J'uergen,
I noticed this paragraph in the readline documentation:
" Readline contains an internal signal handler that is installed for a
number of signals (`SIGINT', `SIGQUIT', `SIGTERM', `SIGALRM',
`SIGTSTP', `SIGTTIN', and `SIGTTOU'). When one of these signals is
received, the signal handler will reset the terminal attributes to
those that were in effect before `readline()' was called, reset the
signal handling to what it was before `readline()' was called, and
resend the signal to the calling application. If and when the calling
application's signal handler returns, Readline will reinitialize the
terminal and continue to accept input. When a `SIGINT' is received,
the Readline signal handler performs some additional work, which will
cause any partially-entered line to be aborted (see the description of
`rl_free_line_state()' below)."
The way I read this, readline() should be transparent w.r.t. ^C. Readline resignals your app, then resets *itself* when control returns from your app's signal handler.