[libc++] Applied `[[nodiscard]]` to Language Support (partially) #169611

H-G-Hristov · 2025-11-26T06:20:24Z

https://wg21.link/#support

[[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

The following was implemented in this patch:

<compare>
<corotine>
<initializer_list>
Integer comparisons

llvmbot · 2025-11-26T06:20:59Z

@llvm/pr-subscribers-libcxx

Author: Hristo Hristov (H-G-Hristov)

Changes

https://wg21.link/#support

[[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

The following was implemented in this patch:

<compare>
<corotine>
<initializer_list>
Integer comparisons

Full diff: https://github.com/llvm/llvm-project/pull/169611.diff

7 Files Affected:

(modified) libcxx/include/__compare/is_eq.h (+6-6)
(modified) libcxx/include/__coroutine/coroutine_handle.h (+9-9)
(modified) libcxx/include/__coroutine/noop_coroutine_handle.h (+6-4)
(modified) libcxx/include/__utility/cmp.h (+7-7)
(modified) libcxx/include/initializer_list (+9-3)
(modified) libcxx/test/libcxx/diagnostics/utility.nodiscard.verify.cpp (+22-6)
(added) libcxx/test/libcxx/language.support/nodiscard.verify.cpp (+92)

diff --git a/libcxx/include/__compare/is_eq.h b/libcxx/include/__compare/is_eq.h
index 9a82df1ebe88b..ee4d11bc7c792 100644
--- a/libcxx/include/__compare/is_eq.h
+++ b/libcxx/include/__compare/is_eq.h
@@ -20,12 +20,12 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool is_eq(partial_ordering __c) noexcept { return __c == 0; }
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool is_neq(partial_ordering __c) noexcept { return __c != 0; }
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool is_lt(partial_ordering __c) noexcept { return __c < 0; }
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool is_lteq(partial_ordering __c) noexcept { return __c <= 0; }
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool is_gt(partial_ordering __c) noexcept { return __c > 0; }
-_LIBCPP_HIDE_FROM_ABI inline constexpr bool is_gteq(partial_ordering __c) noexcept { return __c >= 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_eq(partial_ordering __c) noexcept { return __c == 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_neq(partial_ordering __c) noexcept { return __c != 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_lt(partial_ordering __c) noexcept { return __c < 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_lteq(partial_ordering __c) noexcept { return __c <= 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_gt(partial_ordering __c) noexcept { return __c > 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_gteq(partial_ordering __c) noexcept { return __c >= 0; }
 
 #endif // _LIBCPP_STD_VER >= 20
 
diff --git a/libcxx/include/__coroutine/coroutine_handle.h b/libcxx/include/__coroutine/coroutine_handle.h
index b7add258510eb..b26a650748832 100644
--- a/libcxx/include/__coroutine/coroutine_handle.h
+++ b/libcxx/include/__coroutine/coroutine_handle.h
@@ -44,9 +44,9 @@ struct coroutine_handle<void> {
   }
 
   // [coroutine.handle.export.import], export/import
-  _LIBCPP_HIDE_FROM_ABI constexpr void* address() const noexcept { return __handle_; }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr void* address() const noexcept { return __handle_; }
 
-  _LIBCPP_HIDE_FROM_ABI static constexpr coroutine_handle from_address(void* __addr) noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr coroutine_handle from_address(void* __addr) noexcept {
     coroutine_handle __tmp;
     __tmp.__handle_ = __addr;
     return __tmp;
@@ -55,7 +55,7 @@ struct coroutine_handle<void> {
   // [coroutine.handle.observers], observers
   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return __handle_ != nullptr; }
 
-  _LIBCPP_HIDE_FROM_ABI bool done() const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool done() const {
     _LIBCPP_ASSERT_VALID_EXTERNAL_API_CALL(__is_suspended(), "done() can be called only on suspended coroutines");
     return __builtin_coro_done(__handle_);
   }
@@ -100,7 +100,7 @@ struct coroutine_handle {
 
   _LIBCPP_HIDE_FROM_ABI constexpr coroutine_handle(nullptr_t) noexcept {}
 
-  _LIBCPP_HIDE_FROM_ABI static coroutine_handle from_promise(_Promise& __promise) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static coroutine_handle from_promise(_Promise& __promise) {
     using _RawPromise = __remove_cv_t<_Promise>;
     coroutine_handle __tmp;
     __tmp.__handle_ =
@@ -114,9 +114,9 @@ struct coroutine_handle {
   }
 
