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bpo-41690: Use a loop to collect args in the parser instead of recursion (GH-22053)

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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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Pablo Galindo 2020-09-02 17:44:19 +01:00 • committed by GitHub
parent 3940333637
commit 4a97b1517a
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5 changed files with 916 additions and 803 deletions
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Parser/pegen.h
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@ -257,6 +257,7 @@ stmt_ty _PyPegen_class_def_decorators(Parser *, asdl_seq *, stmt_ty);
KeywordOrStarred *_PyPegen_keyword_or_starred(Parser *, void *, int);
asdl_seq *_PyPegen_seq_extract_starred_exprs(Parser *, asdl_seq *);
asdl_seq *_PyPegen_seq_delete_starred_exprs(Parser *, asdl_seq *);
expr_ty _PyPegen_collect_call_seqs(Parser *, asdl_seq *, asdl_seq *);
expr_ty _PyPegen_concatenate_strings(Parser *p, asdl_seq *);
asdl_seq *_PyPegen_join_sequences(Parser *, asdl_seq *, asdl_seq *);
int _PyPegen_check_barry_as_flufl(Parser *);