[libcxx-commits] [libcxx] [libc++][list] Applied `[[nodiscard]]` (PR #169015)
Hristo Hristov via libcxx-commits
libcxx-commits at lists.llvm.org
Fri Nov 21 08:44:53 PST 2025
https://github.com/H-G-Hristov updated https://github.com/llvm/llvm-project/pull/169015
>From a3e6f8607845ebbe5b10d3121f51265f2384a5f3 Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Fri, 21 Nov 2025 10:08:44 +0200
Subject: [PATCH] [libc++][list] Applied `[[nodiscard]]`
`[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue.
-https://libcxx.llvm.org/CodingGuidelines.html#apply-nodiscard-where-relevant
---
libcxx/include/list | 52 ++++++++++++-------
.../diagnostics/list.nodiscard.verify.cpp | 31 ++++++++++-
2 files changed, 62 insertions(+), 21 deletions(-)
diff --git a/libcxx/include/list b/libcxx/include/list
index 2898a45da0029..a5c84cad51489 100644
--- a/libcxx/include/list
+++ b/libcxx/include/list
@@ -774,57 +774,71 @@ public:
_LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void assign(size_type __n, const value_type& __x);
- _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;
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return this->__size_; }
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT {
+ return this->__size_;
+ }
[[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT {
return __base::empty();
}
- _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>(this->__node_alloc_max_size(), numeric_limits<difference_type >::max());
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT { return __base::begin(); }
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT { return __base::begin(); }
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT { return __base::end(); }
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return __base::end(); }
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT {
+ return __base::begin();
+ }
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT {
+ return __base::begin();
+ }
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT {
+ return __base::end();
+ }
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT {
+ return __base::end();
+ }
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT {
return __base::begin();
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { return __base::end(); }
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT {
+ return __base::end();
+ }
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reverse_iterator rbegin() _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reverse_iterator rbegin() _NOEXCEPT {
return reverse_iterator(end());
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rbegin() const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator
+ rbegin() const _NOEXCEPT {
return const_reverse_iterator(end());
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reverse_iterator rend() _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reverse_iterator rend() _NOEXCEPT {
return reverse_iterator(begin());
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const _NOEXCEPT {
return const_reverse_iterator(begin());
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crbegin() const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator
+ crbegin() const _NOEXCEPT {
return const_reverse_iterator(end());
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const _NOEXCEPT {
return const_reverse_iterator(begin());
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference front() {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference front() {
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "list::front called on empty list");
return __base::__end_.__next_->__as_node()->__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_VALID_ELEMENT_ACCESS(!empty(), "list::front called on empty list");
return __base::__end_.__next_->__as_node()->__get_value();
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference back() {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference back() {
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "list::back called on empty list");
return __base::__end_.__prev_->__as_node()->__get_value();
}
- _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reference back() const {
+ [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI const_reference back() const {
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "list::back called on empty list");
return __base::__end_.__prev_->__as_node()->__get_value();
}
diff --git a/libcxx/test/libcxx/diagnostics/list.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/list.nodiscard.verify.cpp
index f19224a71f5cc..bfce9b85ef76c 100644
--- a/libcxx/test/libcxx/diagnostics/list.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/list.nodiscard.verify.cpp
@@ -13,6 +13,33 @@
#include <list>
void test() {
- std::list<int> list;
- list.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ std::list<int> l;
+ const std::list<int> cl;
+
+ l.get_allocator(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+ l.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.rbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.rbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.rend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.rend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.crbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.crbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.crend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.crend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+ l.front(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.front(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ l.back(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ cl.back(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
}
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