[libcxx-commits] [libcxx] [libc++][memory] Applied `[[nodiscard]]` to more functions (PR #172131)
Hristo Hristov via libcxx-commits
libcxx-commits at lists.llvm.org
Wed Jan 7 09:24:38 PST 2026
https://github.com/H-G-Hristov updated https://github.com/llvm/llvm-project/pull/172131
>From bcfa3216ce2f7db3b806b04fdc1bb65c834ba555 Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Sat, 13 Dec 2025 08:14:12 +0200
Subject: [PATCH 1/7] [libc+] Applied `[[nodiscard]]` to Allocators
Towards #172124
---
libcxx/include/__memory/addressof.h | 12 ++--
libcxx/include/__memory/allocator.h | 7 +-
.../__memory/is_sufficiently_aligned.h | 2 +-
.../include/__memory/raw_storage_iterator.h | 2 +-
.../diagnostics/memory.nodiscard.verify.cpp | 66 +++++++++++++------
5 files changed, 60 insertions(+), 29 deletions(-)
diff --git a/libcxx/include/__memory/addressof.h b/libcxx/include/__memory/addressof.h
index 667071dfc6635..52ec94a5299fa 100644
--- a/libcxx/include/__memory/addressof.h
+++ b/libcxx/include/__memory/addressof.h
@@ -19,7 +19,8 @@
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_NO_CFI _LIBCPP_HIDE_FROM_ABI _Tp* addressof(_Tp& __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_NO_CFI _LIBCPP_HIDE_FROM_ABI _Tp*
+addressof(_Tp& __x) _NOEXCEPT {
return __builtin_addressof(__x);
}
@@ -27,24 +28,25 @@ inline _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_NO_CFI _LIBCPP_HIDE_FROM_ABI _Tp* a
// Objective-C++ Automatic Reference Counting uses qualified pointers
// that require special addressof() signatures.
template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI __strong _Tp* addressof(__strong _Tp& __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI __strong _Tp* addressof(__strong _Tp& __x) _NOEXCEPT {
return &__x;
}
# if __has_feature(objc_arc_weak)
template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI __weak _Tp* addressof(__weak _Tp& __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI __weak _Tp* addressof(__weak _Tp& __x) _NOEXCEPT {
return &__x;
}
# endif
template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI __autoreleasing _Tp* addressof(__autoreleasing _Tp& __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI __autoreleasing _Tp* addressof(__autoreleasing _Tp& __x) _NOEXCEPT {
return &__x;
}
template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI __unsafe_unretained _Tp* addressof(__unsafe_unretained _Tp& __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI __unsafe_unretained _Tp*
+addressof(__unsafe_unretained _Tp& __x) _NOEXCEPT {
return &__x;
}
#endif
diff --git a/libcxx/include/__memory/allocator.h b/libcxx/include/__memory/allocator.h
index 1c96a2ab64578..609b305a1250f 100644
--- a/libcxx/include/__memory/allocator.h
+++ b/libcxx/include/__memory/allocator.h
@@ -120,10 +120,11 @@ class allocator
typedef allocator<_Up> other;
};
- _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI pointer address(reference __x) const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI pointer address(reference __x) const _NOEXCEPT {
return std::addressof(__x);
}
- _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI const_pointer address(const_reference __x) const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI const_pointer
+ address(const_reference __x) const _NOEXCEPT {
return std::addressof(__x);
}
@@ -131,7 +132,7 @@ class allocator
return allocate(__n);
}
- _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
return size_type(~0) / sizeof(_Tp);
}
diff --git a/libcxx/include/__memory/is_sufficiently_aligned.h b/libcxx/include/__memory/is_sufficiently_aligned.h
index 4280920cabb4b..93d24aaf78f0b 100644
--- a/libcxx/include/__memory/is_sufficiently_aligned.h
+++ b/libcxx/include/__memory/is_sufficiently_aligned.h
@@ -23,7 +23,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER >= 26
template <size_t _Alignment, class _Tp>
-_LIBCPP_HIDE_FROM_ABI bool is_sufficiently_aligned(_Tp* __ptr) {
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool is_sufficiently_aligned(_Tp* __ptr) {
return reinterpret_cast<uintptr_t>(__ptr) % _Alignment == 0;
}
diff --git a/libcxx/include/__memory/raw_storage_iterator.h b/libcxx/include/__memory/raw_storage_iterator.h
index d98b3faf48468..7c9b34076de46 100644
--- a/libcxx/include/__memory/raw_storage_iterator.h
+++ b/libcxx/include/__memory/raw_storage_iterator.h
@@ -67,7 +67,7 @@ class _LIBCPP_DEPRECATED_IN_CXX17 raw_storage_iterator
return __t;
}
# if _LIBCPP_STD_VER >= 14
- _LIBCPP_HIDE_FROM_ABI _OutputIterator base() const { return __x_; }
