Re: line-map question

[Devang Patel <dpatel at apple dot com>]

On Apr 18, 2005, at 11:54 AM, Mike Stump wrote:

> On Apr 18, 2005, at 9:55 AM, Devang Patel wrote:
> > From line_map comment at (libcpp/include/line-map.h)
> >
> > /* Physical source file TO_FILE at line TO_LINE at column 0 is  
> > represented
> >    by the logical START_LOCATION.  TO_LINE+L at column C is  
> > represented by
> >    START_LOCATION+(L*(1<<column_bits))+C, as long as C< 
> > (1<<column_bits),
> >
> > What happens when column number is >= 128 ? This is PR 20907.
>
> What should happen?  Well, col==0 would be reasonable.

Well, column 0 is represented as START_LOCATION. Some how, when  
column number
is >= 128, line-map increments physical line number. And I am kind of  
lost
reading code without any kind of comments ;-( See below from line-map.c.

-
Devang


  return map;
}

source_location
linemap_line_start (struct line_maps *set, unsigned int to_line,
                    unsigned int max_column_hint)
{
  struct line_map *map = &set->maps[set->used - 1];
  source_location highest = set->highest_location;
  source_location r;
  unsigned int last_line = SOURCE_LINE (map, set->highest_line);
  int line_delta = to_line - last_line;
  bool add_map = false;
  if (line_delta < 0
      || (line_delta > 10 && line_delta * map->column_bits > 1000)
      || (max_column_hint >= (1U << map->column_bits))
      || (max_column_hint <= 80 && map->column_bits >= 10))
    {
      add_map = true;
    }
  else
    max_column_hint = set->max_column_hint;
  if (add_map)
    {
      int column_bits;
      if (max_column_hint > 100000 || highest > 0xC0000000)
        {
          max_column_hint = 0;
          if (highest >0xF0000000)
            return 0;
          column_bits = 0;
        }
      else
        {
          column_bits = 7;
          while (max_column_hint >= (1U << column_bits))
            column_bits++;
          max_column_hint = 1U << column_bits;
        }
      if (line_delta < 0
          || last_line != map->to_line
          || SOURCE_COLUMN (map, highest) >= (1U << column_bits))
        map = (struct line_map*) linemap_add (set, LC_RENAME, map- 
>sysp,
                                      map->to_file, to_line);
      map->column_bits = column_bits;
      r = map->start_location;
    }
  else
    r = highest - SOURCE_COLUMN (map, highest)
      + (line_delta << map->column_bits);
  set->highest_line = r;
  if (r > set->highest_location)
    set->highest_location = r;
  set->max_column_hint = max_column_hint;
  return r;
}