Michael Gottesman 564b4fc11a [silgenpattern] Fix some stack-use-after-free errors caused by iterating over an Optional<ArrayRef<T>>. ...

Specifically the bad pattern was:

```
   for (auto *vd : *caseStmt->getCaseBodyVariables()) { ... }
```

The problem is that the optional is not lifetime extended over the for loop. To
work around this, I changed the API of CaseStmt's getCaseBodyVariable methods to
never return the inner Optional<MutableArrayRef<T>>. Now we have the following 3
methods (ignoring const differences):

1. CaseStmt::hasCaseBodyVariables().

2. CaseStmt::getCaseBodyVariables(). Asserts if the case body variable array was
   never specified.

3. CaseStmt::getCaseBodyVariablesOrEmptyArray(). Returns either the case body
   variables array or an empty array if we were never given any case body
   variable array.

This should prevent anyone else in the future from hitting this type of bug.

radar://49609717

2019-04-04 13:34:36 -07:00

44 KiB

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