When I use llvm-gcc-4.2 within Xcode4.6.3 to compile 'x265' sources, it reported a strange error: ./source/encoder/reference.h:38:error: forward declaration of 'class x265::MotionReference'.However, the class declaration of x265::MotionReference is complete in reference.h:
Code:
#ifndef X265_REFERENCE_H
#define X265_REFERENCE_H

#include"primitives.h"
#include"picyuv.h"
#include"lowres.h"
#include"mv.h"

namespace X265_NS {
// private x265 namespace

structWeightParam;

classMotionReference:publicReferencePlanes
{
public:

    MotionReference();
    ~MotionReference();
    int  init(PicYuv*,WeightParam* wp,const x265_param& p);
    void applyWeight(int rows,int numRows);

    pixel*  weightBuffer[3];
    int     numInterpPlanes;
    int     numWeightedRows;

protected:

    MotionReference&operator=(constMotionReference&);
};
}

and it's parent class is defined in header file 'lowres.h':
Code:

#ifndef X265_LOWRES_H
#define X265_LOWRES_H

#include"primitives.h"
#include"common.h"
#include"picyuv.h"
#include"mv.h"

namespace X265_NS {
// private namespace

structReferencePlanes
{
    ReferencePlanes(){ memset(this,0,sizeof(ReferencePlanes));}

    pixel*   fpelPlane[3];
    pixel*   lowresPlane[4];
    PicYuv*  reconPic;

    bool     isWeighted;
    bool     isLowres;

    intptr_t lumaStride;
    intptr_t chromaStride;

    struct{
        int      weight;
        int      offset;
        int      shift;
        int      round;
    } w[3];

    pixel* getLumaAddr(uint32_t ctuAddr,uint32_t absPartIdx){return fpelPlane[0]+ reconPic->m_cuOffsetY[ctuAddr]+ reconPic->m_buOffsetY[absPartIdx];}
    pixel* getCbAddr(uint32_t ctuAddr,uint32_t absPartIdx){return fpelPlane[1]+ reconPic->m_cuOffsetC[ctuAddr]+ reconPic->m_buOffsetC[absPartIdx];}
    pixel* getCrAddr(uint32_t ctuAddr,uint32_t absPartIdx){return fpelPlane[2]+ reconPic->m_cuOffsetC[ctuAddr]+ reconPic->m_buOffsetC[absPartIdx];}

    /* lowres motion compensation, you must provide a buffer and stride for QPEL averaged pixels
     * in case QPEL is required.  Else it returns a pointer to the HPEL pixels */
    inline pixel *lowresMC(intptr_t blockOffset,const MV& qmv, pixel *buf,intptr_t& outstride)
    {
        if((qmv.x | qmv.y)&1)
        {
            int hpelA =(qmv.y &2)|((qmv.x &2)>>1);
            pixel *frefA = lowresPlane[hpelA]+ blockOffset +(qmv.x >>2)+(qmv.y >>2)* lumaStride;
            int qmvx = qmv.x +(qmv.x &1);
            int qmvy = qmv.y +(qmv.y &1);
            int hpelB =(qmvy &2)|((qmvx &2)>>1);
            pixel *frefB = lowresPlane[hpelB]+ blockOffset +(qmvx >>2)+(qmvy >>2)* lumaStride;
            primitives.pu[LUMA_8x8].pixelavg_pp(buf, outstride, frefA, lumaStride, frefB, lumaStride,32);
            return buf;
        }
        else
        {
            outstride = lumaStride;
            int hpel =(qmv.y &2)|((qmv.x &2)>>1);
            return lowresPlane[hpel]+ blockOffset +(qmv.x >>2)+(qmv.y >>2)* lumaStride;
        }
    }

    inlineint lowresQPelCost(pixel *fenc,intptr_t blockOffset,const MV& qmv,pixelcmp_t comp)
    {
        if((qmv.x | qmv.y)&1)
        {
            ALIGN_VAR_16(pixel, subpelbuf[8*8]);
            int hpelA =(qmv.y &2)|((qmv.x &2)>>1);
            pixel *frefA = lowresPlane[hpelA]+ blockOffset +(qmv.x >>2)+(qmv.y >>2)* lumaStride;
            int qmvx = qmv.x +(qmv.x &1);
            int qmvy = qmv.y +(qmv.y &1);
            int hpelB =(qmvy &2)|((qmvx &2)>>1);
            pixel *frefB = lowresPlane[hpelB]+ blockOffset +(qmvx >>2)+(qmvy >>2)* lumaStride;
            primitives.pu[LUMA_8x8].pixelavg_pp(subpelbuf,8, frefA, lumaStride, frefB, lumaStride,32);
            return comp(fenc, FENC_STRIDE, subpelbuf,8);
        }
        else
        {
            int hpel =(qmv.y &2)|((qmv.x &2)>>1);
            pixel *fref = lowresPlane[hpel]+ blockOffset +(qmv.x >>2)+(qmv.y >>2)* lumaStride;
            return comp(fenc, FENC_STRIDE, fref, lumaStride);
        }
    }
};

/* lowres buffers, sizes and strides */
structLowres:publicReferencePlanes
{
    pixel *buffer[4];

    int    frameNum;// Presentation frame number
    int    sliceType;// Slice type decided by lookahead
    int    width;// width of lowres frame in pixels
    int    lines;// height of lowres frame in pixel lines
    int    leadingBframes;// number of leading B frames for P or I

    bool   bScenecut;// Set to false if the frame cannot possibly be part of a real scenecut.
    bool   bKeyframe;
    bool   bLastMiniGopBFrame;

    /* lookahead output data */
    int64_t   costEst[X265_BFRAME_MAX +2][X265_BFRAME_MAX +2];
    int64_t   costEstAq[X265_BFRAME_MAX +2][X265_BFRAME_MAX +2];
    int32_t*  rowSatds[X265_BFRAME_MAX +2][X265_BFRAME_MAX +2];
    int       intraMbs[X265_BFRAME_MAX +2];
    int32_t*  intraCost;
    uint8_t*  intraMode;
    int64_t   satdCost;
    uint16_t* lowresCostForRc;
    uint16_t(*lowresCosts[X265_BFRAME_MAX +2][X265_BFRAME_MAX +2]);
    int32_t*  lowresMvCosts[2][X265_BFRAME_MAX +1];
    MV*       lowresMvs[2][X265_BFRAME_MAX +1];
    uint32_t  maxBlocksInRow;
    uint32_t  maxBlocksInCol;

    /* used for vbvLookahead */
    int       plannedType[X265_LOOKAHEAD_MAX +1];
    int64_t   plannedSatd[X265_LOOKAHEAD_MAX +1];
    int       indB;
    int       bframes;

    /* rate control / adaptive quant data */
    double*   qpAqOffset;// AQ QP offset values for each 16x16 CU
    double*   qpCuTreeOffset;// cuTree QP offset values for each 16x16 CU
    int*      invQscaleFactor;// qScale values for qp Aq Offsets
    uint32_t* blockVariance;
    uint64_t  wp_ssd[3];// This is different than SSDY, this is sum(pixel^2) - sum(pixel)^2 for entire frame
    uint64_t  wp_sum[3];
    uint64_t  frameVariance;

    /* cutree intermediate data */
    uint16_t* propagateCost;
    double    weightedCostDelta[X265_BFRAME_MAX +2];
    ReferencePlanes weightedRef[X265_BFRAME_MAX +2];

    bool create(PicYuv*origPic,int _bframes,bool bAqEnabled);
    void destroy();
    void init(PicYuv*origPic,int poc);
};
}

Does anybody knows why?Any clue would be appreciated!Thanks in advance!