[5/7] diagnostics: introduce diagnostic-macro-unwinding.h/cc

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index a2799b8d826..e701d9fb082 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1826,6 +1826,7 @@  OBJS = \
 OBJS-libcommon = diagnostic-spec.o diagnostic.o diagnostic-color.o \
 	diagnostic-format-json.o \
 	diagnostic-format-sarif.o \
+	diagnostic-macro-unwinding.o \
 	diagnostic-show-locus.o \
 	edit-context.o \
 	pretty-print.o intl.o \
diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc
index faaf9ee6350..33114f13c8d 100644
--- a/gcc/c-family/c-opts.cc
+++ b/gcc/c-family/c-opts.cc
@@ -32,7 +32,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "flags.h"
 #include "toplev.h"
 #include "langhooks.h"
-#include "tree-diagnostic.h" /* for virt_loc_aware_diagnostic_finalizer */
+#include "diagnostic-macro-unwinding.h" /* for virt_loc_aware_diagnostic_finalizer */
 #include "intl.h"
 #include "cppdefault.h"
 #include "incpath.h"
diff --git a/gcc/diagnostic-macro-unwinding.cc b/gcc/diagnostic-macro-unwinding.cc
new file mode 100644
index 00000000000..3056d8c8afb
--- /dev/null
+++ b/gcc/diagnostic-macro-unwinding.cc
@@ -0,0 +1,221 @@ 
+/* Code for unwinding macro expansions in diagnostics.
+   Copyright (C) 1999-2024 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "diagnostic.h"
+#include "diagnostic-macro-unwinding.h"
+#include "intl.h"
+
+/* This is a pair made of a location and the line map it originated
+   from.  It's used in the maybe_unwind_expanded_macro_loc function
+   below.  */
+struct loc_map_pair
+{
+  const line_map_macro *map;
+  location_t where;
+};
+
+
+/* Unwind the different macro expansions that lead to the token which
+   location is WHERE and emit diagnostics showing the resulting
+   unwound macro expansion trace.  Let's look at an example to see how
+   the trace looks like.  Suppose we have this piece of code,
+   artificially annotated with the line numbers to increase
+   legibility:
+
+    $ cat -n test.c
+      1    #define OPERATE(OPRD1, OPRT, OPRD2) \
+      2      OPRD1 OPRT OPRD2;
+      3
+      4    #define SHIFTL(A,B) \
+      5      OPERATE (A,<<,B)
+      6
+      7    #define MULT(A) \
+      8      SHIFTL (A,1)
+      9
+     10    void
+     11    g ()
+     12    {
+     13      MULT (1.0);// 1.0 << 1; <-- so this is an error.
+     14    }
+
+   Here is the diagnostic that we want the compiler to generate:
+
+    test.c: In function ‘g’:
+    test.c:5:14: error: invalid operands to binary << (have ‘double’ and ‘int’)
+    test.c:2:9: note: in definition of macro 'OPERATE'
+    test.c:8:3: note: in expansion of macro 'SHIFTL'
+    test.c:13:3: note: in expansion of macro 'MULT'
+
+   The part that goes from the third to the fifth line of this
+   diagnostic (the lines containing the 'note:' string) is called the
+   unwound macro expansion trace.  That's the part generated by this
+   function.  */
+
+void
+maybe_unwind_expanded_macro_loc (diagnostic_context *context,
+                                 location_t where)
+{
+  const struct line_map *map;
+  auto_vec<loc_map_pair> loc_vec;
+  unsigned ix;
+  loc_map_pair loc, *iter;
+
+  const location_t original_loc = where;
+
+  map = linemap_lookup (line_table, where);
+  if (!linemap_macro_expansion_map_p (map))
+    return;
+
+  /* Let's unwind the macros that got expanded and led to the token
+     which location is WHERE.  We are going to store these macros into
+     LOC_VEC, so that we can later walk it at our convenience to
+     display a somewhat meaningful trace of the macro expansion
+     history to the user.  Note that the first macro of the trace
+     (which is OPERATE in the example above) is going to be stored at
+     the beginning of LOC_VEC.  */
+
+  do
+    {
+      loc.where = where;
+      loc.map = linemap_check_macro (map);
+
+      loc_vec.safe_push (loc);
+
+      /* WHERE is the location of a token inside the expansion of a
+         macro.  MAP is the map holding the locations of that macro
+         expansion.  Let's get the location of the token inside the
+         context that triggered the expansion of this macro.
