Skip to content

[libc++][memory_resource] Applied [[nodiscard]] #172134

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
H-G-Hristov wants to merge 3 commits into
base: main
Choose a base branch
from
+65 −15
Open

[libc++][memory_resource] Applied [[nodiscard]] #172134

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
10c5482
[libc++][memory_resource] Applied `[[nodiscard]]`
H-G-Hristov Dec 13, 2025
ef2a79d
Addressed comments
H-G-Hristov Dec 15, 2025
3ac4010
Merge branch 'main' into hgh/libcxx/nodiscard-to-memory_resource
H-G-Hristov Dec 15, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 4 additions & 2 deletions libcxx/include/__memory_resource/memory_resource.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -68,7 +70,7 @@ 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*
Expand Down
2 changes: 1 addition & 1 deletion libcxx/include/__memory_resource/monotonic_buffer_resource.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -93,7 +93,7 @@ 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
Expand Down
6 changes: 4 additions & 2 deletions libcxx/include/__memory_resource/polymorphic_allocator.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down
6 changes: 4 additions & 2 deletions libcxx/include/__memory_resource/synchronized_pool_resource.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -56,9 +56,11 @@ 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 {
Expand Down
2 changes: 1 addition & 1 deletion libcxx/include/__memory_resource/unsynchronized_pool_resource.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ 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;

Expand Down
58 changes: 51 additions & 7 deletions libcxx/test/libcxx/diagnostics/memory_resource.nodiscard.verify.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,20 +6,64 @@
//
//===----------------------------------------------------------------------===//

// 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@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
r->allocate(1);
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
r->is_equal(*r);

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
std::pmr::get_default_resource();
// expected-warning@+1 {{ignoring return value of function declared with const attribute}}
std::pmr::new_delete_resource();
// expected-warning@+1 {{ignoring return value of function declared with const attribute}}
std::pmr::null_memory_resource();
}

{
std::pmr::monotonic_buffer_resource r;

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
r.upstream_resource();
}

{
std::pmr::polymorphic_allocator<int> a;

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
a.allocate(1);
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
a.select_on_container_copy_construction();
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
a.resource();
}

{
std::pmr::synchronized_pool_resource r;

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
r.upstream_resource();
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
r.options();
}

{
std::pmr::unsynchronized_pool_resource r;

std::pmr::polymorphic_allocator<int> polymorphic_allocator;
polymorphic_allocator.allocate(1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
r.upstream_resource();
// expected-warning@+1 {{ignoring return value of function declared with pure attribute}}
r.options();
}
}
Loading