I have found a way to segfault lldb in 7 keystrokes! Steps to reproduce:
- Launch lldb
- Type print and hit enter. lldb will now prompt you to type a list of expressions, followed by an empty line.
- Hit enter, indicating the end of your input.
After some investigation, I've found the issue in Host/common/Editline.cpp.
Editline::MoveCursor() relies on m_input_lines not being empty when the to
argument is CursorPosition::BlockEnd. This scenario, as far as I can tell,
occurs in one specific instance: In Editline::EndOrAddLineCommand() when the
list of lines being processed contains exactly one string (""). Meeting this
condition is fairly simple, I have posted steps to reproduce above.
I see two options: check if the state of m_input_lines is valid while inside
Editline::MoveCursor(), or validate the state of m_input_lines before calling
Editline::MoveCursor(). I have chosen to do the latter, for these 2 reason:
- This happens in one spot in under very specific conditions. Check for it when it could occur, not every time you call Editline::MoveCursor().
- I'm not sure how Editline::MoveCursor() should behave when m_input_lines is empty, nor am I sure if it should be called. I have roughly 4-5 hours experience with the code in Editline.cpp over the course of about 2 days, so
I'm treating this as a learning opportunity. :)
Let me know what you think and/or if you want more context. Thanks!