Linker Error (LNK2001: unresolved external symbol DllCanUnloadNow,DllGetClassObject,DllRegisterServer,DllUnregisterServer) with IntelC++ Compiler, no errors with MS VC++ Compiler

[komal_dutta]

Hi,

I used the latest version of Intel C++ Compiler 11.0.072, and the several Linker Errors that i got with version 10 are not seen anymore. Yipeee!!! But I am still getitng the following Linker Errors, even though this solution compiles fine with MS C++ Compiler,

xilink: executing 'link'
BuildManager.def : error LNK2001: unresolved external symbol DllCanUnloadNow
BuildManager.def : error LNK2001: unresolved external symbol DllGetClassObject
BuildManager.def : error LNK2001: unresolved external symbol DllRegisterServer
BuildManager.def : error LNK2001: unresolved external symbol DllUnregisterServer

Why are these errors coming? Am i missing something here?

Regards,
Komal Dutta

[JenniferJ]

Quoting - komal_dutta

BuildManager.def : error LNK2001: unresolved external symbol DllCanUnloadNow

So is the .cpp file containing "DllCanUnloadNow()" part of the project? Make sure it's not skiped in the build.

If all is ok, add following in front of the function:

__declspec( dllexport )

[komal_dutta]

Hi Jennifer,

I already have "__declspec(dllexport)" added in the function definition. I have the following in my cpp file:
STDAPI DllCanUnloadNow(void)

where STDAPI defined as extern "C" HRESULT __stdcall in winnt.h.

Regards,
Komal

[komal_dutta]

Hi,

I have found the reason why I was getting these errors.
The projects where I got these errors were "ATL Project" DLLs with "Allow merging of proxy/stub code" Enabled (during creation of the projects).

The vcproj files of these projects contains the setting:
WholeProgramOptimization="1"
When this is removed from the vcproj file, the project compiles fine with Intel C++ Compiler, without any errors.

Thanks & Regards,
Komal Dutta

P.S.: I have observed an issue with Intel C++ Compiler. When I make some change to the vcproj file and build it with Intel C++ Compiler, it gives errors. When I close and open the project, and build again; IT BUILDS FINE! Any clue why this is so?

[JenniferJ]

But the Whole Program Optimization could bring some performance for you.
Those functions are defined by MSVC, so function declarations can not be changed.

I'll create feature request to see if those functions can be handled differently.

Thanks,
Jennifer

[komal_dutta]

Hi Jennfer,

Performance is the key reason why we used Intel C++ Compiler.
Please update this forum if you find a way to keep "Whole Program Optimization" on, while building ATL projects.

Thanks & Regards,
Komal Dutta

Quoting - Jennifer Jiang (Intel)

But the Whole Program Optimization could bring some performance for you.
Those functions are defined by MSVC, so function declarations can not be changed.

I'll create feature request to see if those functions can be handled differently.

Thanks,
Jennifer

[JenniferJ]

Hello all,
Good news.

This issue is fixed in our 1st 11.1 update and as well as the Intel Parallel Composer 1st update.

To ensure you're using the 1st update, please log on to Intel Registration & Download center - https://registrationcenter.intel.com/RegCenter/Register.aspx
You may also get the latest version by going to our eval page - http://software.intel.com/en-us/intel-compilers/ (click Evaluate).

Thank you !
Jennifer

[Nikhil_P_]

Hi

I have same problem with my code error LNK2001: unresolved external symbol DllCanUnloadNow

But i found solution 

In the same project properties dialogbox, click on c/c++ go to Preprocessor. Then go to preprocessor definitions edit box. add last line REGISTER_PROXY_DLL 

Press OK

Work it..