Summary:
After rLLDB365761, and with `LLVM_ENABLE_ABI_BREAKING_CHECKS` enabled,
launching any process on FreeBSD crashes lldb with:
```
Expected<T> must be checked before access or destruction.
Expected<T> value was in success state. (Note: Expected<T> values in success mode must still be checked prior to being destroyed).
```
This is because `m_operation_thread` and `m_monitor_thread` were wrapped
in `llvm::Expected<>`, but this requires the objects to be correctly
initialized before accessing them.
To fix the crashes, use `llvm::Optional<>` for the members (as indicated
by labath), and use local variables to store the return values of
`LaunchThread` and `StartMonitoringChildProcess`. Then, only assign to
the member variables after checking if the return values indicated
success.
Reviewers: devnexen, emaste, MaskRay, mgorny
Reviewed By: devnexen
Subscribers: jfb, labath, krytarowski, lldb-commits
Differential Revision: https://reviews.llvm.org/D68723
llvm-svn: 374444
a42942e0ec