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _OutputIterator base() const { return __x_; }
# endif
};
diff --git a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
index 6410c84e926aa..e4e753822688a 100644
--- a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
@@ -6,37 +6,65 @@
//
//===----------------------------------------------------------------------===//
-// UNSUPPORTED: c++03
+// <memory>
-// check that <memory> functions are marked [[nodiscard]]
+// Check that functions are marked [[nodiscard]]
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX20_REMOVED_RAW_STORAGE_ITERATOR
// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX20_REMOVED_TEMPORARY_BUFFER
// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS
-// clang-format off
-
#include <memory>
#include "test_macros.h"
void test() {
- std::get_temporary_buffer<int>(0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-}
+ int i = 0;
-void test_allocator_traits() {
- std::allocator<int> allocator;
- std::allocator_traits<std::allocator<int>> allocator_traits;
- allocator_traits.allocate(allocator, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
- allocator_traits.allocate(allocator, 1, nullptr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-}
+ {
+ std::addressof(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ std::get_temporary_buffer<int>(0);
+#if _LIBCPP_STD_VER >= 26
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ std::is_sufficiently_aligned<2>(&i);
+#endif
+ }
-void test_allocator() {
std::allocator<int> allocator;
- allocator.allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-#if TEST_STD_VER <= 17
- allocator.allocate(1, nullptr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-#endif
+
+ {
+ std::allocator_traits<std::allocator<int> > allocator_traits;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ allocator_traits.allocate(allocator, 1);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ allocator_traits.allocate(allocator, 1, nullptr);
+ }
+
#if TEST_STD_VER >= 23
- allocator.allocate_at_least(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ allocator.allocate_at_least(1);
+#endif
+
+#if TEST_STD_VER <= 17
+ {
+ const int ci = 0;
+
+ allocator.address(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ allocator.address(ci); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ allocator.allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ allocator.allocate(1, nullptr);
+ allocator.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ }
+#endif // TEST_STD_VER <= 17
+
+#if TEST_STD_VER >= 14
+ {
+ std::raw_storage_iterator<int*, int> it{nullptr};
+
+ it.base(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ }
#endif
-}
+}
\ No newline at end of file
>From 55cd9bcef7b1257a028bdd6e791ffb7ec5f1420a Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Sat, 3 Jan 2026 18:14:51 +0200
Subject: [PATCH 2/7] Addressed review comments
---
libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
index e4e753822688a..e9f72e65a98ac 100644
--- a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
@@ -42,6 +42,8 @@ void test() {
allocator_traits.allocate(allocator, 1, nullptr);
}
+ allocator.allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
#if TEST_STD_VER >= 23
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
allocator.allocate_at_least(1);
@@ -53,7 +55,7 @@ void test() {
allocator.address(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
allocator.address(ci); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
- allocator.allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
allocator.allocate(1, nullptr);
allocator.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
>From b569578253a8bd7cb7f746e8ed4bef3e0fcf88b3 Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Tue, 6 Jan 2026 14:09:02 +0200
Subject: [PATCH 3/7] Addressed review comments
---
libcxx/include/__memory/allocator_traits.h | 6 +-
.../include/__memory/raw_storage_iterator.h | 2 +-
.../diagnostics/memory.nodiscard.verify.cpp | 57 ++++++++++++++++---
.../allocate.verify.cpp | 34 -----------
4 files changed, 53 insertions(+), 46 deletions(-)
delete mode 100644 libcxx/test/std/utilities/memory/allocator.traits/allocator.traits.members/allocate.verify.cpp
diff --git a/libcxx/include/__memory/allocator_traits.h b/libcxx/include/__memory/allocator_traits.h
index 46c247f7040e0..c389c1d057b89 100644
--- a/libcxx/include/__memory/allocator_traits.h
+++ b/libcxx/include/__memory/allocator_traits.h
@@ -314,13 +314,15 @@ struct allocator_traits {
}
template <class _Ap = _Alloc, __enable_if_t<__has_max_size_v<const _Ap>, int> = 0>
