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[C++ PATCH] PR c++/91369 - Implement P0784R7: constexpr new


Hi!

The following patch attempts to implement P0784R7, which includes constexpr
destructors and constexpr new/delete/new[]/delete[].

::operator new is allowed during constexpr evaluation and returns address of
an artificial VAR_DECL with special name.  At this point we don't really
know the type of the heap storage, just size.  Later on when we encounter
cast to the corresponding pointer type, we change the name of the var and
type to match the type from the new expression (for new[] we need to do
further stuff as at the point where build_new_1 is called, we might not know
the exact array size, but we shall know that during the constexpr
evaluation, and cookie handling also complicates it a little bit).
When we first store into such heap objects, a ctor is created for them on
the fly.  Finally, ::operator delete marks those heap VAR_DECLs as deleted
and cxx_eval_outermost_constant_expr checks if everything that has been
allocated has been also deallocated and verifies addresses of those heap
vars aren't leaking into the return value.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2019-09-27  Jakub Jelinek  <jakub@redhat.com>

	PR c++/91369 - Implement P0784R7: constexpr new
c-family/
	* c-cppbuiltin.c (c_cpp_builtins): Predefine
	__cpp_constexpr_dynamic_alloc=201907 for -std=c++2a.
cp/
	* cp-tree.h (enum cp_tree_index): Add CPTI_HEAP_UNINIT_IDENTIFIER,
	CPTI_HEAP_IDENTIFIER and CPTI_HEAP_DELETED_IDENTIFIER.
	(heap_uninit_identifier, heap_identifier, heap_deleted_identifier):
	Define.
	(type_has_constexpr_destructor, cxx_constant_dtor): Declare.
	* class.c (type_maybe_constexpr_default_constructor): Make static.
	(type_maybe_constexpr_destructor, type_has_constexpr_destructor): New
	functions.
	(finalize_literal_type_property): For c++2a, don't clear
	CLASSTYPE_LITERAL_P for types without trivial destructors unless they
	have non-constexpr destructors.
	(explain_non_literal_class): For c++2a, complain about non-constexpr
	destructors rather than about non-trivial destructors.
	* constexpr.c: Include stor-layout.h.
	(struct constexpr_ctx): Add heap_vars field.
	(cxx_eval_call_expression): For c++2a allow calls to replaceable
	global allocation functions, for new return address of a heap uninit
	var, for delete record its deletion.
	(initialized_type): Handle destructors for c++2a.
	(cxx_fold_indirect_ref): Also handle array fields in structures.
	(non_const_var_error): Add auto_diagnostic_group sentinel.  Emit
	special diagnostics for heap variables.
	(cxx_eval_store_expression): Create ctor for heap variables on the
	first write.  Formatting fix.  Handle const_object_being_modified
	with array type.
	(cxx_eval_loop_expr): Initialize jump_target if NULL.
	(cxx_eval_constant_expression) <case CLEANUP_STMT>: If not skipping
	upon entry to body, run cleanup with the same *jump_target as it
	started to run the cleanup even if the body returns, breaks or
	continues.
	<case NOP_EXPR>: Formatting fix.  On cast of replaceable global
	allocation function to some pointer type, adjust the type of
	the heap variable and change name from heap_uninit_identifier
	to heap_identifier.
	(find_heap_var_refs): New function.
	(cxx_eval_outermost_constant_expr): Add constexpr_dtor argument,
	handle evaluation of constexpr dtors and add tracking of heap
	variables.  Use tf_no_cleanup for get_target_expr_with_sfinae.
	(cxx_constant_value): Adjust cxx_eval_outermost_constant_expr caller.
	(cxx_constant_dtor): New function.
	(maybe_constant_value, fold_non_dependent_expr_template,
	maybe_constant_init_1): Adjust cxx_eval_outermost_constant_expr
	callers.
	(potential_constant_expression_1): Ignore clobbers.  Allow
	COND_EXPR_IS_VEC_DELETE for c++2a.  Allow CLEANUP_STMT.
	* decl.c (initialize_predefined_identifiers): Add heap identifiers.
	(cp_finish_decl): Don't clear TREE_READONLY for constexpr variables
	with non-trivial, but constexpr destructors.
	(register_dtor_fn): For constexpr variables with constexpr non-trivial
	destructors call cxx_constant_dtor instead of adding destructor calls
	at runtime.
	(expand_static_init): For constexpr variables with constexpr
	non-trivial destructors call cxx_maybe_build_cleanup.
	(grokdeclarator): Allow constexpr destructors for c++2a.  Formatting
	fix.
	(cxx_maybe_build_cleanup): For constexpr variables with constexpr
	non-trivial destructors call cxx_constant_dtor instead of adding
	destructor calls at runtime.
	* init.c: Include stor-layout.h.
	(build_new_1): For c++2a and new[], add cast around the alloc call
	to help constexpr evaluation figure out the type of the heap storage.
	(build_vec_delete_1): Set DECL_INITIAL of tbase and emit a DECL_EXPR
	for it instead of initializing an uninitialized variable.
	* method.c: Include intl.h.
	(SFK_CTOR_P, SFK_DTOR_P, SFK_ASSIGN_P, SFK_COPY_P, SFK_MOVE_P): Move
	definitions earlier.
	(process_subob_fn): Add sfk argument, adjust non-constexpr call
	diagnostics based on it.
	(walk_field_subobs): Formatting fixes.  Adjust process_subob_fn caller.
	(synthesized_method_base_walk): Likewise.
	(synthesized_method_walk): Set *constexpr_p to true for dtors in c++2a.
	Fix up DR number in comment.
	(implicitly_declare_fn): Formatting fix.
	* typeck2.c (store_init_value): Don't call cp_fully_fold_init on
	initializers of automatic non-constexpr variables in constexpr
	functions.
testsuite/
	* g++.dg/cpp0x/constexpr-delete2.C: Adjust expected diagnostics for
	c++2a.
	* g++.dg/cpp0x/locations1.C: Only expect constexpr ~S() diagnostics
	in c++17_down, adjust expected wording.
	* g++.dg/cpp1y/constexpr-new.C: Only expect diagnostics in c++17_down.
	* g++.dg/cpp2a/constexpr-dtor1.C: New test.
	* g++.dg/cpp2a/constexpr-dtor2.C: New test.
	* g++.dg/cpp2a/constexpr-dtor3.C: New test.
	* g++.dg/cpp2a/constexpr-new1.C: New test.
	* g++.dg/cpp2a/constexpr-new2.C: New test.
	* g++.dg/cpp2a/constexpr-new3.C: New test.
	* g++.dg/cpp2a/constexpr-new4.C: New test.
	* g++.dg/cpp2a/feat-cxx2a.C: Add __cpp_constinit and
	__cpp_constexpr_dynamic_alloc tests.  Tweak __cpp_* tests for c++2a
	features to use style like older features, including #ifdef test.
	* g++.dg/ext/is_literal_type3.C: New test.

--- gcc/c-family/c-cppbuiltin.c.jj	2019-09-26 21:34:21.188923996 +0200
+++ gcc/c-family/c-cppbuiltin.c	2019-09-27 18:25:41.346059343 +0200
@@ -989,6 +989,7 @@ c_cpp_builtins (cpp_reader *pfile)
 	  cpp_define (pfile, "__cpp_constinit=201907");
 	  cpp_define (pfile, "__cpp_nontype_template_parameter_class=201806");
 	  cpp_define (pfile, "__cpp_impl_destroying_delete=201806");
+	  cpp_define (pfile, "__cpp_constexpr_dynamic_alloc=201907");
 	}
       if (flag_concepts)
 	cpp_define (pfile, "__cpp_concepts=201507");
--- gcc/cp/cp-tree.h.jj	2019-09-27 12:22:54.042880699 +0200
+++ gcc/cp/cp-tree.h	2019-09-27 18:25:40.903065957 +0200
@@ -172,6 +172,9 @@ enum cp_tree_index
     CPTI_VALUE_IDENTIFIER,
     CPTI_FUN_IDENTIFIER,
     CPTI_CLOSURE_IDENTIFIER,
+    CPTI_HEAP_UNINIT_IDENTIFIER,
+    CPTI_HEAP_IDENTIFIER,
+    CPTI_HEAP_DELETED_IDENTIFIER,
 
     CPTI_LANG_NAME_C,
     CPTI_LANG_NAME_CPLUSPLUS,
@@ -310,6 +313,9 @@ extern GTY(()) tree cp_global_trees[CPTI
 #define value_identifier		cp_global_trees[CPTI_VALUE_IDENTIFIER]
 #define fun_identifier			cp_global_trees[CPTI_FUN_IDENTIFIER]
 #define closure_identifier		cp_global_trees[CPTI_CLOSURE_IDENTIFIER]
+#define heap_uninit_identifier		cp_global_trees[CPTI_HEAP_UNINIT_IDENTIFIER]
+#define heap_identifier			cp_global_trees[CPTI_HEAP_IDENTIFIER]
+#define heap_deleted_identifier		cp_global_trees[CPTI_HEAP_DELETED_IDENTIFIER]
 #define lang_name_c			cp_global_trees[CPTI_LANG_NAME_C]
 #define lang_name_cplusplus		cp_global_trees[CPTI_LANG_NAME_CPLUSPLUS]
 
@@ -6324,6 +6330,7 @@ extern bool vbase_has_user_provided_move
 extern tree default_init_uninitialized_part (tree);
 extern bool trivial_default_constructor_is_constexpr (tree);
 extern bool type_has_constexpr_default_constructor (tree);
+extern bool type_has_constexpr_destructor	(tree);
 extern bool type_has_virtual_destructor		(tree);
 extern bool classtype_has_move_assign_or_move_ctor_p (tree, bool user_declared);
 extern bool classtype_has_non_deleted_move_ctor (tree);
@@ -7729,6 +7736,7 @@ extern bool require_constant_expression
 extern bool require_rvalue_constant_expression (tree);
 extern bool require_potential_rvalue_constant_expression (tree);
 extern tree cxx_constant_value			(tree, tree = NULL_TREE);
+extern void cxx_constant_dtor			(tree, tree);
 extern tree cxx_constant_init			(tree, tree = NULL_TREE);
 extern tree maybe_constant_value		(tree, tree = NULL_TREE, bool = false);
 extern tree maybe_constant_init			(tree, tree = NULL_TREE, bool = false);
--- gcc/cp/class.c.jj	2019-09-26 21:34:21.434920308 +0200
+++ gcc/cp/class.c	2019-09-27 18:25:40.904065942 +0200
@@ -206,6 +206,7 @@ static int empty_base_at_nonzero_offset_
 static tree end_of_base (tree);
 static tree get_vcall_index (tree, tree);
 static bool type_maybe_constexpr_default_constructor (tree);
+static bool type_maybe_constexpr_destructor (tree);
 static bool field_poverlapping_p (tree);
 
