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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r9-9366] libstdc++: Add noexcept to std::begin etc as per LWG 2280 and 3537 Date: Tue, 20 Apr 2021 18:52:03 +0000 (GMT) [thread overview] Message-ID: <20210420185203.92A883886C50@sourceware.org> (raw) https://gcc.gnu.org/g:592ecfc48c73fdb497f1d74cd8d9fe84c3cec208 commit r9-9366-g592ecfc48c73fdb497f1d74cd8d9fe84c3cec208 Author: Jonathan Wakely <jwakely@redhat.com> Date: Mon Mar 22 15:15:12 2021 +0000 libstdc++: Add noexcept to std::begin etc as per LWG 2280 and 3537 This implements the proposed changes for LWG 3537 (which we're allowed to do as an extension whatever the outcome of the issue). I noticed we didn't implement LWG 2280 completely, as the std::begin and std::end overloads for arrays were not noexcept. libstdc++-v3/ChangeLog: * include/bits/range_access.h (begin(T (&)[N]), end(T (&)[N])): Add missing 'noexcept' as per LWG 2280. (rbegin(T (&)[N]), rend(T (&)[N]), rbegin(initializer_list<T>)) (rend(initializer_list<T>)): Add 'noexcept' as per LWG 3537. * testsuite/24_iterators/range_access.cc: Check for expected noexcept specifiers. Check result types of generic std::begin and std::end overloads. * testsuite/24_iterators/range_access_cpp14.cc: Check for expected noexcept specifiers. * testsuite/24_iterators/range_access_cpp17.cc: Likewise. (cherry picked from commit 00b46c00c8d9003c61e8f817668ad3380e16fedb) Diff: --- libstdc++-v3/include/bits/range_access.h | 12 ++++----- .../testsuite/24_iterators/range_access.cc | 30 ++++++++++++++++++++++ .../testsuite/24_iterators/range_access_cpp14.cc | 15 +++++++++++ .../testsuite/24_iterators/range_access_cpp17.cc | 14 ++++++++++ 4 files changed, 65 insertions(+), 6 deletions(-) diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h index dfdcd8e7207..3d99ea92027 100644 --- a/libstdc++-v3/include/bits/range_access.h +++ b/libstdc++-v3/include/bits/range_access.h @@ -84,7 +84,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ template<typename _Tp, size_t _Nm> inline _GLIBCXX14_CONSTEXPR _Tp* - begin(_Tp (&__arr)[_Nm]) + begin(_Tp (&__arr)[_Nm]) noexcept { return __arr; } /** @@ -94,7 +94,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ template<typename _Tp, size_t _Nm> inline _GLIBCXX14_CONSTEXPR _Tp* - end(_Tp (&__arr)[_Nm]) + end(_Tp (&__arr)[_Nm]) noexcept { return __arr + _Nm; } #if __cplusplus >= 201402L @@ -175,7 +175,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ template<typename _Tp, size_t _Nm> inline _GLIBCXX17_CONSTEXPR reverse_iterator<_Tp*> - rbegin(_Tp (&__arr)[_Nm]) + rbegin(_Tp (&__arr)[_Nm]) noexcept { return reverse_iterator<_Tp*>(__arr + _Nm); } /** @@ -185,7 +185,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ template<typename _Tp, size_t _Nm> inline _GLIBCXX17_CONSTEXPR reverse_iterator<_Tp*> - rend(_Tp (&__arr)[_Nm]) + rend(_Tp (&__arr)[_Nm]) noexcept { return reverse_iterator<_Tp*>(__arr); } /** @@ -195,7 +195,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ template<typename _Tp> inline _GLIBCXX17_CONSTEXPR reverse_iterator<const _Tp*> - rbegin(initializer_list<_Tp> __il) + rbegin(initializer_list<_Tp> __il) noexcept { return reverse_iterator<const _Tp*>(__il.end()); } /** @@ -205,7 +205,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ template<typename _Tp> inline _GLIBCXX17_CONSTEXPR reverse_iterator<const _Tp*> - rend(initializer_list<_Tp> __il) + rend(initializer_list<_Tp> __il) noexcept { return reverse_iterator<const _Tp*>(__il.begin()); } /** diff --git