Robert Giesecke's Unmanaged Exports - c++

Question

I'm trying to get an DllExport from vb.net to unmanaged c++ working.
I'm using Robert Giesecke's Unmanaged Exports with Visual Studio 2012 and tried to follow this very helpful hints. I copy the dlls from the .Net project by an post build action in the directory where my *.cpp and *.h files reside.
I checked my dll with dumpbin /EXPORTS Nugget.Discovery.dll and it tells me that there are exports:
File Type: DLL
Section contains the following exports for \Nugget.Discovery.dll
00000000 characteristics
52554A05 time date stamp Wed Oct 09 14:20:21 2013
0.00 version
0 ordinal base
2 number of functions
2 number of names
ordinal hint RVA name
0 0 0000532E StartAnnouncing
1 1 0000533E StopAnnouncing
Summary
2000 .reloc
4000 .rsrc
2000 .sdata
4000 .text
But if I try to import it in the cpp file with
#import "Nugget.Discovery.dll"
void StartAnnouncing(int serial);
I get one IntelliSense error and one error after I try to compile:
IntelliSense: cannot open source file "Debug/Nugget.Discovery.tlh"
error C1083: Cannot open type library file: 'nugget.discovery.dll': Fehler beim Laden der Typbibliothek/DLL.
Any idea what I'm doing wrong?
Best regards!
Stefan

Answer 1

As part of DllExport, a .lib file is generated. You can use that to use the normal C++ linker instead of LoadLibrary/GetProcAddress.
Starting from the managed code you posted, on the native side:
extern CALLBACK void StartAnnouncingType(int serial);
extern CALLBACK int TestType(void);
int _tmain(int argc, _TCHAR* argv[])
{
int test = TestPtr();
StartAnnouncingPtr(1);
}
In the settings of you unmanaged project, add Nugget.Discovery.lib to the project properties: Configuration Properties->Linker->Input. And copy the Nugget.Discovery.dll to the output directory.

Answer 2

Ok, thanks to Hans Passant I came to this solution:
This is my code on the managed side:
Imports System.Runtime.InteropServices
Imports RGiesecke.DllExport
Public NotInheritable Class Beacon
Private Sub New()
End Sub
Private Shared _nuggetAnnouncement As NuggetAnnouncement
' ReSharper disable UnusedMember.Local
''' <remarks>Cannot be called from managed code!</remarks>
<DllExport("StartAnnouncing", CallingConvention.StdCall)>
Private Shared Sub StartAnnouncingNative(serial As Integer)
StartAnnouncing(serial)
End Sub
''' <remarks>Cannot be called from managed code!</remarks>
<DllExport("Test", CallingConvention.StdCall)>
Private Shared Function TestNative() As Integer
Return Test()
End Function
' ReSharper restore UnusedMember.Local
Public Shared Sub StartAnnouncing(serial As Integer)
'do something
End Sub
Public Shared Function Test() As Integer
Return 42
End Function
End Class
Interesting is, that I cannot call functions that are marked with <DllExport> from managed code (even if they are Public).
And this is the code on the native side:
typedef void (CALLBACK* StartAnnouncingType)(int);
typedef int (CALLBACK* TestType)(void);
int _tmain(int argc, _TCHAR* argv[])
{
HINSTANCE dllHandle = NULL;
StartAnnouncingType StartAnnouncingPtr = NULL;
TestType TestPtr = NULL;
wchar_t dllNameWide[64];
int size = mbstowcs(dllNameWide, "Nugget.Discovery.dll", sizeof(dllNameWide));
dllHandle = LoadLibrary(dllNameWide);
if (NULL != dllHandle)
{
//Get pointer to our function using GetProcAddress:
StartAnnouncingPtr = (StartAnnouncingType)GetProcAddress(dllHandle,"StartAnnouncing");
TestPtr = (TestType)GetProcAddress(dllHandle,"Test");
int test;
if (NULL != TestPtr) test = TestPtr();
int serial = 1;
if (NULL != StartAnnouncingPtr) StartAnnouncingPtr(1);
//Free the library:
FreeLibrary(dllHandle);
}
}
Are there any other better solutions?
Ciao!
Stefan