libswscale/swscale.c:1057: error: Uninitialized Value
  The value read from A was never initialized.

libswscale/swscale.c:1057:29: 
1055.             int needAlpha = CONFIG_SWSCALE_ALPHA && c->alpPixBuf;
1056.             YSCALE_YUV_2_RGBX_FULL_C(1<<21, needAlpha)
1057.                 dest[aidx]= needAlpha ? A : 255;
                                  ^
1058.                 dest[0]= B>>22;
1059.                 dest[1]= G>>22;
