RE: Are handles closed automatically when they fall out of scope?

On 25 October 2004 14:24, John Goerzen wrote:

On 2004-10-25, Simon Marlow wrote:

...

On 22 October 2004 21:58, Peter Simons wrote:

On 24 October 2004 23:37, John Goerzen wrote:

...

* What happens when one Handle corresponding to a socket is closed, but another isn't?

You shouldn't have two Handles on the same socket. This is an unchecked error.

This does seem useful, though. I am actually doing this in my code and it works. One Handle is opened ReadOnly, the other WriteOnly. That way, I can use hGetContents on the reading side in my network code.

If I tried that with a single Handle opened ReadWrite, then I'd get errors about it being closed whenever I'd try to write out some data.

I wasn't able to find any other good way around it.

Hmmm, you should still be able to *write* to a socket handle that has had hGetContents applied to it. In GHC, a ReadWrite handle to a socket basically consists of a wrapper around two independent Handles, one for read and one for write, each with its own buffer. ... I just tested it with 6.2.2, and indeed it does work as I expected. But perhaps there's a bug lurking somewhere? If you do socketToHandle twice, then the danger is that one of the Handles will be finalized and close the FD before the other Handle has finished with it. In 6.4 you'll be able to use hDuplicate for this, BTW. Cheers, Simon