diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc
index d7faff10d66..b68ea5e7006 100644
--- a/gcc/c-family/c-opts.cc
+++ b/gcc/c-family/c-opts.cc
@@ -168,7 +168,7 @@ c_common_option_lang_mask (void)
 /* Diagnostic finalizer for C/C++/Objective-C/Objective-C++.  */
 static void
 c_diagnostic_finalizer (diagnostic_context *context,
-			diagnostic_info *diagnostic,
+			const diagnostic_info *diagnostic,
 			diagnostic_t)
 {
   char *saved_prefix = pp_take_prefix (context->printer);
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 6b3ce9d87da..3aa235262b6 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -8071,7 +8071,7 @@ extern void cxx_print_type			(FILE *, tree, int);
 extern void cxx_print_identifier		(FILE *, tree, int);
 extern void cxx_print_error_function		(diagnostic_context *,
 						 const char *,
-						 struct diagnostic_info *);
+						 const diagnostic_info *);
 
 /* in typeck.cc */
 /* Says how we should behave when comparing two arrays one of which
diff --git a/gcc/cp/error.cc b/gcc/cp/error.cc
index 785909c362a..8e9dda33afd 100644
--- a/gcc/cp/error.cc
+++ b/gcc/cp/error.cc
@@ -101,8 +101,10 @@ static void print_instantiation_partial_context (diagnostic_context *,
 						 struct tinst_level *,
 						 location_t);
 static void maybe_print_constraint_context (diagnostic_context *);
-static void cp_diagnostic_starter (diagnostic_context *, diagnostic_info *);
-static void cp_print_error_function (diagnostic_context *, diagnostic_info *);
+static void cp_diagnostic_starter (diagnostic_context *,
+				   const diagnostic_info *);
+static void cp_print_error_function (diagnostic_context *,
+				     const diagnostic_info *);
 
 static bool cp_printer (pretty_printer *, text_info *, const char *,
 			int, bool, bool, bool, bool *, const char **);
@@ -3530,7 +3532,7 @@ eh_spec_to_string (tree p, int /*v*/)
 /* Langhook for print_error_function.  */
 void
 cxx_print_error_function (diagnostic_context *context, const char *file,
-			  diagnostic_info *diagnostic)
+			  const diagnostic_info *diagnostic)
 {
   char *prefix;
   if (file)
@@ -3544,7 +3546,7 @@ cxx_print_error_function (diagnostic_context *context, const char *file,
 
 static void
 cp_diagnostic_starter (diagnostic_context *context,
-		       diagnostic_info *diagnostic)
+		       const diagnostic_info *diagnostic)
 {
   diagnostic_report_current_module (context, diagnostic_location (diagnostic));
   cp_print_error_function (context, diagnostic);
@@ -3559,7 +3561,7 @@ cp_diagnostic_starter (diagnostic_context *context,
    a diagnostic message.  Called from cp_diagnostic_starter.  */
 static void
 cp_print_error_function (diagnostic_context *context,
-			 diagnostic_info *diagnostic)
+			 const diagnostic_info *diagnostic)
 {
   /* If we are in an instantiation context, current_function_decl is likely
      to be wrong, so just rely on print_instantiation_full_context.  */
diff --git a/gcc/diagnostic-format-json.cc b/gcc/diagnostic-format-json.cc
index 141075b7dee..418db74522d 100644
--- a/gcc/diagnostic-format-json.cc
+++ b/gcc/diagnostic-format-json.cc
@@ -43,12 +43,12 @@ public:
     m_cur_children_array = nullptr;
   }
   void
-  on_begin_diagnostic (diagnostic_info *) final override
+  on_begin_diagnostic (const diagnostic_info &) final override
   {
     /* No-op.  */
   }
   void
-  on_end_diagnostic (diagnostic_info *diagnostic,
+  on_end_diagnostic (const diagnostic_info &diagnostic,
 		     diagnostic_t orig_diag_kind) final override;
   void on_diagram (const diagnostic_diagram &) final override
   {
@@ -188,7 +188,7 @@ json_from_metadata (const diagnostic_metadata *metadata)
    within current diagnostic group.  */
 
