From 07f56824fd4da14a48030e698c8eb58de951c741 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Mon, 5 Apr 2021 15:50:48 -0400 Subject: [PATCH] c++: reinterpret_cast from prvalue to rvalue ref [PR98440] In r260622 I allowed this under the general principle that [basic.lval] "Whenever a prvalue appears as an operand of an operator that expects a glvalue for that operand, the temporary materialization conversion (7.3.4) is applied to convert the expression to an xvalue." But [expr.reinterpret.cast] specifically excludes creating a temporary in this case. gcc/cp/ChangeLog: PR c++/98440 * typeck.c (build_reinterpret_cast_1): Don't perform temporary materialization. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/rv-cast6.C: Expect reinterpret_cast error. * g++.dg/cpp0x/reinterpret_cast2.C: Adjust message. * g++.old-deja/g++.jason/rvalue3.C: Likewise. --- gcc/cp/typeck.c | 18 +++++++----------- gcc/testsuite/g++.dg/cpp0x/reinterpret_cast2.C | 2 +- gcc/testsuite/g++.dg/cpp0x/rv-cast6.C | 2 +- gcc/testsuite/g++.old-deja/g++.jason/rvalue3.C | 2 +- 4 files changed, 10 insertions(+), 14 deletions(-) diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c index dff4e9b..8535ecc 100644 --- a/gcc/cp/typeck.c +++ b/gcc/cp/typeck.c @@ -7938,22 +7938,18 @@ build_reinterpret_cast_1 (location_t loc, tree type, tree expr, type = cv_unqualified (type); /* [expr.reinterpret.cast] - A glvalue expression of type T1 can be cast to the type + A glvalue of type T1, designating an object x, 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. */ + explicitly converted to the type "pointer to T2" using a reinterpret_cast. + The result is that of *reinterpret_cast(p) where p is a pointer to x + of type "pointer to T1". No temporary is created, no copy is made, and no + constructors (11.4.4) or conversion functions (11.4.7) are called. */ if (TYPE_REF_P (type)) { - if (TYPE_REF_IS_RVALUE (type) && !VOID_TYPE_P (intype)) - { - if (!obvalue_p (expr)) - /* Perform the temporary materialization conversion. */ - expr = get_target_expr_sfinae (expr, complain); - } - else if (!lvalue_p (expr)) + if (!glvalue_p (expr)) { if (complain & tf_error) - error_at (loc, "invalid cast of an rvalue expression of type " + error_at (loc, "invalid cast of a prvalue expression of type " "%qT to type %qT", intype, type); return error_mark_node; diff --git a/gcc/testsuite/g++.dg/cpp0x/reinterpret_cast2.C b/gcc/testsuite/g++.dg/cpp0x/reinterpret_cast2.C index c173576..5402e82 100644 --- a/gcc/testsuite/g++.dg/cpp0x/reinterpret_cast2.C +++ b/gcc/testsuite/g++.dg/cpp0x/reinterpret_cast2.C @@ -6,5 +6,5 @@ struct S { }; void foo () { - auto a = reinterpret_cast(foo ()); // { dg-error "12:invalid cast of an rvalue expression of type 'void' to type" } + auto a = reinterpret_cast(foo ()); // { dg-error "12:invalid cast of a prvalue expression of type 'void' to type" } } diff --git a/gcc/testsuite/g++.dg/cpp0x/rv-cast6.C b/gcc/testsuite/g++.dg/cpp0x/rv-cast6.C index 3ae5691..3adf683 100644 --- a/gcc/testsuite/g++.dg/cpp0x/rv-cast6.C +++ b/gcc/testsuite/g++.dg/cpp0x/rv-cast6.C @@ -5,7 +5,7 @@ struct A { virtual void f(); }; struct B : A {}; auto && a = static_cast(B()); -auto && b = reinterpret_cast(B()); +auto && b = reinterpret_cast(B()); // { dg-error "prvalue" } auto && c = dynamic_cast(B()); auto && d = dynamic_cast(static_cast(B())); auto && e = const_cast(B()); diff --git a/gcc/testsuite/g++.old-deja/g++.jason/rvalue3.C b/gcc/testsuite/g++.old-deja/g++.jason/rvalue3.C index 49191c9..77969bc 100644 --- a/gcc/testsuite/g++.old-deja/g++.jason/rvalue3.C +++ b/gcc/testsuite/g++.old-deja/g++.jason/rvalue3.C @@ -2,5 +2,5 @@ int main () { int i; - int &ir = (int&)(int)i; // { dg-error "14:invalid cast of an rvalue expression" } casting rvalue to reference type + int &ir = (int&)(int)i; // { dg-error "14:invalid cast of a prvalue expression" } casting rvalue to reference type } -- 2.7.4