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static size_type max_size(const allocator_type& __a) _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static size_type
+ max_size(const allocator_type& __a) _NOEXCEPT {
_LIBCPP_SUPPRESS_DEPRECATED_PUSH
return __a.max_size();
_LIBCPP_SUPPRESS_DEPRECATED_POP
}
template <class _Ap = _Alloc, __enable_if_t<!__has_max_size_v<const _Ap>, int> = 0>
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static size_type max_size(const allocator_type&) _NOEXCEPT {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static size_type
+ max_size(const allocator_type&) _NOEXCEPT {
return numeric_limits<size_type>::max() / sizeof(value_type);
}
diff --git a/libcxx/include/__memory/raw_storage_iterator.h b/libcxx/include/__memory/raw_storage_iterator.h
index 7c9b34076de46..dff0fed3b7565 100644
--- a/libcxx/include/__memory/raw_storage_iterator.h
+++ b/libcxx/include/__memory/raw_storage_iterator.h
@@ -46,7 +46,7 @@ class _LIBCPP_DEPRECATED_IN_CXX17 raw_storage_iterator
typedef void reference;
_LIBCPP_HIDE_FROM_ABI explicit raw_storage_iterator(_OutputIterator __x) : __x_(__x) {}
- _LIBCPP_HIDE_FROM_ABI raw_storage_iterator& operator*() { return *this; }
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI raw_storage_iterator& operator*() { return *this; }
_LIBCPP_HIDE_FROM_ABI raw_storage_iterator& operator=(const _Tp& __element) {
::new ((void*)std::addressof(*__x_)) _Tp(__element);
return *this;
diff --git a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
index e9f72e65a98ac..6ff0f152d85e3 100644
--- a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
@@ -31,26 +31,64 @@ void test() {
#endif
}
- std::allocator<int> allocator;
-
{
- std::allocator_traits<std::allocator<int> > allocator_traits;
+ struct Alloc {
+ typedef int value_type;
+
+ value_type* allocate(std::size_t n);
+ value_type* allocate(std::size_t n, const void* p);
+ } allocator;
+ typedef std::allocator_traits<Alloc> AllocTraits;
+
+ struct HintedAlloc {
+ typedef int value_type;
+ typedef const void* const_void_pointer;
+ value_type* allocate(std::size_t n);
+ value_type* allocate(std::size_t n, const void* p);
+ } hintedAllocator;
+ typedef std::allocator_traits<HintedAlloc> HintedAllocTraits;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ AllocTraits::allocate(allocator, 1);
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
- allocator_traits.allocate(allocator, 1);
+ HintedAllocTraits::allocate(hintedAllocator, 1);
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
- allocator_traits.allocate(allocator, 1, nullptr);
+ AllocTraits::allocate(allocator, 1, nullptr);
+
+#if TEST_STD_VER >= 23
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ AllocTraits::allocate_at_least(allocator, 1, nullptr);
+#endif
+
+ struct SizedAlloc {
+ typedef int value_type;
+ typedef std::size_t size_type;
+
+ value_type* allocate(std::size_t n);
+ value_type* allocate(std::size_t n, const void* p);
+ size_type max_size();
+ } sizedAllocator;
+ typedef std::allocator_traits<SizedAlloc> SizedAllocTraits;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ SizedAllocTraits::max_size(sizedAllocator);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ AllocTraits::max_size(allocator);
}
- allocator.allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ {
+ std::allocator<int> allocator;
+
+ allocator.allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
#if TEST_STD_VER >= 23
- // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
- allocator.allocate_at_least(1);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ allocator.allocate_at_least(1);
#endif
#if TEST_STD_VER <= 17
- {
+
const int ci = 0;
allocator.address(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
@@ -66,6 +104,7 @@ void test() {
{
std::raw_storage_iterator<int*, int> it{nullptr};
+ *it; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
it.base(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
}
#endif
diff --git a/libcxx/test/std/utilities/memory/allocator.traits/allocator.traits.members/allocate.verify.cpp b/libcxx/test/std/utilities/memory/allocator.traits/allocator.traits.members/allocate.verify.cpp
deleted file mode 100644
index adb4d697e1324..0000000000000
--- a/libcxx/test/std/utilities/memory/allocator.traits/allocator.traits.members/allocate.verify.cpp
+++ /dev/null
@@ -1,34 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// <memory>
-
-// template <class Alloc>
-// struct allocator_traits
-// {
-// static constexpr pointer allocate(allocator_type& a, size_type n);
-// ...
