PNG_FREE_UNKN     459 3rdparty/libpng/png.c    if ((mask & PNG_FREE_UNKN) & info_ptr->free_me)
PNG_FREE_UNKN     477 3rdparty/libpng/png.c                png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, i);
PNG_FREE_UNKN    1088 3rdparty/libpng/pngset.c    info_ptr->free_me |= PNG_FREE_UNKN;