C-u C-h i no longer loads a named info file. What's going on?

[Alan Mackenzie]

Hi, Everybody.

Whilst doing some testing, I tried

    C-u C-h i <reg> .../path/to/cc-mode.info

.  I got as an error message,

    Can't find cc-mode.info-1 or any compressed version of it

.  Well, cc-mode.info-1 wasn't actually the file I asked for.  I'm not
happy about this.  What is going on?  How do I load cc-mode.info into an
info buffer?

Have I missed some previous discussion on this list?

-- 
Alan Mackenzie (Nuremberg, Germany).