[Haskell-iPhone] Automatically freeing function pointers

[David Pollak]

On Sun, Jun 19, 2011 at 1:32 PM, Stephen Blackheath [to GHC-iPhone] <
likeliest.complexions.stephen at blacksapphire.com> wrote:

> David,
>
> In GHC-iPhone the number of function pointers that are allowed to be active
> for a given function is limited, but you can change the size of the limit.
>  This is documented in
>
>
Steve,

Yep... I understand that there are not an unlimited number of function
pointers.  However, the function that I wrote was "supposed" to
automatically release the function:

runOnMain :: IO () -> IO ()
runOnMain todo = do
                  func <- funky
                  dispatchFunc func
  where funky =  mkStrCB $ \v -> do
                                   todo
                                   func <- funky
                                   freeHaskellFunPtr func

Note the freeHaskellFunPtr function call at the end of the lambda.

I'm thinking that the "func <- funky" line is being treated as a recursive
call and I'm also thinking that this is a limitation of my understanding the
magic of lazy evaluation.

So, please let me rephrase my question:

How do I get the pointer to a wrapper function so that the pointer can be
used within the wrapped function itself?

I have worked around the particular issue by making a call to
freeHaskellFunPtr in the Objective-C code that invokes the function.  It's
less optimal that being able to have the Haskell code be able to auto-free
the function pointer after the function is invoked.

Thanks,

David



> http://projects.haskell.org/**ghc-iphone/downloads/GHC-**iPhone.pdf<http://projects.haskell.org/ghc-iphone/downloads/GHC-iPhone.pdf>
>
> on p5 under 'Pool sizes for foreign function "wrapper" callbacks'.
>
>
> Steve
>
>
> On 18/06/11 11:29, David Pollak wrote:
>
>> Howdy,
>>
>> I tried to build a function that would create an auto-freeing function
>> pointer:
>>
>> runOnMain :: IO () -> IO ()
>> runOnMain todo = do
>>                   func <- funky
>>                   dispatchFunc func
>>   where funky =  mkStrCB $ \v -> do
>>                                    todo
>>                                    func <- funky
>>                                    freeHaskellFunPtr func
>>
>> Unfortunately, I wind up getting:
>>  internal error: iPhoneCreateAdjustor - adjustor pool 'Main_d2K2' is
>> empty (capacity 32)
>>     (GHC version 6.10.4-iphone-simulator for i386_apple_darwin)
>>
>> I'm not sure why, but I suspect that funky is being called recursively
>> and thus stuff is never being freed.
>>
>> Any hints as to the issue and solutions?
>>
>> Thanks,
>>
>> David
>>
>>
>> --
>> Lift, the simply functional web framework http://liftweb.net
>> Simply Lift http://simply.liftweb.net
>> Follow me: http://twitter.com/dpp
>> Blog: http://goodstuff.im
>>
>>
>>
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>>
>
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>



-- 
Lift, the simply functional web framework http://liftweb.net
Simply Lift http://simply.liftweb.net
Follow me: http://twitter.com/dpp
Blog: http://goodstuff.im
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