Variable offset may uninitialized

[kabeor]

https://github.com/ConsenSys/mythril/blob/develop/mythril/solidity/soliditycontract.py#L368C18-L368C18

    def _get_solc_mappings(self, srcmap, constructor=False):
        """

        :param srcmap:
        :param constructor:
        """
        mappings = self.constructor_mappings if constructor else self.mappings
        prev_item = ""
        for item in srcmap:
            if item == "":
                item = prev_item
            mapping = item.split(":")

            if len(mapping) > 0 and len(mapping[0]) > 0:
                offset = int(mapping[0])

            if len(mapping) > 1 and len(mapping[1]) > 0:
                length = int(mapping[1])

            if len(mapping) > 2 and len(mapping[2]) > 0:
                idx = int(mapping[2])

            if self._is_autogenerated_code(offset, length, idx):
                lineno = None
            else:
                lineno = (
                    self.solc_indices[idx]
                    .data.encode("utf-8")[0:offset]
                    .count("\n".encode("utf-8"))
                    + 1
                )
            prev_item = item
            mappings.append(SourceMapping(idx, offset, length, lineno, item))

L376(if self._is_autogenerated_code(offset, length, idx):) will cause UnboundLocalError: local variable 'offset' referenced before assignment if L367(if len(mapping) > 0 and len(mapping[0]) > 0:) is False.

[kabeor]

Branch: develop

myth analyze xxx.sol --solc-json config.json

config.json is:

{
    "remappings": [ "@openzeppelin/=lib/openzeppelin-contracts/", "@layerzero/=lib/LayerZero/"],
     "optimizer": {
       "enabled": true
     }
}

But works after removing

     "optimizer": {
       "enabled": true
     }

[norhh]

Hi @kabeor , That was intended as previous solc-mapping adhered to such convention starting with non-zero offset and only using "" when a previous offset exists, although I should have used a custom Exception in such scenario.
It could be a change in mapping from the recent solidity version. Can you point out the version of solidity where this bug pops up?

[kabeor]

@norhh Sure, it's 0.8.20