From a11052d98db2f2a61841f0c5ee84de4ca1b3e296 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Tue, 28 Sep 2021 12:35:29 +0100 Subject: [PATCH] libstdc++: Improve std::forward static assert message The previous message told you something was wrong, but not why it happened or why it's bad. This changes it to explain that the function is being misused. Signed-off-by: Jonathan Wakely libstdc++-v3/ChangeLog: * include/bits/move.h (forward(remove_reference_t&&)): Improve text of static_assert. * testsuite/20_util/forward/c_neg.cc: Adjust dg-error. * testsuite/20_util/forward/f_neg.cc: Likewise. --- libstdc++-v3/include/bits/move.h | 4 ++-- libstdc++-v3/testsuite/20_util/forward/c_neg.cc | 2 +- libstdc++-v3/testsuite/20_util/forward/f_neg.cc | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/libstdc++-v3/include/bits/move.h b/libstdc++-v3/include/bits/move.h index 3abbb37..2dd7ed9 100644 --- a/libstdc++-v3/include/bits/move.h +++ b/libstdc++-v3/include/bits/move.h @@ -88,8 +88,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION constexpr _Tp&& forward(typename std::remove_reference<_Tp>::type&& __t) noexcept { - static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument" - " substituting _Tp must not be an lvalue reference type"); + static_assert(!std::is_lvalue_reference<_Tp>::value, + "std::forward must not be used to convert an rvalue to an lvalue"); return static_cast<_Tp&&>(__t); } diff --git a/libstdc++-v3/testsuite/20_util/forward/c_neg.cc b/libstdc++-v3/testsuite/20_util/forward/c_neg.cc index dc7ec51..3875792 100644 --- a/libstdc++-v3/testsuite/20_util/forward/c_neg.cc +++ b/libstdc++-v3/testsuite/20_util/forward/c_neg.cc @@ -17,7 +17,7 @@ // with this library; see the file COPYING3. If not see // . -// { dg-error "must not be an lvalue reference" "" { target *-*-* } 0 } +// { dg-error "convert an rvalue to an lvalue" "" { target *-*-* } 0 } #include diff --git a/libstdc++-v3/testsuite/20_util/forward/f_neg.cc b/libstdc++-v3/testsuite/20_util/forward/f_neg.cc index 4ccd726..51ccaf2 100644 --- a/libstdc++-v3/testsuite/20_util/forward/f_neg.cc +++ b/libstdc++-v3/testsuite/20_util/forward/f_neg.cc @@ -17,7 +17,7 @@ // with this library; see the file COPYING3. If not see // . -// { dg-error "must not be an lvalue reference" "" { target *-*-* } 0 } +// { dg-error "convert an rvalue to an lvalue" "" { target *-*-* } 0 } #include -- 2.7.4