 /* Return a COND_EXPR that executes TRUE_STMT if this execution of the
@@ -5242,7 +5243,7 @@ type_has_constexpr_default_constructor (
    without forcing a lazy declaration (which might cause undesired
    instantiations).  */
 
-bool
+static bool
 type_maybe_constexpr_default_constructor (tree t)
 {
   if (CLASS_TYPE_P (t) && CLASSTYPE_LAZY_DEFAULT_CTOR (t)
@@ -5252,6 +5253,34 @@ type_maybe_constexpr_default_constructor
   return type_has_constexpr_default_constructor (t);
 }
 
+/* Returns true iff class T has a constexpr destructor.  */
+
+bool
+type_has_constexpr_destructor (tree t)
+{
+  tree fns;
+
+  if (CLASSTYPE_LAZY_DESTRUCTOR (t))
+    /* Non-trivial, we need to check subobject destructors.  */
+    lazily_declare_fn (sfk_destructor, t);
+  fns = CLASSTYPE_DESTRUCTOR (t);
+  return (fns && DECL_DECLARED_CONSTEXPR_P (fns));
+}
+
+/* Returns true iff class T has a constexpr destructor or has an
+   implicitly declared destructor that we can't tell if it's constexpr
+   without forcing a lazy declaration (which might cause undesired
+   instantiations).  */
+
+static bool
+type_maybe_constexpr_destructor (tree t)
+{
+  if (CLASS_TYPE_P (t) && CLASSTYPE_LAZY_DESTRUCTOR (t))
+    /* Assume it's constexpr.  */
+    return true;
+  return type_has_constexpr_destructor (t);
+}
+
 /* Returns true iff class TYPE has a virtual destructor.  */
 
 bool
@@ -5503,8 +5532,11 @@ finalize_literal_type_property (tree t)
 {
   tree fn;
 
-  if (cxx_dialect < cxx11
-      || TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t))
+  if (cxx_dialect < cxx11)
+    CLASSTYPE_LITERAL_P (t) = false;
+  else if (CLASSTYPE_LITERAL_P (t)
+	   && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t)
+	   && (cxx_dialect < cxx2a || !type_maybe_constexpr_destructor (t)))
     CLASSTYPE_LITERAL_P (t) = false;
   else if (CLASSTYPE_LITERAL_P (t) && LAMBDA_TYPE_P (t))
     CLASSTYPE_LITERAL_P (t) = (cxx_dialect >= cxx17);
@@ -5558,8 +5590,12 @@ explain_non_literal_class (tree t)
     inform (UNKNOWN_LOCATION,
 	    "  %qT is a closure type, which is only literal in "
 	    "C++17 and later", t);
-  else if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t))
+  else if (cxx_dialect < cxx2a && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t))
     inform (UNKNOWN_LOCATION, "  %q+T has a non-trivial destructor", t);
+  else if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t)
+	   && !type_maybe_constexpr_destructor (t))
+    inform (UNKNOWN_LOCATION, "  %q+T does not have %<constexpr%> destructor",
+	    t);
   else if (CLASSTYPE_NON_AGGREGATE (t)
 	   && !TYPE_HAS_TRIVIAL_DFLT (t)
 	   && !LAMBDA_TYPE_P (t)
--- gcc/cp/constexpr.c.jj	2019-09-27 20:33:37.600208356 +0200
+++ gcc/cp/constexpr.c	2019-09-27 20:38:38.203710246 +0200
@@ -34,6 +34,7 @@ along with GCC; see the file COPYING3.
 #include "gimple-fold.h"
 #include "timevar.h"
 #include "fold-const-call.h"
+#include "stor-layout.h"
 
 static bool verify_constant (tree, bool, bool *, bool *);
 #define VERIFY_CONSTANT(X)						\
@@ -1031,6 +1032,9 @@ struct constexpr_ctx {
      on simple constants or location wrappers) encountered during current
      cxx_eval_outermost_constant_expr call.  */
   HOST_WIDE_INT *constexpr_ops_count;
+  /* Heap VAR_DECLs created during the evaluation of the outermost constant
+     expression.  */
+  vec<tree> *heap_vars;
 
   /* Whether we should error on a non-constant expression or fail quietly.  */
   bool quiet;
@@ -1666,6 +1670,58 @@ cxx_eval_call_expression (const constexp
 					   lval, non_constant_p, overflow_p);
   if (!DECL_DECLARED_CONSTEXPR_P (fun))
     {
+      if (cxx_dialect >= cxx2a
+	  && IDENTIFIER_NEWDEL_OP_P (DECL_NAME (fun))
+	  && CP_DECL_CONTEXT (fun) == global_namespace)
+	{
+	  const int nargs = call_expr_nargs (t);
+	  tree arg0 = NULL_TREE;
+	  for (int i = 0; i < nargs; ++i)
+	    {
+	      tree arg = CALL_EXPR_ARG (t, i);
+	      arg = cxx_eval_constant_expression (ctx, arg, false,
+						  non_constant_p, overflow_p);
+	      VERIFY_CONSTANT (arg);
+	      if (i == 0)
+		arg0 = arg;
+	    }
+	  gcc_assert (arg0);
+	  if (IDENTIFIER_NEW_OP_P (DECL_NAME (fun)))
+	    {
+	      tree type = build_array_type_nelts (char_type_node,
+						  tree_to_uhwi (arg0));
+	      tree var = build_decl (loc, VAR_DECL, heap_uninit_identifier,
+				     type);
+	      DECL_ARTIFICIAL (var) = 1;
+	      TREE_STATIC (var) = 1;
+	      ctx->heap_vars->safe_push (var);
+	      return fold_convert (ptr_type_node, build_address (var));
+	    }
+	  else
+	    {
+	      STRIP_NOPS (arg0);
+	      if (TREE_CODE (arg0) == ADDR_EXPR
+		  && VAR_P (TREE_OPERAND (arg0, 0)))
+		{
+		  tree var = TREE_OPERAND (arg0, 0);
+		  if (DECL_NAME (var) == heap_uninit_identifier
+		      || DECL_NAME (var) == heap_identifier)
+		    {
+		      DECL_NAME (var) = heap_deleted_identifier;
+		      ctx->values->remove (var);
+		      return void_node;
+		    }
+		  else if (DECL_NAME (var) == heap_deleted_identifier)
+		    {
+		      if (!ctx->quiet)
+			error_at (loc, "deallocation of already deallocated "
+				       "storage");
+		      *non_constant_p = true;
+		      return t;
+		    }
+		}
+	    }
+	}
       if (!ctx->quiet)
 	{
 	  if (!lambda_static_thunk_p (fun))
@@ -2998,8 +3054,8 @@ base_field_constructor_elt (vec<construc
 }
 
 /* Some of the expressions fed to the constexpr mechanism are calls to
-   constructors, which have type void.  In that case, return the type being
-   initialized by the constructor.  */
+   constructors or destructors, which have type void.  In that case,
+   return the type being initialized by the constructor.  */
 