+         This is basically how we go "down" in the trace of macro
+         expansions that led to WHERE.  */
+      where = linemap_unwind_toward_expansion (line_table, where, &map);
+    } while (linemap_macro_expansion_map_p (map));
+
+  /* Now map is set to the map of the location in the source that
+     first triggered the macro expansion.  This must be an ordinary map.  */
+  const line_map_ordinary *ord_map = linemap_check_ordinary (map);
+
+  /* Walk LOC_VEC and print the macro expansion trace, unless the
+     first macro which expansion triggered this trace was expanded
+     inside a system header.  */
+  int saved_location_line =
+    expand_location_to_spelling_point (original_loc).line;
+
+  if (!LINEMAP_SYSP (ord_map))
+    FOR_EACH_VEC_ELT (loc_vec, ix, iter)
+      {
+	/* Sometimes, in the unwound macro expansion trace, we want to
+	   print a part of the context that shows where, in the
+	   definition of the relevant macro, is the token (we are
+	   looking at) used.  That is the case in the introductory
+	   comment of this function, where we print:
+
+	       test.c:2:9: note: in definition of macro 'OPERATE'.
+
+	   We print that "macro definition context" because the
+	   diagnostic line (emitted by the call to
+	   pp_ouput_formatted_text in diagnostic_report_diagnostic):
+
+	       test.c:5:14: error: invalid operands to binary << (have ‘double’ and ‘int’)
+
+	   does not point into the definition of the macro where the
+	   token '<<' (that is an argument to the function-like macro
+	   OPERATE) is used.  So we must "display" the line of that
+	   macro definition context to the user somehow.
+
+	   A contrario, when the first interesting diagnostic line
+	   points into the definition of the macro, we don't need to
+	   display any line for that macro definition in the trace
+	   anymore, otherwise it'd be redundant.  */
+
+        /* Okay, now here is what we want.  For each token resulting
+           from macro expansion we want to show: 1/ where in the
+           definition of the macro the token comes from; 2/ where the
+           macro got expanded.  */
+
+        /* Resolve the location iter->where into the locus 1/ of the
+           comment above.  */
+        location_t resolved_def_loc =
+          linemap_resolve_location (line_table, iter->where,
+                                    LRK_MACRO_DEFINITION_LOCATION, NULL);
+
+	/* Don't print trace for locations that are reserved or from
+	   within a system header.  */
+        const line_map_ordinary *m = NULL;
+        location_t l = 
+          linemap_resolve_location (line_table, resolved_def_loc,
+                                    LRK_SPELLING_LOCATION,  &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.  */
+	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, 
+                                    "in definition of macro %qs",
+                                    linemap_map_get_macro_name (iter->map));
+            /* At this step, as we've printed the context of the macro
+               definition, we don't want to print the context of its
+               expansion, otherwise, it'd be redundant.  */
+            continue;
+          }
+
+        /* Resolve the location of the expansion point of the macro
+           which expansion gave the token represented by def_loc.
+           This is the locus 2/ of the earlier comment.  */
+        location_t resolved_exp_loc =
+          linemap_resolve_location (line_table,
+                                    iter->map->get_expansion_point_location (),
+                                    LRK_MACRO_DEFINITION_LOCATION, NULL);
+
+        diagnostic_append_note (context, resolved_exp_loc, 
+                                "in expansion of macro %qs",
+                                linemap_map_get_macro_name (iter->map));
+      }
+}
+
+/*  This is a diagnostic finalizer implementation that is aware of
+    virtual locations produced by libcpp.
+
+    It has to be called by the diagnostic finalizer of front ends that
+    uses libcpp and wish to get diagnostics involving tokens resulting
+    from macro expansion.
+
+    For a given location, if said location belongs to a token
+    resulting from a macro expansion, this starter prints the context
+    of the token.  E.g, for multiply nested macro expansion, it
+    unwinds the nested macro expansions and prints them in a manner
+    that is similar to what is done for function call stacks, or
+    template instantiation contexts.  */
+void
+virt_loc_aware_diagnostic_finalizer (diagnostic_context *context,
+				     const diagnostic_info *diagnostic)
+{
+  maybe_unwind_expanded_macro_loc (context, diagnostic_location (diagnostic));
+}
diff --git a/gcc/diagnostic-macro-unwinding.h b/gcc/diagnostic-macro-unwinding.h
new file mode 100644
index 00000000000..74083cd56de
--- /dev/null
+++ b/gcc/diagnostic-macro-unwinding.h
@@ -0,0 +1,29 @@ 
+/* Code for unwinding macro expansions in diagnostics.
