If anyone's interested, the latest GHC from CVS can now do signal handling
using the Posix library.
Signal handlers now run in separate threads, instead of the old system which
replaced the entire computation with the signal handler. This means you can
do I/O from a signal handler, and even raise exceptions in other threads.
eg. the following program prints "Timer" every second, and quits with the
message "Ctrl-C" when you press ctrl-C.
import IO
import Posix
import Concurrent
import Exception
timerHandler = do
hPutStr stderr "Timer\n"
ctrlCHandler thread = do
raiseInThread thread (ErrorCall "Ctrl-C")
main = do
thread <- myThreadId
installHandler keyboardSignal (Catch (ctrlCHandler thread)) Nothing
installHandler realTimeAlarm (Catch timerHandler) Nothing
let loop = do
scheduleAlarm 1
awaitSignal Nothing
yield
loop
loop
Unfortunately the 'yield' call is quite important to make sure the signal
handler threads get scheduled - otherwise the entire system ends up blocked
in awaitSignal all the time. We're working on a solution to this.
Cheers,
Simon
