[MC] Diagnose unfinished CFI frame from an earlier section (#196775)
Fixes #177852.
The reproducer has two `.cfi_startproc` directives separated by a
`.popsection`. The first is never closed; the second is properly paired
with `.cfi_endproc`. `MCStreamer::finish()` only inspects the last entry
of `DwarfFrameInfos`, so the unfinished earlier frame slips through and
crashes `finishImpl()` when it emits frame data with a null End label.
Use `hasUnfinishedDwarfFrameInfo()` instead, which walks the full
`FrameInfoStack` and catches every unfinished frame.
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Co-authored-by: Fangrui Song <i@maskray.me>
llvm-project
3913c828 - [MC] Diagnose unfinished CFI frame from an earlier section (#196775)