-// };
-
-// UNSUPPORTED: c++03, c++11, c++14, c++17
-
-#include <cstddef>
-#include <memory>
-
-template <class T>
-struct A {
- typedef T value_type;
- value_type* allocate(std::size_t n);
- value_type* allocate(std::size_t n, const void* p);
-};
-
-void f() {
- A<int> a;
- std::allocator_traits<A<int> >::allocate(a, 10); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
- std::allocator_traits<A<int> >::allocate(a, 10, nullptr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-}
>From 2698553d0f9b39e2c91453e89f6eec795a8c0231 Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Tue, 6 Jan 2026 14:37:52 +0200
Subject: [PATCH 4/7] Updated `allocator_traits.h` with `[[nodiscard]]`
---
libcxx/include/__memory/allocator_traits.h | 4 +--
.../diagnostics/memory.nodiscard.verify.cpp | 36 +++++++++++++------
2 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/libcxx/include/__memory/allocator_traits.h b/libcxx/include/__memory/allocator_traits.h
index c389c1d057b89..b38d7293a3fd3 100644
--- a/libcxx/include/__memory/allocator_traits.h
+++ b/libcxx/include/__memory/allocator_traits.h
@@ -327,12 +327,12 @@ struct allocator_traits {
}
template <class _Ap = _Alloc, __enable_if_t<__has_select_on_container_copy_construction_v<const _Ap>, int> = 0>
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static allocator_type
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static allocator_type
select_on_container_copy_construction(const allocator_type& __a) {
return __a.select_on_container_copy_construction();
}
template <class _Ap = _Alloc, __enable_if_t<!__has_select_on_container_copy_construction_v<const _Ap>, int> = 0>
- _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static allocator_type
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static allocator_type
select_on_container_copy_construction(const allocator_type& __a) {
return __a;
}
diff --git a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
index 6ff0f152d85e3..9bd33d4818014 100644
--- a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
@@ -35,8 +35,8 @@ void test() {
struct Alloc {
typedef int value_type;
- value_type* allocate(std::size_t n);
- value_type* allocate(std::size_t n, const void* p);
+ value_type* allocate(std::size_t) { return nullptr; }
+ value_type* allocate(std::size_t, const void*) { return nullptr; }
} allocator;
typedef std::allocator_traits<Alloc> AllocTraits;
@@ -44,8 +44,8 @@ void test() {
typedef int value_type;
typedef const void* const_void_pointer;
- value_type* allocate(std::size_t n);
- value_type* allocate(std::size_t n, const void* p);
+ value_type* allocate(std::size_t) { return nullptr; }
+ value_type* allocate(std::size_t, const void*) { return nullptr; }
} hintedAllocator;
typedef std::allocator_traits<HintedAlloc> HintedAllocTraits;
@@ -58,15 +58,16 @@ void test() {
#if TEST_STD_VER >= 23
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
- AllocTraits::allocate_at_least(allocator, 1, nullptr);
+ AllocTraits::allocate_at_least(allocator, 1);
#endif
struct SizedAlloc {
typedef int value_type;
typedef std::size_t size_type;
- value_type* allocate(std::size_t n);
- value_type* allocate(std::size_t n, const void* p);
+ value_type* allocate(std::size_t) { return nullptr; }
+ value_type* allocate(std::size_t, const void*) { return nullptr; }
+
size_type max_size();
} sizedAllocator;
typedef std::allocator_traits<SizedAlloc> SizedAllocTraits;
@@ -75,6 +76,22 @@ void test() {
SizedAllocTraits::max_size(sizedAllocator);
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
AllocTraits::max_size(allocator);
+
+ struct SelectAlloc {
+ typedef int value_type;
+ typedef const void* const_void_pointer;
+
+ value_type* allocate(std::size_t) { return nullptr; }
+ value_type* allocate(std::size_t, const void*) { return nullptr; }
+
+ SelectAlloc select_on_container_copy_construction() const { return SelectAlloc(); };
+ } selectAllocator;
+ typedef std::allocator_traits<SelectAlloc> SelectAllocTraits;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ SelectAllocTraits::select_on_container_copy_construction(selectAllocator);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ AllocTraits::select_on_container_copy_construction(allocator);
}
{
@@ -88,7 +105,6 @@ void test() {
#endif
#if TEST_STD_VER <= 17
-
const int ci = 0;
allocator.address(i); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
@@ -97,8 +113,8 @@ void test() {
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
allocator.allocate(1, nullptr);
allocator.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+#endif
}
-#endif // TEST_STD_VER <= 17
#if TEST_STD_VER >= 14
{
@@ -108,4 +124,4 @@ void test() {
it.base(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