 void
-json_output_format::on_end_diagnostic (diagnostic_info *diagnostic,
+json_output_format::on_end_diagnostic (const diagnostic_info &diagnostic,
 				       diagnostic_t orig_diag_kind)
 {
   json::object *diag_obj = new json::object ();
@@ -202,7 +202,7 @@ json_output_format::on_end_diagnostic (diagnostic_info *diagnostic,
       "must-not-happen"
     };
     /* Lose the trailing ": ".  */
-    const char *kind_text = diagnostic_kind_text[diagnostic->kind];
+    const char *kind_text = diagnostic_kind_text[diagnostic.kind];
     size_t len = strlen (kind_text);
     gcc_assert (len > 2);
     gcc_assert (kind_text[len - 2] == ':');
@@ -217,15 +217,15 @@ json_output_format::on_end_diagnostic (diagnostic_info *diagnostic,
   diag_obj->set_string ("message", pp_formatted_text (m_context.printer));
   pp_clear_output_area (m_context.printer);
 
-  if (char *option_text = m_context.make_option_name (diagnostic->option_index,
+  if (char *option_text = m_context.make_option_name (diagnostic.option_index,
 						      orig_diag_kind,
-						      diagnostic->kind))
+						      diagnostic.kind))
     {
       diag_obj->set_string ("option", option_text);
       free (option_text);
     }
 
-  if (char *option_url = m_context.make_option_url (diagnostic->option_index))
+  if (char *option_url = m_context.make_option_url (diagnostic.option_index))
     {
       diag_obj->set_string ("option_url", option_url);
       free (option_url);
@@ -249,7 +249,7 @@ json_output_format::on_end_diagnostic (diagnostic_info *diagnostic,
       diag_obj->set_integer ("column-origin", m_context.m_column_origin);
     }
 
-  const rich_location *richloc = diagnostic->richloc;
+  const rich_location *richloc = diagnostic.richloc;
 
   json::array *loc_array = new json::array ();
   diag_obj->set ("locations", loc_array);
@@ -280,9 +280,9 @@ json_output_format::on_end_diagnostic (diagnostic_info *diagnostic,
      TODO: inlining information
      TODO: macro expansion information.  */
 
-  if (diagnostic->metadata)
+  if (diagnostic.metadata)
     {
-      json::object *metadata_obj = json_from_metadata (diagnostic->metadata);
+      json::object *metadata_obj = json_from_metadata (diagnostic.metadata);
       diag_obj->set ("metadata", metadata_obj);
     }
 
diff --git a/gcc/diagnostic-format-sarif.cc b/gcc/diagnostic-format-sarif.cc
index 67775929f85..941fd0f5f74 100644
--- a/gcc/diagnostic-format-sarif.cc
+++ b/gcc/diagnostic-format-sarif.cc
@@ -48,7 +48,7 @@ public:
   {}
 
   void add_notification_for_ice (diagnostic_context *context,
-				 diagnostic_info *diagnostic,
+				 const diagnostic_info &diagnostic,
 				 sarif_builder *builder);
   void prepare_to_flush (diagnostic_context *context);
 
@@ -67,7 +67,7 @@ public:
 
   void
   on_nested_diagnostic (diagnostic_context *context,
-			diagnostic_info *diagnostic,
+			const diagnostic_info &diagnostic,
 			diagnostic_t orig_diag_kind,
 			sarif_builder *builder);
   void on_diagram (diagnostic_context *context,
@@ -90,7 +90,7 @@ class sarif_ice_notification : public sarif_object
 {
 public:
   sarif_ice_notification (diagnostic_context *context,
-			  diagnostic_info *diagnostic,
+			  const diagnostic_info &diagnostic,
 			  sarif_builder *builder);
 };
 
@@ -159,7 +159,8 @@ class sarif_builder
 public:
   sarif_builder (diagnostic_context *context);
 
-  void end_diagnostic (diagnostic_context *context, diagnostic_info *diagnostic,
+  void end_diagnostic (diagnostic_context *context,
+		       const diagnostic_info &diagnostic,
 		       diagnostic_t orig_diag_kind);
   void emit_diagram (diagnostic_context *context,
 		     const diagnostic_diagram &diagram);
@@ -167,7 +168,7 @@ public:
 
   void flush_to_file (FILE *outf);
 
