[libcxx-commits] [libcxx] ffcb0a4 - [libc++] Update polymorphic_allocator to never contain a nullptr (#148423)
via libcxx-commits
libcxx-commits at lists.llvm.org
Wed Jul 16 01:04:00 PDT 2025
Author: Nikolas Klauser
Date: 2025-07-16T10:03:57+02:00
New Revision: ffcb0a4559b850c5ba51003ae1877c7c2ae9836f
URL: https://github.com/llvm/llvm-project/commit/ffcb0a4559b850c5ba51003ae1877c7c2ae9836f
DIFF: https://github.com/llvm/llvm-project/commit/ffcb0a4559b850c5ba51003ae1877c7c2ae9836f.diff
LOG: [libc++] Update polymorphic_allocator to never contain a nullptr (#148423)
According to `[mem.poly.allocator.ctor]` the pointer contained in
`polymorphic_allocator` can never be null. The default constructor uses
`get_default_resource()`, which never returns null and the constructor
taking a pointer explicitly has a precondition that the pointer is
non-null.
This patch adds a warning and an assertion in case a user passes a null
pointer to `polymorphic_allocator` as well as marking `resource()` to
never return null.
This also fixes some tests which contained UB.
Fixes #148420
Added:
libcxx/test/libcxx/mem/mem.res/ctor.nullptr.assert.pass.cpp
libcxx/test/libcxx/mem/mem.res/nonnull.verify.cpp
Modified:
libcxx/include/__memory_resource/polymorphic_allocator.h
libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/resource.pass.cpp
libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/select_on_container_copy_construction.pass.cpp
Removed:
################################################################################
diff --git a/libcxx/include/__memory_resource/polymorphic_allocator.h b/libcxx/include/__memory_resource/polymorphic_allocator.h
index b95c6a37c5c11..1b8711f10811d 100644
--- a/libcxx/include/__memory_resource/polymorphic_allocator.h
+++ b/libcxx/include/__memory_resource/polymorphic_allocator.h
@@ -50,7 +50,9 @@ class _LIBCPP_AVAILABILITY_PMR polymorphic_allocator {
_LIBCPP_HIDE_FROM_ABI polymorphic_allocator() noexcept : __res_(std::pmr::get_default_resource()) {}
- _LIBCPP_HIDE_FROM_ABI polymorphic_allocator(memory_resource* __r) noexcept : __res_(__r) {}
+ _LIBCPP_HIDE_FROM_ABI polymorphic_allocator(memory_resource* _LIBCPP_DIAGNOSE_NULLPTR __r) noexcept : __res_(__r) {
+ _LIBCPP_ASSERT_NON_NULL(__r, "Attempted to pass a nullptr resource to polymorphic_alloator");
+ }
_LIBCPP_HIDE_FROM_ABI polymorphic_allocator(const polymorphic_allocator&) = default;
@@ -174,7 +176,7 @@ class _LIBCPP_AVAILABILITY_PMR polymorphic_allocator {
return polymorphic_allocator();
}
- _LIBCPP_HIDE_FROM_ABI memory_resource* resource() const noexcept { return __res_; }
+ [[__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/test/libcxx/mem/mem.res/ctor.nullptr.assert.pass.cpp b/libcxx/test/libcxx/mem/mem.res/ctor.nullptr.assert.pass.cpp
new file mode 100644
index 0000000000000..831985f2ce37f
--- /dev/null
+++ b/libcxx/test/libcxx/mem/mem.res/ctor.nullptr.assert.pass.cpp
@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_resource>
+
+// Test hardening assertions for std::pmr::polymorphic_allocator.
