Question

I’m getting confused about the scope of ‘using namespace’ declarations… hoping someone can clear this up for me!

I’m using two libraries (OpenCV and Ogre3D). I have two cpp files, one uses exclusively OpenCV (PoseEstimator.cpp) and the other exclusively Ogre3D (OgreLogic.cpp).

The top of OgreLogic.cpp looks like this:

#include "stdafx.h"

#include "PoseEstimator.h"
#include "OgreLogic.h"

using namespace Ogre;

And the top of PoseEstimator.cpp looks like this:

#include "StdAfx.h"
#include "PoseEstimator.h"

using namespace cv;
using namespace std;

This ‘using namespace cv’ is the only occurrence in the whole project (I double checked by doing a search). The are no ‘using namespace’s in headers, only ever in cpp files.

However, when compiling OgreLogic.cpp I get ambiguity errors, e.g.:

cxmat.hpp(3465) : error C2872: ‘uchar’
: ambiguous symbol 1> could be
‘d:\libraries\opencv2.1\include\opencv\cxtypes.h(154)
: unsigned char uchar’ 1> or
‘d:\libraries\ogresdk\include\ogre\OgrePrerequisites.h(106)
: Ogre::uchar’

I seem to be misunderstanding something, because I think this should be OK?

Any help greatly appreciated!

Thanks,

Jack

Answer 1

It looks like what is happening is you have a line declaring a uchar, e.g. uchar x = 12 or something. At the top of your file, you’ve specified that you’re using the Ogre namespace. The compiler is running into a problem determining which uchar you’re using – the cxtypes.h one or the Ogre::uchar.

Try taking out the using namespace Ogre; and do your function calls as Ogre::doStuff() to remove ambiguity.