[libcxx-commits] [libcxx] [libc++][memory_resource] Applied `[[nodiscard]]` (PR #172134)
via libcxx-commits
libcxx-commits at lists.llvm.org
Sat Dec 13 23:53:09 PST 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Hristo Hristov (H-G-Hristov)
<details>
<summary>Changes</summary>
Towards #<!-- -->172124
---
Full diff: https://github.com/llvm/llvm-project/pull/172134.diff
7 Files Affected:
- (modified) libcxx/include/__memory_resource/memory_resource.h (+10-6)
- (modified) libcxx/include/__memory_resource/monotonic_buffer_resource.h (+4-3)
- (modified) libcxx/include/__memory_resource/polymorphic_allocator.h (+4-2)
- (modified) libcxx/include/__memory_resource/synchronized_pool_resource.h (+6-4)
- (modified) libcxx/include/__memory_resource/unsynchronized_pool_resource.h (+5-4)
- (modified) libcxx/test/libcxx/diagnostics/memory_resource.nodiscard.verify.cpp (+84-7)
- (modified) libcxx/test/std/utilities/utility/mem.res/mem.res/mem.res.private/protected_members.verify.cpp (+6-6)
``````````diff
diff --git a/libcxx/include/__memory_resource/memory_resource.h b/libcxx/include/__memory_resource/memory_resource.h
index f93f10fe21a2d..23ef4f4b77084 100644
--- a/libcxx/include/__memory_resource/memory_resource.h
+++ b/libcxx/include/__memory_resource/memory_resource.h
@@ -42,7 +42,9 @@ class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI memory_resource {
do_deallocate(__p, __bytes, __align);
}
- _LIBCPP_HIDE_FROM_ABI bool is_equal(const memory_resource& __other) const noexcept { return do_is_equal(__other); }
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool is_equal(const memory_resource& __other) const noexcept {
+ return do_is_equal(__other);
+ }
private:
virtual void* do_allocate(size_t, size_t) = 0;
@@ -68,17 +70,19 @@ operator!=(const memory_resource& __lhs, const memory_resource& __rhs) noexcept
// [mem.res.global]
-[[__gnu__::__returns_nonnull__]] _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI memory_resource*
+[[nodiscard]] [[__gnu__::__returns_nonnull__]] _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI memory_resource*
get_default_resource() noexcept;
[[__gnu__::__returns_nonnull__]] _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI memory_resource*
set_default_resource(memory_resource*) noexcept;
-[[using __gnu__: __returns_nonnull__, __const__]] _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI memory_resource*
-new_delete_resource() noexcept;
+[[nodiscard]] [[using __gnu__: __returns_nonnull__, __const__]] _LIBCPP_AVAILABILITY_PMR
+ _LIBCPP_EXPORTED_FROM_ABI memory_resource*
+ new_delete_resource() noexcept;
-[[using __gnu__: __returns_nonnull__, __const__]] _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI memory_resource*
-null_memory_resource() noexcept;
+[[nodiscard]] [[using __gnu__: __returns_nonnull__, __const__]] _LIBCPP_AVAILABILITY_PMR
+ _LIBCPP_EXPORTED_FROM_ABI memory_resource*
+ null_memory_resource() noexcept;
} // namespace pmr
diff --git a/libcxx/include/__memory_resource/monotonic_buffer_resource.h b/libcxx/include/__memory_resource/monotonic_buffer_resource.h
index 942d490ce3aea..bb2a6749c8ca6 100644
--- a/libcxx/include/__memory_resource/monotonic_buffer_resource.h
+++ b/libcxx/include/__memory_resource/monotonic_buffer_resource.h
@@ -93,14 +93,15 @@ class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI monotonic_buffer_resour
}
}
- _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
protected:
- void* do_allocate(size_t __bytes, size_t __alignment) override; // key function
+ [[nodiscard]] void* do_allocate(size_t __bytes, size_t __alignment) override; // key function
_LIBCPP_HIDE_FROM_ABI_VIRTUAL void do_deallocate(void*, size_t, size_t) override {}
- _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool
+ do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
return this == std::addressof(__other);
}
diff --git a/libcxx/include/__memory_resource/polymorphic_allocator.h b/libcxx/include/__memory_resource/polymorphic_allocator.h
index 9a351199b5b16..e3d12dcda345c 100644
--- a/libcxx/include/__memory_resource/polymorphic_allocator.h
+++ b/libcxx/include/__memory_resource/polymorphic_allocator.h
