[Bug preprocessor/108900] [libcpp] cpp gives wrong line number information with a file huge number of lines

["libin.dang at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108900

--- Comment #1 from Libin Dang <libin.dang at gmail dot com> ---
For this test case, `-fdump-internal-locations' gives:

...
header3.h:327614|loc:1342177760|#include "header2.h"
                               |77777778888888888888
                               |78889990001112223334
                               |92582581481470470360
                               |24680246802468024680

ORDINARY MAP: 10
  location_t interval: 1342178464 <= loc < 1342178464
  file: header3.h
  starting at line: 327615
  column and range bits: 7
  column bits: 7
  range bits: 0
  reason: 2 (LC_RENAME)
  included from location: 270816 (in ordinary map 8)

ORDINARY MAP: 11
  location_t interval: 1342178464 <= loc < 1342178496
  file: header2.h
  starting at line: 1
  column and range bits: 7
  column bits: 7
  range bits: 0
  reason: 0 (LC_ENTER)
  included from location: 1342178336 (in ordinary map 9)
header2.h:  1|loc:1342178464|
                            |
                            |
                            |
                            |

ORDINARY MAP: 12
  location_t interval: 1342178496 <= loc < 1342178528
  file: header3.h
  starting at line: 327614
  column and range bits: 7
  column bits: 7
  range bits: 0
  reason: 1 (LC_LEAVE)
  included from location: 270816 (in ordinary map 8)
header3.h:327614|loc:1342178496|#include "header2.h"
                               |88888888888888888888
                               |44455555555555555555
                               |99900000000001111111
                               |78901234567890123456
...

Map 10 has `location_t interval: 1342178464 <= loc < 1342178464', this does not
look right.  And Map 12 suppose to have location information for `header3 ends'
instead of `#include "header2.h"'.

Both the following changes can fix this issue (at least for this test case):

diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index 8a390d0..991170e 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -524,6 +524,10 @@ linemap_add (line_maps *set, enum lc_reason reason,
       /* A TO_FILE of NULL is special - we use the natural values.  */
       if (to_file == NULL)
         {
+          /* Adjust for LC_RENAME in some special cases */
+          while (from->to_file == from[1].to_file && from->included_from ==
from[1].included_from)
+            ++from;
+


diff --git a/libcpp/line-map.cc b/libcpp/line-map.cc
index 62077c3857c0..452016f377c9 100644
--- a/libcpp/line-map.cc
+++ b/libcpp/line-map.cc
@@ -775,8 +775,6 @@ linemap_line_start (line_maps *set, linenum_type to_line,
          && line_delta * map->m_column_and_range_bits > 1000)
       || (max_column_hint >= (1U << effective_column_bits))
       || (max_column_hint <= 80 && effective_column_bits >= 10)
-      || (highest > LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES
-         && map->m_range_bits > 0)
       || (highest > LINE_MAP_MAX_LOCATION_WITH_COLS
          && (set->max_column_hint || highest >= LINE_MAP_MAX_LOCATION)))
     add_map = true;


However, neither of them looks right.