 static tree
 initialized_type (tree t)
@@ -3011,8 +3067,10 @@ initialized_type (tree t)
     {
       /* A constructor call has void type, so we need to look deeper.  */
       tree fn = get_function_named_in_call (t);
-      if (fn && TREE_CODE (fn) == FUNCTION_DECL
-	  && DECL_CXX_CONSTRUCTOR_P (fn))
+      if (fn
+	  && TREE_CODE (fn) == FUNCTION_DECL
+	  && (DECL_CXX_CONSTRUCTOR_P (fn)
+	      || (cxx_dialect >= cxx2a && DECL_CXX_DESTRUCTOR_P (fn))))
 	type = DECL_CONTEXT (fn);
     }
   else if (TREE_CODE (t) == COMPOUND_EXPR)
@@ -3434,11 +3492,24 @@ cxx_fold_indirect_ref (location_t loc, t
 	{
 	  tree field = TYPE_FIELDS (optype);
 	  for (; field; field = DECL_CHAIN (field))
-	    if (TREE_CODE (field) == FIELD_DECL
-		&& TREE_TYPE (field) != error_mark_node
-		&& integer_zerop (byte_position (field))
-		&& similar_type_p (TREE_TYPE (field), type))
+	    if (TREE_CODE (field) != FIELD_DECL
+		|| TREE_TYPE (field) == error_mark_node
+		|| !integer_zerop (byte_position (field)))
+	      continue;
+	    else if (similar_type_p (TREE_TYPE (field), type))
 	      return fold_build3 (COMPONENT_REF, type, op, field, NULL_TREE);
+	    else if (TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE
+		     && similar_type_p (TREE_TYPE (TREE_TYPE (field)), type))
+	      {
+		tree type_domain = TYPE_DOMAIN (TREE_TYPE (field));
+		tree min_val = size_zero_node;
+		if (type_domain && TYPE_MIN_VALUE (type_domain))
+		  min_val = TYPE_MIN_VALUE (type_domain);
+		op = fold_build3 (COMPONENT_REF, TREE_TYPE (field),
+				  op, field, NULL_TREE);
+		return build4_loc (loc, ARRAY_REF, type, op, min_val,
+				   NULL_TREE, NULL_TREE);
+	      }
 	}
     }
   else if (TREE_CODE (sub) == POINTER_PLUS_EXPR
@@ -3521,12 +3592,44 @@ cxx_fold_indirect_ref (location_t loc, t
 	    {
 	      tree field = TYPE_FIELDS (op00type);
 	      for (; field; field = DECL_CHAIN (field))
-		if (TREE_CODE (field) == FIELD_DECL
-		    && TREE_TYPE (field) != error_mark_node
-		    && tree_int_cst_equal (byte_position (field), op01)
-		    && similar_type_p (TREE_TYPE (field), type))
+		if (TREE_CODE (field) != FIELD_DECL
+		    || TREE_TYPE (field) == error_mark_node)
+		  continue;
+		else if (tree_int_cst_equal (byte_position (field), op01)
+			 && similar_type_p (TREE_TYPE (field), type))
 		  return fold_build3 (COMPONENT_REF, type, op00,
 				      field, NULL_TREE);
+		else if (TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE
+			 && tree_int_cst_le (byte_position (field), op01)
+			 && similar_type_p (TREE_TYPE (TREE_TYPE (field)),
+					    type))
+		  {
+		    tree type_domain = TYPE_DOMAIN (TREE_TYPE (field));
+		    tree min_val = size_zero_node;
+		    tree max_val = NULL_TREE;
+		    if (type_domain && TYPE_MIN_VALUE (type_domain))
+		      min_val = TYPE_MIN_VALUE (type_domain);
+		    if (type_domain && TYPE_MAX_VALUE (type_domain))
+		      max_val = TYPE_MAX_VALUE (type_domain);
+		    offset_int off = wi::to_offset (op01);
+		    off -= wi::to_offset (byte_position (field));
+		    offset_int el_sz = wi::to_offset (TYPE_SIZE_UNIT (type));
+		    offset_int remainder;
+		    off = wi::divmod_trunc (off, el_sz, SIGNED, &remainder);
+		    if (remainder == 0
+			&& TREE_CODE (min_val) == INTEGER_CST
+			&& (max_val == NULL_TREE
+			    || (TREE_CODE (max_val) == INTEGER_CST
+				&& off <= wi::to_offset (max_val))))
+		      {
+			off = off + wi::to_offset (min_val);
+			op00 = fold_build3 (COMPONENT_REF, TREE_TYPE (field),
+					    op00, field, NULL_TREE);
+			op01 = wide_int_to_tree (sizetype, off);
+			return build4_loc (loc, ARRAY_REF, type, op00, op01,
+					   NULL_TREE, NULL_TREE);
+		      }
+		  }
 	    }
 	}
     }
@@ -3645,7 +3748,23 @@ cxx_eval_indirect_ref (const constexpr_c
 static void
 non_const_var_error (tree r)
 {
+  auto_diagnostic_group d;
   tree type = TREE_TYPE (r);
+  if (DECL_NAME (r) == heap_uninit_identifier
+      || DECL_NAME (r) == heap_identifier)
+    {
+      error ("the content of uninitialized storage is not usable "
+	     "in a constant expression");
+      inform (DECL_SOURCE_LOCATION (r), "allocated here");
+      return;
+    }
+  if (DECL_NAME (r) == heap_deleted_identifier)
+    {
+      error ("use of allocated storage after deallocation in a "
+	     "constant expression");
+      inform (DECL_SOURCE_LOCATION (r), "allocated here");
+      return;
+    }
   error ("the value of %qD is not usable in a constant "
 	 "expression", r);
   /* Avoid error cascade.  */
@@ -3892,6 +4011,15 @@ cxx_eval_store_expression (const constex
     valp = ctx->values->get (object);
   else
     valp = NULL;
+  if (!valp
+      && VAR_P (object)
+      && DECL_NAME (object) == heap_identifier)
+    {
+      tree ctor = build_constructor (type, NULL);
+      CONSTRUCTOR_NO_CLEARING (ctor) = true;
+      ctx->values->put (object, ctor);
+      valp = ctx->values->get (object);
+    }
   if (!valp)
     {
       /* A constant-expression cannot modify objects from outside the
@@ -3905,7 +4033,7 @@ cxx_eval_store_expression (const constex
   bool no_zero_init = true;
 
   releasing_vec ctors;
-  while (!refs->is_empty())
+  while (!refs->is_empty ())
     {
       if (*valp == NULL_TREE)
 	{
@@ -4046,7 +4174,9 @@ cxx_eval_store_expression (const constex
   if (const_object_being_modified)
     {
       bool fail = false;
-      if (!CLASS_TYPE_P (TREE_TYPE (const_object_being_modified)))
+      tree const_objtype
+	= strip_array_types (TREE_TYPE (const_object_being_modified));
+      if (!CLASS_TYPE_P (const_objtype))
 	fail = true;
       else
 	{
@@ -4365,6 +4495,12 @@ cxx_eval_loop_expr (const constexpr_ctx
 		    tree *jump_target)
 {
   constexpr_ctx new_ctx = *ctx;
+  tree local_target;
+  if (!jump_target)
+    {
+      local_target = NULL_TREE;
+      jump_target = &local_target;
+    }
 
   tree body, cond = NULL_TREE, expr = NULL_TREE;
   int count = 0;
@@ -4907,14 +5043,21 @@ cxx_eval_constant_expression (const cons
       break;
 
     case CLEANUP_STMT:
-      r = cxx_eval_constant_expression (ctx, CLEANUP_BODY (t), lval,
+      {
+	tree initial_jump_target = jump_target ? *jump_target : NULL_TREE;
+	r = cxx_eval_constant_expression (ctx, CLEANUP_BODY (t), lval,
+					  non_constant_p, overflow_p,
+					  jump_target);
+	if (!CLEANUP_EH_ONLY (t) && !*non_constant_p)
+	  /* Also evaluate the cleanup.  If we weren't skipping at the
+	     start of the CLEANUP_BODY, change jump_target temporarily
+	     to &initial_jump_target, so that even a return or break or
+	     continue in the body doesn't skip the cleanup.  */
+	  cxx_eval_constant_expression (ctx, CLEANUP_EXPR (t), true,
 					non_constant_p, overflow_p,
-					jump_target);
-      if (!CLEANUP_EH_ONLY (t) && !*non_constant_p)
-	/* Also evaluate the cleanup.  */
-	cxx_eval_constant_expression (ctx, CLEANUP_EXPR (t), true,
-				      non_constant_p, overflow_p,
-				      jump_target);
+					jump_target ? &initial_jump_target
+					: NULL);
+      }
       break;
 
       /* These differ from cxx_eval_unary_expression in that this doesn't
@@ -5203,8 +5346,7 @@ cxx_eval_constant_expression (const cons
 	if (VOID_TYPE_P (type))
 	  return void_node;
 
-	if (TREE_CODE (op) == PTRMEM_CST
-	    && !TYPE_PTRMEM_P (type))
+	if (TREE_CODE (op) == PTRMEM_CST && !TYPE_PTRMEM_P (type))
 	  op = cplus_expand_constant (op);
 
 	if (TREE_CODE (op) == PTRMEM_CST && tcode == NOP_EXPR)
@@ -5258,6 +5400,81 @@ cxx_eval_constant_expression (const cons
 	      }
 	  }
 
+	if (INDIRECT_TYPE_P (type)
+	    && TREE_CODE (op) == NOP_EXPR
+	    && TREE_TYPE (op) == ptr_type_node
+	    && TREE_CODE (TREE_OPERAND (op, 0)) == ADDR_EXPR
+	    && VAR_P (TREE_OPERAND (TREE_OPERAND (op, 0), 0))
+	    && DECL_NAME (TREE_OPERAND (TREE_OPERAND (op, 0),
+					0)) == heap_uninit_identifier)
+	  {
+	    tree var = TREE_OPERAND (TREE_OPERAND (op, 0), 0);
+	    tree var_type = TREE_TYPE (type);
+	    tree cookie_type = NULL_TREE;
+	    bool array_p = false;
+	    HOST_WIDE_INT cookie_size = 0;
+	    if (TREE_CODE (var_type) == ARRAY_TYPE
+		&& TYPE_DOMAIN (var_type) == NULL_TREE)
+	      {
+		var_type = TREE_TYPE (var_type);
+		array_p = true;
+	      }
+	    else if (TREE_CODE (var_type) == RECORD_TYPE
+		     && TYPE_NAME (var_type) == NULL_TREE)
+	      if (tree fld1 = TYPE_FIELDS (var_type))
+		if (TREE_CODE (fld1) == FIELD_DECL
+		    && DECL_NAME (fld1) == NULL_TREE
+		    && DECL_ARTIFICIAL (fld1)
+		    && TREE_CODE (TREE_TYPE (fld1)) == ARRAY_TYPE
+		    && COMPLETE_TYPE_P (TREE_TYPE (fld1)))
+		  if (tree fld2 = DECL_CHAIN (fld1))
+		    if (TREE_CODE (fld2) == FIELD_DECL
+			&& DECL_NAME (fld2) == NULL_TREE
+			&& DECL_ARTIFICIAL (fld2)
+			&& TREE_CODE (TREE_TYPE (fld2)) == ARRAY_TYPE
+			&& TYPE_DOMAIN (TREE_TYPE (fld2)) == NULL_TREE
+			&& DECL_CHAIN (fld2) == NULL_TREE)
+		      {
+			var_type = TREE_TYPE (TREE_TYPE (fld2));
+			array_p = true;
+			cookie_type = TREE_TYPE (fld1);
+			cookie_size = int_size_in_bytes (TREE_TYPE (fld1));
+		      }
+	    HOST_WIDE_INT sz1 = int_size_in_bytes (var_type);
+	    HOST_WIDE_INT sz2 = int_size_in_bytes (TREE_TYPE (var));
+	    if (sz1 <= sz2 && cookie_size <= sz2)
+	      {
+		DECL_NAME (var) = heap_identifier;
+		if (array_p && sz1 > 0)
+		  {
+		    sz2 -= cookie_size;
+		    sz2 /= sz1;
+		    tree idx_type = build_index_type (size_int (sz2 - 1));
+		    var_type = build_cplus_array_type (var_type, idx_type);
+		    if (cookie_type)
+		      {
+			location_t loc = cp_expr_loc_or_input_loc (t);
+			tree vtype = cxx_make_type (RECORD_TYPE);
+			tree fld1 = build_decl (loc, FIELD_DECL, NULL_TREE,
+						cookie_type);
+			tree fld2 = build_decl (loc, FIELD_DECL, NULL_TREE,
+						var_type);
+			DECL_FIELD_CONTEXT (fld1) = vtype;
+			DECL_FIELD_CONTEXT (fld2) = vtype;
+			DECL_ARTIFICIAL (fld1) = true;
+			DECL_ARTIFICIAL (fld2) = true;
+			TYPE_FIELDS (vtype) = fld1;
+			DECL_CHAIN (fld1) = fld2;
+			layout_type (vtype);
+			var_type = vtype;
+		      }
+		  }
+		TREE_TYPE (var) = var_type;
+		TREE_TYPE (TREE_OPERAND (op, 0))
+		  = build_pointer_type (var_type);
+	      }
+	  }
+
 	if (op == oldop && tcode != UNARY_PLUS_EXPR)
 	  /* We didn't fold at the top so we could check for ptr-int
 	     conversion.  */
@@ -5499,6 +5716,7 @@ instantiate_cx_fn_r (tree *tp, int *walk
 
   return NULL_TREE;
 }
+
 static void
 instantiate_constexpr_fns (tree t)
 {
@@ -5507,17 +5725,36 @@ instantiate_constexpr_fns (tree t)
   input_location = loc;
 }
 
