[Haskell-cafe] FFI and modifying haskell memory

[Joel Reymont]

Is there a particular reason why StablePtr cannot provide a "fixed"  
memory address? Then 4 bytes of memory won't need to be allocated so  
that C could write to them and C could just modify the Haskell variable.

On Oct 21, 2005, at 3:17 PM, Simon Marlow wrote:

> yes, something like
>
>    with $ \pculong ->
>      r <- uncompress_ buf pculong ...
>      size <- peek pculong
>
>
>> I thought StablePtr would give me the address of a Haskell value but
>> it gives me an offset into some table instead.
>>
>
> That's right, the reason being that Haskell values move around when GC
> happens.

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