  ft_synthesize_vertical_metrics( FT_Glyph_Metrics*  metrics,
                                  FT_Pos             advance )
  {
    FT_Pos  height = metrics->height;


    /* compensate for glyph with bbox above/below the baseline */
    if ( metrics->horiBearingY < 0 )
    {
      if ( height < metrics->horiBearingY )
        height = metrics->horiBearingY;
    }
    else if ( metrics->horiBearingY > 0 )
      height -= metrics->horiBearingY;

    /* the factor 1.2 is a heuristical value */
    if ( !advance )
      advance = height * 12 / 10;

    metrics->vertBearingX = metrics->horiBearingX - metrics->horiAdvance / 2;
    metrics->vertBearingY = ( advance - height ) / 2;
    metrics->vertAdvance  = advance;
  }

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.