+/* Look for heap variables in the expression *TP.  */
+
+static tree
+find_heap_var_refs (tree *tp, int *walk_subtrees, void */*data*/)
+{
+  if (VAR_P (*tp)
+      && (DECL_NAME (*tp) == heap_uninit_identifier
+	  || DECL_NAME (*tp) == heap_identifier
+	  || DECL_NAME (*tp) == heap_deleted_identifier))
+    return *tp;
+
+  if (TYPE_P (*tp))
+    *walk_subtrees = 0;
+  return NULL_TREE;
+}
+
 /* ALLOW_NON_CONSTANT is false if T is required to be a constant expression.
    STRICT has the same sense as for constant_value_1: true if we only allow
    conforming C++ constant expressions, or false if we want a constant value
    even if it doesn't conform.
    MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated as
-   per P0595 even when ALLOW_NON_CONSTANT is true.  */
+   per P0595 even when ALLOW_NON_CONSTANT is true.
+   CONSTEXPR_DTOR is true when evaluating the dtor of a constexpr variable.
+   OBJECT must be non-NULL in that case.  */
 
 static tree
 cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
 				  bool strict = true,
 				  bool manifestly_const_eval = false,
+				  bool constexpr_dtor = false,
 				  tree object = NULL_TREE)
 {
   auto_timevar time (TV_CONSTEXPR);
@@ -5525,16 +5762,23 @@ cxx_eval_outermost_constant_expr (tree t
   bool non_constant_p = false;
   bool overflow_p = false;
   hash_map<tree,tree> map;
+  auto_vec<tree, 16> heap_vars;
   HOST_WIDE_INT constexpr_ctx_count = 0;
 
   constexpr_ctx ctx = { NULL, &map, NULL, NULL, NULL, NULL,
-			&constexpr_ctx_count, allow_non_constant, strict,
-			manifestly_const_eval || !allow_non_constant };
+			&constexpr_ctx_count, &heap_vars, allow_non_constant,
+			strict, manifestly_const_eval || !allow_non_constant };
 
   tree type = initialized_type (t);
   tree r = t;
   if (VOID_TYPE_P (type))
-    return t;
+    {
+      if (TREE_CODE (t) == BIND_EXPR && constexpr_dtor)
+	/* Used for destructors of array elements.  */
+	type = TREE_TYPE (object);
+      else
+	return t;
+    }
   if (AGGREGATE_TYPE_P (type) || VECTOR_TYPE_P (type))
     {
       /* In C++14 an NSDMI can participate in aggregate initialization,
@@ -5544,8 +5788,22 @@ cxx_eval_outermost_constant_expr (tree t
 	 update ctx.values for the VAR_DECL.  We use the same strategy
 	 for C++11 constexpr constructors that refer to the object being
 	 initialized.  */
-      ctx.ctor = build_constructor (type, NULL);
-      CONSTRUCTOR_NO_CLEARING (ctx.ctor) = true;
+      if (constexpr_dtor)
+	{
+	  gcc_assert (object && VAR_P (object));
+	  gcc_assert (DECL_DECLARED_CONSTEXPR_P (object));
+	  gcc_assert (DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (object));
+	  ctx.ctor = unshare_expr (DECL_INITIAL (object));
+	  TREE_READONLY (ctx.ctor) = false;
+	  /* Temporarily force decl_really_constant_value to return false
+	     for it, we want to use ctx.ctor for the current value instead.  */
+	  DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (object) = false;
+	}
+      else
+	{
+	  ctx.ctor = build_constructor (type, NULL);
+	  CONSTRUCTOR_NO_CLEARING (ctx.ctor) = true;
+	}
       if (!object)
 	{
 	  if (TREE_CODE (t) == TARGET_EXPR)
@@ -5569,13 +5827,15 @@ cxx_eval_outermost_constant_expr (tree t
   r = cxx_eval_constant_expression (&ctx, r,
 				    false, &non_constant_p, &overflow_p);
 
-  verify_constant (r, allow_non_constant, &non_constant_p, &overflow_p);
+  if (!constexpr_dtor)
+    verify_constant (r, allow_non_constant, &non_constant_p, &overflow_p);
+  else
+    DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (object) = true;
 
   /* Mutable logic is a bit tricky: we want to allow initialization of
      constexpr variables with mutable members, but we can't copy those
      members to another constexpr variable.  */
-  if (TREE_CODE (r) == CONSTRUCTOR
-      && CONSTRUCTOR_MUTABLE_POISON (r))
+  if (TREE_CODE (r) == CONSTRUCTOR && CONSTRUCTOR_MUTABLE_POISON (r))
     {
       if (!allow_non_constant)
 	error ("%qE is not a constant expression because it refers to "
@@ -5583,8 +5843,7 @@ cxx_eval_outermost_constant_expr (tree t
       non_constant_p = true;
     }
 
-  if (TREE_CODE (r) == CONSTRUCTOR
-      && CONSTRUCTOR_NO_CLEARING (r))
+  if (TREE_CODE (r) == CONSTRUCTOR && CONSTRUCTOR_NO_CLEARING (r))
     {
       if (!allow_non_constant)
 	error ("%qE is not a constant expression because it refers to "
@@ -5593,6 +5852,32 @@ cxx_eval_outermost_constant_expr (tree t
       non_constant_p = true;
     }
 
+  if (!heap_vars.is_empty ())
+    {
+      tree heap_var = cp_walk_tree_without_duplicates (&r, find_heap_var_refs,
+						       NULL);
+      unsigned int i;
+      if (heap_var)
+	{
+	  if (!allow_non_constant && !non_constant_p)
+	    error_at (DECL_SOURCE_LOCATION (heap_var),
+		      "%qE is not a constant expression because it refers to "
+		      "a result of %<operator new%>", t);
+	  r = t;
+	  non_constant_p = true;
+	}
+      FOR_EACH_VEC_ELT (heap_vars, i, heap_var)
+	if (DECL_NAME (heap_var) != heap_deleted_identifier)
+	  {
+	    if (!allow_non_constant && !non_constant_p)
+	      error_at (DECL_SOURCE_LOCATION (heap_var),
+			"%qE is not a constant expression because allocated "
+			"storage has not been deallocated", t);
+	    r = t;
+	    non_constant_p = true;
+	  }
+    }
+
   /* Technically we should check this for all subexpressions, but that
      runs into problems with our internal representation of pointer
      subtraction and the 5.19 rules are still in flux.  */
@@ -5618,6 +5903,8 @@ cxx_eval_outermost_constant_expr (tree t
 
   if (non_constant_p && !allow_non_constant)
     return error_mark_node;
+  else if (constexpr_dtor)
+    return r;
   else if (non_constant_p && TREE_CONSTANT (r))
     {
       /* If __builtin_is_constant_evaluated () was evaluated to true
@@ -5625,7 +5912,7 @@ cxx_eval_outermost_constant_expr (tree t
 	 punt.  */
       if (manifestly_const_eval)
 	return cxx_eval_outermost_constant_expr (t, true, strict,
-						 false, object);
+						 false, false, object);
       /* This isn't actually constant, so unset TREE_CONSTANT.
 	 Don't clear TREE_CONSTANT on ADDR_EXPR, as the middle-end requires
 	 it to be set if it is invariant address, even when it is not
@@ -5653,7 +5940,7 @@ cxx_eval_outermost_constant_expr (tree t
 	return t;
       else if (TREE_CODE (t) != CONSTRUCTOR)
 	{
-	  r = get_target_expr (r);
+	  r = get_target_expr_sfinae (r, tf_warning_or_error | tf_no_cleanup);
 	  TREE_CONSTANT (r) = true;
 	}
     }
@@ -5668,7 +5955,16 @@ cxx_eval_outermost_constant_expr (tree t
 tree
 cxx_constant_value (tree t, tree decl)
 {
-  return cxx_eval_outermost_constant_expr (t, false, true, true, decl);
+  return cxx_eval_outermost_constant_expr (t, false, true, true, false, decl);
+}
+
+/* Like cxx_constant_value, but used for evaluation of constexpr destructors
+   of constexpr variables.  The actual initializer of DECL is not modified.  */
+
+void
+cxx_constant_dtor (tree t, tree decl)
+{
+  cxx_eval_outermost_constant_expr (t, false, true, true, true, decl);
 }
 
 /* Helper routine for fold_simple function.  Either return simplified
@@ -5772,14 +6068,14 @@ maybe_constant_value (tree t, tree decl,
     return t;
 
   if (manifestly_const_eval)
-    return cxx_eval_outermost_constant_expr (t, true, true, true, decl);
+    return cxx_eval_outermost_constant_expr (t, true, true, true, false, decl);
 
   if (cv_cache == NULL)
     cv_cache = hash_map<tree, tree>::create_ggc (101);
   if (tree *cached = cv_cache->get (t))
     return *cached;
 
