| Message ID | 20171123224048.GA24885@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add [[nodiscard]] attribute to C++17 components | expand |
On 23/11/17 22:40 +0000, Jonathan Wakely wrote: >C++17 added the [[nodiscard]] attribute, similar to GCC's >warn_unused_result. The C++2a draft requires it to be used in several >places. This patch adds it where required on components which are new >to C++17, which are still experimental and so I'm changing them in >stage 3. This adds the other [[nodiscard]] attributes required by C++2a, but using [[__nodiscard__]] so it can be enabled in C++11 and C++14, where nodiscard is not a reserved name. I don't plan to commit this until stage 1 (and don't have tests for it yet anyway). commit 9159c87e19510662eecfeadf8facbe68b40ac2c7 Author: Jonathan Wakely <jwakely@redhat.com> Date: Thu Nov 23 22:42:45 2017 +0000 Add more nodiscard attributes diff --git a/libstdc++-v3/include/bits/alloc_traits.h b/libstdc++-v3/include/bits/alloc_traits.h index 86a48594ea1..ba75f33726d 100644 --- a/libstdc++-v3/include/bits/alloc_traits.h +++ b/libstdc++-v3/include/bits/alloc_traits.h @@ -296,7 +296,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * * Calls @c a.allocate(n) */ - static pointer + [[__nodiscard__]] static pointer allocate(_Alloc& __a, size_type __n) { return __a.allocate(__n); } @@ -311,7 +311,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * Returns <tt> a.allocate(n, hint) </tt> if that expression is * well-formed, otherwise returns @c a.allocate(n) */ - static pointer + [[__nodiscard__]] static pointer allocate(_Alloc& __a, size_type __n, const_void_pointer __hint) { return _S_allocate(__a, __n, __hint, 0); } diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index a4b81137571..bec6e902076 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -1008,7 +1008,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 * Returns true if the %string is empty. Equivalent to * <code>*this == ""</code>. */ - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return this->size() == 0; } diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config index 21e3fbb2741..cfa2534e3f5 100644 --- a/libstdc++-v3/include/bits/c++config +++ b/libstdc++-v3/include/bits/c++config @@ -99,6 +99,11 @@ # define _GLIBCXX_ABI_TAG_CXX11 __attribute ((__abi_tag__ ("cxx11"))) #endif +#if __cplusplus >= 201103L +# define _GLIBCXX_NODISCARD [[__nodiscard__]] +#else +# define _GLIBCXX_NODISCARD +#endif #if __cplusplus diff --git a/libstdc++-v3/include/bits/forward_list.h b/libstdc++-v3/include/bits/forward_list.h index 96494cc20de..b8eb9f3d6fe 100644 --- a/libstdc++-v3/include/bits/forward_list.h +++ b/libstdc++-v3/include/bits/forward_list.h @@ -756,7 +756,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER * Returns true if the %forward_list is empty. (Thus begin() would * equal end().) */ - bool + [[__nodiscard__]] bool empty() const noexcept { return this->_M_impl._M_head._M_next == 0; } diff --git a/libstdc++-v3/include/bits/regex.h b/libstdc++-v3/include/bits/regex.h index 32e7159eec9..4866cb42b00 100644 --- a/libstdc++-v3/include/bits/regex.h +++ b/libstdc++-v3/include/bits/regex.h @@ -1631,7 +1631,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 * @retval true The %match_results object is empty. * @retval false The %match_results object is not empty. */ - bool + [[__nodiscard__]] bool empty() const { return size() == 0; } diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h index ac548846b0e..80a54e78ff3 100644 --- a/libstdc++-v3/include/bits/stl_bvector.h +++ b/libstdc++-v3/include/bits/stl_bvector.h @@ -873,7 +873,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER { return size_type(const_iterator(this->_M_impl._M_end_addr(), 0) - begin()); } - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return begin() == end(); } diff --git a/libstdc++-v3/include/bits/stl_deque.h b/libstdc++-v3/include/bits/stl_deque.h index 93c82ca8909..ae170623247 100644 --- a/libstdc++-v3/include/bits/stl_deque.h +++ b/libstdc++-v3/include/bits/stl_deque.h @@ -1363,7 +1363,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER * Returns true if the %deque is empty. (Thus begin() would * equal end().) */ - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return this->_M_impl._M_finish == this->_M_impl._M_start; } diff --git a/libstdc++-v3/include/bits/stl_list.h b/libstdc++-v3/include/bits/stl_list.h index 8ed97f7c8b0..93378139871 100644 --- a/libstdc++-v3/include/bits/stl_list.h +++ b/libstdc++-v3/include/bits/stl_list.h @@ -1058,7 +1058,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 * Returns true if the %list is empty. (Thus begin() would equal * end().) */ - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return this->_M_impl._M_node._M_next == &this->_M_impl._M_node; } diff --git a/libstdc++-v3/include/bits/stl_map.h b/libstdc++-v3/include/bits/stl_map.h index bec6c47c086..fec8d81c183 100644 --- a/libstdc++-v3/include/bits/stl_map.h +++ b/libstdc++-v3/include/bits/stl_map.h @@ -459,7 +459,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER /** Returns true if the %map is empty. (Thus begin() would equal * end().) */ - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return _M_t.empty(); } diff --git a/libstdc++-v3/include/bits/stl_multimap.h b/libstdc++-v3/include/bits/stl_multimap.h index 24ac4a3c186..bce79c2d587 100644 --- a/libstdc++-v3/include/bits/stl_multimap.h +++ b/libstdc++-v3/include/bits/stl_multimap.h @@ -452,7 +452,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER // capacity /** Returns true if the %multimap is empty. */ - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return _M_t.empty(); } diff --git a/libstdc++-v3/include/bits/stl_multiset.h b/libstdc++-v3/include/bits/stl_multiset.h index ff7d3dca586..aa147467c36 100644 --- a/libstdc++-v3/include/bits/stl_multiset.h +++ b/libstdc++-v3/include/bits/stl_multiset.h @@ -406,7 +406,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER #endif /// Returns true if the %set is empty. - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return _M_t.empty(); } diff --git a/libstdc++-v3/include/bits/stl_queue.h b/libstdc++-v3/include/bits/stl_queue.h index c49f371fbc8..60a2f0e281e 100644 --- a/libstdc++-v3/include/bits/stl_queue.h +++ b/libstdc++-v3/include/bits/stl_queue.h @@ -185,7 +185,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /** * Returns true if the %queue is empty. */ - bool + _GLIBCXX_NODISCARD bool empty() const { return c.empty(); } @@ -563,7 +563,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /** * Returns true if the %queue is empty. */ - bool + _GLIBCXX_NODISCARD bool empty() const { return c.empty(); } diff --git a/libstdc++-v3/include/bits/stl_set.h b/libstdc++-v3/include/bits/stl_set.h index e07d78124eb..9f566a2a6eb 100644 --- a/libstdc++-v3/include/bits/stl_set.h +++ b/libstdc++-v3/include/bits/stl_set.h @@ -410,7 +410,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER #endif /// Returns true if the %set is empty. - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return _M_t.empty(); } diff --git a/libstdc++-v3/include/bits/stl_stack.h b/libstdc++-v3/include/bits/stl_stack.h index 5f2b4ab4486..d115134d0fe 100644 --- a/libstdc++-v3/include/bits/stl_stack.h +++ b/libstdc++-v3/include/bits/stl_stack.h @@ -181,7 +181,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /** * Returns true if the %stack is empty. */ - bool + _GLIBCXX_NODISCARD bool empty() const { return c.empty(); } diff --git a/libstdc++-v3/include/bits/stl_vector.h b/libstdc++-v3/include/bits/stl_vector.h index aeeba820020..75f58e525ae 100644 --- a/libstdc++-v3/include/bits/stl_vector.h +++ b/libstdc++-v3/include/bits/stl_vector.h @@ -890,7 +890,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER * Returns true if the %vector is empty. (Thus begin() would * equal end().) */ - bool + _GLIBCXX_NODISCARD bool empty() const _GLIBCXX_NOEXCEPT { return begin() == end(); } diff --git a/libstdc++-v3/include/bits/unordered_map.h b/libstdc++-v3/include/bits/unordered_map.h index cb5bcb89a16..3400aed47e9 100644 --- a/libstdc++-v3/include/bits/unordered_map.h +++ b/libstdc++-v3/include/bits/unordered_map.h @@ -300,7 +300,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER // size and capacity: /// Returns true if the %unordered_map is empty. - bool + [[__nodiscard__]] bool empty() const noexcept { return _M_h.empty(); } @@ -1433,7 +1433,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER // size and capacity: /// Returns true if the %unordered_multimap is empty. - bool + [[__nodiscard__]] bool empty() const noexcept { return _M_h.empty(); } diff --git a/libstdc++-v3/include/bits/unordered_set.h b/libstdc++-v3/include/bits/unordered_set.h index 550548c42db..279b61ce3d6 100644 --- a/libstdc++-v3/include/bits/unordered_set.h +++ b/libstdc++-v3/include/bits/unordered_set.h @@ -294,7 +294,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER // size and capacity: /// Returns true if the %unordered_set is empty. - bool + [[__nodiscard__]] bool empty() const noexcept { return _M_h.empty(); } @@ -1091,7 +1091,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER // size and capacity: /// Returns true if the %unordered_multiset is empty. - bool + [[__nodiscard__]] bool empty() const noexcept { return _M_h.empty(); } diff --git a/libstdc++-v3/include/experimental/bits/fs_path.h b/libstdc++-v3/include/experimental/bits/fs_path.h index 3e9bc6357af..81c6ac44dd1 100644 --- a/libstdc++-v3/include/experimental/bits/fs_path.h +++ b/libstdc++-v3/include/experimental/bits/fs_path.h @@ -359,7 +359,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 // query - bool empty() const noexcept { return _M_pathname.empty(); } + [[__nodiscard__]] bool + empty() const noexcept { return _M_pathname.empty(); } + bool has_root_name() const; bool has_root_directory() const; bool has_root_path() const; diff --git a/libstdc++-v3/include/experimental/string_view b/libstdc++-v3/include/experimental/string_view index 8eaf9ec3d96..bbe7a46791f 100644 --- a/libstdc++-v3/include/experimental/string_view +++ b/libstdc++-v3/include/experimental/string_view @@ -169,7 +169,7 @@ inline namespace fundamentals_v1 / sizeof(value_type) / 4; } - constexpr bool + [[__nodiscard__]] constexpr bool empty() const noexcept { return this->_M_len == 0; } diff --git a/libstdc++-v3/include/ext/new_allocator.h b/libstdc++-v3/include/ext/new_allocator.h index e1e152c4bf0..de18cc7a4f8 100644 --- a/libstdc++-v3/include/ext/new_allocator.h +++ b/libstdc++-v3/include/ext/new_allocator.h @@ -95,7 +95,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // NB: __n is permitted to be 0. The C++ standard says nothing // about what the return value is when __n == 0. - pointer + _GLIBCXX_NODISCARD pointer allocate(size_type __n, const void* = static_cast<const void*>(0)) { if (__n > this->max_size()) diff --git a/libstdc++-v3/include/std/array b/libstdc++-v3/include/std/array index 01f7100bae0..329d3b33a68 100644 --- a/libstdc++-v3/include/std/array +++ b/libstdc++-v3/include/std/array @@ -177,7 +177,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER constexpr size_type max_size() const noexcept { return _Nm; } - constexpr bool + [[__nodiscard__]] constexpr bool empty() const noexcept { return size() == 0; } // Element access. diff --git a/libstdc++-v3/include/std/future b/libstdc++-v3/include/std/future index d9d446bc2f6..6b51499526a 100644 --- a/libstdc++-v3/include/std/future +++ b/libstdc++-v3/include/std/future @@ -1708,7 +1708,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// async template<typename _Fn, typename... _Args> - future<__async_result_of<_Fn, _Args...>> + [[__nodiscard__]] future<__async_result_of<_Fn, _Args...>> async(launch __policy, _Fn&& __fn, _Args&&... __args) { std::shared_ptr<__future_base::_State_base> __state; @@ -1741,7 +1741,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// async, potential overload template<typename _Fn, typename... _Args> - inline future<__async_result_of<_Fn, _Args...>> + [[__nodiscard__]] inline future<__async_result_of<_Fn, _Args...