#VALUE! when calling DLL function (C++) in 64-bit Excel

[justhumm]

Not sure if this is the right forum for this, but like Ol' Jack always says...what the hell?

I am very new to C-plus-plus and trying to use it to create user-defined functions for excel. I wrote a very simple test function in Cpp that just adds two arguments together (Excel cell references).

I compiled a 32-bit DLL & a seperate 64-bit DLL project using the same *.cpp and *.def files in Visual Studio 2013.

When I run the 32-bit DLL in a 32-bit Excel install, the new excel function works fine (eg: 5 + 10 = 15).

When I run the 64-bit DLL in a 64-bit Excel install, I am getting a #VALUE error in the cell.

Can anyone see something blatantly wrong that I am doing with the 64-bit DLL or the VBA declare? Thanks!

***** VBA (32-bit) *****
Declare Function ExPlus Lib _
"C:\AKH-VSWS\Ex-Plus32\Debug\Ex-Plus32.dll" _
(ByVal a As Double, _
 ByVal b As Double) As Double

Computer 1: Windows 7 (64-bit), Office 2016 (32-bit), Visual Studio 2013

***** VBA (64-bit) *****
Declare PtrSafe Function ExPlus Lib _
"C:\AKH-VSWS\Ex-Plus64\x64\Debug\Ex-Plus64.dll" _
(ByVal a As Double, _
 ByVal b As Double) As Double

Computer 2: Windows 7 (64-bit), Office 2016 (64-bit)

Microsoft (R) COFF/PE Dumper Version 12.00.21005.1
Copyright (C) Microsoft Corporation.  All rights reserved.

Dump of file c:\AKH-VSWS\Ex-Plus64\x64\Debug\Ex-Plus64.dll
PE signature found
File Type: DLL

FILE HEADER VALUES
            8664 machine (x64)
               7 number of sections
        5AC930F1 time date stamp Sat Apr 07 16:58:25 2018
               0 file pointer to symbol table
               0 number of symbols
              F0 size of optional header
            2022 characteristics
                   Executable
                   Application can handle large (>2GB) addresses
                   DLL

 

[xwb]

You can't use a 32-bit DLL in a 64-bit application. Same is true for a 64-bit DLL in a 32-bit application. If you want to use your DLL in 64-bit excel, you need to build a 64-bit version.

 

[IDS]

The problem in the OP was running a 64 bit DLL in 64 bit Excel:

When I run the 64-bit DLL in a 64-bit Excel install, I am getting a #VALUE error in the cell.

It is some time since I looked at linking directly to C++ DLLs from Excel, mainly because of the 64 bit/ 32 bit problems, but you might find something useful in the blog post below, or the links:

https://newtonexcelbach.com/2013/03/28/installing-dlls-on-64-bit-windows/

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[justhumm]

Thanks for the responses!

I think I figured out what my issues were...

I was compiling it in debugger mode, so it was adding a "D" onto the name of one of the dependency files. And when I moved the DLL to a computer without Visual Studio, it wouldn't run. I had to switch my compile settings to release mode.

In the *.cpp file, I was missing one of the two underscores (_) in the __stdcall statement. And Visual Studio's debugger and I weren't catching it. So the user-defined-function wasn't being exported with the DLL.

I also didn't properly register / set-up the *.def file within Visual Studio. So even if the __stdcall statement was correct, the function still wouldn't have exported correctly.

And apparently, if you don't somehow register the UDF with excel/windows, you need to run the C++/DLL function through a local VBA function. I have to read up on that (XLL's and all that fun stuff).

So, in conclusion, yeah...I was being stupid.