New signal-handling API

[simonmar]

The current API for handling signals in System.Posix is lacking in a couple of ways:

• it isn't modular: there's no way for a library to install a private signal handler, there is only a singla global handler per signal.

• it isn't possible to get hold of the information from siginfo_t (#592).

I want to propose a new API. This has already undergone a round of changes after discussion with Duncan Coutts, and we ended up with something quite simple. Haddock docs are here:

 http://www.haskell.org/~simonmar/unix/System-Posix-Signals.html#4

(also attached as unix-html.tar.gz).

I have working patches to implement this. The old API is still available, and is reimplemented using the new API. Signal handlers installed using the old API will coexist with those installed using the new API.

The main motivation for this change was so that I could hook the SIGCHLD signal in the System.Process library without disturbing users of the System.Posix library who might also want to install a SIGCHLD handler.

Deadline: 1 Aug (2 weeks)

[simonmar]

Haddock docs for the unix package with new signal API

[simonmar]

Update: the internals of the rewrite have now been committed, so far with no API changes.

Thu Feb 19 02:05:32 PST 2009  Simon Marlow <marlowsd@gmail.com>
  * Rewrite of signal-handling.

[golubovsky]

The change of Feb 19 (namely in System.Posix.Process.Internals) does not work with Hugs as GHC.Conc is not known to Hugs. As a result, the whole Unix package is skipped while building. Please consider this in future updates.

[igloo]

We should fix this, although it's not immediately clear to me how at first glance. Perhaps move Signal to a portable module? Perhaps even System.Posix.Process.Internals?

[simonmar]

No time before 6.12.1.

[simonmar]

See also #592 (expose siginfo_t to signal handlers)

[simonmar]

Fixed URL to haddock docs in description.