DLL export, decorated function

[=?Utf-8?B?UGF0cmljayBXZXN0ZXJob2Zm?=]

Hello,

I'm currently working on a small DLL that will be used as an extension to a
working application. It is required that the DLL has only one export named
"C16_DLLCAL L". So I started creating a DLL in Visual C++ 2008 using the Win32
application wizard for DLLs and changed it so it would work for our
application.
However when I build the DLL file and look at it using dumpbin.exe /exports,
the exported function is not exactly called "C16_DLLCAL L". Depending on the
function declaration I get one of the following export names:

?C16_DLLCALL@@Y AHPAUvC16_CCB@@ @Z = ?C16_DLLCALL@@Y AHPAUvC16_CCB@@ @Z (int
__cdecl C16_DLLCALL(str uct vC16_CCB *))
when using: __declspec(dlle xport) [...]

C16_DLLCALL = _C16_DLLCALL
when using: extern "C" __declspec(dlle xport) [...]

I have got a example DLL from the application developers and when I look at
it using dumpbin, it exactly has the required name, without equally signs or
other characters, just a plain "C16_DLLCAL L" - and in that case the
application finds the entry point within the dll. However with any of my
DLLs, it fails.
How can I export the function without having its export name changed at all?

Thank you,
Patrick Westerhoff

[SvenC]

Re: DLL export, decorated function

Hi Patrick,

... I like to have one export named "C16_DLLCAL L".
... but I get ...
C16_DLLCALL = _C16_DLLCALL
when using: extern "C" __declspec(dlle xport) [...]

Add a def file to your project

http://msdn.microsoft.com/en-us/library/d91k01sh(VS.80).aspx

--
SvenC

[=?Utf-8?B?UGF0cmljayBXZXN0ZXJob2Zm?=]

Re: DLL export, decorated function

Hi SvenC,

thank you for your answer. I tried that now but received the following
exports:

C16_DDLCALL = ?C16_DLLCALL@@C AHPAUvC16_CCB@@ @Z (int __cdecl
C16_DLLCALL(str uct vC16_CCB *))
when using only the .def file without any additional things in the function
declaration
and
C16_DDLCALL = _C16_DDLCALL
when using the .def with extern "C" __declspec(dlle xport)

both don't work in the application :(

Patrick Westerhoff

"SvenC" wrote:

Hi Patrick,
>
Add a def file to your project
>

http://msdn.microsoft.com/en-us/library/d91k01sh(VS.80).aspx

>
--
SvenC
>

[SvenC]

Re: DLL export, decorated function

Hi Patrick,

thank you for your answer. I tried that now but received the following
exports

Reread the article and find:
"If you are *not using* the __declspec(dlle xport) keyword to export
the DLL's functions, the DLL requires a .def file."

Instead you should specify the calling convention explicitly in your
header so that you do not depend on vc project defaults.

extern "C" __stdcall C16_DDLCALL(str uct vC16_CCB *);


--
SvenC

[=?Utf-8?B?UGF0cmljayBXZXN0ZXJob2Zm?=]

Re: DLL export, decorated function

Hm, sorry but I don't get it :( So before I continue misunderstandin g, I'll
post a bit from my code:

C16DLL.def
----
LIBRARY "C16DLL"
EXPORTS
C16_DLLCALL @1
----

C16DLL.h (apart from that only has the standard definition of C16DLL_API
__declspec(dlle xport) etc.)
----
extern "C" vERROR __stdcall C16_DLLCALL( vC16_CCB* aCCB );
----

C16DLL.cpp (includes also stdafx.h which is including some header files for
the different types/structs I have to use so that they work with the target
application)
----
vERROR __stdcall C16_DLLCALL ( vC16_CCB* aCCB )
{
// ...
}
----

Apart from that I only have the default dllmain.cpp which contains BOOL
APIENTRY DllMain

Whatever suggestion I tried until now, I never was able to reduce the export
listed with dumpbin to only C16_DLLCALL resulting in the application not
recognizing the function (it actually returns an error which says that the
entry point was not found).
When I try it with the dll the developers sent to me, it works fine; I also
have the "source" (=.c file only) of that dll but I don't have any settings
for it so I'm probably not able to compile it to test if the problem is maybe
the Studio 2008 compiler (which I believe by now :/).
If it helps within the developers source, the function is defined with:
vERROR WINAPI C16_DLLCALL( vC16_CCB* aCCB )
and instead of the DllMain function they use
vINT APIENTRY LibMain ( ... )
which is the same according to what I read yesterday on the msdn library..

