How to reference C++ library with no class / namespace? - visual-c++

Question

I have a 3rd party C++ .lib that I would like to use in a C# application.
My intent is to write a managed C++ wrapper .dll for the .lib, and then include that wrapper dll in my C# application, using a process roughly like the one outlined at this link.
The header file for the .lib does not indicate any class declaration or namespace, just method names:
int CheckNamedVariable(const char* _name);
int RegisterNamedVariable(const char* _name);
double GetNamedVariableValue(int _id);
double GetNamedVariableTypedValue(int _id, int _units);
void SetNamedVariableValue(int _id, double _value);
... (etc)
I checked the lib with DUMPBIN /exports to see if I could glean any additional information, and got the following:
File Type: LIBRARY
Exports
ordinal name
?AircraftVarGet##YANHHH#Z (double __cdecl AircraftVarGet(int,int,int))
?CheckNamedVariable##YAHPBD#Z (int __cdecl CheckNamedVariable(char const *))
?DLLStart##YGXXZ (void __stdcall DLLStart(void))
?DLLStop##YGXXZ (void __stdcall DLLStop(void))
?GetAircraftVarEnum##YAHPBD#Z (int __cdecl GetAircraftVarEnum(char const *))
?GetModuleVar##YANW4GAUGE_TOKEN###Z (double __cdecl GetModuleVar(enum GAUGE_TOKEN))
?GetNameOfNamedVariable##YAPBDH#Z (char const * __cdecl GetNameOfNamedVariable(int))
?GetNamedVariableTypedValue##YANHH#Z (double __cdecl GetNamedVariableTypedValue(int,int))
?GetNamedVariableValue##YANH#Z (double __cdecl GetNamedVariableValue(int))
?GetUnitsEnum##YAHPBD#Z (int __cdecl GetUnitsEnum(char const *))
?IsPanelWindowVisibleIdent##YAHI#Z (int __cdecl IsPanelWindowVisibleIdent(unsigned int))
?Panels##3PAUPANELS##A (struct PANELS * Panels)
?RegisterNamedVariable##YAHPBD#Z (int __cdecl RegisterNamedVariable(char const *))
?SendKeyEvent##YAXII#Z (void __cdecl SendKeyEvent(unsigned int,unsigned int))
?SetNamedVariableTypedValue##YAXHNH#Z (void __cdecl SetNamedVariableTypedValue(int,double,int))
?SetNamedVariableValue##YAXHN#Z (void __cdecl SetNamedVariableValue(int,double))
_ImportTable
_Linkage
Summary
ED .debug$S
14 .idata$2
14 .idata$3
4 .idata$4
4 .idata$5
1A .idata$6
In my managed wrapper project, I can point the Linker input to the .lib, but I'm not sure how to call the methods in the lib (the tutorial I linked to makes use of namespaces and classes). If it were a plain old DLL in a C#/VB project, I could view the object browser and get some idea of how to call the library.
But given my C++ ignorance, I'm in the dark. Any help appreciated.
EDIT:
I tried just creating methods with the same name as the methods listed in the header, e.g.:
int VariableExporter::IsPanelWindowVisibleIdent(unsigned int panel_id)
{
return IsPanelWindowVisibleIdent(panel_id);
}
This is not doing what I'd hope, it's just recursively calling itself (until it has a - wait for it - Stack Overflow).
Then I tried renaming the wrapper method like this:
int VariableExporter::IsPanelWindowVisibleIdent_New_Name(unsigned int panel_id)
{
return IsPanelWindowVisibleIdent(panel_id);
}
Now, although the C++ .DLL project and the C# project both compile, the C# project throws a FileNotFound exception when it tries to load that .DLL.

Answer 1

First thing, to call global level function, you need to use the scope resolution operator ::
int VariableExporter::IsPanelWindowVisibleIdent(unsigned int panel_id)
{
return ::IsPanelWindowVisibleIdent(panel_id);
}
There is no need (at least for this simple case), to rename your method.
Secondly, for DLL-not-found issue, check that DLL is present in the bin path of your C# application. Also, check that wrapper-DLL itself is loadable (use Dependency Walker). Ensure that bit-ness of wrapper DLL and C# application also matches. A 64-bit application cannot load 32-bit DLL (and vice versa).