-  json::array *make_locations_arr (diagnostic_info *diagnostic);
+  json::array *make_locations_arr (const diagnostic_info &diagnostic);
   json::object *make_location_object (const rich_location &rich_loc,
 				      const logical_location *logical_loc);
   json::object *make_message_object (const char *msg) const;
@@ -177,7 +178,7 @@ public:
 
 private:
   sarif_result *make_result_object (diagnostic_context *context,
-				    diagnostic_info *diagnostic,
+				    const diagnostic_info &diagnostic,
 				    diagnostic_t orig_diag_kind);
   void set_any_logical_locs_arr (json::object *location_obj,
 				 const logical_location *logical_loc);
@@ -208,7 +209,7 @@ private:
   json::object *make_tool_component_reference_object_for_cwe () const;
   json::object *
   make_reporting_descriptor_object_for_warning (diagnostic_context *context,
-						diagnostic_info *diagnostic,
+						const diagnostic_info &diagnostic,
 						diagnostic_t orig_diag_kind,
 						const char *option_text);
   json::object *make_reporting_descriptor_object_for_cwe_id (int cwe_id) const;
@@ -275,7 +276,7 @@ sarif_object::get_or_create_properties ()
 
 void
 sarif_invocation::add_notification_for_ice (diagnostic_context *context,
-					    diagnostic_info *diagnostic,
+					    const diagnostic_info &diagnostic,
 					    sarif_builder *builder)
 {
   m_success = false;
@@ -310,7 +311,7 @@ sarif_invocation::prepare_to_flush (diagnostic_context *context)
 
 void
 sarif_result::on_nested_diagnostic (diagnostic_context *context,
-				    diagnostic_info *diagnostic,
+				    const diagnostic_info &diagnostic,
 				    diagnostic_t /*orig_diag_kind*/,
 				    sarif_builder *builder)
 {
@@ -318,7 +319,7 @@ sarif_result::on_nested_diagnostic (diagnostic_context *context,
      sometimes these will related to current_function_decl, but
      often they won't.  */
   json::object *location_obj
-    = builder->make_location_object (*diagnostic->richloc, NULL);
+    = builder->make_location_object (*diagnostic.richloc, NULL);
   json::object *message_obj
     = builder->make_message_object (pp_formatted_text (context->printer));
   pp_clear_output_area (context->printer);
@@ -366,7 +367,7 @@ sarif_result::add_related_location (json::object *location_obj)
    DIAGNOSTIC is an internal compiler error.  */
 
 sarif_ice_notification::sarif_ice_notification (diagnostic_context *context,
-						diagnostic_info *diagnostic,
+						const diagnostic_info &diagnostic,
 						sarif_builder *builder)
 {
   /* "locations" property (SARIF v2.1.0 section 3.58.4).  */
@@ -416,10 +417,10 @@ sarif_builder::sarif_builder (diagnostic_context *context)
 
 void
 sarif_builder::end_diagnostic (diagnostic_context *context,
-			       diagnostic_info *diagnostic,
+			       const diagnostic_info &diagnostic,
 			       diagnostic_t orig_diag_kind)
 {
-  if (diagnostic->kind == DK_ICE || diagnostic->kind == DK_ICE_NOBT)
+  if (diagnostic.kind == DK_ICE || diagnostic.kind == DK_ICE_NOBT)
     {
       m_invocation_obj->add_notification_for_ice (context, diagnostic, this);
       return;
@@ -528,7 +529,7 @@ make_rule_id_for_diagnostic_kind (diagnostic_t diag_kind)
 
 sarif_result *
 sarif_builder::make_result_object (diagnostic_context *context,
-				   diagnostic_info *diagnostic,
+				   const diagnostic_info &diagnostic,
 				   diagnostic_t orig_diag_kind)
 {
   sarif_result *result_obj = new sarif_result ();
@@ -536,8 +537,8 @@ sarif_builder::make_result_object (diagnostic_context *context,
   /* "ruleId" property (SARIF v2.1.0 section 3.27.5).  */
   /* Ideally we'd have an option_name for these.  */
   if (char *option_text
-	= context->make_option_name (diagnostic->option_index,
-				     orig_diag_kind, diagnostic->kind))
+	= context->make_option_name (diagnostic.option_index,
+				     orig_diag_kind, diagnostic.kind))
     {
       /* Lazily create reportingDescriptor objects for and add to m_rules_arr.
 	 Set ruleId referencing them.  */
@@ -569,10 +570,10 @@ sarif_builder::make_result_object (diagnostic_context *context,
       free (rule_id);
     }
 
