re PR preprocessor/20907 (long comments throw off line numbers)

	PR preprocessor/20907
	* line-map.c (linemap_line_start): Fix bug when we need to increse
	column_bits but can re-use the current line_map.

From-SVN: r98515

libcpp/ChangeLog

+2005-04-19  Per Bothner  <per@bothner.com>
+
+	PR preprocessor/20907
+	* line-map.c (linemap_line_start): Fix bug when we need to increse
+	column_bits but can re-use the current line_map.
+
 2005-04-19  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* system.h (fopen, fdopen, freopen): Define these to the unlocked

libcpp/line-map.c

@@ -199,6 +199,8 @@ linemap_line_start (struct line_maps *set, unsigned int to_line,
       int column_bits;
       if (max_column_hint > 100000 || highest > 0xC0000000)
 	{
+	  /* If the column number is ridiculous or we've allocated a huge
+	     number of source_locations, give up on column numbers. */
 	  max_column_hint = 0;
 	  if (highest >0xF0000000)
 	    return 0;
@@ -211,13 +213,15 @@ linemap_line_start (struct line_maps *set, unsigned int to_line,
 	    column_bits++;
 	  max_column_hint = 1U << column_bits;
 	}
+      /* Allocate the new line_map.  However, if the current map only has a
+	 single line we can sometimes just increase its column_bits instead. */
       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;
+      r = map->start_location + ((to_line - map->to_line) << column_bits);
     }
   else
     r = highest - SOURCE_COLUMN (map, highest)