[Haskell-cafe] Design and state...
magnus at therning.org
Wed Mar 21 05:28:15 EDT 2007
Recently I've been hacking together a small Haskell module on top of
ptrace(2). It's comming along nicely, but it's very low level. The
signals arrive in a list:
wait :: Int -> IO [Signal]
and processing of the signals can be done using e.g. mapM_:
wait childPid >>= mapM_ processSignal
In a few cases this low level requires quite a bit of extra code. Code
needs to be repeated in every program using the module. Dealing with
breakpoints is a good example:
- Setting a breakpoint requires storing the old instruction at the
- When hitting a breakpoint the old instruction should be put back, EIP
backed up, perform one single-step, and last put the breakpoint back
I believe adding another layer on top of what I have now seems like a
good idea. AFAICS that means having a state (I must keep track of the
original instruction). That can easily be done by wrapping IO in a
forEachSignal:: Int -> (Signal -> IO ()) -> StateT DbgEnv IO ()
forEachSignal childPid procSignal = ...
(Or would it be better using IORefs and "OO" in the way described in "IO
What I am struggling with is how to allow the user of the module to have
state as well. I can see how "OO" can be used to solve it, but is
there a more elegant, maybe more idiomatic (Haskellic??), way?
Or am I missing a more elegant way of dealing with this?
Magnus Therning (OpenPGP: 0xAB4DFBA4)
magnus at therning.org Jabber: magnus.therning at gmail.com
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Size: 189 bytes
Desc: not available
Url : http://www.haskell.org/pipermail/haskell-cafe/attachments/20070321/5664eaf7/attachment.bin
More information about the Haskell-Cafe