program can segfault the parser by stack overflow: ``` import ast code = "f(" + ",".join(['a' for _ in range(100000)]) + ")" print("Ready!") ast.parse(code) ``` the reason is that the rule for arguments has a simple recursion when collecting args: args[expr_ty]: [...] | a=named_expression b=[',' c=args { c }] { [...] }
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‎Grammar/python.gram

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@@ -535,22 +535,11 @@ arguments[expr_ty] (memo):
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| a=args [','] &')' { a }
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| incorrect_arguments
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args[expr_ty]:
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| a=starred_expression b=[',' c=args { c }] {
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_Py_Call(_PyPegen_dummy_name(p),
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(b) ? CHECK(_PyPegen_seq_insert_in_front(p, a, ((expr_ty) b)->v.Call.args))
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: CHECK(_PyPegen_singleton_seq(p, a)),
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(b) ? ((expr_ty) b)->v.Call.keywords : NULL,
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EXTRA) }
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| a=','.(starred_expression | named_expression !'=')+ b=[',' k=kwargs {k}] { _PyPegen_collect_call_seqs(p, a, b) }
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| a=kwargs { _Py_Call(_PyPegen_dummy_name(p),
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CHECK_NULL_ALLOWED(_PyPegen_seq_extract_starred_exprs(p, a)),
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CHECK_NULL_ALLOWED(_PyPegen_seq_delete_starred_exprs(p, a)),
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EXTRA) }
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| a=named_expression b=[',' c=args { c }] {
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_Py_Call(_PyPegen_dummy_name(p),
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(b) ? CHECK(_PyPegen_seq_insert_in_front(p, a, ((expr_ty) b)->v.Call.args))
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: CHECK(_PyPegen_singleton_seq(p, a)),
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(b) ? ((expr_ty) b)->v.Call.keywords : NULL,
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EXTRA) }
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kwargs[asdl_seq*]:
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| a=','.kwarg_or_starred+ ',' b=','.kwarg_or_double_starred+ { _PyPegen_join_sequences(p, a, b) }
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| ','.kwarg_or_starred+

‎Misc/NEWS.d/next/Core and Builtins/2020-09-02-12-00-57.bpo-41690.Ny-Sfy.rst

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Fix a possible stack overflow in the parser when parsing functions and
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classes with a huge ammount of arguments. Patch by Pablo Galindo.

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