Dnia śro 4. czerwca 2003 14:16, Bayley, Alistair napisał:
> Is alloca the idiomatic technique when you want to create a pointer to a
> pointer? Or are there other ways?
It's an idiomatic technique for creating a temporary C object whose lifetime
is explicit. You could use malloc, but then you have to remember to free it.
alloca is an analogue of local variables in C (they are really allocated on
GHC heap in GHC or with malloc in other implementations).
> Initially I tried to pass a Ptr (Ptr SomeType), but I couldn't because Ptr
> has no constructors To create values of type Ptr I must use the functions
> in Foreign.Marshal.Alloc (and Foreign.Marshal.Utils). Correct?
More or less yes (there is nullPtr, you can 'foreign import' pointers to
global C variables, you can return pointers from imported C functions if it
makes sense...).
--
__("< Marcin Kowalczyk
\__/ [EMAIL PROTECTED]
^^ http://qrnik.knm.org.pl/~qrczak/
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