>> async(_Fn&& __fn, _Args&&... __args) { return std::async(launch::async|launch::deferred, diff --git a/libstdc++-v3/include/std/scoped_allocator b/libstdc++-v3/include/std/scoped_allocator index 725f5471444..ee955e9fa90 100644 --- a/libstdc++-v3/include/std/scoped_allocator +++ b/libstdc++-v3/include/std/scoped_allocator @@ -335,10 +335,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION const outer_allocator_type& outer_allocator() const noexcept { return static_cast<const _OuterAlloc&>(*this); } - pointer allocate(size_type __n) + [[__nodiscard__]] pointer + allocate(size_type __n) { return __traits::allocate(outer_allocator(), __n); } - pointer allocate(size_type __n, const_void_pointer __hint) + [[__nodiscard__]] pointer + allocate(size_type __n, const_void_pointer __hint) { return __traits::allocate(outer_allocator(), __n, __hint); } void deallocate(pointer __p, size_type __n) diff --git a/libstdc++-v3/libsupc++/new b/libstdc++-v3/libsupc++/new index 795b33c4e6a..cc4cb294be7 100644 --- a/libstdc++-v3/libsupc++/new +++ b/libstdc++-v3/libsupc++/new @@ -117,8 +117,10 @@ namespace std * Placement new and delete signatures (take a memory address argument, * does nothing) may not be replaced by a user's program. */ +_GLIBCXX_NODISCARD void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc) __attribute__((__externally_visible__)); +_GLIBCXX_NODISCARD void* operator new[](std::size_t) _GLIBCXX_THROW (std::bad_alloc) __attribute__((__externally_visible__)); void operator delete(void*) _GLIBCXX_USE_NOEXCEPT @@ -131,8 +133,10 @@ void operator delete(void*, std::size_t) _GLIBCXX_USE_NOEXCEPT void operator delete[](void*, std::size_t) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); #endif +_GLIBCXX_NODISCARD void* operator new(std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); +_GLIBCXX_NODISCARD void* operator new[](std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); void operator delete(void*, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT @@ -140,16 +144,20 @@ void operator delete(void*, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT void operator delete[](void*, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); #if __cpp_aligned_new +_GLIBCXX_NODISCARD void* operator new(std::size_t, std::align_val_t) __attribute__((__externally_visible__)); +_GLIBCXX_NODISCARD void* operator new(std::size_t, std::align_val_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); void operator delete(void*, std::align_val_t) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); void operator delete(void*, std::align_val_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); +_GLIBCXX_NODISCARD void* operator new[](std::size_t, std::align_val_t) __attribute__((__externally_visible__)); +_GLIBCXX_NODISCARD void* operator new[](std::size_t, std::align_val_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__)); void operator delete[](void*, std::align_val_t) @@ -165,8 +173,10 @@ void operator delete[](void*, std::size_t, std::align_val_t) #endif // __cpp_aligned_new // Default placement versions of operator new. +_GLIBCXX_NODISCARD inline void* operator new(std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT { return __p; } +_GLIBCXX_NODISCARD inline void* operator new[](std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT { return __p; } diff --git a/libstdc++-v3/testsuite/17_intro/headers/c++1998/all_attributes.cc b/libstdc++-v3/testsuite/17_intro/headers/c++1998/all_attributes.cc index 6d6d7980396..8090cce8b9c 100644 --- a/libstdc++-v3/testsuite/17_intro/headers/c++1998/all_attributes.cc +++ b/libstdc++-v3/testsuite/17_intro/headers/c++1998/all_attributes.cc @@ -22,6 +22,7 @@ // Don't test 'const' because it is reserved anyway. #define abi_tag 1 #define always_inline 1 +#define nodiscard 1 #ifndef __APPLE__ // darwin headers use these, see PR 64883 # define deprecated 1 diff --git a/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc b/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc index 415ece0296f..809f001a384 100644 --- a/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc +++ b/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc @@ -22,6 +22,7 @@ // Don't test 'const' and 'noreturn' because they are reserved anyway. #define abi_tag 1 #define always_inline 1 +#define nodiscard 1 #ifndef __APPLE__ // darwin headers use these, see PR 64883 # define visibility 1 diff --git a/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc b/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc index d4ef52412a3..70533610a1f 100644 --- a/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc +++ b/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc @@ -22,6 +22,7 @@ // Don't test 'const' and 'noreturn' because they are reserved anyway. #define abi_tag 1 #define always_inline 1 +#define nodiscard 1 #ifndef __APPLE__ // darwin headers use these, see PR 64883 # define deprecated 1
