From 1174314811af52779497462f26d21ea0038d1a85 Mon Sep 17 00:00:00 2001
From: Eric Botcazou <ebotcazou@adacore.com>
Date: Tue, 13 Apr 2021 11:57:55 +0200
Subject: [PATCH] Fix thinko in libcpp preparation patch for modules

The problem is that the new IS_MACRO_LOC macro:

inline bool
IS_MACRO_LOC (location_t loc)
{
  return !IS_ORDINARY_LOC (loc) && !IS_ADHOC_LOC (loc);
}

is not fully correct since the position of the macro lines is not fixed:

/* Returns the lowest location [of a token resulting from macro
   expansion] encoded in this line table.  */
inline location_t
LINEMAPS_MACRO_LOWEST_LOCATION (const line_maps *set)
{
  return LINEMAPS_MACRO_USED (set)
         ? MAP_START_LOCATION (LINEMAPS_LAST_MACRO_MAP (set))
         : MAX_LOCATION_T + 1;
}

In Ada, LINEMAPS_MACRO_USED is false so LINEMAPS_MACRO_LOWEST_LOCATION is
MAX_LOCATION_T + 1, but IS_MACRO_LOC nevertheless returns true for anything
in the range [LINE_MAP_MAX_LOCATION; MAX_LOCATION_T], thus yielding an ICE
in linemap_macro_map_lookup for very large files.

libcpp/
	* include/line-map.h (IS_MACRO_LOC): Delete.
	* line-map.c (linemap_location_from_macro_expansion_p): Test
	LINEMAPS_MACRO_LOWEST_LOCATION of the linemap.
gcc/cp/
	* module.cc (ordinary_loc_of): Test LINEMAPS_MACRO_LOWEST_LOCATION
	of the linemap.
	(module_state::write_location): Likewise.
---
 gcc/cp/module.cc          |  4 ++--
 libcpp/include/line-map.h | 10 +++-------
 libcpp/line-map.c         |  2 +-
 3 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index c80c7bcc70f..ab8b1f1caad 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -13709,7 +13709,7 @@ ordinary_loc_of (line_maps *lmaps, location_t from)
     {
       if (IS_ADHOC_LOC (from))
 	from = get_location_from_adhoc_loc (lmaps, from);
-      if (IS_MACRO_LOC (from))
+      if (from >= LINEMAPS_MACRO_LOWEST_LOCATION (lmaps))
 	{
 	  /* Find the ordinary location nearest FROM.  */
 	  const line_map *map = linemap_lookup (lmaps, from);
@@ -15554,7 +15554,7 @@ module_state::write_location (bytes_out &sec, location_t loc)
       write_location (sec, range.m_start);
       write_location (sec, range.m_finish);
     }
-  else if (IS_MACRO_LOC (loc))
+  else if (loc >= LINEMAPS_MACRO_LOWEST_LOCATION (line_table))
     {
       if (const loc_spans::span *span = spans.macro (loc))
 	{
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index 40919d088ac..7d964172469 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -563,7 +563,7 @@ struct GTY((tag ("2"))) line_map_macro : public line_map {
 #define linemap_assert_fails(EXPR) (! (EXPR))
 #endif
 
-/* Get whether location LOC is an ad-hoc, ordinary or macro location.  */
+/* Get whether location LOC is an ordinary location.  */
 
 inline bool
 IS_ORDINARY_LOC (location_t loc)
@@ -571,18 +571,14 @@ IS_ORDINARY_LOC (location_t loc)
   return loc < LINE_MAP_MAX_LOCATION;
 }
 
+/* Get whether location LOC is an ad-hoc location.  */
+
 inline bool
 IS_ADHOC_LOC (location_t loc)
 {
   return loc > MAX_LOCATION_T;
 }
 
-inline bool
-IS_MACRO_LOC (location_t loc)
-{
-  return !IS_ORDINARY_LOC (loc) && !IS_ADHOC_LOC (loc);
-}
-
 /* Categorize line map kinds.  */
 
 inline bool
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index a003af8533c..1bf0e8211f2 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -1321,7 +1321,7 @@ linemap_location_from_macro_expansion_p (const class line_maps *set,
   if (IS_ADHOC_LOC (location))
     location = get_location_from_adhoc_loc (set, location);
 
-  return IS_MACRO_LOC (location);
+  return location >= LINEMAPS_MACRO_LOWEST_LOCATION (set);
 }
 
 /* Given two virtual locations *LOC0 and *LOC1, return the first