-  if (diagnostic->metadata)
+  if (diagnostic.metadata)
     {
       /* "taxa" property (SARIF v2.1.0 section 3.27.8).  */
-      if (int cwe_id = diagnostic->metadata->get_cwe ())
+      if (int cwe_id = diagnostic.metadata->get_cwe ())
 	{
 	  json::array *taxa_arr = new json::array ();
 	  json::object *cwe_id_obj
@@ -581,11 +582,11 @@ sarif_builder::make_result_object (diagnostic_context *context,
 	  result_obj->set ("taxa", taxa_arr);
 	}
 
-      diagnostic->metadata->maybe_add_sarif_properties (*result_obj);
+      diagnostic.metadata->maybe_add_sarif_properties (*result_obj);
     }
 
   /* "level" property (SARIF v2.1.0 section 3.27.10).  */
-  if (const char *sarif_level = maybe_get_sarif_level (diagnostic->kind))
+  if (const char *sarif_level = maybe_get_sarif_level (diagnostic.kind))
     result_obj->set_string ("level", sarif_level);
 
   /* "message" property (SARIF v2.1.0 section 3.27.11).  */
@@ -599,7 +600,7 @@ sarif_builder::make_result_object (diagnostic_context *context,
   result_obj->set ("locations", locations_arr);
 
   /* "codeFlows" property (SARIF v2.1.0 section 3.27.18).  */
-  if (const diagnostic_path *path = diagnostic->richloc->get_path ())
+  if (const diagnostic_path *path = diagnostic.richloc->get_path ())
     {
       json::array *code_flows_arr = new json::array ();
       json::object *code_flow_obj = make_code_flow_object (*path);
@@ -612,7 +613,7 @@ sarif_builder::make_result_object (diagnostic_context *context,
      group.  */
 
   /* "fixes" property (SARIF v2.1.0 section 3.27.30).  */
-  const rich_location *richloc = diagnostic->richloc;
+  const rich_location *richloc = diagnostic.richloc;
   if (richloc->get_num_fixit_hints ())
     {
       json::array *fix_arr = new json::array ();
@@ -630,7 +631,7 @@ sarif_builder::make_result_object (diagnostic_context *context,
 json::object *
 sarif_builder::
 make_reporting_descriptor_object_for_warning (diagnostic_context *context,
-					      diagnostic_info *diagnostic,
+					      const diagnostic_info &diagnostic,
 					      diagnostic_t /*orig_diag_kind*/,
 					      const char *option_text)
 {
@@ -643,7 +644,7 @@ make_reporting_descriptor_object_for_warning (diagnostic_context *context,
      it seems redundant compared to "id".  */
 
   /* "helpUri" property (SARIF v2.1.0 section 3.49.12).  */
-  if (char *option_url = context->make_option_url (diagnostic->option_index))
+  if (char *option_url = context->make_option_url (diagnostic.option_index))
     {
       reporting_desc->set_string ("helpUri", option_url);
       free (option_url);
@@ -725,7 +726,7 @@ make_tool_component_reference_object_for_cwe () const
    - a "notification" object (SARIF v2.1.0 section 3.58.4).  */
 
 json::array *
-sarif_builder::make_locations_arr (diagnostic_info *diagnostic)
+sarif_builder::make_locations_arr (const diagnostic_info &diagnostic)
 {
   json::array *locations_arr = new json::array ();
   const logical_location *logical_loc = NULL;
@@ -733,7 +734,7 @@ sarif_builder::make_locations_arr (diagnostic_info *diagnostic)
     logical_loc = client_data_hooks->get_current_logical_location ();
 
   json::object *location_obj
-    = make_location_object (*diagnostic->richloc, logical_loc);
+    = make_location_object (*diagnostic.richloc, logical_loc);
   locations_arr->append (location_obj);
   return locations_arr;
 }
@@ -1704,12 +1705,12 @@ public:
     m_builder.end_group ();
   }
   void
-  on_begin_diagnostic (diagnostic_info *) final override
+  on_begin_diagnostic (const diagnostic_info &) final override
   {
     /* No-op,  */
   }
   void
-  on_end_diagnostic (diagnostic_info *diagnostic,
+  on_end_diagnostic (const diagnostic_info &diagnostic,
 		     diagnostic_t orig_diag_kind) final override
   {
     m_builder.end_diagnostic (&m_context, diagnostic, orig_diag_kind);
diff --git a/gcc/diagnostic.cc b/gcc/diagnostic.cc
index 2e3d37b04cc..5854c89a387 100644
--- a/gcc/diagnostic.cc
+++ b/gcc/diagnostic.cc
@@ -1077,7 +1077,7 @@ diagnostic_path::interprocedural_p () const
 
