[Qt-creator] Qt Creator 4.2.0 - Blank outline for some C++ files in imported autotools project

[OmegaPhil]

I'm looking at curve-view.cpp
(https://git.xfce.org/panel-plugins/xfce4-hardware-monitor-plugin/tree/src/curve-view.cpp),
and the Outline is blank on the left (and '<No Symbols>' is shown on the
top bar).

Looking at Tools -> C++ -> Inspect C++ Code Model... -> Snapshots and
Documents: Current Editor's Snapshot, the bottom Symbols tab has useful
symbols, and there is no Diagnostic Messages or Undefined Macros output.
Same for other listed snapshots.

As a normal user, is there any way for me to investigate why Qt Creator
(presumably) doesn't like the file?

Thanks for any help.

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