Segmentation fault when accesing a dict class attribute that is empty

[variux]

I have the following code

class Row:
    __slots__ = ("_values", "_index")
    _values: Tuple[int, List[Any]]
    _index: Dict[str, int]

    def __init__(self, values: Tuple[int, List[Any]], colnames: List[str]):
        self._values = values
        self._index = {name: i for i, name in enumerate(colnames)}

values: List[Any] = List[Any]()
values.append(1)
values.append(2)
values.append(3)
row = Row((0, values), ["id", "name", "data"])
print(row._index)

if you try to un it, it works, but

This code

class Row:
    __slots__ = ("_values", "_index")
    _values: Tuple[int, List[Any]]
    _index: Dict[str, int]

    def __init__(self, values: Tuple[int, List[Any]], colnames: List[str]):
        self._values = values

values: List[Any] = List[Any]()
values.append(1)
values.append(2)
values.append(3)
row = Row((0, values), ["id", "name", "data"])
print(row._index)

when self._index is not filled, fails with Segmentation Fault, defining as _index: Dict[str, int] = Dict[str, int]() won't work neither

[variux]

setting _index without a type and initializing as _index = dict() make the code works, so I assume is something related to typing

[yfinkelstein]

Dict field should be initialized in init:

 class Row:
     __slots__ = ("_values", "_index")
     _values: Tuple[int, List[Any]]
     _index: Dict[str, int]

     def __init__(self, values: Tuple[int, List[Any]], colnames: List[str]):
         self._values = values
         self._index = Dict[str, int]()

 values: List[Any] = List[Any]()
 values.append(1)
 values.append(2)
 values.append(3)
 row = Row((0, values), ["id", "name", "data"])
 print(row._index)

If you put initializer in the class definition it's treated as static variable

But this example brings up a valid question : are codon programs allowed to crash with segv after referencing a null pointer ? A better solution would be to throw a checked exception that can be caught and handled to recover

[inumanag]

Yes, if you do not initialize stuff in __init__ the values will be garbage (and compiler will not warn you). This definitely needs fixing, and should be done in the next release or so.

Btw. __slots__ hack is not needed in Codon