'Redefinition; Different type of modifiers'

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sm - 13 Oct 2004 12:09 GMT

Hi All,

I am trying to build a dll from a lib file.

On compilation, I get errors stating 'redefinition; different type of
modifiers', though the dll export statement in the cpp file and the prototype
in the header have no specified modifiers.

The dll export statement looks like this
__declspec(dllexport) DWORD Functionname(Datatype Parameter1);

and the function declaration in the header file is as follows
DWORD WINAPI Functionname(Datatype Parameter1);

Does anybody know how to get over this issue?

Regards

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David Lowndes - 14 Oct 2004 11:13 GMT

>I am trying to build a dll from a lib file.
>
[quoted text clipped - 7 lines]
>and the function declaration in the header file is as follows
>DWORD WINAPI Functionname(Datatype Parameter1);

You need to have WINAPI in both places (if that's what you really
want), and the declaration should also have __declspec(dllimport).
Have a look at the topic titled "Importing into an Application Using
__declspec(dllimport)" for an example of how to use a single macro in
the 2 circumstances.

Dave

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sm - 16 Oct 2004 09:49 GMT

Thanks David for your response.

I observed that when WINAPI is used, I won't be able to use
__declspec(dllexport) to export the functions of my dll; since WINAPI uses
__stdcall and dllexport cannot be used with __stdcall.

Is there a workaround to export WINAPI functions?

Thanks once again.

> >I am trying to build a dll from a lib file.
> >
[quoted text clipped - 15 lines]
>
> Dave

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David Lowndes - 16 Oct 2004 09:59 GMT

>I observed that when WINAPI is used, I won't be able to use
>__declspec(dllexport) to export the functions of my dll; since WINAPI uses
>__stdcall and dllexport cannot be used with __stdcall.

I'm not sure why you think that - you can:

DWORD __declspec (dllexport) __stdcall Functionname(Datatype
Parameter1);

Dave

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sm - 16 Oct 2004 11:31 GMT

Declaring the export function as follows:

DWORD __declspec (dllexport) __stdcall FunctionName(Datatype
Parameter1);

gives the following error on compilation:
d:\testproj\test.cpp(23): error C2375: 'FunctionName' : redefinition;
different linkage

How to get over this error?

Regards.

> >I observed that when WINAPI is used, I won't be able to use
> >__declspec(dllexport) to export the functions of my dll; since WINAPI uses
[quoted text clipped - 6 lines]
>
> Dave

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David Lowndes - 16 Oct 2004 23:37 GMT

>Declaring the export function as follows:
>
[quoted text clipped - 6 lines]
>
>How to get over this error?

This is where we came in isn't it?

The definition in the header file needs to be the same.

Dave

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sm - 17 Oct 2004 06:19 GMT

Thanks again for your response.

Do you mean that when the export statement is
DWORD __declspec (dllexport) __stdcall FunctionName(Datatype
Parameter1);

the function declaration in the header file needs to be
DWORD __declspec Functionname(Datatype Parameter1);

But won't such a declaration still give linker errors, since the lib file
would be using __stdcall calling convention in the definition of the function?

So, the question again is, how to export functions which use __stdcall
calling convention?

Regards.

> >Declaring the export function as follows:
> >
[quoted text clipped - 12 lines]
>
> Dave

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David Lowndes - 17 Oct 2004 09:36 GMT

>Do you mean that when the export statement is
>DWORD __declspec (dllexport) __stdcall FunctionName(Datatype
>Parameter1);
>
>the function declaration in the header file needs to be
>DWORD __declspec Functionname(Datatype Parameter1);

No.

When you build your DLL, the header & source file needs to be the
same:

DWORD __declspec (dllexport) __stdcall FunctionName(Datatype
Parameter1);

otherwise you'll get that redefinition error you are seeing.

When you use the header file from the project where you'll call the
function, it needs to be:

DWORD __declspec (dllimport) __stdcall FunctionName(Datatype
Parameter1);

Have a look at that MSDN topic I referred you to originally, that
shows how to use a preprocessor definition to get the correct form of
declspec (dllexport/dllimport) in both circumstances.

Dave

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sm - 19 Oct 2004 06:39 GMT

I'll try that.

Thanks.

> >Do you mean that when the export statement is
> >DWORD __declspec (dllexport) __stdcall FunctionName(Datatype
[quoted text clipped - 24 lines]
>
> Dave

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