+   Copyright (C) 2000-2024 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_DIAGNOSTIC_MACRO_UNWINDING_H
+#define GCC_DIAGNOSTIC_MACRO_UNWINDING_H
+
+void virt_loc_aware_diagnostic_finalizer (diagnostic_context *,
+					  const diagnostic_info *);
+
+extern void maybe_unwind_expanded_macro_loc (diagnostic_context *context,
+					     location_t where);
+
+#endif /* ! GCC_DIAGNOSTIC_MACRO_UNWINDING_H */
diff --git a/gcc/tree-diagnostic-path.cc b/gcc/tree-diagnostic-path.cc
index 40b197d971c..adaaf30b84f 100644
--- a/gcc/tree-diagnostic-path.cc
+++ b/gcc/tree-diagnostic-path.cc
@@ -27,7 +27,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "coretypes.h"
 #include "tree.h"
 #include "diagnostic.h"
-#include "tree-diagnostic.h"
+#include "diagnostic-macro-unwinding.h"
 #include "intl.h"
 #include "diagnostic-path.h"
 #include "gcc-rich-location.h"
diff --git a/gcc/tree-diagnostic.cc b/gcc/tree-diagnostic.cc
index f6e2a73497a..f236f3db0b2 100644
--- a/gcc/tree-diagnostic.cc
+++ b/gcc/tree-diagnostic.cc
@@ -51,201 +51,6 @@  default_tree_diagnostic_starter (diagnostic_context *context,
 							    diagnostic));
 }
 
-/* This is a pair made of a location and the line map it originated
-   from.  It's used in the maybe_unwind_expanded_macro_loc function
-   below.  */
-struct loc_map_pair
-{
-  const line_map_macro *map;
-  location_t where;
-};
-
-
-/* Unwind the different macro expansions that lead to the token which
-   location is WHERE and emit diagnostics showing the resulting
-   unwound macro expansion trace.  Let's look at an example to see how
-   the trace looks like.  Suppose we have this piece of code,
-   artificially annotated with the line numbers to increase
-   legibility:
-
-    $ cat -n test.c
-      1    #define OPERATE(OPRD1, OPRT, OPRD2) \
-      2      OPRD1 OPRT OPRD2;
-      3
-      4    #define SHIFTL(A,B) \
-      5      OPERATE (A,<<,B)
-      6
-      7    #define MULT(A) \
-      8      SHIFTL (A,1)
-      9
-     10    void
-     11    g ()
-     12    {
-     13      MULT (1.0);// 1.0 << 1; <-- so this is an error.
-     14    }
-
-   Here is the diagnostic that we want the compiler to generate:
-
-    test.c: In function ‘g’:
-    test.c:5:14: error: invalid operands to binary << (have ‘double’ and ‘int’)
-    test.c:2:9: note: in definition of macro 'OPERATE'
-    test.c:8:3: note: in expansion of macro 'SHIFTL'
-    test.c:13:3: note: in expansion of macro 'MULT'
-
-   The part that goes from the third to the fifth line of this
-   diagnostic (the lines containing the 'note:' string) is called the
-   unwound macro expansion trace.  That's the part generated by this
-   function.  */
-
-void
-maybe_unwind_expanded_macro_loc (diagnostic_context *context,
-                                 location_t where)
-{
-  const struct line_map *map;
-  auto_vec<loc_map_pair> loc_vec;
-  unsigned ix;
-  loc_map_pair loc, *iter;
-
-  const location_t original_loc = where;
-
-  map = linemap_lookup (line_table, where);
-  if (!linemap_macro_expansion_map_p (map))
-    return;
-
-  /* Let's unwind the macros that got expanded and led to the token
-     which location is WHERE.  We are going to store these macros into
-     LOC_VEC, so that we can later walk it at our convenience to
-     display a somewhat meaningful trace of the macro expansion
-     history to the user.  Note that the first macro of the trace
-     (which is OPERATE in the example above) is going to be stored at
-     the beginning of LOC_VEC.  */
-
-  do
-    {
-      loc.where = where;
-      loc.map = linemap_check_macro (map);
-
-      loc_vec.safe_push (loc);
-
-      /* WHERE is the location of a token inside the expansion of a
-         macro.  MAP is the map holding the locations of that macro
-         expansion.  Let's get the location of the token inside the
-         context that triggered the expansion of this macro.
-         This is basically how we go "down" in the trace of macro
-         expansions that led to WHERE.  */
-      where = linemap_unwind_toward_expansion (line_table, where, &map);
-    } while (linemap_macro_expansion_map_p (map));
-
-  /* Now map is set to the map of the location in the source that
-     first triggered the macro expansion.  This must be an ordinary map.  */
-  const line_map_ordinary *ord_map = linemap_check_ordinary (map);
-
-  /* Walk LOC_VEC and print the macro expansion trace, unless the
-     first macro which expansion triggered this trace was expanded
-     inside a system header.  */
-  int saved_location_line =
-    expand_location_to_spelling_point (original_loc).line;
-
-  if (!LINEMAP_SYSP (ord_map))
-    FOR_EACH_VEC_ELT (loc_vec, ix, iter)
-      {
-	/* Sometimes, in the unwound macro expansion trace, we want to
-	   print a part of the context that shows where, in the
-	   definition of the relevant macro, is the token (we are
-	   looking at) used.  That is the case in the introductory
-	   comment of this function, where we print:
-
-	       test.c:2:9: note: in definition of macro 'OPERATE'.
