Question

I have something like this:

union MyBBox3D
{
    struct
    {
        float  m_fBox[6]; 
        float  m_fCenter[3];
        float  m_fDiagonalLen;
        float  m_fNormalizeFactor;
        float  m_fScaling[3];
    };
    struct
    {
        float  m_fMin[3];
        float  m_fMax[3];
        float  m_fCenter[3]; 
        float  m_fDiagonalLen;
        float  m_fNormalizeFactor;
        float  m_fScaling[3];
    };
    struct
    {
        float  m_fMinX, m_fMinY, m_fMinZ;
        float  m_fMaxX, m_fMaxY, m_fMaxZ;
        float  m_fCenterX, m_fCenterY, m_fCenterZ;
        float  m_fDiagonalLen;
        float  m_fNormalizeFactor;
        float  m_fScalingX, m_fScalingY, m_fScalingZ;
    };
};

It compiles well with vs2008 and intel compiler 12.0, but cant be compiled with gcc4.6.3, it gives the following errors:

In file included from Mesh/MyMeshTool.cpp:17:0:
Mesh/MyMeshTool.h:68:28: error: declaration of ‘float                   nsMeshLib::MyBBox3D::<anonymous struct>::m_fCenter [3]’
Mesh/MyMeshTool.h:59:28: error: conflicts with previous declaration ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fCenter [3]’
Mesh/MyMeshTool.h:69:17: error: declaration of ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fDiagonalLen’
Mesh/MyMeshTool.h:60:17: error: conflicts with previous declaration ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fDiagonalLen’
Mesh/MyMeshTool.h:70:20: error: declaration of ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fNormalizeFactor’
Mesh/MyMeshTool.h:61:20: error: conflicts with previous declaration ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fNormalizeFactor’
Mesh/MyMeshTool.h:71:32: error: declaration of ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fScaling [3]’
Mesh/MyMeshTool.h:62:32: error: conflicts with previous declaration ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fScaling [3]’
Mesh/MyMeshTool.h:78:17: error: declaration of ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fDiagonalLen’
Mesh/MyMeshTool.h:60:17: error: conflicts with previous declaration ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fDiagonalLen’
Mesh/MyMeshTool.h:79:20: error: declaration of ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fNormalizeFactor’
Mesh/MyMeshTool.h:61:20: error: conflicts with previous declaration ‘float nsMeshLib::MyBBox3D::<anonymous struct>::m_fNormalizeFactor’

How can I solve this problem? Thanks in advance!

Answer 1

I think in this case (where the separate structures making up the union share identifier names), you’re probably better off not using anonymous structures.

Either that or make the names unique across the entire union.

Anything else is just asking for trouble 🙂