Why the object is created also , When creating precompiled header?

Question

I want to create a .pch within a make file. cl /nologo /c /YcPrecompiled.hpp /FpPrecompiled.pch Precompiled.cpp

What confused me is : Why this command also create a object named Precompiled.obj

Should I link this object to the finale exe?

After I search on the web, I found a tutorial on msdn: http://msdn.microsoft.com/en-us/library/d9b6wk21(v=VS.71).aspx I cann't understand one line:

$(CPP) $(CLFLAGS) /Yc$(BOUNDRY)    applib.cpp myapp.cpp

When creating a pch, why does it need applib.cpp and myapp.cpp. And It also create two objects, applib.obj, myapp.obj, except the .pch file....Why?

Any indication is welcomed. Thanks very much!

Answer 1

MSDN does mention it at least in other 2 places:

STDAFX.CPP, STDAFX.H : These files are used to build a precompiled header file PROJNAME.PCH and a precompiled types file STDAFX.OBJ.

This description indeed doesn't clearly distinguish between precompiled header and precompiled types. Running dumpbin on a typical stdafx.obj from an MFC project, you'd see it contains a whole bunch of static ATL types, whose definition is buried somewhere deep in the include tree:

     ...
     COMDAT; sym= "struct ATL::IAtlAutoThreadModule * ATL::_pAtlAutoThreadModule" (?_pAtlAutoThreadModule@ATL@@3PEAUIAtlAutoThreadModule@1@EA)
     COMDAT; sym= "public: static int const ATL::AtlLimits<int>::_Min" (?_Min@?$AtlLimits@H@ATL@@2HB)
     COMDAT; sym= "public: static int const ATL::AtlLimits<int>::_Max" (?_Max@?$AtlLimits@H@ATL@@2HB)
     COMDAT; sym= "public: static unsigned int const ATL::AtlLimits<unsigned int>::_Min" (?_Min@?$AtlLimits@I@ATL@@2IB)
     COMDAT; sym= "private: static int (__cdecl* ATL::CNoUIAssertHook::s_pfnPrevHook)(int,char *,int *)" (?s_pfnPrevHook@CNoUIAssertHook@ATL@@0P6AHHPEADPEAH@ZEA)
     COMDAT; sym= "public: static bool ATL::CAtlBaseModule::m_bInitFailed" (?m_bInitFailed@CAtlBaseModule@ATL@@2_NA)
     COMDAT; sym= "public: static unsigned short const ATL::CVarTypeInfo<char>::VT" (?VT@?$CVarTypeInfo@D@ATL@@2GB)
     COMDAT; sym= "public: static char tagVARIANT::* ATL::CVarTypeInfo<char>::pmField" (?pmField@?$CVarTypeInfo@D@ATL@@2QEQtagVARIANT@@DEQ3@)
     COMDAT; sym= "public: static unsigned short const ATL::CVarTypeInfo<unsigned char>::VT" (?VT@?$CVarTypeInfo@E@ATL@@2GB)
     ...

Which kind of makes sense - if you define a static variable in a pch, there's no other reasonable place to put it in.