}
#endif
-}
\ No newline at end of file
+}
>From 907feee70aca17353094eca4445021600b416a41 Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Tue, 6 Jan 2026 14:43:08 +0200
Subject: [PATCH 5/7] Fixed test
---
libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
index 9bd33d4818014..f276291a61cf9 100644
--- a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
@@ -52,7 +52,7 @@ void test() {
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
AllocTraits::allocate(allocator, 1);
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
- HintedAllocTraits::allocate(hintedAllocator, 1);
+ HintedAllocTraits::allocate(hintedAllocator, 1, nullptr);
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
AllocTraits::allocate(allocator, 1, nullptr);
@@ -68,7 +68,7 @@ void test() {
value_type* allocate(std::size_t) { return nullptr; }
value_type* allocate(std::size_t, const void*) { return nullptr; }
- size_type max_size();
+ size_type max_size() const { return 0; }
} sizedAllocator;
typedef std::allocator_traits<SizedAlloc> SizedAllocTraits;
>From 66f91a4fee958f74d761199e70e5e3f4a68e6e15 Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Tue, 6 Jan 2026 14:53:53 +0200
Subject: [PATCH 6/7] Final fix
---
libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
index f276291a61cf9..563c9c753e3a0 100644
--- a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
@@ -36,16 +36,16 @@ void test() {
typedef int value_type;
value_type* allocate(std::size_t) { return nullptr; }
- value_type* allocate(std::size_t, const void*) { return nullptr; }
} allocator;
typedef std::allocator_traits<Alloc> AllocTraits;
struct HintedAlloc {
typedef int value_type;
+ typedef std::size_t size_type;
typedef const void* const_void_pointer;
- value_type* allocate(std::size_t) { return nullptr; }
- value_type* allocate(std::size_t, const void*) { return nullptr; }
+ value_type* allocate(size_type) { return nullptr; }
+ value_type* allocate(size_type, const_void_pointer) { return nullptr; }
} hintedAllocator;
typedef std::allocator_traits<HintedAlloc> HintedAllocTraits;
>From fd283cdd64848673552eeebd5eb5a5bb679e6a61 Mon Sep 17 00:00:00 2001
From: Hristo Hristov <hghristov.rmm at gmail.com>
Date: Wed, 7 Jan 2026 19:24:18 +0200
Subject: [PATCH 7/7] Use `using`
---
.../diagnostics/memory.nodiscard.verify.cpp | 24 +++++++++----------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
index 563c9c753e3a0..6bddeceb9951a 100644
--- a/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory.nodiscard.verify.cpp
@@ -33,21 +33,21 @@ void test() {
{
struct Alloc {
- typedef int value_type;
+ using value_type = int;
value_type* allocate(std::size_t) { return nullptr; }
} allocator;
- typedef std::allocator_traits<Alloc> AllocTraits;
+ using AllocTraits = std::allocator_traits<Alloc>;
struct HintedAlloc {
- typedef int value_type;
- typedef std::size_t size_type;
- typedef const void* const_void_pointer;
+ using value_type = int;
+ using size_type = std::size_t;
+ using const_void_pointer = const void*;
value_type* allocate(size_type) { return nullptr; }
value_type* allocate(size_type, const_void_pointer) { return nullptr; }
} hintedAllocator;
- typedef std::allocator_traits<HintedAlloc> HintedAllocTraits;
+ using HintedAllocTraits = std::allocator_traits<HintedAlloc>;
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
AllocTraits::allocate(allocator, 1);
@@ -62,15 +62,15 @@ void test() {
#endif
struct SizedAlloc {
- typedef int value_type;
- typedef std::size_t size_type;
+ using value_type = int;
+ using size_type = std::size_t;
value_type* allocate(std::size_t) { return nullptr; }
value_type* allocate(std::size_t, const void*) { return nullptr; }
size_type max_size() const { return 0; }
} sizedAllocator;
- typedef std::allocator_traits<SizedAlloc> SizedAllocTraits;
+ using SizedAllocTraits = std::allocator_traits<SizedAlloc>;
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
SizedAllocTraits::max_size(sizedAllocator);
@@ -78,15 +78,15 @@ void test() {
AllocTraits::max_size(allocator);
struct SelectAlloc {
- typedef int value_type;
- typedef const void* const_void_pointer;
+ using value_type = int;
+ using const_void_pointer = const void*;
value_type* allocate(std::size_t) { return nullptr; }
value_type* allocate(std::size_t, const void*) { return nullptr; }
SelectAlloc select_on_container_copy_construction() const { return SelectAlloc(); };
} selectAllocator;
- typedef std::allocator_traits<SelectAlloc> SelectAllocTraits;
+ using SelectAllocTraits = std::allocator_traits<SelectAlloc>;
// expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
SelectAllocTraits::select_on_container_copy_construction(selectAllocator);
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