Set start_location to 0 if we ran out of line map space

With profiledbootstrap and --with-build-config=bootstrap-lto, linemap_add
may create a macro map when we run out of line map space.  This patch
changes start_location to UNKNOWN_LOCATION (0) in this case.

Tested with profiledbootstrap and --with-build-config=bootstrap-lto on
Linux/x86-64.

	PR bootstrap/86872
	* line-map.c (pure_location_p): Return true if linemap_lookup
	returns NULL.
	(linemap_add): Set start_location to 0 if we run out of line map
	space.

From-SVN: r263845

libcpp/ChangeLog

+2018-08-24  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR bootstrap/86872
+	* line-map.c (pure_location_p): Return true if linemap_lookup
+	returns NULL.
+	(linemap_add): Set start_location to 0 if we run out of line map
+	space.
+
 2018-08-20  Nathan Sidwell  <nathan@acm.org>
 
 	* include/cpplib.h: Fixup some whitespace.

libcpp/line-map.c

@@ -304,6 +304,8 @@ pure_location_p (line_maps *set, source_location loc)
     return false;
 
   const line_map *map = linemap_lookup (set, loc);
+  if (map == NULL)
+    return true;
   const line_map_ordinary *ordmap = linemap_check_ordinary (map);
 
   if (loc & ((1U << ordmap->m_range_bits) - 1))
@@ -492,6 +494,11 @@ linemap_add (struct line_maps *set, enum lc_reason reason,
     }
 
   linemap_assert (reason != LC_ENTER_MACRO);
+
+  if (start_location >= LINE_MAP_MAX_LOCATION)
+    /* We ran out of line map space.   */
+    start_location = 0;
+
   line_map_ordinary *map
     = linemap_check_ordinary (new_linemap (set, start_location));
   map->reason = reason;