Re: [Haskell-cafe] C++ exception (from *.so) catchable by Haskell??

thank you :-) Injecting the example pointed to by Alexander to my code, e.g. void myUnexpected () { std::cerr << "unexpected called\n"; throw 0; } ... std::set_unexpected (myUnexpected); try { throw runtime_error("OOOPS..."); } catch (int) { std::cerr << "caught int\n"; } catch (...) { std::cerr << "caught some other exception type\n"; } still is the problem that the STDERR message of myUnexpected doesn't appear – is there anywhere code applying what you told about? Cheers, Nick 2014-02-13 15:44 GMT+01:00 Brandon Allbery :

On Thu, Feb 13, 2014 at 6:43 AM, Nick Rudnick wrote:

...

3) To my surprise, every time the output stays the same:

terminate called after throwing an instance of 'std::runtime_error' what(): OOOPS.

It's calling terminate which calls exit(), in the C++ runtime. You can't catch it at that level.

set_unexpected() may or may not help you since it's not clear that you can make it pop back to the FFI call and no further. Maybe you can use setjmp()/longjmp() or setcontext() and friends, but I'm betting its interaction with C++ is undefined (and in particular C++ finalizers/destructors don't get called).

Your best bet is to catch the exception in C++, in whatever code you are invoking from the (C context) FFI call.

Upshot: there is no global concept of exceptions that applies across all languages unless you're using something like JVM or CLR.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net