LinkError: unresolved external symbol LNK Error in Release Mode Only

When I compile my program in release mode the compiler terminate with the message

error LNK2001: unresolved external symbol _[methodename].

in debug mode the programm works fine.

i call a method from a cpp

CPP:

extern "C" { 

	void GPUCudaCall(const int argc, const char** argv, float* vector1, float* vector2, int size, float* result);

}

...

GPUCudaCall(argc, (const char**)argv, vector1, vector2, size, result);

CU-File:

extern "C" void GPUCudaCall(const int argc, const char** argv, float* vector1, float* vector2, int size, float* result){

...

[Kernel Call]

...

}

Thanks for help