@@ -173,11 +173,13 @@ class _LIBCPP_AVAILABILITY_PMR polymorphic_allocator {
__p->~_Tp();
}
- _LIBCPP_HIDE_FROM_ABI polymorphic_allocator select_on_container_copy_construction() const noexcept {
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI polymorphic_allocator select_on_container_copy_construction() const noexcept {
return polymorphic_allocator();
}
- [[__gnu__::__returns_nonnull__]] _LIBCPP_HIDE_FROM_ABI memory_resource* resource() const noexcept { return __res_; }
+ [[nodiscard]] [[__gnu__::__returns_nonnull__]] _LIBCPP_HIDE_FROM_ABI memory_resource* resource() const noexcept {
+ return __res_;
+ }
_LIBCPP_HIDE_FROM_ABI friend bool
operator==(const polymorphic_allocator& __lhs, const polymorphic_allocator& __rhs) noexcept {
diff --git a/libcxx/include/__memory_resource/synchronized_pool_resource.h b/libcxx/include/__memory_resource/synchronized_pool_resource.h
index bcc1ac4a172e3..f2633e58bd3a2 100644
--- a/libcxx/include/__memory_resource/synchronized_pool_resource.h
+++ b/libcxx/include/__memory_resource/synchronized_pool_resource.h
@@ -56,12 +56,14 @@ class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI synchronized_pool_resou
__unsync_.release();
}
- _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __unsync_.upstream_resource(); }
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const {
+ return __unsync_.upstream_resource();
+ }
- _LIBCPP_HIDE_FROM_ABI pool_options options() const { return __unsync_.options(); }
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI pool_options options() const { return __unsync_.options(); }
protected:
- _LIBCPP_HIDE_FROM_ABI_VIRTUAL void* do_allocate(size_t __bytes, size_t __align) override {
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI_VIRTUAL void* do_allocate(size_t __bytes, size_t __align) override {
# if _LIBCPP_HAS_THREADS
unique_lock<mutex> __lk(__mut_);
# endif
@@ -75,7 +77,7 @@ class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI synchronized_pool_resou
return __unsync_.deallocate(__p, __bytes, __align);
}
- bool do_is_equal(const memory_resource& __other) const noexcept override; // key function
+ [[nodiscard]] bool do_is_equal(const memory_resource& __other) const noexcept override; // key function
private:
# if _LIBCPP_HAS_THREADS
diff --git a/libcxx/include/__memory_resource/unsynchronized_pool_resource.h b/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
index 92da16c559fea..3ea2c0a032f13 100644
--- a/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
+++ b/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
@@ -76,16 +76,17 @@ class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI unsynchronized_pool_res
void release();
- _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
- [[__gnu__::__pure__]] pool_options options() const;
+ [[nodiscard]] [[__gnu__::__pure__]] pool_options options() const;
protected:
- void* do_allocate(size_t __bytes, size_t __align) override; // key function
+ [[nodiscard]] void* do_allocate(size_t __bytes, size_t __align) override; // key function
void do_deallocate(void* __p, size_t __bytes, size_t __align) override;
- _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool
+ do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
return &__other == this;
}
diff --git a/libcxx/test/libcxx/diagnostics/memory_resource.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/memory_resource.nodiscard.verify.cpp
index 57c3823ba3fdc..4a996c536e057 100644
--- a/libcxx/test/libcxx/diagnostics/memory_resource.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/memory_resource.nodiscard.verify.cpp
@@ -6,20 +6,97 @@
//
//===----------------------------------------------------------------------===//
-// UNSUPPORTED: c++03, c++11, c++14
+// REQUIRES: std-at-least-c++17
// check that <memory_resource> functions are marked [[nodiscard]]
-// clang-format off
-
#include <memory_resource>
#include "test_macros.h"
void test() {
- std::pmr::memory_resource* resource = std::pmr::null_memory_resource();
- resource->allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ {
+ std::pmr::memory_resource* r = std::pmr::null_memory_resource();
