The generated code inPython-ast.c is missing error checks following the construction of C-levelalias,arg,comprehension,keyword,match_item, andwithitem nodes from their Python object counterparts. This means it's possible to crash the interpreter by attempting to compile an AST where a required member of these nodes is replaced withNone:

>>>importast>>>tree=ast.parse("""... match ...:...     case THIS:...         ...... """)>>>tree.body[0].cases[0].pattern=None>>>compile(tree,"<crash>","exec")Segmentationfault

I'll have a PR up in a minute with the one-line fix.

Linked PRs

• GH-105588: Add missing error checks to someobj2ast_* converters #105589
• [3.12] GH-105588: Add missing error checks to some obj2ast_* converters (GH-105589) #105838
• [3.11] GH-105588: Add missing error checks to some obj2ast_* converters (GH-105589) #105839