png_handle_gAMA(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
{
   png_fixed_point igamma;
#ifdef PNG_FLOATING_POINT_SUPPORTED
   float file_gamma;
#endif
   png_byte buf[4];

   png_debug(1, "in png_handle_gAMA");

   if (!(png_ptr->mode & PNG_HAVE_IHDR))
      png_error(png_ptr, "Missing IHDR before gAMA");
   else if (png_ptr->mode & PNG_HAVE_IDAT)
   {
      png_warning(png_ptr, "Invalid gAMA after IDAT");
      png_crc_finish(png_ptr, length);
      return;
   }
   else if (png_ptr->mode & PNG_HAVE_PLTE)
      /* Should be an error, but we can cope with it */
      png_warning(png_ptr, "Out of place gAMA chunk");

   if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_gAMA)
#ifdef PNG_READ_sRGB_SUPPORTED
      && !(info_ptr->valid & PNG_INFO_sRGB)
#endif
      )
   {
      png_warning(png_ptr, "Duplicate gAMA chunk");
      png_crc_finish(png_ptr, length);
      return;
   }

   if (length != 4)
   {
      png_warning(png_ptr, "Incorrect gAMA chunk length");
      png_crc_finish(png_ptr, length);
      return;
   }

   png_crc_read(png_ptr, buf, 4);
   if (png_crc_finish(png_ptr, 0))
      return;

   igamma = (png_fixed_point)png_get_uint_32(buf);
   /* Check for zero gamma */
   if (igamma == 0)
      {
         png_warning(png_ptr,
           "Ignoring gAMA chunk with gamma=0");
         return;
      }

#ifdef PNG_READ_sRGB_SUPPORTED
   if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sRGB))
      if (PNG_OUT_OF_RANGE(igamma, 45500L, 500))
      {
         png_warning(png_ptr,
           "Ignoring incorrect gAMA value when sRGB is also present");
#ifdef PNG_CONSOLE_IO_SUPPORTED
         fprintf(stderr, "gamma = (%d/100000)", (int)igamma);
#endif
         return;
      }
#endif /* PNG_READ_sRGB_SUPPORTED */

#ifdef PNG_FLOATING_POINT_SUPPORTED
   file_gamma = (float)igamma / (float)100000.0;
#  ifdef PNG_READ_GAMMA_SUPPORTED
     png_ptr->gamma = file_gamma;
#  endif
     png_set_gAMA(png_ptr, info_ptr, file_gamma);
#endif
#ifdef PNG_FIXED_POINT_SUPPORTED
   png_set_gAMA_fixed(png_ptr, info_ptr, igamma);
#endif
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.