   // [coroutine.handle.export.import], export/import
-  _LIBCPP_HIDE_FROM_ABI constexpr void* address() const noexcept { return __handle_; }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr void* address() const noexcept { return __handle_; }
 
-  _LIBCPP_HIDE_FROM_ABI static constexpr coroutine_handle from_address(void* __addr) noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr coroutine_handle from_address(void* __addr) noexcept {
     coroutine_handle __tmp;
     __tmp.__handle_ = __addr;
     return __tmp;
@@ -130,7 +130,7 @@ struct coroutine_handle {
   // [coroutine.handle.observers], observers
   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return __handle_ != nullptr; }
 
-  _LIBCPP_HIDE_FROM_ABI bool done() const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool done() const {
     _LIBCPP_ASSERT_VALID_EXTERNAL_API_CALL(__is_suspended(), "done() can be called only on suspended coroutines");
     return __builtin_coro_done(__handle_);
   }
@@ -150,7 +150,7 @@ struct coroutine_handle {
   }
 
   // [coroutine.handle.promise], promise access
-  _LIBCPP_HIDE_FROM_ABI _Promise& promise() const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _Promise& promise() const {
     return *static_cast<_Promise*>(__builtin_coro_promise(this->__handle_, alignof(_Promise), false));
   }
 
@@ -165,7 +165,7 @@ struct coroutine_handle {
 // [coroutine.handle.hash]
 template <class _Tp>
 struct hash<coroutine_handle<_Tp>> {
-  _LIBCPP_HIDE_FROM_ABI size_t operator()(const coroutine_handle<_Tp>& __v) const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI size_t operator()(const coroutine_handle<_Tp>& __v) const noexcept {
     return hash<void*>()(__v.address());
   }
 };
diff --git a/libcxx/include/__coroutine/noop_coroutine_handle.h b/libcxx/include/__coroutine/noop_coroutine_handle.h
index 692398a8a8431..b9c54d3b42bef 100644
--- a/libcxx/include/__coroutine/noop_coroutine_handle.h
+++ b/libcxx/include/__coroutine/noop_coroutine_handle.h
@@ -35,7 +35,7 @@ struct coroutine_handle<noop_coroutine_promise> {
 
   // [coroutine.handle.noop.observers], observers
   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return true; }
-  _LIBCPP_HIDE_FROM_ABI constexpr bool done() const noexcept { return false; }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool done() const noexcept { return false; }
 
   // [coroutine.handle.noop.resumption], resumption
   _LIBCPP_HIDE_FROM_ABI constexpr void operator()() const noexcept {}
@@ -43,13 +43,13 @@ struct coroutine_handle<noop_coroutine_promise> {
   _LIBCPP_HIDE_FROM_ABI constexpr void destroy() const noexcept {}
 
   // [coroutine.handle.noop.promise], promise access
-  _LIBCPP_HIDE_FROM_ABI noop_coroutine_promise& promise() const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI noop_coroutine_promise& promise() const noexcept {
     return *static_cast<noop_coroutine_promise*>(
         __builtin_coro_promise(this->__handle_, alignof(noop_coroutine_promise), false));
   }
 
   // [coroutine.handle.noop.address], address
-  _LIBCPP_HIDE_FROM_ABI constexpr void* address() const noexcept { return __handle_; }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr void* address() const noexcept { return __handle_; }
 
 private:
   _LIBCPP_HIDE_FROM_ABI friend coroutine_handle<noop_coroutine_promise> noop_coroutine() noexcept;
@@ -86,7 +86,9 @@ inline noop_coroutine_handle::__noop_coroutine_frame_ty_ noop_coroutine_handle::
 #  endif
 