-  r = cxx_eval_outermost_constant_expr (t, true, true, false, decl);
+  r = cxx_eval_outermost_constant_expr (t, true, true, false, false, decl);
   gcc_checking_assert (r == t
 		       || CONVERT_EXPR_P (t)
 		       || TREE_CODE (t) == VIEW_CONVERT_EXPR
@@ -5841,7 +6137,7 @@ fold_non_dependent_expr_template (tree t
 
       tree r = cxx_eval_outermost_constant_expr (t, true, true,
 						 manifestly_const_eval,
-						 NULL_TREE);
+						 false, NULL_TREE);
       /* cp_tree_equal looks through NOPs, so allow them.  */
       gcc_checking_assert (r == t
 			   || CONVERT_EXPR_P (t)
@@ -5945,7 +6241,7 @@ maybe_constant_init_1 (tree t, tree decl
   else
     t = cxx_eval_outermost_constant_expr (t, allow_non_constant,
 					  /*strict*/false,
-					  manifestly_const_eval, decl);
+					  manifestly_const_eval, false, decl);
   if (TREE_CODE (t) == TARGET_EXPR)
     {
       tree init = TARGET_EXPR_INITIAL (t);
@@ -6239,7 +6535,12 @@ potential_constant_expression_1 (tree t,
 		if (!DECL_DECLARED_CONSTEXPR_P (fun)
 		    /* Allow any built-in function; if the expansion
 		       isn't constant, we'll deal with that then.  */
-		    && !fndecl_built_in_p (fun))
+		    && !fndecl_built_in_p (fun)
+		    /* In C++2a, replaceable global allocation functions
+		       are constant expressions.  */
+		    && (cxx_dialect < cxx2a
+			|| !IDENTIFIER_NEWDEL_OP_P (DECL_NAME (fun))
+			|| CP_DECL_CONTEXT (fun) != global_namespace))
 		  {
 		    if (flags & tf_error)
 		      {
@@ -6468,6 +6769,9 @@ potential_constant_expression_1 (tree t,
 	goto fail;
       if (!RECUR (TREE_OPERAND (t, 0), any))
 	return false;
+      /* Just ignore clobbers.  */
+      if (TREE_CLOBBER_P (TREE_OPERAND (t, 1)))
+	return true;
       if (!RECUR (TREE_OPERAND (t, 1), rval))
 	return false;
       return true;
@@ -6937,7 +7241,7 @@ potential_constant_expression_1 (tree t,
      return true;
 
     case COND_EXPR:
-      if (COND_EXPR_IS_VEC_DELETE (t))
+      if (COND_EXPR_IS_VEC_DELETE (t) && cxx_dialect < cxx2a)
 	{
 	  if (flags & tf_error)
 	    error_at (loc, "%<delete[]%> is not a constant expression");
@@ -6983,6 +7287,12 @@ potential_constant_expression_1 (tree t,
       return true;
 
     case CLEANUP_STMT:
+      if (!RECUR (CLEANUP_BODY (t), any))
+	return false;
+      if (!CLEANUP_EH_ONLY (t) && !RECUR (CLEANUP_EXPR (t), any))
+	return false;
+      return true;
+
     case EMPTY_CLASS_EXPR:
     case PREDICT_EXPR:
       return false;
--- gcc/cp/decl.c.jj	2019-09-26 21:34:21.673916726 +0200
+++ gcc/cp/decl.c	2019-09-27 18:25:40.898066032 +0200
@@ -4146,6 +4146,9 @@ initialize_predefined_identifiers (void)
     {"value", &value_identifier, cik_normal},
     {"_FUN", &fun_identifier, cik_normal},
     {"__closure", &closure_identifier, cik_normal},
+    {"heap uninit", &heap_uninit_identifier, cik_normal},
+    {"heap ", &heap_identifier, cik_normal},
+    {"heap deleted", &heap_deleted_identifier, cik_normal},
     {NULL, NULL, cik_normal}
   };
 
@@ -7430,7 +7433,11 @@ cp_finish_decl (tree decl, tree init, bo
 	    TREE_READONLY (decl) = 1;
 
 	  /* Likewise if it needs destruction.  */
-	  if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type))
+	  if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type)
+	      && (cxx_dialect < cxx2a
+		  || !DECL_DECLARED_CONSTEXPR_P (decl)
+		  || !type_has_constexpr_destructor
+						(strip_array_types (type))))
 	    TREE_READONLY (decl) = 0;
 	}
 
@@ -8319,6 +8326,27 @@ register_dtor_fn (tree decl)
   if (TYPE_HAS_TRIVIAL_DESTRUCTOR (type))
     return void_node;
 
+  if (cxx_dialect >= cxx2a
+      && DECL_DECLARED_CONSTEXPR_P (decl)
+      && DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (decl)
+      && type_has_constexpr_destructor (strip_array_types (type)))
+    {
+      int flags = LOOKUP_NORMAL|LOOKUP_NONVIRTUAL|LOOKUP_DESTRUCTOR;
+      tree addr, call;
+
+      if (TREE_CODE (type) == ARRAY_TYPE)
+	addr = decl;
+      else
+	addr = build_address (decl);
+
+      call = build_delete (TREE_TYPE (addr), addr,
+			   sfk_complete_destructor, flags, 0,
+			   tf_warning_or_error);
+      if (call != error_mark_node)
+	cxx_constant_dtor (call, decl);
+      return void_node;
+    }
+
   /* If we're using "__cxa_atexit" (or "__cxa_thread_atexit" or
      "__aeabi_atexit"), and DECL is a class object, we can just pass the
      destructor to "__cxa_atexit"; we don't have to build a temporary
@@ -8432,11 +8460,15 @@ register_dtor_fn (tree decl)
 static void
 expand_static_init (tree decl, tree init)
 {
+  tree type = TREE_TYPE (decl);
   gcc_assert (VAR_P (decl));
   gcc_assert (TREE_STATIC (decl));
 
   /* Some variables require no dynamic initialization.  */
-  if (TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (decl)))
+  if (TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (decl))
+      || (cxx_dialect >= cxx2a
+	  && DECL_DECLARED_CONSTEXPR_P (decl)
+	  && type_has_constexpr_destructor (strip_array_types (type))))
     {
       /* Make sure the destructor is callable.  */
       cxx_maybe_build_cleanup (decl, tf_warning_or_error);
@@ -12702,12 +12734,13 @@ grokdeclarator (const cp_declarator *dec
 			      "a destructor cannot be %<concept%>");
                     return error_mark_node;
                   }
-                if (constexpr_p)
-                  {
-                    error_at (declspecs->locations[ds_constexpr],
-			      "a destructor cannot be %<constexpr%>");
-                    return error_mark_node;
-                  }
+		if (constexpr_p && cxx_dialect < cxx2a)
+		  {
+		    error_at (declspecs->locations[ds_constexpr],
+			      "%<constexpr%> destructors only available"
+			      " with %<-std=c++2a%> or %<-std=gnu++2a%>");
+		    return error_mark_node;
+		  }
 	      }
 	    else if (sfk == sfk_constructor && friendp && !ctype)
 	      {
@@ -12744,10 +12777,11 @@ grokdeclarator (const cp_declarator *dec
 	      }
 
 	    /* Tell grokfndecl if it needs to set TREE_PUBLIC on the node.  */
-	    function_context = (ctype != NULL_TREE) ?
-	      decl_function_context (TYPE_MAIN_DECL (ctype)) : NULL_TREE;
-	    publicp = (! friendp || ! staticp)
-	      && function_context == NULL_TREE;
+	    function_context
+	      = (ctype != NULL_TREE
+		 ? decl_function_context (TYPE_MAIN_DECL (ctype)) : NULL_TREE);
+	    publicp = ((! friendp || ! staticp)
+		       && function_context == NULL_TREE);
 
 	    decl = grokfndecl (ctype, type,
 			       TREE_CODE (unqualified_id) != TEMPLATE_ID_EXPR
@@ -16752,6 +16786,12 @@ cxx_maybe_build_cleanup (tree decl, tsub
 	cleanup = error_mark_node;
       else if (TYPE_HAS_TRIVIAL_DESTRUCTOR (type))
 	/* Discard the call.  */;
+      else if (cxx_dialect >= cxx2a
+	       && VAR_P (decl)
+	       && DECL_DECLARED_CONSTEXPR_P (decl)
+	       && DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (decl)
+	       && type_has_constexpr_destructor (strip_array_types (type)))
+	cxx_constant_dtor (call, decl);
       else if (cleanup)
 	cleanup = cp_build_compound_expr (cleanup, call, complain);
       else
--- gcc/cp/init.c.jj	2019-09-26 21:34:21.598917851 +0200
+++ gcc/cp/init.c	2019-09-27 19:15:56.473042238 +0200
@@ -33,6 +33,7 @@ along with GCC; see the file COPYING3.
 #include "stringpool.h"
 #include "attribs.h"
 #include "asan.h"
+#include "stor-layout.h"
 
 static bool begin_init_stmts (tree *, tree *);
 static tree finish_init_stmts (bool, tree, tree);
@@ -3332,6 +3333,48 @@ build_new_1 (vec<tree, va_gc> **placemen
 	}
     }
 