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ r->allocate(1);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ r->is_equal(*r);
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ std::pmr::get_default_resource();
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ std::pmr::new_delete_resource();
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ std::pmr::null_memory_resource();
+ }
+
+ {
+ std::pmr::monotonic_buffer_resource r;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ r.upstream_resource();
+
+ struct test_protected : public std::pmr::monotonic_buffer_resource {
+ void test() {
+ std::pmr::monotonic_buffer_resource other;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ do_allocate(94, 82);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ is_equal(other);
+ }
+ };
+ }
+
+ {
+ std::pmr::polymorphic_allocator<int> a;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ a.allocate(1);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ a.select_on_container_copy_construction();
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ a.resource();
+ }
+
+ {
+ std::pmr::synchronized_pool_resource r;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ r.upstream_resource();
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ r.options();
+
+ struct test_protected : public std::pmr::synchronized_pool_resource {
+ void test() {
+ std::pmr::synchronized_pool_resource other;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ do_allocate(94, 82);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ is_equal(other);
+ }
+ };
+ }
+
+ {
+ std::pmr::unsynchronized_pool_resource r;
+
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ r.upstream_resource();
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ r.options();
+
+ struct test_protected : public std::pmr::unsynchronized_pool_resource {
+ void test() {
+ std::pmr::unsynchronized_pool_resource other;
- std::pmr::polymorphic_allocator<int> polymorphic_allocator;
- polymorphic_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}}
+ do_allocate(94, 82);
+ // expected-warning at +1 {{ignoring return value of function declared with 'nodiscard' attribute}}
+ is_equal(other);
+ }
+ };
+ }
}
diff --git a/libcxx/test/std/utilities/utility/mem.res/mem.res/mem.res.private/protected_members.verify.cpp b/libcxx/test/std/utilities/utility/mem.res/mem.res/mem.res.private/protected_members.verify.cpp
index e19d7e93ca354..d546e4f077b34 100644
--- a/libcxx/test/std/utilities/utility/mem.res/mem.res/mem.res.private/protected_members.verify.cpp
+++ b/libcxx/test/std/utilities/utility/mem.res/mem.res/mem.res.private/protected_members.verify.cpp
@@ -29,20 +29,20 @@
void test() {
{
std::pmr::monotonic_buffer_resource m;
- m.do_allocate(0, 0); // expected-error{{'do_allocate' is a protected member}}
+ (void)m.do_allocate(0, 0); // expected-error{{'do_allocate' is a protected member}}
m.do_deallocate(nullptr, 0, 0); // expected-error{{'do_deallocate' is a protected member}}
- m.do_is_equal(m); // expected-error{{'do_is_equal' is a protected member}}
+ (void)m.do_is_equal(m); // expected-error{{'do_is_equal' is a protected member}}
}
{
std::pmr::synchronized_pool_resource m;
- m.do_allocate(0, 0); // expected-error{{'do_allocate' is a protected member}}
+ (void)m.do_allocate(0, 0); // expected-error{{'do_allocate' is a protected member}}
m.do_deallocate(nullptr, 0, 0); // expected-error{{'do_deallocate' is a protected member}}
- m.do_is_equal(m); // expected-error{{'do_is_equal' is a protected member}}
+ (void)m.do_is_equal(m); // expected-error{{'do_is_equal' is a protected member}}
}
{
std::pmr::unsynchronized_pool_resource m;
- m.do_allocate(0, 0); // expected-error{{'do_allocate' is a protected member}}
+ (void)m.do_allocate(0, 0); // expected-error{{'do_allocate' is a protected member}}
m.do_deallocate(nullptr, 0, 0); // expected-error{{'do_deallocate' is a protected member}}
- m.do_is_equal(m); // expected-error{{'do_is_equal' is a protected member}}
+ (void)m.do_is_equal(m); // expected-error{{'do_is_equal' is a protected member}}
}
}
``````````
</details>
https://github.com/llvm/llvm-project/pull/172134
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