[gcc r13-4069] diagnostics: Fix macro tracking for ad-hoc locations

[Lewis Hyatt <lhyatt@gcc.gnu.org>]

https://gcc.gnu.org/g:6238cc20f0e588f272569230b33458fedf755ab2

commit r13-4069-g6238cc20f0e588f272569230b33458fedf755ab2
Author: Lewis Hyatt <lhyatt@gmail.com>
Date:   Tue Nov 1 17:50:27 2022 -0400

    diagnostics: Fix macro tracking for ad-hoc locations
    
    The result of linemap_resolve_location() can be an ad-hoc location, if that is
    what was stored in a relevant macro map.  maybe_unwind_expanded_macro_loc()
    did not previously handle this case, causing it to print the wrong tracking
    information for an example such as the new testcase macro-trace-1.c.  Fix that
    by checking for ad-hoc locations where needed.
    
    gcc/ChangeLog:
    
            * tree-diagnostic.cc (maybe_unwind_expanded_macro_loc): Handle ad-hoc
            location in return value of linemap_resolve_location().
    
    gcc/testsuite/ChangeLog:
    
            * c-c++-common/cpp/macro-trace-1.c: New test.

Diff:
---
 gcc/testsuite/c-c++-common/cpp/macro-trace-1.c | 4 ++++
 gcc/tree-diagnostic.cc                         | 7 +++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/c-c++-common/cpp/macro-trace-1.c b/gcc/testsuite/c-c++-common/cpp/macro-trace-1.c
new file mode 100644
index 00000000000..34cfbb3dad3
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/cpp/macro-trace-1.c
@@ -0,0 +1,4 @@
+/* This token is long enough to require an ad-hoc location. Make sure that
+   the macro trace still prints properly.  */
+#define X "0123456789012345678901234567689" /* { dg-error {expected .* before string constant} } */
+X /* { dg-note {in expansion of macro 'X'} } */
diff --git a/gcc/tree-diagnostic.cc b/gcc/tree-diagnostic.cc
index 0d79fe3c3c1..5cf3a1c17d2 100644
--- a/gcc/tree-diagnostic.cc
+++ b/gcc/tree-diagnostic.cc
@@ -190,14 +190,17 @@ maybe_unwind_expanded_macro_loc (diagnostic_context *context,
         location_t l = 
           linemap_resolve_location (line_table, resolved_def_loc,
                                     LRK_SPELLING_LOCATION,  &m);
-        if (l < RESERVED_LOCATION_COUNT || LINEMAP_SYSP (m))
+	location_t l0 = l;
+	if (IS_ADHOC_LOC (l0))
+	  l0 = get_location_from_adhoc_loc (line_table, l0);
+	if (l0 < RESERVED_LOCATION_COUNT || LINEMAP_SYSP (m))
           continue;
         
 	/* We need to print the context of the macro definition only
 	   when the locus of the first displayed diagnostic (displayed
 	   before this trace) was inside the definition of the
 	   macro.  */
-        int resolved_def_loc_line = SOURCE_LINE (m, l);
+	const int resolved_def_loc_line = SOURCE_LINE (m, l0);
         if (ix == 0 && saved_location_line != resolved_def_loc_line)
           {
             diagnostic_append_note (context, resolved_def_loc,