-
-	   We print that "macro definition context" because the
-	   diagnostic line (emitted by the call to
-	   pp_ouput_formatted_text in diagnostic_report_diagnostic):
-
-	       test.c:5:14: error: invalid operands to binary << (have ‘double’ and ‘int’)
-
-	   does not point into the definition of the macro where the
-	   token '<<' (that is an argument to the function-like macro
-	   OPERATE) is used.  So we must "display" the line of that
-	   macro definition context to the user somehow.
-
-	   A contrario, when the first interesting diagnostic line
-	   points into the definition of the macro, we don't need to
-	   display any line for that macro definition in the trace
-	   anymore, otherwise it'd be redundant.  */
-
-        /* Okay, now here is what we want.  For each token resulting
-           from macro expansion we want to show: 1/ where in the
-           definition of the macro the token comes from; 2/ where the
-           macro got expanded.  */
-
-        /* Resolve the location iter->where into the locus 1/ of the
-           comment above.  */
-        location_t resolved_def_loc =
-          linemap_resolve_location (line_table, iter->where,
-                                    LRK_MACRO_DEFINITION_LOCATION, NULL);
-
-	/* Don't print trace for locations that are reserved or from
-	   within a system header.  */
-        const line_map_ordinary *m = NULL;
-        location_t l = 
-          linemap_resolve_location (line_table, resolved_def_loc,
-                                    LRK_SPELLING_LOCATION,  &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.  */
-	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, 
-                                    "in definition of macro %qs",
-                                    linemap_map_get_macro_name (iter->map));
-            /* At this step, as we've printed the context of the macro
-               definition, we don't want to print the context of its
-               expansion, otherwise, it'd be redundant.  */
-            continue;
-          }
-
-        /* Resolve the location of the expansion point of the macro
-           which expansion gave the token represented by def_loc.
-           This is the locus 2/ of the earlier comment.  */
-        location_t resolved_exp_loc =
-          linemap_resolve_location (line_table,
-                                    iter->map->get_expansion_point_location (),
-                                    LRK_MACRO_DEFINITION_LOCATION, NULL);
-
-        diagnostic_append_note (context, resolved_exp_loc, 
-                                "in expansion of macro %qs",
-                                linemap_map_get_macro_name (iter->map));
-      }
-}
-
-/*  This is a diagnostic finalizer implementation that is aware of
-    virtual locations produced by libcpp.
-
-    It has to be called by the diagnostic finalizer of front ends that
-    uses libcpp and wish to get diagnostics involving tokens resulting
-    from macro expansion.
-
-    For a given location, if said location belongs to a token
-    resulting from a macro expansion, this starter prints the context
-    of the token.  E.g, for multiply nested macro expansion, it
-    unwinds the nested macro expansions and prints them in a manner
-    that is similar to what is done for function call stacks, or
-    template instantiation contexts.  */
-void
-virt_loc_aware_diagnostic_finalizer (diagnostic_context *context,
-				     const diagnostic_info *diagnostic)
-{
-  maybe_unwind_expanded_macro_loc (context, diagnostic_location (diagnostic));
-}
-
 /* Default tree printer.   Handles declarations only.  */
 bool
 default_tree_printer (pretty_printer *pp, text_info *text, const char *spec,
diff --git a/gcc/tree-diagnostic.h b/gcc/tree-diagnostic.h
index 7959294f489..648d6e6ab91 100644
--- a/gcc/tree-diagnostic.h
+++ b/gcc/tree-diagnostic.h
@@ -50,8 +50,6 @@  along with GCC; see the file COPYING3.  If not see
 
 void diagnostic_report_current_function (diagnostic_context *,
 					 const diagnostic_info *);
-void virt_loc_aware_diagnostic_finalizer (diagnostic_context *,
-					  const diagnostic_info *);
 
 void tree_diagnostics_defaults (diagnostic_context *context);
 bool default_tree_printer (pretty_printer *, text_info *, const char *,
@@ -60,7 +58,4 @@  bool default_tree_printer (pretty_printer *, text_info *, const char *,
 extern void default_tree_diagnostic_path_printer (diagnostic_context *,
 						  const diagnostic_path *);
 
-extern void maybe_unwind_expanded_macro_loc (diagnostic_context *context,
-					     location_t where);
-
 #endif /* ! GCC_TREE_DIAGNOSTIC_H */