Re: SIGWINCH updates the SCREEN's idea of window size

[<don...@is...>]

Vladimir Tzankov writes:

 > When running within a signal handler you have very limited set of safe
 > functions to use (see at the end of
 > http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html).
 > No lisp code can be run safely from signal handler.
 > I see two ways to handle this:
 > 
 > 1. With single thread builds: handle signals with signal handler, add
 > them to some queue of deferred (pending to be handled) signals and add
 > checkpoints in interpreter/bytecode to invoke handlers.
For now let's start with case 2, which seems simpler, at least from my
perspective.

 > 2. With MT: handle signals in main (non-lisp) thread via sigwait() and
 > use thread-interrupt to invoke handler in specific (or arbitrary) lisp
 > thread - that's the way CTRL-C and call-with-timeout are implemented.
In this case I'd suggest creating a new thread to handle the signal.
The general mechanism I had in mind was having a list of functions
to call on each supported signal so the programmer can just push his
own function onto that list.
With-timeout presumably interrupts the calling thread.  
I suggest that if there are multiple running threads, c-c ask which
one to interrupt.

 > Note that SIGUSR1 and SIGUSR2 are used internally for implementing
 > thread-interrupt and call-with-timeout - thus are not available.
I gather there are several others that are used internally.

 > Besides SIGWINCH, what other signals would you like to be able to
 > handle? Some (SIGPIPE, SIGCLD) are already handled in special way by
 > the runtime.
I don't know.  I guess I should start by finding out which ones exist.