2019-08-06 Jonathan Wakely <jwakely@redhat.com>
+ P1651R0 bind_front should not unwrap reference_wrapper
+ * include/std/functional (bind_front): Don't unwrap reference_wrapper.
+ * include/std/version (__cpp_lib_bind_front): Update value.
+ * testsuite/20_util/function_objects/bind_front/1.cc: Fix test for
+ feature test macro.
+ * testsuite/20_util/function_objects/bind_front/2.cc: New test.
+
* include/std/numbers [!__STRICT_ANSI__ && _GLIBCXX_USE_FLOAT128]
(e_v, log2e_v, log10e_v, pi_v, inv_pi_v, inv_sqrtpi_v, ln2_v, ln10_v)
(sqrt2_v, sqrt3_v, inv_sqrt3, egamma_v, phi_v): Add explicit
}
#if __cplusplus > 201703L
-#define __cpp_lib_bind_front 201902L
+#define __cpp_lib_bind_front 201907L
template<typename _Fd, typename... _BoundArgs>
struct _Bind_front
template<typename _Fn, typename... _Args>
using _Bind_front_t
- = _Bind_front<decay_t<_Fn>, unwrap_ref_decay_t<_Args>...>;
+ = _Bind_front<decay_t<_Fn>, decay_t<_Args>...>;
template<typename _Fn, typename... _Args>
_Bind_front_t<_Fn, _Args...>
--- /dev/null
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <testsuite_hooks.h>
+
+// P1651R0 bind_front should not unwrap reference_wrapper
+
+#ifndef __cpp_lib_bind_front
+# error "Feature test macro for bind_front is missing"
+#elif __cpp_lib_bind_front < 201907L
+# error "Feature test macro for bind_front has wrong value"
+#endif
+
+void functionAcceptingStringView(std::string_view) { }
+
+void
+test01()
+{
+ std::string s;
+ auto fs = std::bind_front(&functionAcceptingStringView, std::string_view(s));
+ fs();
+}
+
+template <typename F>
+struct PartialApply {
+ PartialApply(F f) : f(f) {}
+ F f;
+
+ template <typename... A> decltype(auto) operator()(A const&... a) const {
+ if constexpr (std::is_invocable<F const&, A const&...>::value) {
+ return f(a...);
+ } else {
+ return bind_front(*this, a...);
+ }
+ }
+};
+
+void
+test02()
+{
+ struct Thingy { };
+ std::unique_ptr<Thingy> thingy;
+ auto func = [](const std::unique_ptr<Thingy>&, int) {};
+ PartialApply{func}(std::ref(thingy))(10);
+}
+
+void
+test03()
+{
+ std::string str;
+ auto func = [](const std::string& s, int) -> const std::string& { return s; };
+
+ // sref refers to copy of str stored in bind_front result:
+ const std::string& sref = PartialApply{func}(std::ref(str))(10);
+
+ // pre-P1651R0 this is a use of a dangling reference:
+ const char& c = sref[0];
+
+ // post-P1651R0 the bind_front result stores a reference_wrapper by value,
+ // and so sref is bound to str instead of dangling:
+ VERIFY( &c == str.data() );
+ VERIFY( &sref == &str );
+}
+
+int
+main()
+{
+ test01();
+ test02();
+ test03();
+}
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