From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: [committed] libstdc++: Add conditional noexcept to std::exchange
Date: Tue, 17 Aug 2021 14:26:55 +0100 [thread overview]
Message-ID: <YRu5HwCa3reYcyB5@redhat.com> (raw)
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This is not required by the standard, but seems useful.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/std/utility (exchange): Add noexcept-specifier.
* testsuite/20_util/exchange/noexcept.cc: New test.
Tested powerpc64le-linux. Committed to trunk.
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commit 42cfa1bd6c05f2dc0d6269155950d16064310f56
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Mon Aug 16 18:00:08 2021
libstdc++: Add conditional noexcept to std::exchange
This is not required by the standard, but seems useful.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/std/utility (exchange): Add noexcept-specifier.
* testsuite/20_util/exchange/noexcept.cc: New test.
diff --git a/libstdc++-v3/include/std/utility b/libstdc++-v3/include/std/utility
index c2697f87dc5..69d274ff194 100644
--- a/libstdc++-v3/include/std/utility
+++ b/libstdc++-v3/include/std/utility
@@ -91,6 +91,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX20_CONSTEXPR
inline _Tp
exchange(_Tp& __obj, _Up&& __new_val)
+ noexcept(__and_<is_nothrow_move_constructible<_Tp>,
+ is_nothrow_assignable<_Tp&, _Up>>::value)
{ return std::__exchange(__obj, std::forward<_Up>(__new_val)); }
#if __cplusplus >= 201703L
diff --git a/libstdc++-v3/testsuite/20_util/exchange/noexcept.cc b/libstdc++-v3/testsuite/20_util/exchange/noexcept.cc
new file mode 100644
index 00000000000..6363a4d4c06
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/exchange/noexcept.cc
@@ -0,0 +1,39 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <utility>
+
+// This is a GCC extension. std::exchange is not required to be noexcept.
+
+static_assert( noexcept( std::exchange(std::declval<int&>(), 1) ) );
+
+struct X
+{
+ X(const X&);
+ X(X&&) noexcept;
+ X& operator=(const X&);
+ X& operator=(X&&) noexcept;
+ X& operator=(int);
+};
+
+extern X x, x2;
+static_assert( noexcept( std::exchange(x, std::move(x2)) ) );
+static_assert( ! noexcept( std::exchange(x, 1) ) );
+
+struct Y
+{
+ Y(Y&&) noexcept;
+ Y& operator=(Y&&);
+};
+
+extern Y y, y2;
+static_assert( ! noexcept( std::exchange(y, std::move(y2)) ) );
+
+struct Z
+{
+ Z(Z&&)noexcept;
+ Z& operator=(Z&&) ;
+};
+
+extern Z z, z2;
+static_assert( ! noexcept( std::exchange(z, std::move(z2)) ) );
reply other threads:[~2021-08-17 13:26 UTC|newest]
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