Vedant Kumar e05af081bf [lldb/StackFrameList] Convert assert to defensive check in SynthesizeTailCallFrames ...

In order to synthesize tail call frames, the stack frame list must not
be empty (otherwise, there is no "previous" frame to infer a tail call
from).

This case is hard to hit. To trigger it, we must first fail to push
`unwind_frame_sp` because we either fail to get its SymbolContext, or
given its SymbolContext the GetParentOfInlineScope call fails. This
causes m_concrete_frames_fetched to be incremented while m_frames
remains empty. Then, the next frame in the stack may fail within
SynthesizeTailCallFrames. This crash arose during a kernel debugging
session.

rdar://59147051

2020-02-04 10:43:50 -08:00

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