Question

Good afternoon, all.

I was playing around today with Excel & VBA loading some DLLs and seeing what kind of trouble I could get into.

I made my own, very simple DLL to try it out. I can’t for the life of me figure out why, but I keep getting the “Specified DLL function not found” message when I try to run.

Here’s what I have in my workbook…

    Private Declare Sub MouseClick Lib "\location\of\myDLL" Alias "_MouseClick" ()
    'I have also tried...
    'Private Declare Sub MouseClick Lib "\location\of\myDLL" ()

    Sub Test()
            MouseClick
    End Sub

Here’s my simple function declaration in the DLL…

    extern "C" 
    {
            void MouseClick();
            ...
    }

I thought that maybe the name of my function was being mangled when compiled, so I used ‘nm’ to check…

    $ nm myDLL.dll | grep MouseClick
    6df81254 T _MouseClick

    $ nm -C myDLL.dll | grep MouseClick
    6df81254 T MouseClick

I don’t understand… I’ve used both of those to try to get it to work.
Also, I disassembled a function that calls the MouseClick function using gdb…

    $ gdb myDll.dll
    (gdb) disass testFunction
    Dump of assembler code for function testFunction:
       0x6df81327 <+0>:     push   %ebp
       0x6df81328 <+1>:     mov    %esp,%ebp
                       ...
       0x6df81361 <+58>:    call   0x6df81a44 <SetCursorPos@8>
       0x6df81366 <+63>:    sub    $0x8,%esp
    -> 0x6df81369 <+66>:    call   0x6df81254 <MouseClick>
       0x6df8136e <+71>:    jmp    0x6df8138a <testFunction+99>
                       ...
       0x6df8138a <+99>:    leave
       0x6df8138b <+100>:   ret
    End of assembler dump.

Here, too the function is referred to as “MouseClick”.

I may be going about this all the wrong way, but I don’t understand why gdb and nm are both showing a “clean” function name, but Excel won’t work with either of the ones I assumed it would be. I did get the dll to work with my VBA sub for a time, but I changed the document and now it’s not working.

Would someone that has done this before be kind enough to point me in the right direction about all this? What should I name the function in Excel? Why is nm showing a function name that isn’t mangled? Am I even going about this the right way?

Thanks to all in advance!

Answer 1

Somebody went through all this already and updated his question to include the solution:

Compile a DLL in C/C++, then call it from another program

The answer is specific for gcc, which is what you seem to use.