Completion on symbols nonfunctional, gdb 7.8.1

Hello!
Does anyone know why some gdbs (in this case 7.8.1, as built into a
yocto sdk) might not have working tab completion?

If I type "break wr" and then press <tab>, it does nothing.  However
gdb does know about the symbols!  To wit, if I type:
(gdb) complete b wr<return>
b write
b [email protected]
b write@plt
b writer.h

So, the completions are there, but something is not hooked up
properly... Strangely, it seems that the tab key is hooked up to
something, as when I press <tab> from an empty gdb prompt, I get lots
of good completions, like "actions", "add-auto-load-safe-path", etc.
However, completion on symbols, like "write" above, seems to not work.

I never realized how much I depend on tab completion for productivity
while debugging, so any help would be much appreciated!

Thanks!
Jonah