 void
 default_diagnostic_starter (diagnostic_context *context,
-			    diagnostic_info *diagnostic)
+			    const diagnostic_info *diagnostic)
 {
   diagnostic_report_current_module (context, diagnostic_location (diagnostic));
   pp_set_prefix (context->printer, diagnostic_build_prefix (context,
@@ -1095,7 +1095,7 @@ default_diagnostic_start_span_fn (diagnostic_context *context,
 
 void
 default_diagnostic_finalizer (diagnostic_context *context,
-			      diagnostic_info *diagnostic,
+			      const diagnostic_info *diagnostic,
 			      diagnostic_t)
 {
   char *saved_prefix = pp_take_prefix (context->printer);
@@ -1602,7 +1602,7 @@ diagnostic_context::report_diagnostic (diagnostic_info *diagnostic)
   m_diagnostic_groups.m_emission_count++;
 
   pp_format (this->printer, &diagnostic->message, m_urlifier);
-  m_output_format->on_begin_diagnostic (diagnostic);
+  m_output_format->on_begin_diagnostic (*diagnostic);
   pp_output_formatted_text (this->printer);
   if (m_show_cwe)
     print_any_cwe (*diagnostic);
@@ -1610,7 +1610,7 @@ diagnostic_context::report_diagnostic (diagnostic_info *diagnostic)
     print_any_rules (*diagnostic);
   if (m_show_option_requested)
     print_option_information (*diagnostic, orig_diag_kind);
-  m_output_format->on_end_diagnostic (diagnostic, orig_diag_kind);
+  m_output_format->on_end_diagnostic (*diagnostic, orig_diag_kind);
   switch (m_extra_output_kind)
     {
     default:
@@ -2396,16 +2396,17 @@ diagnostic_text_output_format::~diagnostic_text_output_format ()
 }
 
 void
-diagnostic_text_output_format::on_begin_diagnostic (diagnostic_info *diagnostic)
+diagnostic_text_output_format::on_begin_diagnostic (const diagnostic_info &diagnostic)
 {
-  (*diagnostic_starter (&m_context)) (&m_context, diagnostic);
+  (*diagnostic_starter (&m_context)) (&m_context, &diagnostic);
 }
 
 void
-diagnostic_text_output_format::on_end_diagnostic (diagnostic_info *diagnostic,
+diagnostic_text_output_format::on_end_diagnostic (const diagnostic_info &diagnostic,
 						  diagnostic_t orig_diag_kind)
 {
-  (*diagnostic_finalizer (&m_context)) (&m_context, diagnostic, orig_diag_kind);
+  (*diagnostic_finalizer (&m_context)) (&m_context, &diagnostic,
+					orig_diag_kind);
 }
 
 void
diff --git a/gcc/diagnostic.h b/gcc/diagnostic.h
index b57556f9759..4fc31438b16 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -171,13 +171,13 @@ struct diagnostic_info
 
 /*  Forward declarations.  */
 typedef void (*diagnostic_starter_fn) (diagnostic_context *,
-				       diagnostic_info *);
+				       const diagnostic_info *);
 
 typedef void (*diagnostic_start_span_fn) (diagnostic_context *,
 					  expanded_location);
 
 typedef void (*diagnostic_finalizer_fn) (diagnostic_context *,
-					 diagnostic_info *,
+					 const diagnostic_info *,
 					 diagnostic_t);
 
 typedef int (*diagnostic_option_enabled_cb) (int, unsigned, void *);
@@ -205,8 +205,8 @@ public:
 
   virtual void on_begin_group () = 0;
   virtual void on_end_group () = 0;
-  virtual void on_begin_diagnostic (diagnostic_info *) = 0;
-  virtual void on_end_diagnostic (diagnostic_info *,
+  virtual void on_begin_diagnostic (const diagnostic_info &) = 0;
+  virtual void on_end_diagnostic (const diagnostic_info &,
 				  diagnostic_t orig_diag_kind) = 0;
   virtual void on_diagram (const diagnostic_diagram &diagram) = 0;
 
@@ -233,8 +233,8 @@ public:
   ~diagnostic_text_output_format ();
   void on_begin_group () override {}
   void on_end_group () override {}
-  void on_begin_diagnostic (diagnostic_info *) override;
-  void on_end_diagnostic (diagnostic_info *,
+  void on_begin_diagnostic (const diagnostic_info &) override;
+  void on_end_diagnostic (const diagnostic_info &,
 			  diagnostic_t orig_diag_kind) override;
   void on_diagram (const diagnostic_diagram &diagram) override;
 };
@@ -985,10 +985,11 @@ extern void diagnostic_append_note (diagnostic_context *, location_t,
                                     const char *, ...) ATTRIBUTE_GCC_DIAG(3,4);
 #endif
 extern char *diagnostic_build_prefix (diagnostic_context *, const diagnostic_info *);
-void default_diagnostic_starter (diagnostic_context *, diagnostic_info *);
+void default_diagnostic_starter (diagnostic_context *, const diagnostic_info *);
 void default_diagnostic_start_span_fn (diagnostic_context *,
 				       expanded_location);
-void default_diagnostic_finalizer (diagnostic_context *, diagnostic_info *,
+void default_diagnostic_finalizer (diagnostic_context *,
+				   const diagnostic_info *,
 				   diagnostic_t);
 void diagnostic_set_caret_max_width (diagnostic_context *context, int value);
 
diff --git a/gcc/fortran/error.cc b/gcc/fortran/error.cc
index 56d2e63622d..76113def7c8 100644
--- a/gcc/fortran/error.cc
+++ b/gcc/fortran/error.cc
@@ -1207,7 +1207,7 @@ gfc_diagnostic_build_locus_prefix (diagnostic_context *context,
 */
 static void
 gfc_diagnostic_starter (diagnostic_context *context,
-			diagnostic_info *diagnostic)
+			const diagnostic_info *diagnostic)
 {
   char * kind_prefix = gfc_diagnostic_build_kind_prefix (context, diagnostic);
 
@@ -1283,7 +1283,7 @@ gfc_diagnostic_start_span (diagnostic_context *context,
 
 static void
 gfc_diagnostic_finalizer (diagnostic_context *context,
-			  diagnostic_info *diagnostic ATTRIBUTE_UNUSED,
+			  const diagnostic_info *diagnostic ATTRIBUTE_UNUSED,
 			  diagnostic_t orig_diag_kind ATTRIBUTE_UNUSED)
 {
   pp_destroy_prefix (context->printer);
diff --git a/gcc/jit/dummy-frontend.cc b/gcc/jit/dummy-frontend.cc
index 61cc0e1ae66..f5fb40178c2 100644
--- a/gcc/jit/dummy-frontend.cc
+++ b/gcc/jit/dummy-frontend.cc
@@ -563,7 +563,7 @@ struct ggc_root_tab jit_root_tab[] =
 
 static void
 jit_begin_diagnostic (diagnostic_context */*context*/,
-		      diagnostic_info */*diagnostic*/)
+		      const diagnostic_info */*diagnostic*/)
 {
   gcc_assert (gcc::jit::active_playback_ctxt);
   JIT_LOG_SCOPE (gcc::jit::active_playback_ctxt->get_logger ());
@@ -576,7 +576,7 @@ jit_begin_diagnostic (diagnostic_context */*context*/,
 
 static void
 jit_end_diagnostic (diagnostic_context *context,
-		    diagnostic_info *diagnostic,
+		    const diagnostic_info *diagnostic,
 		    diagnostic_t)
 {
   gcc_assert (gcc::jit::active_playback_ctxt);
@@ -584,7 +584,8 @@ jit_end_diagnostic (diagnostic_context *context,
 
   /* Delegate to the playback context (and thence to the
      recording context).  */
-  gcc::jit::active_playback_ctxt->add_diagnostic (context, diagnostic);
+  gcc_assert (diagnostic);
+  gcc::jit::active_playback_ctxt->add_diagnostic (context, *diagnostic);
 }
 
 /* Language hooks.  */
diff --git a/gcc/jit/jit-playback.cc b/gcc/jit/jit-playback.cc
index 18cc4da25b8..dddd537f3b1 100644
--- a/gcc/jit/jit-playback.cc
+++ b/gcc/jit/jit-playback.cc
@@ -3513,7 +3513,7 @@ add_error_va (location *loc, const char *fmt, va_list ap)
 void
 playback::context::
 add_diagnostic (diagnostic_context *diag_context,
-		struct diagnostic_info *diagnostic)
+		const diagnostic_info &diagnostic)
 {
   /* At this point the text has been formatted into the pretty-printer's
      output buffer.  */
@@ -3526,7 +3526,7 @@ add_diagnostic (diagnostic_context *diag_context,
      from the file/line/column since any playback location instances
      may have been garbage-collected away by now, so instead we create
      another recording::location directly.  */
-  location_t gcc_loc = diagnostic_location (diagnostic);
+  location_t gcc_loc = diagnostic_location (&diagnostic);
   recording::location *rec_loc = NULL;
   if (gcc_loc)
     {
diff --git a/gcc/jit/jit-playback.h b/gcc/jit/jit-playback.h
index f9e29d0baec..b0166f8f6ce 100644
--- a/gcc/jit/jit-playback.h
+++ b/gcc/jit/jit-playback.h
@@ -248,7 +248,7 @@ public:
 
   void
   add_diagnostic (diagnostic_context *context,
-		  struct diagnostic_info *diagnostic);
+		  const diagnostic_info &diagnostic);
 
   void
   set_tree_location (tree t, location *loc);
diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
index c9cb65759c2..cedc8fd85fc 100644
--- a/gcc/langhooks-def.h
+++ b/gcc/langhooks-def.h
@@ -50,7 +50,8 @@ extern const char *lhd_decl_printable_name (tree, int);
 extern const char *lhd_dwarf_name (tree, int);
 extern int lhd_types_compatible_p (tree, tree);
 extern void lhd_print_error_function (diagnostic_context *,
-				      const char *, struct diagnostic_info *);
+				      const char *,
+				      const struct diagnostic_info *);
 extern void lhd_set_decl_assembler_name (tree decl);
 extern void lhd_overwrite_decl_assembler_name (tree decl, tree name);
 extern bool lhd_warn_unused_global_decl (const_tree);
diff --git a/gcc/langhooks.cc b/gcc/langhooks.cc
index cf047d9e530..bc3fd3531b0 100644
--- a/gcc/langhooks.cc
+++ b/gcc/langhooks.cc
@@ -369,7 +369,7 @@ lhd_handle_option (size_t code ATTRIBUTE_UNUSED,
    an error.  */
 void
 lhd_print_error_function (diagnostic_context *context, const char *file,
-			  diagnostic_info *diagnostic)
+			  const diagnostic_info *diagnostic)
 {
   if (diagnostic_last_function_changed (context, diagnostic))
     {
diff --git a/gcc/langhooks.h b/gcc/langhooks.h
index 2785a0070fc..bba64d1412a 100644
--- a/gcc/langhooks.h
+++ b/gcc/langhooks.h
@@ -516,7 +516,7 @@ struct lang_hooks
 
   /* Called by report_error_function to print out function name.  */
   void (*print_error_function) (diagnostic_context *, const char *,
-				struct diagnostic_info *);
+				const struct diagnostic_info *);
 
   /* Convert a character from the host's to the target's character
      set.  The character should be in what C calls the "basic source
diff --git a/gcc/testsuite/g++.dg/plugin/show_template_tree_color_plugin.c b/gcc/testsuite/g++.dg/plugin/show_template_tree_color_plugin.c
index af568bf622a..e1af2cf25a4 100644
--- a/gcc/testsuite/g++.dg/plugin/show_template_tree_color_plugin.c
+++ b/gcc/testsuite/g++.dg/plugin/show_template_tree_color_plugin.c
@@ -21,7 +21,7 @@
 int plugin_is_GPL_compatible;
 
 void
-noop_starter_fn (diagnostic_context *, diagnostic_info *)
+noop_starter_fn (diagnostic_context *, const diagnostic_info *)
 {
 }
 
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic_group_plugin.c b/gcc/testsuite/gcc.dg/plugin/diagnostic_group_plugin.c
index ce0b3225dfc..e9d4b7276cc 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic_group_plugin.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic_group_plugin.c
@@ -165,7 +165,7 @@ pass_test_groups::execute (function *fun)
 
 void
 test_diagnostic_starter (diagnostic_context *context,
-			 diagnostic_info *diagnostic)
+			 const diagnostic_info *diagnostic)
 {
   pp_set_prefix (context->printer, xstrdup ("PREFIX: "));
 }
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c b/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
index 6cc661b026d..3bd8cab8c7f 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
@@ -129,7 +129,7 @@ static bool force_show_locus_color = false;
 
 static void
 custom_diagnostic_finalizer (diagnostic_context *context,
-			     diagnostic_info *diagnostic,
+			     const diagnostic_info *diagnostic,
 			     diagnostic_t)
 {
   bool old_show_color = pp_show_color (context->printer);
diff --git a/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c b/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c
index 09bac50d2af..d0a6b075564 100644
--- a/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c
+++ b/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c
@@ -42,7 +42,7 @@ static diagnostic_finalizer_fn original_finalizer = NULL;
 
 static void
 verify_unpacked_ranges  (diagnostic_context *context,
-			 diagnostic_info *diagnostic,
+			 const diagnostic_info *diagnostic,
 			 diagnostic_t orig_diag_kind)
 {
   /* Verify that the locations are ad-hoc, not packed. */
@@ -56,7 +56,7 @@ verify_unpacked_ranges  (diagnostic_context *context,
 
 static void
 verify_no_columns  (diagnostic_context *context,
-		    diagnostic_info *diagnostic,
+		    const diagnostic_info *diagnostic,
 		    diagnostic_t orig_diag_kind)
 {
   /* Verify that the locations have no columns. */
diff --git a/gcc/tree-diagnostic.cc b/gcc/tree-diagnostic.cc
index de853bc4fd7..dae8a42b8bc 100644
--- a/gcc/tree-diagnostic.cc
+++ b/gcc/tree-diagnostic.cc
@@ -35,7 +35,7 @@ along with GCC; see the file COPYING3.  If not see
    that caused an error.  Called from all error and warning functions.  */
 void
 diagnostic_report_current_function (diagnostic_context *context,
-				    diagnostic_info *diagnostic)
+				    const diagnostic_info *diagnostic)
 {
   location_t loc = diagnostic_location (diagnostic);
   diagnostic_report_current_module (context, loc);
@@ -44,7 +44,7 @@ diagnostic_report_current_function (diagnostic_context *context,
 
 static void
 default_tree_diagnostic_starter (diagnostic_context *context,
-				 diagnostic_info *diagnostic)
+				 const diagnostic_info *diagnostic)
 {
   diagnostic_report_current_function (context, diagnostic);
   pp_set_prefix (context->printer, diagnostic_build_prefix (context,
@@ -241,7 +241,7 @@ maybe_unwind_expanded_macro_loc (diagnostic_context *context,
     template instantiation contexts.  */
 void
 virt_loc_aware_diagnostic_finalizer (diagnostic_context *context,
-				     diagnostic_info *diagnostic)
+				     const diagnostic_info *diagnostic)
 {
   maybe_unwind_expanded_macro_loc (context, diagnostic_location (diagnostic));
 }
diff --git a/gcc/tree-diagnostic.h b/gcc/tree-diagnostic.h
index 9089f2ded1e..a3ea18ca61b 100644
--- a/gcc/tree-diagnostic.h
+++ b/gcc/tree-diagnostic.h
@@ -49,9 +49,9 @@ along with GCC; see the file COPYING3.  If not see
        : current_function_decl)
 
 void diagnostic_report_current_function (diagnostic_context *,
-					 diagnostic_info *);
+					 const diagnostic_info *);
 void virt_loc_aware_diagnostic_finalizer (diagnostic_context *,
-					  diagnostic_info *);
+					  const diagnostic_info *);
 
 void tree_diagnostics_defaults (diagnostic_context *context);
 bool default_tree_printer (pretty_printer *, text_info *, const char *,
diff --git a/libcc1/context.cc b/libcc1/context.cc
index 3263c167ff2..fbe468f0286 100644
--- a/libcc1/context.cc
+++ b/libcc1/context.cc
@@ -63,7 +63,7 @@ cc1_plugin::plugin_context *cc1_plugin::current_context;
 
 static void
 plugin_print_error_function (diagnostic_context *context, const char *file,
-			     diagnostic_info *diagnostic)
+			     const diagnostic_info *diagnostic)
 {
   if (current_function_decl != NULL_TREE
       && DECL_NAME (current_function_decl) != NULL_TREE
