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[libc++][forward_list] Applied [[nodiscard]] #169019

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Nov 24, 2025
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[libc++][forward_list] Applied [[nodiscard]] #169019

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[libc++][forward_list] Applied `[[nodiscard]]`
H-G-Hristov Nov 21, 2025
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H-G-Hristov Nov 24, 2025
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H-G-Hristov Nov 24, 2025
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28 changes: 15 additions & 13 deletions libcxx/include/forward_list
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Original file line number Diff line number Diff line change
Expand Up @@ -732,50 +732,52 @@ public:

_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void assign(size_type __n, const value_type& __v);

_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT {
return allocator_type(this->__alloc_);
}

_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT {
return iterator(__base::__before_begin()->__next_);
}
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT {
return const_iterator(__base::__before_begin()->__next_);
}
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT { return iterator(nullptr); }
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT {
return iterator(nullptr);
}
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT {
return const_iterator(nullptr);
}

_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT {
return const_iterator(__base::__before_begin()->__next_);
}
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT {
return const_iterator(nullptr);
}

_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator before_begin() _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator before_begin() _NOEXCEPT {
return iterator(__base::__before_begin());
}
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator before_begin() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator before_begin() const _NOEXCEPT {
return const_iterator(__base::__before_begin());
}
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cbefore_begin() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cbefore_begin() const _NOEXCEPT {
return const_iterator(__base::__before_begin());
}

[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT {
return __base::__before_begin()->__next_ == nullptr;
}
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
return std::min<size_type>(__node_traits::max_size(this->__alloc_), numeric_limits<difference_type>::max());
}

_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference front() {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference front() {
_LIBCPP_ASSERT_NON_NULL(!empty(), "forward_list::front called on an empty list");
return __base::__before_begin()->__next_->__get_value();
}
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reference front() const {
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reference front() const {
_LIBCPP_ASSERT_NON_NULL(!empty(), "forward_list::front called on an empty list");
return __base::__before_begin()->__next_->__get_value();
}
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25 changes: 23 additions & 2 deletions libcxx/test/libcxx/diagnostics/forward_list.nodiscard.verify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,27 @@
#include <forward_list>

void test() {
std::forward_list<int> forward_list;
forward_list.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::forward_list<int> fl;
const std::forward_list<int> cfl;

fl.get_allocator(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

fl.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cfl.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
fl.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cfl.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
fl.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cfl.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
fl.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cfl.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
fl.before_begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cfl.before_begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
fl.cbefore_begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cfl.cbefore_begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

fl.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
fl.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

fl.front(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cfl.front(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
}
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