DLLCall not working with my DLL

[sharrakor]

I created a DLL in visual c++ with the express intent of calling it from Autoit. However, @error keeps getting set to 1 when I try to call it in my program.

Here is the code:

$myDll=dllOpen("testbasicdll.dll")

$test=dllCall("testbasicdll.dll","int","addnums","int",2,"int",3)

msgbox(0,@error,$test)

This is the code for the DLL:

#include "stdafx.h"

int returnval;

__declspec(dllexport) int addnums(int one, int two)
{
    returnval=one+two;
    return returnval;
}

And this is Exports.def:

LIBRARY testbasicdll
EXPORTS
     addnums

I have the .dll placed in the same directory as the Autoit script. I compiled the dll in visual c++ express edition 2008.

EDIT: I just realized that dllopen is returning -1. Anyone know why that is?

Edited March 27, 2009 by sharrakor

[monoceres]

Add ' extern "C" ' to the function declaration, and since you're using the cdecl calling convention you need to add ":cdecl" to the return type in the DllCall() function.

Also, why are declaring returnval as global variable and you really don't need that exports.def file.

[sharrakor]

Add ' extern "C" ' to the function declaration, and since you're using the cdecl calling convention you need to add ":cdecl" to the return type in the DllCall() function.

Also, why are declaring returnval as global variable and you really don't need that exports.def file.

I just saw a simple tutorial on how to create a basic dll and that was how they said to do it. Glad to know I don't need the exports file.

When you say add extern, do you mean like this? Sorry, I haven't used extern before. This gives me an error still.

extern __declspec(dllexport) int addnums(int one, int two)

Edited March 27, 2009 by sharrakor

[monoceres]

I just saw a simple tutorial on how to create a basic dll and that was how they said to do it. Glad to know I don't need the exports file.

When you say add extern, do you mean like this? Sorry, I haven't used extern before. This gives me an error still.

extern __declspec(dllexport) int addnums(int one, int two)

Not quite.

Please see this post for a description of how to create a dll and call it

[sharrakor]

Awesome, thank you!

[sharrakor]

Ok, I saw that, and I'm still having issues. The thing is, I'm getting -1 as my dllopen return value, so I'm assuming its some other sort of error. Opening user32.dll works fine.

The dll is in the same directory as the script, so it shouldn't be that. My project is a standard DLL that doesn't export any symbols.

I'm running XP btw. Any ideas?

[monoceres]

Upload the dll and I'll have a look.

[sharrakor]

I attached the dll.

The code is:

#include "stdafx.h"


extern "C" int __declspec(dllexport) addnums(int one, int two)
{
    int returnval=one+two;
    return returnval;
}

dllup.rar

[monoceres]

The following code works without problems with your dll:

$handle=DllOpen("dlltest2.dll")
MsgBox(0,"",$handle)

$call=DllCall($handle,"int:cdecl","addnums","int",3,"int",4)
MsgBox(0,"",$call[0])

[sharrakor]

Hmm... copied and pasted it and it still gave me -1. Where are you storing the DLL file? Are you running it uncomplied? This is weird.

[monoceres]

Hmm... copied and pasted it and it still gave me -1. Where are you storing the DLL file? Are you running it uncomplied? This is weird.

In the script directory. Even though unlikely the problem, try link the dll statically with the runtime.

Project Properties -> C/C++ -> Code generation -> Runtiem library -> change to just "multi-threading"

[sharrakor]

Still isn't working for me. Any other ideas?

[monoceres]

Just checking, you're not running the 64 bit version of autoit are you?

[sharrakor]

I am. I'm on windows XP 64 bit.

Calling any other DLL works fine for me though. I say this because I've got an appointment to go to now... So I won't be able to respond for a while.

So, might I ask what the problem is and how I fix it?

Thanks

[monoceres]

64 bit applications cannot load 32 bit libraries and vice versa.

To fix this you either compile the dll as a 64 bit library or you run the 32 bit version of autoit (32 bit apps can still run on 64 bit os's).

[sharrakor]

Wow. I had no idea 64 bit programs couldn't use 32 bit DLLs. Thanks for letting me know that. It does make sense though.

[Richard Robertson]

It has to do with the width of pointers. In a real 64 bit application, pointers are 64 bits wide. In 32 bit applications, 32 bit pointers. When initializing the dll, the dll gets an HINSTANCE value, which is a pointer. If it's the wrong width, the function call fails, and the dll is not loaded.