+  tree alloc_call_call = extract_call_expr (alloc_call);
+  tree alloc_call_fndecl = NULL_TREE;
+  if (alloc_call_call != error_mark_node)
+    alloc_call_fndecl = cp_get_callee_fndecl_nofold (alloc_call_call);
+  if (array_p
+      && cxx_dialect >= cxx2a
+      && (current_function_decl == NULL_TREE
+	  || DECL_DECLARED_CONSTEXPR_P (current_function_decl))
+      && alloc_call_fndecl
+      && IDENTIFIER_NEW_OP_P (DECL_NAME (alloc_call_fndecl))
+      && CP_DECL_CONTEXT (alloc_call_fndecl) == global_namespace)
+    {
+      /* Help the constexpr code to find the right type for the heap variable
+	 by adding a NOP_EXPR around alloc_call.
+	 If not using cookies, use array type, otherwise structure with
+	 two array types.  */
+      tree atype = build_cplus_array_type (elt_type, NULL_TREE);
+      if (cookie_size)
+	{
+	  gcc_assert (tree_fits_uhwi_p (cookie_size));
+	  unsigned HOST_WIDE_INT sz = tree_to_uhwi (cookie_size);
+	  sz /= int_size_in_bytes (sizetype);
+	  tree atype2 = build_index_type (size_int (sz - 1));
+	  atype2 = build_cplus_array_type (sizetype, atype2);
+	  tree atype3 = cxx_make_type (RECORD_TYPE);
+	  tree fld1 = build_decl (input_location, FIELD_DECL, NULL_TREE,
+				  atype2);
+	  tree fld2 = build_decl (input_location, FIELD_DECL, NULL_TREE,
+				  atype);
+	  DECL_FIELD_CONTEXT (fld1) = atype3;
+	  DECL_FIELD_CONTEXT (fld2) = atype3;
+	  DECL_ARTIFICIAL (fld1) = true;
+	  DECL_ARTIFICIAL (fld2) = true;
+	  TYPE_FIELDS (atype3) = fld1;
+	  DECL_CHAIN (fld1) = fld2;
+	  layout_type (atype3);
+	  atype = atype3;
+	}
+      pointer_type = build_pointer_type (atype);
+      alloc_call = build_nop (pointer_type, alloc_call);
+    }
+
   /* In the simple case, we can stop now.  */
   pointer_type = build_pointer_type (type);
   if (!cookie_size && !is_initialized)
@@ -3905,17 +3948,11 @@ build_vec_delete_1 (tree base, tree maxi
 			     fold_convert (sizetype, maxindex));
 
   tbase = create_temporary_var (ptype);
-  tbase_init
-    = cp_build_modify_expr (input_location, tbase, NOP_EXPR,
-			    fold_build_pointer_plus_loc (input_location,
-							 fold_convert (ptype,
-								       base),
-							 virtual_size),
-			    complain);
-  if (tbase_init == error_mark_node)
-    return error_mark_node;
-  controller = build3 (BIND_EXPR, void_type_node, tbase,
-		       NULL_TREE, NULL_TREE);
+  DECL_INITIAL (tbase)
+    = fold_build_pointer_plus_loc (input_location, fold_convert (ptype, base),
+				   virtual_size);
+  tbase_init = build_stmt (input_location, DECL_EXPR, tbase);
+  controller = build3 (BIND_EXPR, void_type_node, tbase, NULL_TREE, NULL_TREE);
   TREE_SIDE_EFFECTS (controller) = 1;
 
   body = build1 (EXIT_EXPR, void_type_node,
--- gcc/cp/method.c.jj	2019-09-26 21:34:21.331921851 +0200
+++ gcc/cp/method.c	2019-09-27 18:25:40.902065972 +0200
@@ -30,6 +30,7 @@ along with GCC; see the file COPYING3.
 #include "cgraph.h"
 #include "varasm.h"
 #include "toplev.h"
+#include "intl.h"
 #include "common/common-target.h"
 
 static void do_build_copy_assign (tree);
@@ -1237,12 +1238,24 @@ is_xible (enum tree_code code, tree to,
   return !!expr;
 }
 
+/* Categorize various special_function_kinds.  */
+#define SFK_CTOR_P(sfk) \
+  ((sfk) >= sfk_constructor && (sfk) <= sfk_move_constructor)
+#define SFK_DTOR_P(sfk) \
+  ((sfk) == sfk_destructor || (sfk) == sfk_virtual_destructor)
+#define SFK_ASSIGN_P(sfk) \
+  ((sfk) == sfk_copy_assignment || (sfk) == sfk_move_assignment)
+#define SFK_COPY_P(sfk) \
+  ((sfk) == sfk_copy_constructor || (sfk) == sfk_copy_assignment)
+#define SFK_MOVE_P(sfk) \
+  ((sfk) == sfk_move_constructor || (sfk) == sfk_move_assignment)
+
 /* Subroutine of synthesized_method_walk.  Update SPEC_P, TRIVIAL_P and
    DELETED_P or give an error message MSG with argument ARG.  */
 
 static void
-process_subob_fn (tree fn, tree *spec_p, bool *trivial_p,
-		  bool *deleted_p, bool *constexpr_p,
+process_subob_fn (tree fn, special_function_kind sfk, tree *spec_p,
+		  bool *trivial_p, bool *deleted_p, bool *constexpr_p,
 		  bool diag, tree arg, bool dtor_from_ctor = false)
 {
   if (!fn || fn == error_mark_node)
@@ -1283,24 +1296,15 @@ process_subob_fn (tree fn, tree *spec_p,
       if (diag)
 	{
 	  inform (DECL_SOURCE_LOCATION (fn),
-		  "defaulted constructor calls non-%<constexpr%> %qD", fn);
+		  SFK_DTOR_P (sfk)
+		  ? G_("destructor calls non-%<constexpr%> %qD")
+		  : G_("defaulted constructor calls non-%<constexpr%> %qD"),
+		  fn);
 	  explain_invalid_constexpr_fn (fn);
 	}
     }
 }
 
-/* Categorize various special_function_kinds.  */
-#define SFK_CTOR_P(sfk) \
-  ((sfk) >= sfk_constructor && (sfk) <= sfk_move_constructor)
-#define SFK_DTOR_P(sfk) \
-  ((sfk) == sfk_destructor || (sfk) == sfk_virtual_destructor)
-#define SFK_ASSIGN_P(sfk) \
-  ((sfk) == sfk_copy_assignment || (sfk) == sfk_move_assignment)
-#define SFK_COPY_P(sfk) \
-  ((sfk) == sfk_copy_constructor || (sfk) == sfk_copy_assignment)
-#define SFK_MOVE_P(sfk) \
-  ((sfk) == sfk_move_constructor || (sfk) == sfk_move_assignment)
-
 /* Subroutine of synthesized_method_walk to allow recursion into anonymous
    aggregates.  If DTOR_FROM_CTOR is true, we're walking subobject destructors
    called from a synthesized constructor, in which case we don't consider
@@ -1318,8 +1322,7 @@ walk_field_subobs (tree fields, special_
     {
       tree mem_type, argtype, rval;
 
-      if (TREE_CODE (field) != FIELD_DECL
-	  || DECL_ARTIFICIAL (field))
+      if (TREE_CODE (field) != FIELD_DECL || DECL_ARTIFICIAL (field))
 	continue;
 
       /* Variant members only affect deletedness.  In particular, they don't
@@ -1457,7 +1460,7 @@ walk_field_subobs (tree fields, special_
 
       rval = locate_fn_flags (mem_type, fnname, argtype, flags, complain);
 
-      process_subob_fn (rval, spec_p, trivial_p, deleted_p,
+      process_subob_fn (rval, sfk, spec_p, trivial_p, deleted_p,
 			constexpr_p, diag, field, dtor_from_ctor);
     }
 }
@@ -1510,23 +1513,23 @@ synthesized_method_base_walk (tree binfo
       && DECL_CONTEXT (*inheriting_ctor) == DECL_CONTEXT (rval))
     *inheriting_ctor = DECL_CLONED_FUNCTION (rval);
 
-  process_subob_fn (rval, spec_p, trivial_p, deleted_p,
+  process_subob_fn (rval, sfk, spec_p, trivial_p, deleted_p,
 		    constexpr_p, diag, BINFO_TYPE (base_binfo));
-  if (SFK_CTOR_P (sfk) &&
-      (!BINFO_VIRTUAL_P (base_binfo)
-       || TYPE_HAS_NONTRIVIAL_DESTRUCTOR (BINFO_TYPE (base_binfo))))
+  if (SFK_CTOR_P (sfk)
+      && (!BINFO_VIRTUAL_P (base_binfo)
+	  || TYPE_HAS_NONTRIVIAL_DESTRUCTOR (BINFO_TYPE (base_binfo))))
     {
       /* In a constructor we also need to check the subobject
 	 destructors for cleanup of partially constructed objects.  */
       tree dtor = locate_fn_flags (base_binfo, complete_dtor_identifier,
 				   NULL_TREE, flags,
 				   diag ? tf_warning_or_error : tf_none);
-	  /* Note that we don't pass down trivial_p; the subobject
-	     destructors don't affect triviality of the constructor.  Nor
-	     do they affect constexpr-ness (a constant expression doesn't
-	     throw) or exception-specification (a throw from one of the
-	     dtors would be a double-fault).  */
-      process_subob_fn (dtor, NULL, NULL, deleted_p, NULL, false,
+      /* Note that we don't pass down trivial_p; the subobject
+	 destructors don't affect triviality of the constructor.  Nor
+	 do they affect constexpr-ness (a constant expression doesn't
+	 throw) or exception-specification (a throw from one of the
+	 dtors would be a double-fault).  */
+      process_subob_fn (dtor, sfk, NULL, NULL, deleted_p, NULL, false,
 			BINFO_TYPE (base_binfo), /*dtor_from_ctor*/true);
     }
 
@@ -1608,7 +1611,8 @@ synthesized_method_walk (tree ctype, spe
 	member is a constexpr function.  */
   if (constexpr_p)
     *constexpr_p = (SFK_CTOR_P (sfk)
-		    || (SFK_ASSIGN_P (sfk) && cxx_dialect >= cxx14));
+		    || (SFK_ASSIGN_P (sfk) && cxx_dialect >= cxx14)
+		    || (SFK_DTOR_P (sfk) && cxx_dialect >= cxx2a));
 
   bool expected_trivial = type_has_trivial_fn (ctype, sfk);
   if (trivial_p)
@@ -1704,8 +1708,8 @@ synthesized_method_walk (tree ctype, spe
   else if (vec_safe_is_empty (vbases))
     /* No virtual bases to worry about.  */;
   else if (ABSTRACT_CLASS_TYPE_P (ctype) && cxx_dialect >= cxx14
-	   /* DR 1658 specifis that vbases of abstract classes are
-	      ignored for both ctors and dtors.  Except DR 2338
+	   /* DR 1658 specifies that vbases of abstract classes are
+	      ignored for both ctors and dtors.  Except DR 2336
 	      overrides that skipping when determing the eh-spec of a
 	      virtual destructor.  */
 	   && sfk != sfk_virtual_destructor)
@@ -2046,7 +2050,8 @@ implicitly_declare_fn (special_function_
     constexpr_p = false;
   /* A trivial copy/move constructor is also a constexpr constructor,
      unless the class has virtual bases (7.1.5p4).  */
-  else if (trivial_p && cxx_dialect >= cxx11
+  else if (trivial_p
+	   && cxx_dialect >= cxx11
 	   && (kind == sfk_copy_constructor
 	       || kind == sfk_move_constructor)
 	   && !CLASSTYPE_VBASECLASSES (type))
--- gcc/cp/typeck2.c.jj	2019-09-26 21:34:26.299847376 +0200
+++ gcc/cp/typeck2.c	2019-09-27 18:25:40.899066017 +0200
@@ -902,7 +902,13 @@ store_init_value (tree decl, tree init,
 	    value = oldval;
 	}
     }
-  value = cp_fully_fold_init (value);
+  /* Don't fold initializers of automatic variables in constexpr functions,
+     that might fold away something that needs to be diagnosed at constexpr
+     evaluation time.  */
+  if (!current_function_decl
+      || !DECL_DECLARED_CONSTEXPR_P (current_function_decl)
+      || TREE_STATIC (decl))
+    value = cp_fully_fold_init (value);
 
