问题
I'm on the haskell platform, GHC 6.12.1 as apt-get installed on Debian Squeeze. How can I get the underlying errno out of an IOError, given that I need it on a different thread to where it was originally raised?
The reason I need this is because I'm implementing a network protocol which exposes the actual errno value on the wire. Do I need to reconstruct it?
回答1:
errno is thread-local in GHC. You'll need to trap the errno in one thread; then send the value down a Chan or other communication abstraction to your listening thread.
The value itself is stored in thread TSO structure.
来源：https://stackoverflow.com/questions/10497765/how-to-get-the-errno-from-an-ioerror-in-haskell