Is readline's SIGINT handler supposed to set quit_flag?

[Doug Evans]

Hi.
While playing with tab-completion speedups I found that ^c never
sets quit_flag, and thus QUITs in completion routines are useless
(when invoked from readline).

Am I missing something?
[It's possible I messed up and quit_flag is indeed set,
but I'm not sure what I'm missing.]

Or is ^c when in readline not intended to invoke the QUIT machinery?
[It may be that more is needed to make it work, I'm just a bit surprised
and am looking for guidance on how things are expected to work.]

e.g.

(gdb) b functi<tab><^c>

Is that ^c intended to terminate all the symbol completion machinery?