   /* Handle aggregate NSDMI in non-constant initializers, too.  */
   value = replace_placeholders (value, decl);
--- gcc/testsuite/g++.dg/cpp0x/constexpr-delete2.C.jj	2016-03-05 07:46:49.554128302 +0100
+++ gcc/testsuite/g++.dg/cpp0x/constexpr-delete2.C	2019-09-27 20:26:06.317971681 +0200
@@ -5,8 +5,9 @@ struct A { ~A(); };
 constexpr int f(int i) { return i; }
 constexpr int g(A* ap)
 {
-  return f((delete[] ap, 42)); // { dg-message "" }
+  return f((delete[] ap, 42)); // { dg-message "" "" { target c++17_down } }
 }
 
 A a;
 constexpr int i = g(&a);	// { dg-error "" }
+				// { dg-message "in 'constexpr' expansion of" "" { target c++2a } .-1 }
--- gcc/testsuite/g++.dg/cpp0x/locations1.C.jj	2019-09-26 21:34:22.205908750 +0200
+++ gcc/testsuite/g++.dg/cpp0x/locations1.C	2019-09-27 18:25:41.346059343 +0200
@@ -11,7 +11,7 @@ struct S
 {
   virtual S();  // { dg-error "3:constructors cannot be declared .virtual." }
   constexpr int s = 1;  // { dg-error "3:non-static data member .s. declared .constexpr." }
-  constexpr ~S();  // { dg-error "3:a destructor cannot be .constexpr." }
+  constexpr ~S();  // { dg-error "3:'constexpr' destructors only available with" "" { target c++17_down } }
 };
 
 typedef constexpr int my_int;  // { dg-error "9:.constexpr. cannot appear in a typedef declaration" }
--- gcc/testsuite/g++.dg/cpp1y/constexpr-new.C.jj	2019-09-26 21:34:22.281907610 +0200
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-new.C	2019-09-27 18:25:41.303059984 +0200
@@ -4,7 +4,7 @@ constexpr int *f4(bool b) {
   if (b) {
     return nullptr;
   } else {
-    return new int{42}; // { dg-error "call to non-.constexpr." }
+    return new int{42}; // { dg-error "call to non-.constexpr." "" { target c++17_down } }
   }
 }
 static_assert(f4(true) == nullptr, "");
--- gcc/testsuite/g++.dg/cpp2a/constexpr-dtor1.C.jj	2019-09-27 18:25:41.320059731 +0200
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-dtor1.C	2019-09-27 18:25:41.320059731 +0200
@@ -0,0 +1,9 @@
+// P0784R7
+// { dg-do compile { target c++11 } }
+
+struct S
+{
+  constexpr S () : s (0) {}
+  constexpr ~S () {}	// { dg-error "'constexpr' destructors only available with" "" { target c++17_down } }
+  int s;
+};
--- gcc/testsuite/g++.dg/cpp2a/constexpr-dtor2.C.jj	2019-09-27 18:25:41.303059984 +0200
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-dtor2.C	2019-09-27 18:25:41.303059984 +0200
@@ -0,0 +1,66 @@
+// P0784R7
+// { dg-do compile { target c++2a } }
+
+struct S
+{
+  constexpr S () : r (4), s (3) { --r; s -= 2; }
+  constexpr ~S () { if (s == 1) s = 0; else asm (""); if (s == 0 && r == 3) r = 0; else asm (""); }
+  int r, s;
+};
+struct T : public S
+{
+  constexpr T () : t (2) {}
+  int t;
+  S u;
+};
+struct U : public S
+{
+  constexpr U (int x) : u (x) {}
+  constexpr ~U () = default;
+  int u;
+  S v;
+};
+
+constexpr S a;
+constexpr T b;
+constexpr U c = 3;
+static_assert (a.s == 1 && a.r == 3);
+static_assert (b.s == 1 && b.r == 3 && b.t == 2 && b.u.s == 1 && b.u.r == 3);
+static_assert (c.s == 1 && c.r == 3 && c.u == 3 && c.v.s == 1 && c.v.r == 3);
+
+void
+foo ()
+{
+  static constexpr S d;
+  static constexpr T e;
+  static constexpr U f = 4;
+  static_assert (d.s == 1 && d.r == 3);
+  static_assert (e.s == 1 && e.r == 3 && e.t == 2 && e.u.s == 1 && e.u.r == 3);
+  static_assert (f.s == 1 && f.r == 3 && f.u == 4 && f.v.s == 1 && f.v.r == 3);
+  if (1)
+    {
+      constexpr S g;
+      constexpr T h;
+      constexpr U i = 5;
+      static_assert (g.s == 1 && g.r == 3);
+      static_assert (h.s == 1 && h.r == 3 && h.t == 2 && h.u.s == 1 && h.u.r == 3);
+      static_assert (i.s == 1 && i.r == 3 && i.u == 5 && i.v.s == 1 && i.v.r == 3);
+    }
+}
+
+constexpr bool
+bar ()
+{
+  S j;
+  T k;
+  U l = 6;
+  if (j.s != 1 || j.r != 3)
+    return false;
+  if (k.s != 1 || k.r != 3 || k.t != 2 || k.u.s != 1 || k.u.r != 3)
+    return false;
+  if (l.s != 1 || l.r != 3 || l.u != 6 || l.v.s != 1 || l.v.r != 3)
+    return false;
+  return true;
+}
+
+static_assert (bar ());
--- gcc/testsuite/g++.dg/cpp2a/constexpr-dtor3.C.jj	2019-09-27 18:25:41.303059984 +0200
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-dtor3.C	2019-09-27 18:25:41.303059984 +0200
@@ -0,0 +1,185 @@
+// P0784R7
+// { dg-do compile { target c++2a } }
+
+struct S
+{
+  constexpr S () : s (0) {}
+  constexpr ~S () {}
+  int s;
+};
+struct T	// { dg-message "'T' is not literal because" }
+{		// { dg-message "'T' does not have 'constexpr' destructor" "" { target *-*-* } .-1 }
+  constexpr T () : t (0) {}
+  ~T () {}	// { dg-message "destructor calls non-'constexpr' 'T::~T\\(\\)'" }
+  int t;
+};
+struct U : public S
+{
+  constexpr U () : u (0) {}
+  constexpr ~U () = default;	// { dg-error "explicitly defaulted function 'constexpr U::~U\\(\\)' cannot be declared 'constexpr' because the implicit declaration is not 'constexpr'" }
+  int u;
+  T t;
+};
+struct V : virtual public S
+{
+  V () : v (0) {}
+  constexpr ~V () = default;	// { dg-error "explicitly defaulted function 'constexpr V::~V\\(\\)' cannot be declared 'constexpr' because the implicit declaration is not 'constexpr'" }
+  int v;
+};
+struct W0
+{
+  constexpr W0 () : w (0) {}
+  constexpr W0 (int x) : w (x) {}
+  constexpr ~W0 () { if (w == 5) asm (""); w = 3; }
+  int w;
+};
+struct W1
+{
+  constexpr W1 () : w (0) {}
+  constexpr W1 (int x) : w (x) {}
+  constexpr ~W1 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct W2
+{
+  constexpr W2 () : w (0) {}
+  constexpr W2 (int x) : w (x) {}
+  constexpr ~W2 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct W3
+{
+  constexpr W3 () : w (0) {}
+  constexpr W3 (int x) : w (x) {}
+  constexpr ~W3 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct W4
+{
+  constexpr W4 () : w (0) {}
+  constexpr W4 (int x) : w (x) {}
+  constexpr ~W4 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct W5
+{
+  constexpr W5 () : w (0) {}
+  constexpr W5 (int x) : w (x) {}
+  constexpr ~W5 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct W6
+{
+  constexpr W6 () : w (0) {}
+  constexpr W6 (int x) : w (x) {}
+  constexpr ~W6 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct W7
+{
+  constexpr W7 () : w (0) {}
+  constexpr W7 (int x) : w (x) {}
+  constexpr ~W7 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct W8
+{
+  constexpr W8 () : w (0) {}
+  constexpr W8 (int x) : w (x) {}
+  constexpr ~W8 () { if (w == 5) asm (""); w = 3; }	// { dg-error "inline assembly is not a constant expression" }
+							// { dg-message "only unevaluated inline assembly is allowed in a 'constexpr' function" "" { target *-*-* } .-1 }
+  int w;
+};
+struct X : public T
+{
+  constexpr X () : x (0) {}
+  constexpr ~X () = default;	// { dg-error "explicitly defaulted function 'constexpr X::~X\\(\\)' cannot be declared 'constexpr' because the implicit declaration is not 'constexpr'" }
+  int x;
+};
+constexpr S s;
+constexpr T t;	// { dg-error "the type 'const T' of 'constexpr' variable 't' is not literal" }
+constexpr W0 w1;
+constexpr W0 w2 = 12;
+constexpr W1 w3 = 5;	// { dg-message "in 'constexpr' expansion of" }
+constexpr W0 w4[3] = { 1, 2, 3 };
+constexpr W2 w5[3] = { 4, 5, 6 };	// { dg-message "in 'constexpr' expansion of" }
+
+void
+f1 ()
+{
+  constexpr S s2;
+  constexpr W0 w6;
+  constexpr W0 w7 = 12;
+  constexpr W3 w8 = 5;	// { dg-message "in 'constexpr' expansion of" }
+  constexpr W0 w9[3] = { 1, 2, 3 };
+  constexpr W4 w10[3] = { 4, 5, 6 };	// { dg-message "in 'constexpr' expansion of" }
+}
+
+constexpr int
+f2 ()
+{
+  constexpr S s3;
+  constexpr W0 w11;
+  constexpr W0 w12 = 12;
+  constexpr W5 w13 = 5;	// { dg-message "in 'constexpr' expansion of" }
+  constexpr W0 w14[3] = { 1, 2, 3 };
+  constexpr W6 w15[3] = { 4, 5, 6 };	// { dg-message "in 'constexpr' expansion of" }
+  return 0;
+}
+
+constexpr int
+f3 ()
+{
+  S s3;
+  W0 w11;
+  W0 w12 = 12;
+  W0 w14[3] = { 1, 2, 3 };
+  return 0;
+}
+
+constexpr int x3 = f3 ();
+
+constexpr int
+f4 ()
+{
+  W7 w13 = 5;
+  return 0;
+}
+
+constexpr int x4 = f4 ();	// { dg-message "in 'constexpr' expansion of" }
+
+constexpr int
+f5 ()
+{
+  W8 w15[3] = { 4, 5, 6 };	// { dg-message "in 'constexpr' expansion of" }
+  return 0;
+}
+
+constexpr int x5 = f5 ();	// { dg-message "in 'constexpr' expansion of" }
+
+void
+f6 ()
+{
+  constexpr T t2;	// { dg-error "the type 'const T' of 'constexpr' variable 't2' is not literal" }
+}
+
+constexpr int
+f7 ()
+{
+  constexpr T t3;	// { dg-error "the type 'const T' of 'constexpr' variable 't3' is not literal" }
+  return 0;
+}
+
+constexpr int
+f8 ()
+{
+  T t4;			// { dg-error "variable 't4' of non-literal type 'T' in 'constexpr' function" }
+  return 0;
+}
--- gcc/testsuite/g++.dg/cpp2a/constexpr-new1.C.jj	2019-09-27 18:25:41.320059731 +0200
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-new1.C	2019-09-27 20:06:50.047298452 +0200
@@ -0,0 +1,39 @@
+// P0784R7
+// { dg-do compile { target c++2a } }
+
+struct S { constexpr S () : s (5) {} constexpr S (int x) : s (x) {} int s; };
+
+constexpr bool
+foo ()
+{
+  int r = 0;
+  S *p = new S ();
+  p->s += 3;
+  r += p->s;
+  delete p;
+  p = new S (12);
+  p->s = p->s * 2;
+  r += p->s;
+  delete p;
+  int *q = new int;
+  *q = 25;
+  r += *q;
+  delete q;
+  q = new int (1);
+  r += *q;
+  if (!q)
+    return false;
+  delete q;
+  q = new int[5]{1,2,3,4,5};
+  r += q[0] + q[4];
+  delete[] q;
+  q = new int[4];
+  q[0] = 6;
+  q[1] = 7;
+  q[3] = 8;
+  r += q[0] + q[1] + q[3];
+  delete[] q;
+  return r == 5 + 3 + 2 * 12 + 25 + 1 + 1 + 5 + 6 + 7 + 8;
+}
+constexpr bool a = foo ();
+static_assert (a);
--- gcc/testsuite/g++.dg/cpp2a/constexpr-new2.C.jj	2019-09-27 18:25:41.320059731 +0200
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-new2.C	2019-09-27 20:23:16.107524585 +0200
@@ -0,0 +1,21 @@
+// P0784R7
+// { dg-do compile { target c++2a } }
+
+template <int N>
+constexpr bool
+foo (const char (&x)[N])
+{
+  int **p = new int *[N];
+  for (int i = 0; i < N; i++)
+    p[i] = new int (x[i]);
+  for (int i = 0; i < N; i++)
+    if (*p[i] != x[i])
+      return false;
+  for (int i = 0; i < N; ++i)
+    delete p[i];
+  delete[] p;
+  return true;
+}
+
+constexpr bool a = foo ("foobar");
+static_assert (a);
--- gcc/testsuite/g++.dg/cpp2a/constexpr-new3.C.jj	2019-09-27 18:25:41.320059731 +0200
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-new3.C	2019-09-27 18:25:41.320059731 +0200
@@ -0,0 +1,63 @@
+// P0784R7
+// { dg-do compile { target c++2a } }
+
+constexpr int *
+f1 ()
+{
+  return new int (2);		// { dg-error "is not a constant expression because it refers to a result of 'operator new'" }
+}
+
+constexpr auto v1 = f1 ();
+
+constexpr bool
+f2 ()
+{
+  int *p = new int (3);		// { dg-error "is not a constant expression because allocated storage has not been deallocated" }
+  return false;
+}
+
+constexpr auto v2 = f2 ();
+
+constexpr bool
+f3 ()
+{
+  int *p = new int (3);
+  int *q = p;
+  delete p;
+  delete q;			// { dg-error "deallocation of already deallocated storage" }
+  return false;
+}
+
+constexpr auto v3 = f3 ();	// { dg-message "in 'constexpr' expansion of" }
+
+constexpr bool
+f4 (int *p)
+{
+  delete p;			// { dg-error "call to non-'constexpr' function" }
+  return false;
+}
+
+int q;
+constexpr auto v4 = f4 (&q);	// { dg-message "in 'constexpr' expansion of" }
+
+constexpr bool
+f5 ()
+{
+  int *p = new int;		// { dg-message "allocated here" }
+  return *p == 1;
+}
+
+constexpr auto v5 = f5 ();	// { dg-error "the content of uninitialized storage is not usable in a constant expression" }
+				// { dg-message "in 'constexpr' expansion of" "" { target *-*-* } .-1 }
+
+constexpr bool
+f6 ()
+{
+  int *p = new int (2);		// { dg-message "allocated here" }
+  int *q = p;
+  delete p;
+  return *q == 2;
+}
+
+constexpr auto v6 = f6 ();	// { dg-error "use of allocated storage after deallocation in a constant expression" }
+				// { dg-message "in 'constexpr' expansion of" "" { target *-*-* } .-1  }
--- gcc/testsuite/g++.dg/cpp2a/constexpr-new4.C.jj	2019-09-27 18:25:41.319059745 +0200
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-new4.C	2019-09-27 20:07:33.928641928 +0200
@@ -0,0 +1,29 @@
+// P0784R7
+// { dg-do compile { target c++2a } }
+
+struct S
+{
+  constexpr S () : s (0) { s++; }
+  constexpr S (int x) : s (x) { s += 2; }
+  constexpr ~S () { if (s != 35) asm (""); s = 5; }
+  int s;
+};
+
+constexpr bool
+foo ()
+{
+  S *p = new S (7);
+  if (p->s != 9) return false;
+  p->s = 35;
+  delete p;
+  p = new S[3] { 11, 13, 15 };
+  if (p[0].s != 13 || p[1].s != 15 || p[2].s != 17) return false;
+  p[0].s = 35;
+  p[2].s = 35;
+  p[1].s = 35;
+  delete[] p;
+  return true;
+}
+
+constexpr bool a = foo ();
+static_assert (a);
--- gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C.jj	2019-09-26 21:34:22.341906710 +0200
+++ gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C	2019-09-27 18:25:41.319059745 +0200
@@ -430,16 +430,34 @@
 
