Hi -
I've found a workaround to the problem below: instead of trying to use
hs_free_fun_ptr, I instead pass a FunPtr to the Haskell function
freeHaskellFunPtr into my DLL, and use this to free everything, finally
using it to free itself (!) which I assume should be safe.
Thus there is no need to try to link against hs_free_fun_ptr (or
hs_free_stable_ptr which can be obtained by wrapping
Foreign.StablePtr.freeStablePtr)
Regards, Brian.
PS: as an aside, it is interesting to note the strange naming for
Foreign.Ptr.freeHaskellFunPtr (why the "Haskell"?) as opposed to
freeStablePtr... :-)
Brian Hulley wrote:
Hi -
I have the following declaration and code in part of a DLL I'm
writing:
extern "C" {
typedef void (*HsFunPtr)();
extern __declspec(dllimport) void hs_free_fun_ptr(HsFunPtr fp);
}
enum ECallback { ECallback_Render, ECallback_COUNT};
HsFunPtr callback[ECallback_COUNT];
void SetCallback(ECallback c, HsFunPtr fp){
if (callback[c]){
hs_free_fun_ptr(callback[c]);
}
callback[c] = fp;
}
However when I try to build the DLL, I get the following error from
Visual Studio:
Duma.obj : error LNK2019: unresolved external symbol
__imp__hs_free_fun_ptr
So the problem is that the VS is adding __imp__ onto the function
name even though I've specified it as extern "C" and is moreover just
ignoring the dllimport directive and complaining that it can't find
the function.
I've also tried deleting the "extern" before the "__declspec" but this
doesn't make any difference. Also, I've tried putting hs_free_fun_ptr
into the IMPORTS section of the def file but this doesn't make any
difference either (I don't even think def files have an IMPORTS
section so it's probably just being ignored).
I've got a horrible feeling that VS will need a .lib file for ghc to
allow it to link against hs_free_fun_ptr but I don't have a clue how
to generate one...
Does anyone know how I can get everything to link?
Thanks, Brian.
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