Shoutbox

Ok... I have a DLL written in VC++ that exports a function that uses the __cdecl calling convention and I want to call the function from a VB program. However VB uses the __stdcall calling convention so I can't use the DLL (actually I haven't tested that, but I'm sure I won't be albe to use the DLL).

So the question is: Is there anything I can do to force VB use the __cdecl calling convention? What can I do? Ideas?

I'd prefer not to modify the DLL code, because the DLL will be used by another program too, and it needs to stay as __cdecl. I've thought about making another DLL (in VC++) that exports a __stdcall function that calls the __cdecl one in the original DLL, however I'm not very good in VC++ and don't know how to call an exported function of a DLL .

Thanks for your help!

I believe all the functions in the Win32 API use __cdecl, but VB can still use them.

Typical VB API access declaration:
Private Declare Function RegOpenKeyEx Lib "advapi32.dll" Alias "RegOpenKeyExA" (ByVal hKey As Long, ByVal lpSubKey As String, ByVal ulOptions As Long, ByVal samDesired As Long, phkResult As Long) As Long

'Template':
Private Declare Function <functionname> Lib "<filename>.dll" Alias "<funcnamefromdll>" (<arglist>) As <returntype>

EDIT: Tell you what, you post the function header from your DLL, and I'll see if I can come up with a VB declaration statement to allow you to use it.

quote:

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Originally posted by raceprouk
I believe all the functions in the Win32 API use __cdecl, but VB can still use them

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No, the Windows API use __stdcall, that's why VB can use them.

quote:

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Originally posted by raceprouk
Typical VB API access declaration:
Private Declare Function RegOpenKeyEx Lib "advapi32.dll" Alias "RegOpenKeyExA" (ByVal hKey As Long, ByVal lpSubKey As String, ByVal ulOptions As Long, ByVal samDesired As Long, phkResult As Long) As Long

'Template':
Private Declare Function <functionname> Lib "<filename>.dll" Alias "<funcnamefromdll>" (<arglist>) As <returntype>

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yes, I know   I have several years of experience in calling APIs from VB

quote:

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Originally posted by raceprouk
EDIT: Tell you what, you post the function header from your DLL, and I'll see if I can come up with a VB declaration statement to allow you to use it.

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the problem is not that i don't know who to declare it in VB... anyway, if you're happier with this :

the VC++ DLL (traductor.dll) exports this function:

code:

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int __cdecl TRADUCIR(const char *p_fichero_iso,const char *p_fichero_mac,const char *p_fichero_mec)

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in VB i have this declaration:

code:

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Public Declare Function TRADUCIR Lib "traductor.dll" (ByVal iso As Long, ByVal mac As Long, ByVal mec As Long) As Long

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and when I try to call it from VB it says wrong call convention (logic)

well, I've solved that doing this (however I'm still interested if vb can call __cdelc functions or how would be done if I couldn't modify the dll code) :
in VC++, add and export this function

code:

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int __stdcall TRADUCIR__stdcall(const char *p_fichero_iso,const char *p_fichero_mac,const char *p_fichero_mec) {
    return TRADUCIR(p_fichero_iso,p_fichero_mac,p_fichero_mec);
}

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and in VB change the declaration by this one:

code:

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Public Declare Function TRADUCIR Lib "traductor.dll" Alias "TRADUCIR__stdcall" (ByVal iso As Long, ByVal mac As Long, ByVal mec As Long) As Long

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I've really got to start reading up on stuff before answering questions...

Well Choli, it seems that you haven't searched whole MSDN and Microsoft KB... (OK, I'm joking )

Would this work?

code:

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Public Declare Function TRADUCIR CDecl Lib "traductor.dll" (ByVal iso As Long, ByVal mac As Long, ByVal mec As Long) As Long

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quote:

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Originally posted by Mnjul
Well Choli, it seems that you haven't searched whole MSDN and Microsoft KB...

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lol, can you give me the link where you found that, please?

quote:

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Originally posted by Mnjul
Would this work?

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yes and no, dodgy things are happening here... err... I mean:

When in VB (btw, VB 6, not .net) I put the CDecl keywork, VB recognices it (yay! ) but I've found this things: I call the function in the DLL and when I put the CDelc, VB says wrong calling convention and if i remove CDecl it works. That was a quick test, so I said, I'll repeat later. Now, I've exported 2 functions, one with __cdecl and the other with __stdcall. If un VB I use the CDecl I can't call the function with __stdcall but I can call it if don't use CDecl (), but I can't call the __cdecl using nor not using CDecl

Also, if in VC++ I export a function without saying __cdecl nor __stdcall, I can't call it from VB either (the default setting at the VC++ proyect is __cdecl).

So I'm starting to be paranoid Once the DLL is built, how can I know the calling convention of an exported function (with the dependency walker I can see the exported functions, but not their calling convention).

I'm using VC++ .NET 2002, if that helps

I'm sure I'm doing something wrong but it seems I missed it

Well, thanks a lot for your help... After seeing how VB compiles the code with the CDecl keyword I'm sure that doing that is possible... Definetely I have to do more tests

Choli,

VB6 hasta donde se, solo puede usar una DLL que usen la convension STDCALL.
La unica forma que encuentro es que cambies la funcion de CDECL a STDCALL para que pueda ser usada por un programa de VB6.
Cuando lo quieras llamar a la DLL desde otro programa tienes que asigname STDCALL tambien porque si no leera pura basura la DLL.
te escribo en castellano porque mi ingles es malo
chao

And in English?