 // [coroutine.noop.coroutine]
-inline _LIBCPP_HIDE_FROM_ABI noop_coroutine_handle noop_coroutine() noexcept { return noop_coroutine_handle(); }
+[[nodiscard]] inline _LIBCPP_HIDE_FROM_ABI noop_coroutine_handle noop_coroutine() noexcept {
+  return noop_coroutine_handle();
+}
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/libcxx/include/__utility/cmp.h b/libcxx/include/__utility/cmp.h
index 68864e23e0397..7cfe640ceb423 100644
--- a/libcxx/include/__utility/cmp.h
+++ b/libcxx/include/__utility/cmp.h
@@ -31,7 +31,7 @@ concept __comparison_can_promote_to =
     sizeof(_Tp) < sizeof(_Ip) || (sizeof(_Tp) == sizeof(_Ip) && __signed_integer<_Tp>);
 
 template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Up>
-_LIBCPP_HIDE_FROM_ABI constexpr bool cmp_equal(_Tp __t, _Up __u) noexcept {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_equal(_Tp __t, _Up __u) noexcept {
   if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
     return __t == __u;
   else if constexpr (__comparison_can_promote_to<_Tp, int> && __comparison_can_promote_to<_Up, int>)
@@ -45,12 +45,12 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_equal(_Tp __t, _Up __u) noexcept {
 }
 
 template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Up>
-_LIBCPP_HIDE_FROM_ABI constexpr bool cmp_not_equal(_Tp __t, _Up __u) noexcept {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_not_equal(_Tp __t, _Up __u) noexcept {
   return !std::cmp_equal(__t, __u);
 }
 
 template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Up>
-_LIBCPP_HIDE_FROM_ABI constexpr bool cmp_less(_Tp __t, _Up __u) noexcept {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_less(_Tp __t, _Up __u) noexcept {
   if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
     return __t < __u;
   else if constexpr (__comparison_can_promote_to<_Tp, int> && __comparison_can_promote_to<_Up, int>)
@@ -64,22 +64,22 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_less(_Tp __t, _Up __u) noexcept {
 }
 
 template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Up>
-_LIBCPP_HIDE_FROM_ABI constexpr bool cmp_greater(_Tp __t, _Up __u) noexcept {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_greater(_Tp __t, _Up __u) noexcept {
   return std::cmp_less(__u, __t);
 }
 
 template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Up>
-_LIBCPP_HIDE_FROM_ABI constexpr bool cmp_less_equal(_Tp __t, _Up __u) noexcept {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_less_equal(_Tp __t, _Up __u) noexcept {
   return !std::cmp_greater(__t, __u);
 }
 
 template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Up>
-_LIBCPP_HIDE_FROM_ABI constexpr bool cmp_greater_equal(_Tp __t, _Up __u) noexcept {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool cmp_greater_equal(_Tp __t, _Up __u) noexcept {
   return !std::cmp_less(__t, __u);
 }
 
 template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Up>
-_LIBCPP_HIDE_FROM_ABI constexpr bool in_range(_Up __u) noexcept {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool in_range(_Up __u) noexcept {
   return std::cmp_less_equal(__u, numeric_limits<_Tp>::max()) &&
          std::cmp_greater_equal(__u, numeric_limits<_Tp>::min());
 }
diff --git a/libcxx/include/initializer_list b/libcxx/include/initializer_list
index 00e0d4ea4a2df..44cd45668388b 100644
--- a/libcxx/include/initializer_list
+++ b/libcxx/include/initializer_list
@@ -78,11 +78,17 @@ public:
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 initializer_list() _NOEXCEPT : __begin_(nullptr), __size_(0) {}
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t size() const _NOEXCEPT { return __size_; }
+  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t size() const _NOEXCEPT {
+    return __size_;
+  }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _Ep* begin() const _NOEXCEPT { return __begin_; }
+  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _Ep* begin() const _NOEXCEPT {
+    return __begin_;
+  }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _Ep* end() const _NOEXCEPT { return __begin_ + __size_; }
+  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const _Ep* end() const _NOEXCEPT {
+    return __begin_ + __size_;
+  }
 };
 
 template <class _Ep>
diff --git a/libcxx/test/libcxx/diagnostics/utility.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/utility.nodiscard.verify.cpp
index 524be96736bad..2f5b3ba0fc642 100644
--- a/libcxx/test/libcxx/diagnostics/utility.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/utility.nodiscard.verify.cpp
@@ -10,8 +10,6 @@
 
 // check that <utility> functions are marked [[nodiscard]]
 
-// clang-format off
-
 #include <utility>
 
 #include "test_macros.h"
@@ -19,15 +17,33 @@
 void test() {
   int i = 0;
 
-  std::forward<int>(i);     // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  std::forward<int>(1);     // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  std::move(i);             // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  std::move_if_noexcept(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::forward<int>(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::forward<int>(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::move(i);         // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::move_if_noexcept(i);
 
 #if TEST_STD_VER >= 17
   std::as_const(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 #endif
 
