John Meacham wrote:
I am not sure if you can't use them for some reason, but this sounds like exactly the problem that stable pointers are meant to solve:
http://haskell.org/ghc/docs/latest/html/libraries/base/Foreign-StablePtr.htm...
Which problem? Mostly, I noticed that evaluated Haskell values greatly resemble a header word plus a C struct, and was thinking this could be (ab)used for working with C code, and might make it easier to manipulate values on the Haskell side. Plus, it was fun figuring out how use unsafeCoerce# and Box to manufacture a Ptr to an ordinary Haskell value. Stable pointers might help with the GC relocating things, except I don't think having a stable pointer guarantees that the object won't be moved around, just that the stable pointer won't be invalidated by GC.
On Mon, Oct 23, 2006 at 06:43:26PM -0700, Brandon Moore wrote:
A different and in all likelihood saner approach is building up more tools for manipulating pointers to C data from Haskell, perhaps along the lines of cmucl's support for "Alien Objects". http://www.math.sunysb.edu/~sorin/online-docs/cmucl/aliens.html
sorry to respond twice to the same mail, but have you seen hsc2hs? it can let you access arbitrary components of structures defined in C, or have haskell values that map to unknown c integral types in a portable way.
hsc2hs is nice. it is the minimum needed to write portable haskell ffi using code. Thanks, I've seen related things in c2hs, but I didn't realize hsc2hs came with GHC.
Brandon