a/libstdc++-v3/testsuite/24_iterators/range_access.cc b/libstdc++-v3/testsuite/24_iterators/range_access.cc index 8b1ac966503..a374e5a199c 100644 --- a/libstdc++-v3/testsuite/24_iterators/range_access.cc +++ b/libstdc++-v3/testsuite/24_iterators/range_access.cc @@ -27,4 +27,34 @@ test01() int arr[3] = {1, 2, 3}; std::begin(arr); std::end(arr); + + static_assert( noexcept(std::begin(arr)), "LWG 2280" ); + static_assert( noexcept(std::end(arr)), "LWG 2280" ); +} + +void +test02() +{ + extern void require_int(int*); + extern void require_long(long*); + + struct B + { + int* begin() { return nullptr; } + long* begin() const { return nullptr; } + }; + + B b; + require_int( std::begin(b) ); + require_long( std::begin(const_cast<const B&>(b)) ); + + struct E + { + int* end() { return nullptr; } + long* end() const { return nullptr; } + }; + + E e; + require_int( std::end(e) ); + require_long( std::end(const_cast<const E&>(e)) ); } diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp14.cc b/libstdc++-v3/testsuite/24_iterators/range_access_cpp14.cc index 29a469d7d6b..4cd239673ef 100644 --- a/libstdc++-v3/testsuite/24_iterators/range_access_cpp14.cc +++ b/libstdc++-v3/testsuite/24_iterators/range_access_cpp14.cc @@ -39,10 +39,21 @@ void test02() { static int i[1]; + // LWG 2280 constexpr auto b __attribute__((unused)) = std::begin(i); constexpr auto e __attribute__((unused)) = std::end(i); constexpr auto cb __attribute__((unused)) = std::cbegin(i); constexpr auto ce __attribute__((unused)) = std::cend(i); + + // LWG 2280 + static_assert( noexcept(std::begin(i)), "LWG 2280" ); + static_assert( noexcept(std::end(i)), "LWG 2280" ); + static_assert( noexcept(std::cbegin(i)), "LWG 2280" ); + static_assert( noexcept(std::cend(i)), "LWG 2280" ); + + // LWG 3537 + static_assert( noexcept(std::rbegin(i)), "LWG 3537" ); + static_assert( noexcept(std::rend(i)), "LWG 3537" ); } void @@ -55,6 +66,10 @@ test03() VERIFY(std::rend(il) == std::reverse_iterator<const int*>(il.begin())); VERIFY(std::crbegin(il) == std::reverse_iterator<const int*>(il.end())); VERIFY(std::crend(il) == std::reverse_iterator<const int*>(il.begin())); + + // LWG 3537 + static_assert( noexcept(std::rbegin(il)), "LWG 3537" ); + static_assert( noexcept(std::rend(il)), "LWG 3537" ); } void diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp17.cc b/libstdc++-v3/testsuite/24_iterators/range_access_cpp17.cc index 9ba20090c77..e5085516ca6 100644 --- a/libstdc++-v3/testsuite/24_iterators/range_access_cpp17.cc +++ b/libstdc++-v3/testsuite/24_iterators/range_access_cpp17.cc @@ -41,6 +41,16 @@ test02() static int i[] = { 1, 2 }; static_assert(std::distance(std::begin(i), std::end(i)) == 2); static_assert(std::distance(std::cbegin(i), std::cend(i)) == 2); + + // LWG 2280 + static_assert( noexcept(std::begin(i)), "LWG 2280" ); + static_assert( noexcept(std::end(i)), "LWG 2280" ); + static_assert( noexcept(std::cbegin(i)), "LWG 2280" ); + static_assert( noexcept(std::cend(i)), "LWG 2280" ); + + // LWG 3537 + static_assert( noexcept(std::rbegin(i)), "LWG 3537" ); + static_assert( noexcept(std::rend(i)), "LWG 3537" ); } void @@ -54,4 +64,8 @@ test03() static_assert(std::rend(il) == reverse_iterator<const int*>(il.begin())); static_assert(std::crbegin(il) == reverse_iterator<const int*>(il.end())); static_assert(std::crend(il) == reverse_iterator<const int*>(il.begin())); + + // LWG 3537 + static_assert( noexcept(std::rbegin(il)), "LWG 3537" ); + static_assert( noexcept(std::rend(il)), "LWG 3537" ); }
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