+#if TEST_STD_VER >= 20
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::cmp_equal(94, 82);
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::cmp_not_equal(94, 82);
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::cmp_less(94, 82);
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::cmp_greater(94, 82);
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::cmp_less_equal(94, 82);
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::cmp_greater_equal(94, 82);
+  // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::in_range<long>(49);
+#endif
+
 #if TEST_STD_VER >= 23
   enum E { Apple, Orange } e = Apple;
   std::to_underlying(e); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
diff --git a/libcxx/test/libcxx/language.support/nodiscard.verify.cpp b/libcxx/test/libcxx/language.support/nodiscard.verify.cpp
new file mode 100644
index 0000000000000..88a7f728f1c67
--- /dev/null
+++ b/libcxx/test/libcxx/language.support/nodiscard.verify.cpp
@@ -0,0 +1,92 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+// check that <utility> functions are marked [[nodiscard]]
+
+#include <compare>
+#include <coroutine>
+#include <initializer_list>
+
+#include "test_macros.h"
+
+void test() {
+#if TEST_STD_VER >= 20
+  { // <compare>
+    int x     = 94;
+    int y     = 82;
+    auto oRes = x <=> y;
+
+    std::is_eq(oRes);   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    std::is_neq(oRes);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    std::is_lt(oRes);   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    std::is_lteq(oRes); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    std::is_gt(oRes);   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    std::is_gteq(oRes); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  }
+#endif
+
+#if TEST_STD_VER >= 20
+  { // <coroutine>
+    struct EmptyPromise {
+    } promise;
+
+    {
+      std::coroutine_handle<void> cr{};
+
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.address();
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      std::coroutine_handle<void>::from_address(&promise);
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.done();
+
+      std::hash<std::coroutine_handle<void>> hash;
+      hash(cr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    }
+    {
+      std::coroutine_handle<EmptyPromise> cr;
+
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      std::coroutine_handle<EmptyPromise>::from_promise(promise);
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.address();
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      std::coroutine_handle<EmptyPromise>::from_address(&promise);
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.done();
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.promise();
+    }
+    {
+      std::coroutine_handle<std::noop_coroutine_promise> cr = std::noop_coroutine();
+
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.done();
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.promise();
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      cr.address();
+
+      // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+      std::noop_coroutine();
+    }
+  }
+#endif
+
+#if TEST_STD_VER >= 20
+  { // <initializer_list>
+    std::initializer_list<int> il{94, 82, 49};
+
+    il.size();  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    il.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+    il.end();   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  }
+#endif
+}

https://wg21.link/#support `[[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 The following was implemented in this patch: - [x] `<compare>` - [x] `<corotine>` - [x] `<initializer_list>` - [x] Integer comparisons

libcxx/test/libcxx/language.support/nodiscard.verify.cpp

Co-authored-by: A. Jiang <de34@live.cn>

libcxx/test/libcxx/language.support/nodiscard.verify.cpp

…m#169611) https://wg21.link/#support `[[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 The following was implemented in this patch: - [x] `<compare>` - [x] `<corotine>` - [x] `<initializer_list>` - [x] Integer comparisons --------- Co-authored-by: Hristo Hristov <zingam@outlook.com> Co-authored-by: A. Jiang <de34@live.cn>

H-G-Hristov requested a review from a team as a code owner November 26, 2025 06:20

llvmbot added the libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. label Nov 26, 2025

H-G-Hristov force-pushed the hgh/libcxx/nodiscard-to-language-support branch from 171cdc0 to 253c4d8 Compare November 26, 2025 07:13

H-G-Hristov force-pushed the hgh/libcxx/nodiscard-to-language-support branch from 253c4d8 to 31a4b79 Compare November 26, 2025 07:15

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[libc++] std.functional.hash should be exported from Clang modules for some standard library headers #169634

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Zingam merged commit 8706d82 into llvm:main Nov 26, 2025
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H-G-Hristov deleted the hgh/libcxx/nodiscard-to-language-support branch November 26, 2025 21:48

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[libc++] Applied [[nodiscard]] to Language Support (partially) #169611

[libc++] Applied [[nodiscard]] to Language Support (partially) #169611

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H-G-Hristov commented Nov 26, 2025

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llvmbot commented Nov 26, 2025

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[libc++] Applied `[[nodiscard]]` to Language Support (partially) #169611

[libc++] Applied `[[nodiscard]]` to Language Support (partially) #169611