Thank you,

You give me and idea, and I fixed this annoying bug - we should only wrap all
curl code into withCurlDo function, so the longTask function should be following:

longTask = do
  putStrLn "Long task started (curl)"
  withCurlDo $ do
             curl <- initialize
             setopts curl [CurlCookieJar "cookies"]
 
             handle (errorHandler ()) $
                    mapM_ (\_ -> getSite curl link >> return ()) [0..100]
  return ()

Now it works fine and handles interrupts correctly.

Best regards,
Vasyl Pasternak

2009/9/24 Brandon S. Allbery KF8NH <allbery@ece.cmu.edu>
On Sep 24, 2009, at 06:20 , Brandon S. Allbery KF8NH wrote:
On Sep 24, 2009, at 05:30 , Vasyl Pasternak wrote:
Yesterday I tried to implement simple tool to download pages, and wanted catch Ctrl-C (and other 'killing' messages) from haskell to handle state saving. Without curl (when I perform some long operation) haskell throws UserInterrupt exception immediately, but if I put long operation, which downloads page from the WEB (from the far-far-away server :) ) than I noticed following issues:

You're going to have problems any time a C library installs its own signal handler, which I would expect libcurl to do so it can clean up after itself.  This is true even in C-to-C calling; you need a way to hook the signal handler, which some libraries provide in their API and others you just lose.

Just occurred to me I should clarify:  while most exception handling mechanisms support the concept of re-throwing exceptions to outer exception handlers, POSIX signals do not.  The best you could hope for in a library routine which handles signals itself is an API hook into the signal handler; next best is the API returning a signal-occurred error/exception value.

Note that I have no idea how the equivalent signaling mechanism works on Win32.

-- 
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH