libcpp: Improve encapsulation of label_text

This adjusts the API of label_text so that the data members are private
and cannot be modified by callers.  Add accessors for them instead, and
make the accessors const-correct.  Also rename moved_from () to the more
idiomatic release ().  Also remove the unused take_or_copy () member
function which has confusing ownership semantics.

gcc/analyzer/ChangeLog:

	* call-info.cc (call_info::print): Adjust to new label_text API.
	* checker-path.cc (checker_event::dump): Likewise.
	(region_creation_event::get_desc): Likewise.
	(state_change_event::get_desc): Likewise.
	(superedge_event::should_filter_p): Likewise.
	(start_cfg_edge_event::get_desc): Likewise.
	(call_event::get_desc): Likewise.
	(return_event::get_desc): Likewise.
	(warning_event::get_desc): Likewise.
	(checker_path::dump): Likewise.
	(checker_path::debug): Likewise.
	* diagnostic-manager.cc (diagnostic_manager::prune_for_sm_diagnostic):
	Likewise.
	(diagnostic_manager::prune_interproc_events): Likewise.
	* engine.cc (feasibility_state::maybe_update_for_edge):
	Likewise.
	* program-state.cc (sm_state_map::to_json): Likewise.
	* region-model-impl-calls.cc (region_model::impl_call_analyzer_describe): Likewise.
	(region_model::impl_call_analyzer_dump_capacity): Likewise.
	* region.cc (region::to_json): Likewise.
	* sm-malloc.cc (inform_nonnull_attribute): Likewise.
	* store.cc (binding_map::to_json): Likewise.
	(store::to_json): Likewise.
	* supergraph.cc (superedge::dump): Likewise.
	* svalue.cc (svalue::to_json): Likewise.

gcc/c-family/ChangeLog:

	* c-format.cc (class range_label_for_format_type_mismatch):
	Adjust to new label_text API.

gcc/ChangeLog:

	* diagnostic-format-json.cc (json_from_location_range): Adjust
	to new label_text API.
	* diagnostic-format-sarif.cc (sarif_builder::make_location_object):
	Likewise.
	* diagnostic-show-locus.cc (struct pod_label_text): Likewise.
	(layout::print_any_labels): Likewise.
	* tree-diagnostic-path.cc (class path_label): Likewise.
	(struct event_range): Likewise.
	(default_tree_diagnostic_path_printer): Likewise.
	(default_tree_make_json_for_path): Likewise.

libcpp/ChangeLog:

	* include/line-map.h (label_text::take_or_copy): Remove.
	(label_text::moved_from): Rename to release.
	(label_text::m_buffer, label_text::m_owned): Make private.
	(label_text::get, label_text::is_owned): New accessors.

17 files changed, 80 insertions, 78 deletions

diff --git a/gcc/analyzer/call-info.cc b/gcc/analyzer/call-info.cc
index e1142d7..efc070b 100644
--- a/gcc/analyzer/call-info.cc
+++ b/gcc/analyzer/call-info.cc
@@ -75,7 +75,7 @@ void
 call_info::print (pretty_printer *pp) const
 {
   label_text desc (get_desc (pp_show_color (pp)));
-  pp_string (pp, desc.m_buffer);
+  pp_string (pp, desc.get ());
 }
 
 /* Implementation of custom_edge_info::add_events_to_path vfunc for
diff --git a/gcc/analyzer/checker-path.cc b/gcc/analyzer/checker-path.cc
index 211cf3e..273f40d 100644
--- a/gcc/analyzer/checker-path.cc
+++ b/gcc/analyzer/checker-path.cc
@@ -195,7 +195,7 @@ checker_event::dump (pretty_printer *pp) const
 {
   label_text event_desc (get_desc (false));
   pp_printf (pp, "\"%s\" (depth %i",
-	     event_desc.m_buffer, m_effective_depth);
+	     event_desc.get (), m_effective_depth);
 
   if (m_effective_depth != m_original_depth)
     pp_printf (pp, " corrected from %i",
@@ -307,7 +307,7 @@ region_creation_event::get_desc (bool can_colorize) const
       label_text custom_desc
 	    = m_pending_diagnostic->describe_region_creation_event
 		(evdesc::region_creation (can_colorize, m_reg));
-      if (custom_desc.m_buffer)
+      if (custom_desc.get ())
 	return custom_desc;
     }
 
@@ -390,7 +390,7 @@ state_change_event::get_desc (bool can_colorize) const
 	= m_pending_diagnostic->describe_state_change
 	    (evdesc::state_change (can_colorize, var, origin,
 				   m_from, m_to, m_emission_id, *this));
-      if (custom_desc.m_buffer)
+      if (custom_desc.get ())
 	{
 	  if (flag_analyzer_verbose_state_changes)
 	    {
@@ -404,7 +404,7 @@ state_change_event::get_desc (bool can_colorize) const
 		return make_label_text
 		  (can_colorize,
 		   "%s (state of %qE: %qs -> %qs, origin: %qE, meaning: %s)",
-		   custom_desc.m_buffer,
+		   custom_desc.get (),
 		   var,
 		   m_from->get_name (),
 		   m_to->get_name (),
@@ -414,7 +414,7 @@ state_change_event::get_desc (bool can_colorize) const
 		return make_label_text
 		  (can_colorize,
 		   "%s (state of %qE: %qs -> %qs, NULL origin, meaning: %s)",
-		   custom_desc.m_buffer,
+		   custom_desc.get (),
 		   var,
 		   m_from->get_name (),
 		   m_to->get_name (),
@@ -435,16 +435,16 @@ state_change_event::get_desc (bool can_colorize) const
 	  return make_label_text
 	    (can_colorize,
 	     "state of %qs: %qs -> %qs (origin: %qs)",
-	     sval_desc.m_buffer,
+	     sval_desc.get (),
 	     m_from->get_name (),
 	     m_to->get_name (),
-	     origin_desc.m_buffer);
+	     origin_desc.get ());
 	}
       else
 	return make_label_text
 	  (can_colorize,
 	   "state of %qs: %qs -> %qs (NULL origin)",
-	   sval_desc.m_buffer,
+	   sval_desc.get (),
 	   m_from->get_name (),
 	   m_to->get_name ());
     }
@@ -509,8 +509,8 @@ superedge_event::should_filter_p (int verbosity) const
 	    /* Filter events with empty descriptions.  This ought to filter
 	       FALLTHRU, but retain true/false/switch edges.  */
 	    label_text desc = get_desc (false);
-	    gcc_assert (desc.m_buffer);
-	    if (desc.m_buffer[0] == '\0')
+	    gcc_assert (desc.get ());
+	    if (desc.get ()[0] == '\0')
 	      return true;
 	  }
       }
@@ -597,28 +597,28 @@ start_cfg_edge_event::get_desc (bool can_colorize) const
   label_text edge_desc (m_sedge->get_description (user_facing));
   if (user_facing)
     {
-      if (edge_desc.m_buffer && strlen (edge_desc.m_buffer) > 0)
+      if (edge_desc.get () && strlen (edge_desc.get ()) > 0)
 	{
 	  label_text cond_desc = maybe_describe_condition (can_colorize);
 	  label_text result;
-	  if (cond_desc.m_buffer)
+	  if (cond_desc.get ())
 	    return make_label_text (can_colorize,
 				    "following %qs branch (%s)...",
-				    edge_desc.m_buffer, cond_desc.m_buffer);
+				    edge_desc.get (), cond_desc.get ());
 	  else
 	    return make_label_text (can_colorize,
 				    "following %qs branch...",
-				    edge_desc.m_buffer);
+				    edge_desc.get ());
 	}
       else
 	return label_text::borrow ("");
     }
   else
     {
-      if (strlen (edge_desc.m_buffer) > 0)
+      if (strlen (edge_desc.get ()) > 0)
 	return make_label_text (can_colorize,
 				"taking %qs edge SN:%i -> SN:%i",
-				edge_desc.m_buffer,
+				edge_desc.get (),
 				m_sedge->m_src->m_index,
 				m_sedge->m_dest->m_index);
       else
@@ -798,7 +798,7 @@ call_event::get_desc (bool can_colorize) const
 				      m_dest_snode->m_fun->decl,
 				      var,
 				      m_critical_state));
-      if (custom_desc.m_buffer)
+      if (custom_desc.get ())
 	return custom_desc;
     }
 
@@ -878,7 +878,7 @@ return_event::get_desc (bool can_colorize) const
 				      m_dest_snode->m_fun->decl,
 				      m_src_snode->m_fun->decl,
 				      m_critical_state));
-      if (custom_desc.m_buffer)
+      if (custom_desc.get ())
 	return custom_desc;
     }
   return make_label_text (can_colorize,
@@ -1105,19 +1105,19 @@ warning_event::get_desc (bool can_colorize) const
       label_text ev_desc
 	= m_pending_diagnostic->describe_final_event
 	    (evdesc::final_event (can_colorize, var, m_state));
-      if (ev_desc.m_buffer)
+      if (ev_desc.get ())
 	{
 	  if (m_sm && flag_analyzer_verbose_state_changes)
 	    {
 	      if (var)
 		return make_label_text (can_colorize,
 					"%s (%qE is in state %qs)",
-					ev_desc.m_buffer,
+					ev_desc.get (),
 					var, m_state->get_name ());
 	      else
 		return make_label_text (can_colorize,
 					"%s (in global state %qs)",
-					ev_desc.m_buffer,
+					ev_desc.get (),
 					m_state->get_name ());
 	    }
 	  else
@@ -1163,7 +1163,7 @@ checker_path::dump (pretty_printer *pp) const
       if (i > 0)
 	pp_string (pp, ", ");
       label_text event_desc (e->get_desc (false));
-      pp_printf (pp, "\"%s\"", event_desc.m_buffer);
+      pp_printf (pp, "\"%s\"", event_desc.get ());
     }
   pp_character (pp, ']');
 }
@@ -1203,7 +1203,7 @@ checker_path::debug () const
 	       "[%i]: %s \"%s\"\n",
 	       i,
 	       event_kind_to_string (m_events[i]->m_kind),
-	       event_desc.m_buffer);
+	       event_desc.get ());
     }
 }
 
diff --git a/gcc/analyzer/diagnostic-manager.cc b/gcc/analyzer/diagnostic-manager.cc
index 083f66b..fded828 100644
--- a/gcc/analyzer/diagnostic-manager.cc
+++ b/gcc/analyzer/diagnostic-manager.cc
@@ -2297,7 +2297,7 @@ diagnostic_manager::prune_for_sm_diagnostic (checker_path *path,
 		  label_text sval_desc = sval->get_desc ();
 		  log ("considering event %i (%s), with sval: %qs, state: %qs",
 		       idx, event_kind_to_string (base_event->m_kind),
-		       sval_desc.m_buffer, state->get_name ());
+		       sval_desc.get (), state->get_name ());
 		}
 	      else
 		log ("considering event %i (%s), with global state: %qs",
@@ -2363,8 +2363,8 @@ diagnostic_manager::prune_for_sm_diagnostic (checker_path *path,
 			  = state_change->m_origin->get_desc ();
 			log ("event %i:"
 			     " switching var of interest from %qs to %qs",
-			     idx, sval_desc.m_buffer,
-			     origin_sval_desc.m_buffer);
+			     idx, sval_desc.get (),
+			     origin_sval_desc.get ());
 		      }
 		    sval = state_change->m_origin;
 		  }
@@ -2386,12 +2386,12 @@ diagnostic_manager::prune_for_sm_diagnostic (checker_path *path,
 			    label_text sval_desc = sval->get_desc ();
 			    log ("filtering event %i:"
 				 " state change to %qs unrelated to %qs",
-				 idx, change_sval_desc.m_buffer,
-				 sval_desc.m_buffer);
+				 idx, change_sval_desc.get (),
+				 sval_desc.get ());
 			  }
 			else
 			  log ("filtering event %i: state change to %qs",
-			       idx, change_sval_desc.m_buffer);
+			       idx, change_sval_desc.get ());
 		      }
 		    else
 		      log ("filtering event %i: global state change", idx);
@@ -2460,7 +2460,7 @@ diagnostic_manager::prune_for_sm_diagnostic (checker_path *path,
 		    log ("event %i:"
 			 " recording critical state for %qs at call"
 			 " from %qE in callee to %qE in caller",
-			 idx, sval_desc.m_buffer, callee_var, caller_var);
+			 idx, sval_desc.get (), callee_var, caller_var);
 		  }
 		if (expr.param_p ())
 		  event->record_critical_state (caller_var, state);
@@ -2503,7 +2503,7 @@ diagnostic_manager::prune_for_sm_diagnostic (checker_path *path,
 			log ("event %i:"
 			     " recording critical state for %qs at return"
 			     " from %qE in caller to %qE in callee",
-			     idx, sval_desc.m_buffer, callee_var, callee_var);
+			     idx, sval_desc.get (), callee_var, callee_var);
 		      }
 		    if (expr.return_value_p ())
 		      event->record_critical_state (callee_var, state);
@@ -2586,7 +2586,7 @@ diagnostic_manager::prune_interproc_events (checker_path *path) const
 		    (path->get_checker_event (idx)->get_desc (false));
 		  log ("filtering events %i-%i:"
 		       " irrelevant call/entry/return: %s",
-		       idx, idx + 2, desc.m_buffer);
+		       idx, idx + 2, desc.get ());
 		}
 	      path->delete_event (idx + 2);
 	      path->delete_event (idx + 1);
@@ -2608,7 +2608,7 @@ diagnostic_manager::prune_interproc_events (checker_path *path) const
 		    (path->get_checker_event (idx)->get_desc (false));
 		  log ("filtering events %i-%i:"
 		       " irrelevant call/return: %s",
-		       idx, idx + 1, desc.m_buffer);
+		       idx, idx + 1, desc.get ());
 		}
 	      path->delete_event (idx + 1);
 	      path->delete_event (idx);
diff --git a/gcc/analyzer/engine.cc b/gcc/analyzer/engine.cc
index 888123f..9ffcc41 100644
--- a/gcc/analyzer/engine.cc
+++ b/gcc/analyzer/engine.cc
@@ -4590,7 +4590,7 @@ feasibility_state::maybe_update_for_edge (logger *logger,
 	  logger->log ("  sedge: SN:%i -> SN:%i %s",
 		       sedge->m_src->m_index,
 		       sedge->m_dest->m_index,
-		       desc.m_buffer);
+		       desc.get ());
 	}
 
       const gimple *last_stmt = src_point.get_supernode ()->get_last_stmt ();
diff --git a/gcc/analyzer/program-state.cc b/gcc/analyzer/program-state.cc
index 90a56e3..f0f4046 100644
--- a/gcc/analyzer/program-state.cc
+++ b/gcc/analyzer/program-state.cc
@@ -300,7 +300,7 @@ sm_state_map::to_json () const
       entry_t e = (*iter).second;
 
       label_text sval_desc = sval->get_desc ();
-      map_obj->set (sval_desc.m_buffer, e.m_state->to_json ());
+      map_obj->set (sval_desc.get (), e.m_state->to_json ());
 
       /* This doesn't yet JSONify e.m_origin.  */
     }
diff --git a/gcc/analyzer/region-model-impl-calls.cc b/gcc/analyzer/region-model-impl-calls.cc
index 55d6fa7..8c38e92 100644
--- a/gcc/analyzer/region-model-impl-calls.cc
+++ b/gcc/analyzer/region-model-impl-calls.cc
@@ -255,7 +255,7 @@ region_model::impl_call_analyzer_describe (const gcall *call,
   const svalue *sval = get_rvalue (t_val, ctxt);
   bool simple = zerop (t_verbosity);
   label_text desc = sval->get_desc (simple);
-  warning_at (call->location, 0, "svalue: %qs", desc.m_buffer);
+  warning_at (call->location, 0, "svalue: %qs", desc.get ());
 }
 
 /* Handle a call to "__analyzer_dump_capacity".
@@ -274,7 +274,7 @@ region_model::impl_call_analyzer_dump_capacity (const gcall *call,
   const region *base_reg = reg->get_base_region ();
   const svalue *capacity = get_capacity (base_reg);
   label_text desc = capacity->get_desc (true);
-  warning_at (call->location, 0, "capacity: %qs", desc.m_buffer);
+  warning_at (call->location, 0, "capacity: %qs", desc.get ());
 }
 
 /* Compare D1 and D2 using their names, and then IDs to order them.  */
diff --git a/gcc/analyzer/region.cc b/gcc/analyzer/region.cc
index 5b00e6a..a8d1ae9 100644
--- a/gcc/analyzer/region.cc
+++ b/gcc/analyzer/region.cc
@@ -589,7 +589,7 @@ json::value *
 region::to_json () const
 {
   label_text desc = get_desc (true);
-  json::value *reg_js = new json::string (desc.m_buffer);
+  json::value *reg_js = new json::string (desc.get ());
   return reg_js;
 }
 
diff --git a/gcc/analyzer/sm-malloc.cc b/gcc/analyzer/sm-malloc.cc
index 553fcd8..608aceb 100644
--- a/gcc/analyzer/sm-malloc.cc
+++ b/gcc/analyzer/sm-malloc.cc
@@ -1007,7 +1007,7 @@ inform_nonnull_attribute (tree fndecl, int arg_idx)
   label_text arg_desc = describe_argument_index (fndecl, arg_idx);
   inform (DECL_SOURCE_LOCATION (fndecl),
 	  "argument %s of %qD must be non-null",
-	  arg_desc.m_buffer, fndecl);
+	  arg_desc.get (), fndecl);
   /* Ideally we would use the location of the parm and underline the
      attribute also - but we don't have the location_t values at this point
      in the middle-end.
@@ -1065,12 +1065,12 @@ public:
     if (m_origin_of_unchecked_event.known_p ())
       result = ev.formatted_print ("argument %s (%qE) from %@ could be NULL"
 				   " where non-null expected",
-				   arg_desc.m_buffer, ev.m_expr,
+				   arg_desc.get (), ev.m_expr,
 				   &m_origin_of_unchecked_event);
     else
       result = ev.formatted_print ("argument %s (%qE) could be NULL"
 				   " where non-null expected",
-				   arg_desc.m_buffer, ev.m_expr);
+				   arg_desc.get (), ev.m_expr);
     return result;
   }
 
@@ -1173,11 +1173,11 @@ public:
     label_text result;
     if (zerop (ev.m_expr))
       result = ev.formatted_print ("argument %s NULL where non-null expected",
-				   arg_desc.m_buffer);
+				   arg_desc.get ());
     else
       result = ev.formatted_print ("argument %s (%qE) NULL"
 				   " where non-null expected",
-				   arg_desc.m_buffer, ev.m_expr);
+				   arg_desc.get (), ev.m_expr);
     return result;
   }
 
diff --git a/gcc/analyzer/store.cc b/gcc/analyzer/store.cc
index d558d47..06151d8 100644
--- a/gcc/analyzer/store.cc
+++ b/gcc/analyzer/store.cc
@@ -675,7 +675,7 @@ binding_map::to_json () const
     {
       const svalue *value = *const_cast <map_t &> (m_map).get (key);
       label_text key_desc = key->get_desc ();
-      map_obj->set (key_desc.m_buffer, value->to_json ());
+      map_obj->set (key_desc.get (), value->to_json ());
     }
 
   return map_obj;
@@ -2402,11 +2402,11 @@ store::to_json () const
 	  binding_cluster *cluster
 	    = *const_cast<cluster_map_t &> (m_cluster_map).get (base_reg);
 	  label_text base_reg_desc = base_reg->get_desc ();
-	  clusters_in_parent_reg_obj->set (base_reg_desc.m_buffer,
+	  clusters_in_parent_reg_obj->set (base_reg_desc.get (),
 					   cluster->to_json ());
 	}
       label_text parent_reg_desc = parent_reg->get_desc ();
-      store_obj->set (parent_reg_desc.m_buffer, clusters_in_parent_reg_obj);
+      store_obj->set (parent_reg_desc.get (), clusters_in_parent_reg_obj);
     }
 
   store_obj->set ("called_unknown_fn", new json::literal (m_called_unknown_fn));
diff --git a/gcc/analyzer/supergraph.cc b/gcc/analyzer/supergraph.cc
index 52b48524..01e30f7 100644
--- a/gcc/analyzer/supergraph.cc
+++ b/gcc/analyzer/supergraph.cc
@@ -855,10 +855,10 @@ superedge::dump (pretty_printer *pp) const
 {
   pp_printf (pp, "edge: SN: %i -> SN: %i", m_src->m_index, m_dest->m_index);
   label_text desc (get_description (false));
-  if (strlen (desc.m_buffer) > 0)
+  if (strlen (desc.get ()) > 0)
     {
       pp_space (pp);
-      pp_string (pp, desc.m_buffer);
+      pp_string (pp, desc.get ());
     }
 }
 
