From 4acb3af3669db4ca79ffc97cd615fcea205bcccb Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Tue, 13 Apr 2021 05:03:19 -0700
Subject: [PATCH] preprocessor: Fix column adjustment [PR 99446]

This ICE was because when adjusting a column offset we could advance
into a linemap for a different file.  We only checked the next line
map was not for a line further advanced in any file, forgetting that
it could be for an earlier line in a different file.  The testcase
needed adjusting as column 512 was unrepresentable, once that was
taken into consideration.

	PR preprocessor/99446
	libcpp/
	* line-map.c (line-map.c): Do not advance to linemaps for
	different files.
	gcc/testsuite/
	* g++.dg/diagnostic/pr72803.C: Adjust expected column.
---
 gcc/testsuite/g++.dg/diagnostic/pr72803.C |  5 +++--
 libcpp/line-map.c                         | 19 +++++++++----------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/gcc/testsuite/g++.dg/diagnostic/pr72803.C b/gcc/testsuite/g++.dg/diagnostic/pr72803.C
index 0a9a390b9c3..ca522b74bad 100644
--- a/gcc/testsuite/g++.dg/diagnostic/pr72803.C
+++ b/gcc/testsuite/g++.dg/diagnostic/pr72803.C
@@ -5,5 +5,6 @@ class test {
 // The line directive appears to be necessary to trigger the ICE
 // { dg-error "style of line directive is a GCC extension" "" { target *-*-* } .-2 }
 
-/* Verify that we get the correct line and column for the diagnostic.  */
-// { dg-error "512: expected .;. after class definition" "" { target *-*-* } 3 }
+/* Verify that we get the best line and column for the diagnostic.
+   512 is not representable in the line-maps created for this test.  */
+// { dg-error "511: expected .;. after class definition" "" { target *-*-* } 3 }
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index 1bf0e8211f2..2f5e44447d2 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -981,16 +981,15 @@ linemap_position_for_loc_and_offset (line_maps *set,
      (loc + offset) should be less than the first location encoded by
      the next line map of the set.  Otherwise, we try to encode the
      location in the next map.  */
-  while (map != LINEMAPS_LAST_ORDINARY_MAP (set)
-	 && (loc + (column_offset << map->m_range_bits)
-	     >= MAP_START_LOCATION (&map[1])))
-    {
-      map = &map[1];
-      /* If the next map starts in a higher line, we cannot encode the
-	 location there.  */
-      if (line < ORDINARY_MAP_STARTING_LINE_NUMBER (map))
-	return loc;
-    }
+  for (; map != LINEMAPS_LAST_ORDINARY_MAP (set)
+	 && (loc + (column << map->m_range_bits)
+	     >= MAP_START_LOCATION (map + 1)); map++)
+    /* If the next map is a different file, or starts in a higher line, we
+       cannot encode the location there.  */
+    if ((map + 1)->reason != LC_RENAME
+	|| line < ORDINARY_MAP_STARTING_LINE_NUMBER (map + 1)
+	|| 0 != strcmp (LINEMAP_FILE (map + 1), LINEMAP_FILE (map)))
+      return loc;
 
   column += column_offset;