+
+// REQUIRES: has-unix-headers
+// REQUIRES: libcpp-hardening-mode={{extensive|debug}}
+// UNSUPPORTED: c++03, c++11, c++14
+// XFAIL: libcpp-hardening-mode=debug && availability-verbose_abort-missing
+
+// We're testing nullptr assertions
+// ADDITIONAL_COMPILE_FLAGS: -Wno-nonnull
+
+#include <memory_resource>
+
+#include "check_assertion.h"
+
+int main(int, char**) {
+ TEST_LIBCPP_ASSERT_FAILURE(
+ std::pmr::polymorphic_allocator<int>(nullptr), "Attempted to pass a nullptr resource to polymorphic_alloator");
+
+ return 0;
+}
diff --git a/libcxx/test/libcxx/mem/mem.res/nonnull.verify.cpp b/libcxx/test/libcxx/mem/mem.res/nonnull.verify.cpp
new file mode 100644
index 0000000000000..c5a6c8a3db3cf
--- /dev/null
+++ b/libcxx/test/libcxx/mem/mem.res/nonnull.verify.cpp
@@ -0,0 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// 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, c++11, c++14
+
+// Ensure that passing a nullptr to polymorphic_allocator is diagnosed
+
+#include <memory_resource>
+
+void test() {
+ std::pmr::polymorphic_allocator<int> alloc(nullptr); // expected-warning {{null passed}}
+}
diff --git a/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/resource.pass.cpp b/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/resource.pass.cpp
index 23865f67a694b..22cb72414e975 100644
--- a/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/resource.pass.cpp
+++ b/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/resource.pass.cpp
@@ -17,11 +17,19 @@
// memory_resource *
// polymorphic_allocator<T>::resource() const
-#include <memory_resource>
#include <cassert>
+#include <cstddef>
+#include <memory_resource>
+#include <new>
#include "test_macros.h"
+struct resource : std::pmr::memory_resource {
+ void* do_allocate(size_t, size_t) override { TEST_THROW(std::bad_alloc()); }
+ void do_deallocate(void*, size_t, size_t) override { assert(false); }
+ bool do_is_equal(const std::pmr::memory_resource&) const noexcept override { return false; }
+};
+
int main(int, char**) {
typedef std::pmr::polymorphic_allocator<void> A;
{
@@ -29,24 +37,19 @@ int main(int, char**) {
ASSERT_SAME_TYPE(decltype(a.resource()), std::pmr::memory_resource*);
}
{
- std::pmr::memory_resource* mptr = (std::pmr::memory_resource*)42;
- A const a(mptr);
- assert(a.resource() == mptr);
- }
- {
- A const a(nullptr);
- assert(a.resource() == nullptr);
- assert(a.resource() == nullptr);
+ resource res;
+ A const a(&res);
+ assert(a.resource() == &res);
}
{
A const a;
assert(a.resource() == std::pmr::get_default_resource());
}
{
- std::pmr::memory_resource* mptr = (std::pmr::memory_resource*)42;
- std::pmr::set_default_resource(mptr);
+ resource res;
+ std::pmr::set_default_resource(&res);
A const a;
- assert(a.resource() == mptr);
+ assert(a.resource() == &res);
assert(a.resource() == std::pmr::get_default_resource());
}
diff --git a/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/select_on_container_copy_construction.pass.cpp b/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/select_on_container_copy_construction.pass.cpp
index 58d6cccd244cf..ccac1178fe516 100644
--- a/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/select_on_container_copy_construction.pass.cpp
+++ b/libcxx/test/std/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/select_on_container_copy_construction.pass.cpp
@@ -17,11 +17,19 @@
// polymorphic_allocator
// polymorphic_allocator<T>::select_on_container_copy_construction() const
-#include <memory_resource>
#include <cassert>
+#include <cstddef>
+#include <memory_resource>
+#include <new>
#include "test_macros.h"
+struct resource : std::pmr::memory_resource {
+ void* do_allocate(size_t, size_t) override { TEST_THROW(std::bad_alloc()); }
+ void do_deallocate(void*, size_t, size_t) override { assert(false); }
+ bool do_is_equal(const std::pmr::memory_resource&) const noexcept override { return false; }
+};
+
int main(int, char**) {
typedef std::pmr::polymorphic_allocator<void> A;
{
@@ -29,22 +37,12 @@ int main(int, char**) {
ASSERT_SAME_TYPE(decltype(a.select_on_container_copy_construction()), A);
}
{
- std::pmr::memory_resource* mptr = (std::pmr::memory_resource*)42;
- A const a(mptr);
- assert(a.resource() == mptr);
- A const other = a.select_on_container_copy_construction();
- assert(other.resource() == std::pmr::get_default_resource());
- assert(a.resource() == mptr);
- }
- {
- std::pmr::memory_resource* mptr = (std::pmr::memory_resource*)42;
- std::pmr::set_default_resource(mptr);
- A const a(nullptr);
- assert(a.resource() == nullptr);
+ resource res;
+ A const a(&res);
+ assert(a.resource() == &res);
A const other = a.select_on_container_copy_construction();
assert(other.resource() == std::pmr::get_default_resource());
- assert(other.resource() == mptr);
- assert(a.resource() == nullptr);
+ assert(a.resource() == &res);
}
return 0;
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