release/19.x: [libc++] Fix bug in atomic_ref's calculation of lock_free-ness (#99570) #100792
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@dalg24 What do you think about merging this PR to the release branch? |
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@llvm/pr-subscribers-libcxx Author: None (llvmbot) ChangesBackport cc1dfb3 Requested by: @ldionne Patch is 25.03 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/100792.diff 5 Files Affected:
diff --git a/libcxx/include/__atomic/atomic_ref.h b/libcxx/include/__atomic/atomic_ref.h
index 156f1961151c1..2849b82e1a3dd 100644
--- a/libcxx/include/__atomic/atomic_ref.h
+++ b/libcxx/include/__atomic/atomic_ref.h
@@ -42,6 +42,19 @@ _LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER >= 20
+// These types are required to make __atomic_is_always_lock_free work across GCC and Clang.
+// The purpose of this trick is to make sure that we provide an object with the correct alignment
+// to __atomic_is_always_lock_free, since that answer depends on the alignment.
+template <size_t _Alignment>
+struct __alignment_checker_type {
+ alignas(_Alignment) char __data;
+};
+
+template <size_t _Alignment>
+struct __get_aligner_instance {
+ static constexpr __alignment_checker_type<_Alignment> __instance{};
+};
+
template <class _Tp>
struct __atomic_ref_base {
protected:
@@ -105,7 +118,7 @@ struct __atomic_ref_base {
// that the pointer is going to be aligned properly at runtime because that is a (checked) precondition
// of atomic_ref's constructor.
static constexpr bool is_always_lock_free =
- __atomic_always_lock_free(sizeof(_Tp), reinterpret_cast<void*>(-required_alignment));
+ __atomic_always_lock_free(sizeof(_Tp), &__get_aligner_instance<required_alignment>::__instance);
_LIBCPP_HIDE_FROM_ABI bool is_lock_free() const noexcept { return __atomic_is_lock_free(sizeof(_Tp), __ptr_); }
diff --git a/libcxx/test/std/atomics/atomics.lockfree/is_always_lock_free.cpp b/libcxx/test/std/atomics/atomics.lockfree/is_always_lock_free.cpp
new file mode 100644
index 0000000000000..2dc7f5c765419
--- /dev/null
+++ b/libcxx/test/std/atomics/atomics.lockfree/is_always_lock_free.cpp
@@ -0,0 +1,165 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// <atomic>
+//
+// template <class T>
+// class atomic;
+//
+// static constexpr bool is_always_lock_free;
+
+#include <atomic>
+#include <cassert>
+#include <cstddef>
+
+#include "test_macros.h"
+#include "atomic_helpers.h"
+
+template <typename T>
+void check_always_lock_free(std::atomic<T> const& a) {
+ using InfoT = LockFreeStatusInfo<T>;
+
+ constexpr std::same_as<const bool> decltype(auto) is_always_lock_free = std::atomic<T>::is_always_lock_free;
+
+ // If we know the status of T for sure, validate the exact result of the function.
+ if constexpr (InfoT::status_known) {
+ constexpr LockFreeStatus known_status = InfoT::value;
+ if constexpr (known_status == LockFreeStatus::always) {
+ static_assert(is_always_lock_free, "is_always_lock_free is inconsistent with known lock-free status");
+ assert(a.is_lock_free() && "is_lock_free() is inconsistent with known lock-free status");
+ } else if constexpr (known_status == LockFreeStatus::never) {
+ static_assert(!is_always_lock_free, "is_always_lock_free is inconsistent with known lock-free status");
+ assert(!a.is_lock_free() && "is_lock_free() is inconsistent with known lock-free status");
+ } else {
+ assert(a.is_lock_free() || !a.is_lock_free()); // This is kinda dumb, but we might as well call the function once.
+ }
+ }
+
+ // In all cases, also sanity-check it based on the implication always-lock-free => lock-free.