On 23/11/17 22:40 +0000, Jonathan Wakely wrote: >C++17 added the [[nodiscard]] attribute, similar to GCC's >warn_unused_result. The C++2a draft requires it to be used in several >places. This patch adds it where required on components which are new >to C++17, which are still experimental and so I'm changing them in >stage 3. I missed one of the C++17 pieces that should have [[nodiscard]]. Tested powerpc64le-linux, committed to trunk. commit 65c20af6ec193916e390462ccfbd8e8e6b54ba8c Author: Jonathan Wakely <jwakely@redhat.com> Date: Thu Nov 23 22:51:31 2017 +0000 Add [[nodiscard]] attribute to std::launder * libsupc++/new (launder): Add nodiscard attribute. * testsuite/18_support/launder/nodiscard.cc: New test. diff --git a/libstdc++-v3/libsupc++/new b/libstdc++-v3/libsupc++/new index 795b33c4e6a..0e408b1019c 100644 --- a/libstdc++-v3/libsupc++/new +++ b/libstdc++-v3/libsupc++/new @@ -176,7 +176,7 @@ inline void operator delete[](void*, void*) _GLIBCXX_USE_NOEXCEPT { } //@} } // extern "C++" -#if __cplusplus > 201402L +#if __cplusplus >= 201703L #if __GNUC__ >= 7 # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1 #elif defined __has_builtin @@ -192,7 +192,7 @@ namespace std #define __cpp_lib_launder 201606 /// Pointer optimization barrier [ptr.launder] template<typename _Tp> - constexpr _Tp* + [[nodiscard]] constexpr _Tp* launder(_Tp* __p) noexcept { return __builtin_launder(__p); } diff --git a/libstdc++-v3/testsuite/18_support/launder/nodiscard.cc b/libstdc++-v3/testsuite/18_support/launder/nodiscard.cc new file mode 100644 index 00000000000..1741465abed --- /dev/null +++ b/libstdc++-v3/testsuite/18_support/launder/nodiscard.cc @@ -0,0 +1,29 @@ +// Copyright (C) 2017 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++17" } +// { dg-do compile { target c++17 } } + +#include <new> + +struct A { const int i; }; + +void +test01(A* a) +{ + std::launder(a); // { dg-warning "ignoring return value" } +}
diff --git a/libstdc++-v3/include/bits/fs_path.h b/libstdc++-v3/include/bits/fs_path.h index 7d97cdfbb81..99740c9b383 100644 --- a/libstdc++-v3/include/bits/fs_path.h +++ b/libstdc++-v3/include/bits/fs_path.h @@ -370,7 +370,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 // query - bool empty() const noexcept { return _M_pathname.empty(); } + [[nodiscard]] bool empty() const noexcept { return _M_pathname.empty(); } bool has_root_name() const; bool has_root_directory() const; bool has_root_path() const; diff --git a/libstdc++-v3/include/bits/node_handle.h b/libstdc++-v3/include/bits/node_handle.h index 4a830630c89..0d8dbeb4110 100644 --- a/libstdc++-v3/include/bits/node_handle.h +++ b/libstdc++-v3/include/bits/node_handle.h @@ -62,7 +62,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION explicit operator bool() const noexcept { return _M_ptr != nullptr; } - bool empty() const noexcept { return _M_ptr == nullptr; } + [[nodiscard]] bool empty() const noexcept { return _M_ptr == nullptr; } protected: constexpr _Node_handle_common() noexcept : _M_ptr(), _M_alloc() {} diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h index 2a037ad8082..a5044f11976 100644 --- a/libstdc++-v3/include/bits/range_access.h +++ b/libstdc++-v3/include/bits/range_access.h @@ -257,7 +257,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * @param __cont Container. */ template <typename _Container> - constexpr auto + [[nodiscard]] constexpr auto empty(const _Container& __cont) noexcept(noexcept(__cont.empty())) -> decltype(__cont.empty()) { return __cont.empty(); } @@ -267,7 +267,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * @param __array Container. */ template <typename _Tp, size_t _Nm> - constexpr bool + [[nodiscard]] constexpr bool empty(const _Tp (&/*__array*/)[_Nm]) noexcept { return false; } @@ -276,7 +276,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * @param __il Initializer list. */ template <typename _Tp> - constexpr bool + [[nodiscard]] constexpr bool empty(initializer_list<_Tp> __il) noexcept { return __il.size() == 0;} diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view index 1900b867841..fa834002726 100644 --- a/libstdc++-v3/include/std/string_view +++ b/libstdc++-v3/include/std/string_view @@ -160,7 +160,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION / sizeof(value_type) / 4; } - constexpr bool + [[nodiscard]] constexpr bool empty() const noexcept { return this->_M_len == 0; } diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/capacity/empty_neg.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/capacity/empty_neg.cc new file mode 100644 index 00000000000..59c87d007d8 --- /dev/null +++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/capacity/empty_neg.cc @@ -0,0 +1,28 @@ +// Copyright (C) 2017 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++17" } +// { dg-do compile { target c++17 } } + +#include <string_view> + +void +test01() +{ + std::string_view s; + s.empty(); // { dg-warning "ignoring return value" } +} diff --git a/libstdc++-v3/testsuite/24_iterators/range_access_cpp17_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access_cpp17_neg.cc new file mode 100644 index 00000000000..12de34eb6e4 --- /dev/null +++ b/libstdc++-v3/testsuite/24_iterators/range_access_cpp17_neg.cc @@ -0,0 +1,44 @@ +// Copyright (C) 2017 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++17" } +// { dg-do compile { target c++17 } } + +#include <iterator> +#include <initializer_list> + +void +test01() +{ + struct A { bool empty() const { return true; } }; + A a; + std::empty(a); // { dg-warning "ignoring return value" } +} + +void +test02() +{ + int a[2]; + std::empty(a); // { dg-warning "ignoring return value" } +} + +void +test03() +{ + std::initializer_list<int> a{}; + std::empty(a); // { dg-warning "ignoring return value" } +} diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/query/empty_neg.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/query/empty_neg.cc new file mode 100644 index 00000000000..7d38b494e9e --- /dev/null +++ b/libstdc++-v3/testsuite/27_io/filesystem/path/query/empty_neg.cc @@ -0,0 +1,28 @@ +// Copyright (C) 2017 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++17" } +// { dg-do compile { target c++17 } } + +#include <filesystem> + +void +test01() +{ + std::filesystem::path p; + p.empty(); // { dg-warning "ignoring return value" } +}
C++17 added the [[nodiscard]] attribute, similar to GCC's warn_unused_result. The C++2a draft requires it to be used in several places. This patch adds it where required on components which are new to C++17, which are still experimental and so I'm changing them in stage 3. * include/bits/fs_path.h (path::empty): Add nodiscard attribute. * include/bits/range_access.h (empty): Likewise. * include/std/string_view (basic_string_view::empty): Likewise. * testsuite/21_strings/basic_string_view/capacity/empty_neg.cc: New test. * testsuite/24_iterators/range_access_cpp17_neg.cc: New test. * testsuite/27_io/filesystem/path/query/empty_neg.cc: New test. Tested powerpc64le-linux, committed to trunk. commit b5d8dfbb291b02c071173612c63fd806e844e191 Author: Jonathan Wakely <jwakely@redhat.com> Date: Thu Nov 23 21:39:30 2017 +0000 Add [[nodiscard]] attribute to C++17 components * include/bits/fs_path.h (path::empty): Add nodiscard attribute. * include/bits/range_access.h (empty): Likewise. * include/std/string_view (basic_string_view::empty): Likewise. * testsuite/21_strings/basic_string_view/capacity/empty_neg.cc: New test. * testsuite/24_iterators/range_access_cpp17_neg.cc: New test. * testsuite/27_io/filesystem/path/query/empty_neg.cc: New test.