diff --git a/gcc/analyzer/svalue.cc b/gcc/analyzer/svalue.cc
index 78a6eef..f5a5f1c 100644
--- a/gcc/analyzer/svalue.cc
+++ b/gcc/analyzer/svalue.cc
@@ -96,7 +96,7 @@ json::value *
 svalue::to_json () const
 {
   label_text desc = get_desc (true);
-  json::value *sval_js = new json::string (desc.m_buffer);
+  json::value *sval_js = new json::string (desc.get ());
   return sval_js;
 }
 
diff --git a/gcc/c-family/c-format.cc b/gcc/c-family/c-format.cc
index 2faed0c..68b94da 100644
--- a/gcc/c-family/c-format.cc
+++ b/gcc/c-family/c-format.cc
@@ -4617,14 +4617,14 @@ class range_label_for_format_type_mismatch
   label_text get_text (unsigned range_idx) const final override
   {
     label_text text = range_label_for_type_mismatch::get_text (range_idx);
-    if (text.m_buffer == NULL)
+    if (text.get () == NULL)
       return text;
 
     indirection_suffix suffix (m_pointer_count);
     char *p = (char *) alloca (suffix.get_buffer_size ());
     suffix.fill_buffer (p);
 
-    char *result = concat (text.m_buffer, p, NULL);
+    char *result = concat (text.get (), p, NULL);
     return label_text::take (result);
   }
 
diff --git a/gcc/diagnostic-format-json.cc b/gcc/diagnostic-format-json.cc
index 872c67e..baadc4b2 100644
--- a/gcc/diagnostic-format-json.cc
+++ b/gcc/diagnostic-format-json.cc
@@ -102,8 +102,8 @@ json_from_location_range (diagnostic_context *context,
   if (loc_range->m_label)
     {
       label_text text (loc_range->m_label->get_text (range_idx));
-      if (text.m_buffer)
-	result->set ("label", new json::string (text.m_buffer));
+      if (text.get ())
+	result->set ("label", new json::string (text.get ()));
     }
 
   return result;
diff --git a/gcc/diagnostic-format-sarif.cc b/gcc/diagnostic-format-sarif.cc
index 1e4ebc8..fc28d16 100644
--- a/gcc/diagnostic-format-sarif.cc
+++ b/gcc/diagnostic-format-sarif.cc
@@ -582,7 +582,7 @@ sarif_builder::make_location_object (const diagnostic_event &event)
 
   /* "message" property (SARIF v2.1.0 section 3.28.5).  */
   label_text ev_desc = event.get_desc (false);
-  json::object *message_obj = make_message_object (ev_desc.m_buffer);
+  json::object *message_obj = make_message_object (ev_desc.get ());
   location_obj->set ("message", message_obj);
 
   return location_obj;
diff --git a/gcc/diagnostic-show-locus.cc b/gcc/diagnostic-show-locus.cc
index 08dab20..9d430b5 100644
--- a/gcc/diagnostic-show-locus.cc
+++ b/gcc/diagnostic-show-locus.cc
@@ -1877,9 +1877,10 @@ struct pod_label_text
   {}
 
   pod_label_text (label_text &&other)
-  : m_buffer (other.m_buffer), m_caller_owned (other.m_owned)
+  : m_buffer (const_cast<char*> (other.get ())),
+    m_caller_owned (other.is_owner ())
   {
-    other.moved_from ();
+    other.release ();
   }
 
   void maybe_free ()
@@ -1963,7 +1964,7 @@ layout::print_any_labels (linenum_type row)
 	/* Allow for labels that return NULL from their get_text
 	   implementation (so e.g. such labels can control their own
 	   visibility).  */
-	if (text.m_buffer == NULL)
+	if (text.get () == NULL)
 	  continue;
 
