[gcc r12-3678] Don't record string concatenation data for 'RESERVED_LOCATION_P'

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:7d79c3ebc3f3f6f8aecf83726c97474ae5cfe957

commit r12-3678-g7d79c3ebc3f3f6f8aecf83726c97474ae5cfe957
Author: Thomas Schwinge <thomas@codesourcery.com>
Date:   Fri Sep 3 18:25:10 2021 +0200

    Don't record string concatenation data for 'RESERVED_LOCATION_P'
    
    'RESERVED_LOCATION_P' means 'UNKNOWN_LOCATION' or 'BUILTINS_LOCATION'.
    We're using 'UNKNOWN_LOCATION' as a spare value for 'Empty', so should
    ascertain that we don't use it as a key additionally.  Similarly for
    'BUILTINS_LOCATION' that we'd later like to use as a spare value for
    'Deleted'.
    
    As discussed in the source code comment added, for these we didn't have
    stable behavior anyway.
    
    Follow-up to r239175 (commit 88fa5555a309e5d6c6171b957daaf2f800920869)
    "On-demand locations within string-literals".
    
            gcc/
            * input.c (string_concat_db::record_string_concatenation)
            (string_concat_db::get_string_concatenation): Skip for
            'RESERVED_LOCATION_P'.
            gcc/testsuite/
            * gcc.dg/plugin/diagnostic-test-string-literals-1.c: Adjust
            expected error diagnostics.

Diff:
---
 gcc/input.c                                                     | 9 +++++++++
 gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c | 4 ++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/gcc/input.c b/gcc/input.c
index 4b809862e02..dd753decfa0 100644
--- a/gcc/input.c
+++ b/gcc/input.c
@@ -1437,6 +1437,11 @@ string_concat_db::record_string_concatenation (int num, location_t *locs)
   gcc_assert (locs);
 
   location_t key_loc = get_key_loc (locs[0]);
+  /* We don't record data for 'RESERVED_LOCATION_P (key_loc)' key values:
+     any data now recorded under key 'key_loc' would be overwritten by a
+     subsequent call with the same key 'key_loc'.  */
+  if (RESERVED_LOCATION_P (key_loc))
+    return;
 
   string_concat *concat
     = new (ggc_alloc <string_concat> ()) string_concat (num, locs);
@@ -1460,6 +1465,10 @@ string_concat_db::get_string_concatenation (location_t loc,
   gcc_assert (out_locs);
 
   location_t key_loc = get_key_loc (loc);
+  /* We don't record data for 'RESERVED_LOCATION_P (key_loc)' key values; see
+     discussion in 'string_concat_db::record_string_concatenation'.  */
+  if (RESERVED_LOCATION_P (key_loc))
+    return false;
 
   string_concat **concat = m_table->get (key_loc);
   if (!concat)
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c
index 4cba87be2ae..8818192eb45 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c
@@ -332,8 +332,8 @@ pr87652 (const char *stem, int counter)
 				OFFSET + end_idx);		\
   } while (0)
 
-/* { dg-error "unable to read substring location: unable to read source line" "" { target c } 329 } */
-/* { dg-error "unable to read substring location: failed to get ordinary maps" "" { target c++ } 329 } */
+/* { dg-error "unable to read substring location: failed to get ordinary maps" "" { target c } 329 } */
+/* { dg-error "unable to read substring location: macro expansion" "" { target c++ } 329 } */
 /* { dg-begin-multiline-output "" }
      __emit_string_literal_range(__FILE__":%5d: " format,        \
                                  ^~~~~~~~