 // C++20 features
 
-#if __cpp_conditional_explicit != 201806
-# error "__cpp_conditional_explicit != 201806"
+#ifndef __cpp_conditional_explicit
+#  error "__cpp_conditional_explicit"
+#elif __cpp_conditional_explicit != 201806
+#  error "__cpp_conditional_explicit != 201806"
 #endif
 
-#if __cpp_nontype_template_parameter_class != 201806
-# error "__cpp_nontype_template_parameter_class != 201806"
+#ifndef __cpp_nontype_template_parameter_class
+#  error "__cpp_nontype_template_parameter_class"
+#elif __cpp_nontype_template_parameter_class != 201806
+#  error "__cpp_nontype_template_parameter_class != 201806"
 #endif
 
-#if __cpp_impl_destroying_delete != 201806
-# error "__cpp_impl_destroying_delete != 201806"
+#ifndef __cpp_impl_destroying_delete
+#  error "__cpp_impl_destroying_delete"
+#elif __cpp_impl_destroying_delete != 201806
+#  error "__cpp_impl_destroying_delete != 201806"
+#endif
+
+#ifndef __cpp_constinit
+#  error "__cpp_constinit"
+#elif __cpp_constinit != 201907
+#  error "__cpp_constinit != 201907"
+#endif
+
+#ifndef __cpp_constexpr_dynamic_alloc
+#  error "__cpp_constexpr_dynamic_alloc"
+#elif __cpp_constexpr_dynamic_alloc != 201907
+#  error "__cpp_constexpr_dynamic_alloc != 201907"
 #endif
 
 #ifdef __has_cpp_attribute
@@ -484,8 +502,6 @@
 #  error "__has_cpp_attribute"
 #endif
 
-// C++2A features:
-
 #ifndef __cpp_char8_t
 #  error "__cpp_char8_t"
 #elif __cpp_char8_t != 201811
--- gcc/testsuite/g++.dg/ext/is_literal_type3.C.jj	2019-09-27 18:25:40.904065942 +0200
+++ gcc/testsuite/g++.dg/ext/is_literal_type3.C	2019-09-27 18:25:40.904065942 +0200
@@ -0,0 +1,26 @@
+// { dg-do compile { target c++11 } }
+
+struct S {
+  constexpr S () : n{} { }
+  ~S () { n = 1; }
+  int n;
+};
+
+static_assert(!__is_literal_type(S), "");
+
+#ifdef __cpp_constexpr_dynamic_alloc
+struct T {
+  constexpr T () : n{} { }
+  constexpr ~T () { n = 1; }
+  int n;
+};
+
+static_assert(__is_literal_type(T), "");
+
+struct U : public T {
+  constexpr U () : u{} { }
+  int u;
+};
+
+static_assert(__is_literal_type(U), "");
+#endif

	Jakub


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