Good to hear that a solution is in sight. :)
On Tue, Jul 22, 2014 at 12:04 PM, Juergen Sauermann < juergen.sauerm...@t-online.de> wrote: > Hi David, > > thank you very much. I read the paragraph below several times. > Unfortunately > the behavior of readline is somewhat different. The problem seemed to be > that > signal handling is "too transparent" in that it ignores settings made in > the signal > handler. > > But I am on the way towards a solution. The first ingredient was Blakes > recommendation > to bind ^C. That was correct, except that it didn't work. It worked for > ^A, ^B, etc but > not for ^C. The missing piece was to entirely hide ^C's special role from > readline > before calling readline(). After that ^C could be bound like any other > ^something. > > I am currently running a number of tests with this and I am hoping that I > can commit > the solution tomorrow. That should include your ^C comments and also > Blake's printout > issues. > > /// Jürgen > > > > On 07/22/2014 08:03 PM, David Lamkins wrote: > > 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. > > I believe that it's a mistake (or at best, needless) to call > rl_delete_text() from Input::got_control_C(), but that's not the crux of > the problem. > > The real problem seems to be that readline() isn't seeing rl_done. In the > context of the above-quoted paragraph, though, this may be explained by: " > If and when the calling application's signal handler returns, Readline will > reinitialize the terminal and continue to accept input". My best guess is > that the reinitialization also affects other state in readline and clobbers > the signal handler's having set rl_done. > > That's my best working hyphothesis at this point. > > I can envision a couple ways to deal with this: > > 1. Build some additional scaffolding using setjmp() and longjmp(). The > idea is that a longjmp() from the handler would return *after* the > readline() call. Note the need to call rl_cleanup_after_signal() in this > case. > > 2. Look for a readline hook that gets called after the reinitialization > that's supposedly done after return from the signal handler. Consider > rl_startup_hook and rl_pre_input_hook. The idea is that the hook function > would test the value of attention_raised (and interrupt_raised) and set > rl_done. > > I'd start with (2). The thought of setjmp()/longjmp() in a C++ program > makes me itch... ;) > > If you don't get to this today, I may have some time tonight to > experiment with case (2). > > > > > On Tue, Jul 22, 2014 at 7:36 AM, Juergen Sauermann < > juergen.sauerm...@t-online.de> wrote: > >> Hi Blake, >> >> I tried, but it did not work. >> >> The deeper I go into readline the more weird it gets. >> >> If I do nothing then I get the first ^C delivered as signal but not >> subsequent ones. >> I would have preferred if two ^Cs (i.e. INTERRUPT rather than ATTENTION) >> would >> stop printouts, but readline delivers only one. >> >> I also tried binding to ^C; interestingly I can bind to any other key >> except ^C. The >> bind to ^C succeeds (returns no error) but the function bound to it is not >> called. For other keys this works. >> >> /// Jürgen >> >> >> >> On 07/21/2014 08:12 PM, Blake McBride wrote: >> >> Does this help? >> >> This may be related to the cooked/uncooked/rare >> <http://en.wikipedia.org/wiki/POSIX_terminal_interface#Early_Unices%3a_Seventh_Edition_Unix> >> terminal >> modes; ^C does not always send a signal. It seems likely that readline >> uncooks the terminal, and thus any signals caused by keyboard input must be >> due to logic within readline itself; it seems plausible that it might only >> trigger a SIGINT on two sequential ^Cs (especially since for many >> programs that utilise readline such as shells and REPLs, the program >> exiting on a single ^C would be very annoying!). >> >> You might be able to change this behaviour by using the readline API to >> rebind ^C to some of your own code that triggers a SIGINT. I haven't >> used readline from Haskell, just from C, so I'm not sure exactly how you'd >> go about this, but the binding >> <http://hackage.haskell.org/packages/archive/readline/latest/doc/html/System-Console-Readline.html> >> seems >> rich enough to achieve it. >> >> >> >> *Blake McBride* >> >> www.arahant.com >> Cell: 615-394-6760 >> Office: 615-376-5500 >> Fax: 615-377-6006 >> >> >> >> >>> >> >> > > > -- > "Far out in the uncharted backwaters of the unfashionable end of the > Western Spiral arm of the Galaxy lies a small unregarded yellow sun. > Orbiting this at a distance of roughly ninety-eight million miles is an > utterly insignificant little blue-green planet whose ape-descended life > forms are so amazingly primitive that they still think programming in Java > is a pretty neat idea." > > -- With apologies to Douglas Adams, who I like to think would have > appreciated this. > > > http://soundcloud.com/davidlamkins > http://reverbnation.com/lamkins > http://reverbnation.com/lcw > http://lamkins-guitar.com/ > http://lamkins.net/ > http://successful-lisp.com/ > > > -- "The secret to creativity is knowing how to hide your sources." Albert Einstein http://soundcloud.com/davidlamkins http://reverbnation.com/lamkins http://reverbnation.com/lcw http://lamkins-guitar.com/ http://lamkins.net/ http://successful-lisp.com/
