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Specifying a .obj at LIB time.

Started by C0balt May 24, 2008 at 10:05 PM 6 replies 1k views

Original Post

May 24, 2008 at 10:05 PM

Is there anyway to specify which .obj file is used by the librarian to avoid the following error...

1>DEF.obj : warning LNK4006: "protected: __thiscall ####::CGraphics::CGraphics(struct HWND__ *)" (??0CGraphics@H####@@IAE@PAUHWND__@@@Z) already defined in ABC.obj; second definition ignored

and allow this:

#ifdef USE_ABC
#include "ABC.H"
#endif
#ifdef USE_DEF
#include "DEF.H"
#endif

I'm trying to avoid one of the obvious solutions:

#ifdef USE_ABC
#pragma comment(lib, "ABC.LIB")
#endif
#ifdef USE_DEF
#pragma comment(lib, "DEF.LIB")
#endif

due to the structure of the project (the desire for a single .lib) Any thoughts? I know there are probably a dozen ways to tackle this problem, I just have not found a simple elegant solution yet.

force_of_will

May 24, 2008 at 10:10 PM

Can you post some code, or try to explain better what you are trying to do.

fpsgamer

May 24, 2008 at 10:18 PM

None of what you said makes any sense.

Anyways, you have a duplicate symbol somewhere in your project.

C0balt

May 24, 2008 at 10:23 PM

I'm trying to create a graphics object based on a simple global define macro. Instead of chopping up the entire code base with a million ifdefs... I have one global file that defines what includes to use based on a single #define.

ABC.H would define how CGraphics functions X way. DEF.h would define how CGraphics functions Y way. And then App just calls the following based on what .h is included (based on what #define USE_ is set to).

	void CApp::InitGFX(void)	{		CGraphics::Create(Window()->GetHWND(), m_Width, m_Height);	}

App.h has the following define.

#include "Global.h"

Containing:

#ifdef USE_ABC#include "ABC.H"#endif#ifdef USE_DEF#include "DEF.H"#endif

C0balt

May 24, 2008 at 10:26 PM

Quote:
Original post by fpsgamer
None of what you said makes any sense.

Anyways, you have a duplicate symbol somewhere in your project.

Obviously. =) By design. ABC and DEF both have class CGraphics implemented. See my last post. I need to choose either ABC's OR DEF's implementation, not both.

fpsgamer

May 24, 2008 at 10:36 PM

Quote:
Original post by C0balt
Quote:
Original post by fpsgamer
None of what you said makes any sense.

Anyways, you have a duplicate symbol somewhere in your project.

Obviously. =) By design. ABC and DEF both have class CGraphics implemented. See my last post. I need to choose either ABC's OR DEF's implementation, not both.

Use a pragma as you mentioned before, or create a new build configuration. You can create a new build configuration by going into "Build > Configuration Manager". Once you've done that go into your project properties and specify the include directories and library dependencies for each of your build configurations.

erissian

May 25, 2008 at 12:03 AM

You can set up a new configuration in your project; ie "Release|Debug_foo" and "Release|Debug_bar".

Preferably, you would use logic directives to determine the contents of the file being linked, for instance:

// someobject1.hclass SomeObject {  ...};// someobject1.cppvoid SomeObject::SomeFunction() {  ...  // exhibits behavior A  ...}// someobject2.hclass SomeObject {  ...};// someobject2.cppvoid SomeObject::SomeFunction() {  ...  // exhibits behavior B  ...}// someobjectwrapper.h#ifdef USE_OBJECT_1#include "someobject1.h"#else#include "someobject2.h"#endif// someobjectwrapper.cpp#ifdef USE_OBJECT_1#include "someobject1.cpp"#else#include "someobject2.cpp"#endif

In this case, someobjectwrapper.obj gets built and linked, but not someobject1|2.obj.

It would, however, be more elegant to leave it all in one file and #ifdef the differences.

C0balt

May 25, 2008 at 9:54 AM

Thanks for the ideas guys. I'll let you know what I end up with.

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