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Fix cast to rvalue reference from prvalue.

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* cvt.c (diagnose_ref_binding): Handle rvalue reference.
	* rtti.c (build_dynamic_cast_1): Don't try to build a reference to
	non-class type.  Handle xvalue argument.
	* typeck.c (build_reinterpret_cast_1): Allow cast from prvalue to
	rvalue reference.
	* semantics.c (finish_compound_literal): Do direct-initialization,
	not cast, to initialize a reference.

From-SVN: r260622
This commit is contained in:
Jason Merrill 2018-05-23 13:21:39 -04:00 • committed by Jason Merrill
parent 955da5e544
commit a347241b93
6 changed files with 39 additions and 9 deletions
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9
gcc/cp/ChangeLog
View file

@ -1,5 +1,14 @@
2018-05-23 Jason Merrill <jason@redhat.com>
Fix cast to rvalue reference from prvalue.
* cvt.c (diagnose_ref_binding): Handle rvalue reference.
* rtti.c (build_dynamic_cast_1): Don't try to build a reference to
non-class type. Handle xvalue argument.
* typeck.c (build_reinterpret_cast_1): Allow cast from prvalue to
rvalue reference.
* semantics.c (finish_compound_literal): Do direct-initialization,
not cast, to initialize a reference.
CWG 616, 1213 - value category of subobject references.
* tree.c (lvalue_kind): A reference to a subobject of a prvalue is
an xvalue.

3
gcc/cp/cvt.c
View file

@ -381,7 +381,8 @@ diagnose_ref_binding (location_t loc, tree reftype, tree intype, tree decl)
{
tree ttl = TREE_TYPE (reftype);
if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
if (!TYPE_REF_IS_RVALUE (reftype)
&& !CP_TYPE_CONST_NON_VOLATILE_P (ttl))
{
const char *msg;

10
gcc/cp/rtti.c
View file

@ -616,22 +616,22 @@ build_dynamic_cast_1 (tree type, tree expr, tsubst_flags_t complain)
else
{
expr = mark_lvalue_use (expr);
exprtype = build_reference_type (TREE_TYPE (expr));
exprtype = TREE_TYPE (expr);
/* T is a reference type, v shall be an lvalue of a complete class
type, and the result is an lvalue of the type referred to by T. */
if (! MAYBE_CLASS_TYPE_P (TREE_TYPE (exprtype)))
if (! MAYBE_CLASS_TYPE_P (exprtype))
{
errstr = _("source is not of class type");
goto fail;
}
if (!COMPLETE_TYPE_P (complete_type (TREE_TYPE (exprtype))))
if (!COMPLETE_TYPE_P (complete_type (exprtype)))
{
errstr = _("source is of incomplete class type");
goto fail;
}
exprtype = cp_build_reference_type (exprtype, !lvalue_p (expr));
}
/* The dynamic_cast operator shall not cast away constness. */

5
gcc/cp/semantics.c
View file

@ -2734,7 +2734,10 @@ finish_compound_literal (tree type, tree compound_literal,
compound_literal
= finish_compound_literal (TREE_TYPE (type), compound_literal,
complain, fcl_context);
return cp_build_c_cast (type, compound_literal, complain);
/* The prvalue is then used to direct-initialize the reference. */
tree r = (perform_implicit_conversion_flags
(type, compound_literal, complain, LOOKUP_NORMAL));
return convert_from_reference (r);
}
if (!TYPE_OBJ_P (type))

10
gcc/cp/typeck.c
View file

@ -7315,13 +7315,19 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
type = cv_unqualified (type);
/* [expr.reinterpret.cast]
An lvalue expression of type T1 can be cast to the type
A glvalue expression of type T1 can be cast to the type
"reference to T2" if an expression of type "pointer to T1" can be
explicitly converted to the type "pointer to T2" using a
reinterpret_cast. */
if (TYPE_REF_P (type))
{
if (! lvalue_p (expr))
if (TYPE_REF_IS_RVALUE (type))
{
if (!obvalue_p (expr))
/* Perform the temporary materialization conversion. */
expr = get_target_expr_sfinae (expr, complain);
}
else if (!lvalue_p (expr))
{
if (complain & tf_error)
error ("invalid cast of an rvalue expression of type "

11
gcc/testsuite/g++.dg/cpp0x/rv-cast6.C Normal file
View file

@ -0,0 +1,11 @@
// Test that a prvalue can be used where a glvalue is expected.
// { dg-do compile { target c++11 } }
struct A { virtual void f(); };
struct B : A {};
auto && a = static_cast<A&&>(B());
auto && b = reinterpret_cast<A&&>(B());
auto && c = dynamic_cast<A&&>(B());
auto && d = dynamic_cast<B&&>(static_cast<A&&>(B()));
auto && e = const_cast<B&&>(B());