 	labels.safe_push (line_label (m_policy, i, disp_col, std::move (text)));
diff --git a/gcc/tree-diagnostic-path.cc b/gcc/tree-diagnostic-path.cc
index 2f297fa..6612b61 100644
--- a/gcc/tree-diagnostic-path.cc
+++ b/gcc/tree-diagnostic-path.cc
@@ -61,11 +61,11 @@ class path_label : public range_label
        is special-cased for diagnostic paths.  */
     bool colorize = pp_show_color (global_dc->printer);
     label_text event_text (event.get_desc (colorize));
-    gcc_assert (event_text.m_buffer);
+    gcc_assert (event_text.get ());
     pretty_printer pp;
     pp_show_color (&pp) = pp_show_color (global_dc->printer);
     diagnostic_event_id_t event_id (event_idx);
-    pp_printf (&pp, "%@ %s", &event_id, event_text.m_buffer);
+    pp_printf (&pp, "%@ %s", &event_id, event_text.get ());
     label_text result = label_text::take (xstrdup (pp_formatted_text (&pp)));
     return result;
   }
@@ -173,7 +173,7 @@ struct event_range
 	    diagnostic_event_id_t event_id (i);
 	    label_text event_text (iter_event.get_desc (true));
 	    pretty_printer *pp = dc->printer;
-	    pp_printf (pp, " %@: %s", &event_id, event_text.m_buffer);
+	    pp_printf (pp, " %@: %s", &event_id, event_text.get ());
 	    pp_newline (pp);
 	  }
 	return;
@@ -459,7 +459,7 @@ default_tree_diagnostic_path_printer (diagnostic_context *context,
 	  {
 	    const diagnostic_event &event = path->get_event (i);
 	    label_text event_text (event.get_desc (false));
-	    gcc_assert (event_text.m_buffer);
+	    gcc_assert (event_text.get ());
 	    diagnostic_event_id_t event_id (i);
 	    if (context->show_path_depths)
 	      {
@@ -471,17 +471,17 @@ default_tree_diagnostic_path_printer (diagnostic_context *context,
 		if (fndecl)
 		  inform (event.get_location (),
 			  "%@ %s (fndecl %qD, depth %i)",
-			  &event_id, event_text.m_buffer,
+			  &event_id, event_text.get (),
 			  fndecl, stack_depth);
 		else
 		  inform (event.get_location (),
 			  "%@ %s (depth %i)",
-			  &event_id, event_text.m_buffer,
+			  &event_id, event_text.get (),
 			  stack_depth);
 	      }
 	    else
 	      inform (event.get_location (),
-		      "%@ %s", &event_id, event_text.m_buffer);
+		      "%@ %s", &event_id, event_text.get ());
 	  }
       }
       break;
@@ -519,7 +519,7 @@ default_tree_make_json_for_path (diagnostic_context *context,
 			json_from_expanded_location (context,
 						     event.get_location ()));
       label_text event_text (event.get_desc (false));
-      event_obj->set ("description", new json::string (event_text.m_buffer));
+      event_obj->set ("description", new json::string (event_text.get ()));
       if (tree fndecl = event.get_fndecl ())
 	{
 	  const char *function
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index c434a24..9bdd5b9 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -1851,7 +1851,7 @@ public:
   label_text (label_text &&other)
   : m_buffer (other.m_buffer), m_owned (other.m_owned)
   {
-    other.moved_from ();
+    other.release ();
   }
 
   /* Move assignment.  */
@@ -1861,7 +1861,7 @@ public:
       free (m_buffer);
     m_buffer = other.m_buffer;
     m_owned = other.m_owned;
-    other.moved_from ();
+    other.release ();
     return *this;
   }
 
@@ -1882,25 +1882,26 @@ public:
     return label_text (buffer, true);
   }
 
-  /* Take ownership of the buffer, copying if necessary.  */
-  char *take_or_copy ()
+  void release ()
   {
-    if (m_owned)
-      return m_buffer;
-    else
-      return xstrdup (m_buffer);
+    m_buffer = NULL;
+    m_owned = false;
   }
 
-  void moved_from ()
+  const char *get () const
   {
-    m_buffer = NULL;
-    m_owned = false;
+    return m_buffer;
   }
 
+  bool is_owner () const
+  {
+    return m_owned;
+  }
+
+private:
   char *m_buffer;
   bool m_owned;
 
-private:
   label_text (char *buffer, bool owned)
   : m_buffer (buffer), m_owned (owned)
   {}