So where is the problem? :|

Patrick Westerhoff


"SvenC" wrote:

Hi Patrick,
>

thank you for your answer. I tried that now but received the following
exports

>
Reread the article and find:
"If you are *not using* the __declspec(dlle xport) keyword to export
the DLL's functions, the DLL requires a .def file."
>
Instead you should specify the calling convention explicitly in your
header so that you do not depend on vc project defaults.
>
extern "C" __stdcall C16_DDLCALL(str uct vC16_CCB *);
>
>
--
SvenC
>
>

[SvenC]

Re: DLL export, decorated function

Hi Patrick,

Hm, sorry but I don't get it :( So before I continue
misunderstandin g, I'll post a bit from my code:
>
C16DLL.def
----
LIBRARY "C16DLL"
EXPORTS
C16_DLLCALL @1
----
>
C16DLL.h (apart from that only has the standard definition of
C16DLL_API __declspec(dlle xport) etc.)
----
extern "C" vERROR __stdcall C16_DLLCALL( vC16_CCB* aCCB );

Did you add the def file to your project property settings?

Config Props/Linker/Input/Module Definition File

--
SvenC

[=?Utf-8?B?UGF0cmljayBXZXN0ZXJob2Zm?=]

Re: DLL export, decorated function

Hi SvenC,

yes, it was added there automatically when I created it.

Patrick

"SvenC" wrote:

Hi Patrick,
>
Did you add the def file to your project property settings?
>
Config Props/Linker/Input/Module Definition File
>
--
SvenC
>

[Giovanni Dicanio]

Re: DLL export, decorated function


"Patrick Westerhoff" <PatrickWesterh off@discussions .microsoft.comh a
scritto nel messaggio
news:89376758-F7A3-45C6-BED0-98C8B553C7FC@mi crosoft.com...

C16DLL.def
----
LIBRARY "C16DLL"
EXPORTS
C16_DLLCALL @1

That is good.

C16DLL.h (apart from that only has the standard definition of C16DLL_API
__declspec(dlle xport) etc.)
----
extern "C" vERROR __stdcall C16_DLLCALL( vC16_CCB* aCCB );

OK.
(But I would prefer useinga #ifdef __cplusplus guard here...)

C16DLL.cpp (includes also stdafx.h which is including some header files
for
the different types/structs I have to use so that they work with the
target
application)
----
vERROR __stdcall C16_DLLCALL ( vC16_CCB* aCCB )
{

I think the problem is here.
This is a .CPP file, so I think that you should add 'extern "C"' explicitly
here:

// Function implementation in .cpp file
extern "C" vERROR __stdcall C16_DLLCALL ( vC16_CCB* aCCB )
{
...
}

HTH,
Giovanni

[=?Utf-8?B?UGF0cmljayBXZXN0ZXJob2Zm?=]

Re: DLL export, decorated function

Hi Giovanni,

thank you for your answer, however sadly it didn't solve the problem either..

"Giovanni Dicanio" wrote:

C16DLL.h (apart from that only has the standard definition of C16DLL_API
__declspec(dlle xport) etc.)
----
extern "C" vERROR __stdcall C16_DLLCALL( vC16_CCB* aCCB );

>
OK.
(But I would prefer useinga #ifdef __cplusplus guard here...)
>

I actually tried that in between, but it will probably not change the
results if it doesn't work without.

I think the problem is here.
This is a .CPP file, so I think that you should add 'extern "C"' explicitly
here:
>
// Function implementation in .cpp file
extern "C" vERROR __stdcall C16_DLLCALL ( vC16_CCB* aCCB )
{
...
}

When I try this explicitely, it gives me
C16_DDLCALL = _C16_DDLCALL@4
Does it help if I would change the file extensions to .c or change the
compiler settings so that it would compile as a C project?

Thank you,
Patrick Westerhoff

[Giovanni Dicanio]

Re: DLL export, decorated function

Hi Patrick,

"Patrick Westerhoff" <PatrickWesterh off@discussions .microsoft.comh a
scritto nel messaggio
news:6C3755BD-BA1D-49AC-8810-6BA637DFC434@mi crosoft.com...

>I think the problem is here.
>This is a .CPP file, so I think that you should add 'extern "C"'
>explicitly
>here:
>>
>// Function implementation in .cpp file
>extern "C" vERROR __stdcall C16_DLLCALL ( vC16_CCB* aCCB )
>{
> ...
>}

>
When I try this explicitely, it gives me
C16_DDLCALL = _C16_DDLCALL@4
Does it help if I would change the file extensions to .c or change the
compiler settings so that it would compile as a C project?

You could change the extension to .c, but I think it is not necessary; I
mean: you can still use C++ and have a "pure-C" interface.

Note that my answer is an addition to correct Sven's suggestion of using
..def files for exporting.

I will do a test...

Giovanni

[SvenC]

Re: DLL export, decorated function

Hi Patrick,

>Did you add the def file to your project property settings?
>>
>Config Props/Linker/Input/Module Definition File

yes, it was added there automatically when I created it.

I do expect the same as Giovanni and I guess his test project
should work for you.

Maybe you should give us a minimal sample, which includes the
missing types: vERROR and vC16_CCB.

extern "C" vERROR __stdcall C16_DLLCALL( vC16_CCB* aCCB );

Maybe some weird preprocessor side effects are going on?

What happens when you put this test function in your header:

extern "C" int __stdcall TestFoo(int);


And this in your cpp:

extern "C" int __stdcall TestFoo(int x)
{
return x;
}

--
SvenC