How to delete warnings LNK4217 and LNK4049

I have warnings on the link step. These warnings appear only in release mode.

My program is composed of two parts: a library which generates a .lib and an executable which uses this library.

When I build the library I have no warnings. But when I build my executable, on the link I have warnings LNK4217 and LNK4049. For example:

3>DaemonCommon.lib(Exception.obj) : warning LNK4217: locally defined symbol ??0exception@std@@QAE@ABQBD@Z (public: __thiscall std::exception::exception(char const * const &)) imported in function "public: __thiscall std::bad_alloc::bad_alloc(char const *)" (??0bad_alloc@std@@QAE@PBD@Z)
3>DaemonCommon.lib(CommAnetoException.obj) : warning LNK4217: locally defined symbol ??0exception@std@@QAE@ABQBD@Z (public: __thiscall std::exception::exception(char const * const &)) imported in function "public: __thiscall std::bad_alloc::bad_alloc(char const *)" (??0bad_alloc@std@@QAE@PBD@Z)

I have read in the MSDN, these warnings may be caused by the declaration of __declspec(dllimport). But, in my classes of my lib, I haven't things declared like this. For example, here is my class Exception:

#ifndef _EXCEPTION_HPP__
#define _EXCEPTION_HPP__

#include <string>

namespace Exception
{
    class Exception  
    {
    public:
        // Constructor by default
        Exception();

        // Constructor parametrized
        Exception(std::string& strMessage);

        // Get the message of the exception
        virtual std::string getMessage() const;

        // Destructor
        virtual ~Exception();

    protected:

        // String containing the message of the exception
        std::string mStrMessage;
    };
}

#endif

Can somebody tell me why these warnings appear and how to delete them ?