Export Haskell lib as DLL - excel

Question

I am working with GHC version 7.6.1, following the steps in the docs for creating a DLL from a Haskell lib for using it in VBA:
GHC Docs 7.6.1 # Make a DLL
The files I use are the exact same ones as in the Docs. When it comes to compiling, the following to commands work nearly as expected:
ghc -c Adder.hs
ghc -c StartEnd.c
The first command returns this:
Adder.hs:7:1: Warning:
the 'stdcall' calling convention is unsupported on this platform,
treating as ccall
When checking declaration:
foreign export stdcall "adder" adder :: Int -> Int -> IO Int
Which I guess should be fine...
However, the last command ghc -shared -o Adder.dll Adder.o Adder_stub.o StartEnd.o produces this error:
Adder_stub.h:1:19: fatal error: HsFFI.h: No such file or directory
compilation terminated.
This thread pointed me towards recognizing that GHC isn't using the header files located in its GHC-HOME/lib/include.
The solution in this thread was to use GHC with the option -I [path to include-folder], however, when trying it (and looking at the man and docs) there is no such option for this version of GHC; nor is there in the newer versions up to 8.4.3.
When reading this docs I also encountered that it should be possible to use the option mk-dll under windows to generate dlls; however, according to the man page of my installed GHC, there is no such option, even though I downloaded and installed the windows 64-bit installer.
I then tried to just copy the include folder to some other location; copying the files needed by the third compilation command into the folder too and tried it again. It successfully compiled the DLL;
However, when I try to use the DLL from an Excel(macro-enabled) workbook, I get the error DLL not found. When attempting to reference the DLL in excel (via Tools->References->Browse-> chooseDll) it tells me that it can't add the DLL.
Examining the DLL with DependencyWalker, I get this error:
Error: At least one required implicit or forwarded dependency was not found.
Error: At least one module has an unresolved import due to a missing export function in an implicitly dependent module.
Error: Modules with different CPU types were found.
Warning: At least one delay-load dependency module was not found.
Warning: At least one module has an unresolved import due to a missing export function in a delay-load dependent module.
Do you have any ideas on how to resolve this?
Thanks a lot...
Update
When I try to use the compiled library from C++ as discribed in the docs I end up with this error message:
PS C:\Users\dev\programming\excel_haskell_binding> ghc -o tester.exe .\Tester.cpp .\include\Adder.dll.a
C:\Users\dev\AppData\Local\Temp\ghc4088_0\ghc4088_0.o:ghc4088_0.c:(.text+0x0): multiple definition of `main'
Tester.o:Tester.cpp:(.text+0x0): first defined here
C:\Users\dev\AppData\Local\Temp\ghc4088_0\ghc4088_0.o:ghc4088_0.c:(.text+0x4f): undefined reference to `ZCMain_main_closure'
c:/ghc/ghc-7.6.1/mingw/bin/../lib/gcc/x86_64-w64-mingw32/4.6.3/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\dev\AppData\Local\Temp\ghc4088_0\ghc4088_0.o: bad reloc address 0x0 in section `.pdata'
collect2: ld returned 1 exit status
Update 2
I am also trying a different approach; see this question GHC compile DLL for use in VBA

Answer 1

I was struggling with the same problem, but after a long fight, I managed to run the command from 64bit Excel. Follow these steps:
1) Create Adder.hs (notice ccall, not stdcall):
{-# LANGUAGE ForeignFunctionInterface #-}
module Adder where
adder :: Int -> Int -> IO Int -- gratuitous use of IO
adder x y = return (x+y)
foreign export ccall adder :: Int -> Int -> IO Int
2) Create StartEnd.c:
#include <Rts.h>
void HsStart()
{
int argc = 1;
char* argv[] = {"ghcDll", NULL}; // argv must end with NULL
// Initialize Haskell runtime
char** args = argv;
hs_init(&argc, &args);
}
void HsEnd()
{
hs_exit();
}
3) Compile these files:
ghc -c Adder.hs
ghc -c StartEnd.c
4) Copy following files from "C:\Program Files\Haskell Platform\8.6.3\lib\include" to your build folder (remember to put stg/Types.h into stg folder). You may also copy all the contents of /include folder if you wish:
HsFFI.h
ghcconfig.h
ghcautoconf.h
ghcplatform.h
stg/Types.h
5) Create the dll:
ghc -shared -o Adder.dll Adder.o Adder_stub.h StartEnd.o
6) Now open the Excel and use this macro (use first HsStart before Adder). Remember to link to your own folder:
Private Declare PtrSafe Function Adder Lib "C:\Users\User\haskell\Adder.dll" Alias "adder" _
(ByVal x As Long, ByVal y As Long) As Long
Private Declare PtrSafe Sub HsStart Lib "C:\Users\User\haskell\Adder.dll" ()
Private Declare PtrSafe Sub HsEnd Lib "C:\Users\User\haskell\Adder.dll" ()
Private Sub Document_Close()
HsEnd
End Sub
Private Sub Document_Open()
HsStart
End Sub
Public Sub Test()
MsgBox "12 + 5 = " & Adder(12, 5)
End Sub
7) Be amazed!