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_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 + +// This is a GCC extension. std::exchange is not required to be noexcept. + +static_assert( noexcept( std::exchange(std::declval(), 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)) ) );