+ if (is_always_lock_free) {
+ std::same_as<bool> decltype(auto) is_lock_free = a.is_lock_free();
+ assert(is_lock_free);
+ }
+ ASSERT_NOEXCEPT(a.is_lock_free());
+}
+
+#define CHECK_ALWAYS_LOCK_FREE(T) \
+ do { \
+ typedef T type; \
+ type obj{}; \
+ std::atomic<type> a(obj); \
+ check_always_lock_free(a); \
+ } while (0)
+
+void test() {
+ char c = 'x';
+ check_always_lock_free(std::atomic<char>(c));
+
+ int i = 0;
+ check_always_lock_free(std::atomic<int>(i));
+
+ float f = 0.f;
+ check_always_lock_free(std::atomic<float>(f));
+
+ int* p = &i;
+ check_always_lock_free(std::atomic<int*>(p));
+
+ CHECK_ALWAYS_LOCK_FREE(bool);
+ CHECK_ALWAYS_LOCK_FREE(char);
+ CHECK_ALWAYS_LOCK_FREE(signed char);
+ CHECK_ALWAYS_LOCK_FREE(unsigned char);
+#if TEST_STD_VER > 17 && defined(__cpp_char8_t)
+ CHECK_ALWAYS_LOCK_FREE(char8_t);
+#endif
+ CHECK_ALWAYS_LOCK_FREE(char16_t);
+ CHECK_ALWAYS_LOCK_FREE(char32_t);
+ CHECK_ALWAYS_LOCK_FREE(wchar_t);
+ CHECK_ALWAYS_LOCK_FREE(short);
+ CHECK_ALWAYS_LOCK_FREE(unsigned short);
+ CHECK_ALWAYS_LOCK_FREE(int);
+ CHECK_ALWAYS_LOCK_FREE(unsigned int);
+ CHECK_ALWAYS_LOCK_FREE(long);
+ CHECK_ALWAYS_LOCK_FREE(unsigned long);
+ CHECK_ALWAYS_LOCK_FREE(long long);
+ CHECK_ALWAYS_LOCK_FREE(unsigned long long);
+ CHECK_ALWAYS_LOCK_FREE(std::nullptr_t);
+ CHECK_ALWAYS_LOCK_FREE(void*);
+ CHECK_ALWAYS_LOCK_FREE(float);
+ CHECK_ALWAYS_LOCK_FREE(double);
+ CHECK_ALWAYS_LOCK_FREE(long double);
+#if __has_attribute(vector_size) && defined(_LIBCPP_VERSION)
+ CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(1 * sizeof(int)))));
+ CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(2 * sizeof(int)))));
+ CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(4 * sizeof(int)))));
+ CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(16 * sizeof(int)))));
+ CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(32 * sizeof(int)))));
+ CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(1 * sizeof(float)))));
+ CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(2 * sizeof(float)))));
+ CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(4 * sizeof(float)))));
+ CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(16 * sizeof(float)))));
+ CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(32 * sizeof(float)))));
+ CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(1 * sizeof(double)))));
+ CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(2 * sizeof(double)))));
+ CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(4 * sizeof(double)))));
+ CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(16 * sizeof(double)))));
+ CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(32 * sizeof(double)))));
+#endif // __has_attribute(vector_size) && defined(_LIBCPP_VERSION)
+ CHECK_ALWAYS_LOCK_FREE(struct Empty{});
+ CHECK_ALWAYS_LOCK_FREE(struct OneInt { int i; });
+ CHECK_ALWAYS_LOCK_FREE(struct IntArr2 { int i[2]; });
+ CHECK_ALWAYS_LOCK_FREE(struct FloatArr3 { float i[3]; });
+ CHECK_ALWAYS_LOCK_FREE(struct LLIArr2 { long long int i[2]; });
+ CHECK_ALWAYS_LOCK_FREE(struct LLIArr4 { long long int i[4]; });
+ CHECK_ALWAYS_LOCK_FREE(struct LLIArr8 { long long int i[8]; });
+ CHECK_ALWAYS_LOCK_FREE(struct LLIArr16 { long long int i[16]; });
+ CHECK_ALWAYS_LOCK_FREE(struct Padding {
+ char c; /* padding */
+ long long int i;
+ });
+ CHECK_ALWAYS_LOCK_FREE(union IntFloat {
+ int i;
+ float f;
+ });
+ CHECK_ALWAYS_LOCK_FREE(enum class CharEnumClass : char{foo});
+
+ // C macro and static constexpr must be consistent.
+ enum class CharEnumClass : char { foo };
+ static_assert(std::atomic<bool>::is_always_lock_free == (2 == ATOMIC_BOOL_LOCK_FREE), "");
+ static_assert(std::atomic<char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
+ static_assert(std::atomic<CharEnumClass>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
+ static_assert(std::atomic<signed char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
+ static_assert(std::atomic<unsigned char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
+#if TEST_STD_VER > 17 && defined(__cpp_char8_t)
+ static_assert(std::atomic<char8_t>::is_always_lock_free == (2 == ATOMIC_CHAR8_T_LOCK_FREE), "");
+#endif
+ static_assert(std::atomic<char16_t>::is_always_lock_free == (2 == ATOMIC_CHAR16_T_LOCK_FREE), "");
+ static_assert(std::atomic<char32_t>::is_always_lock_free == (2 == ATOMIC_CHAR32_T_LOCK_FREE), "");
+ static_assert(std::atomic<wchar_t>::is_always_lock_free == (2 == ATOMIC_WCHAR_T_LOCK_FREE), "");
+ static_assert(std::atomic<short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE), "");
+ static_assert(std::atomic<unsigned short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE), "");
+ static_assert(std::atomic<int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE), "");
+ static_assert(std::atomic<unsigned int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE), "");
+ static_assert(std::atomic<long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE), "");
+ static_assert(std::atomic<unsigned long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE), "");
+ static_assert(std::atomic<long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
+ static_assert(std::atomic<unsigned long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
+ static_assert(std::atomic<void*>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE), "");
+ static_assert(std::atomic<std::nullptr_t>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE), "");
+
+#if TEST_STD_VER >= 20
+ static_assert(std::atomic_signed_lock_free::is_always_lock_free, "");
+ static_assert(std::atomic_unsigned_lock_free::is_always_lock_free, "");
+#endif
+}
+
+int main(int, char**) {
+ test();
+ return 0;
+}
diff --git a/libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp b/libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
deleted file mode 100644
index 6d6e6477bc251..0000000000000
--- a/libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
+++ /dev/null
@@ -1,120 +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
-//
-//===----------------------------------------------------------------------===//
-//
-// UNSUPPORTED: c++03, c++11, c++14
-
-// <atomic>
-
-// static constexpr bool is_always_lock_free;
-
-#include <atomic>
-#include <cassert>
-#include <cstddef>
-
-#include "test_macros.h"
-
-template <typename T>
-void checkAlwaysLockFree() {
- if (std::atomic<T>::is_always_lock_free) {
- assert(std::atomic<T>().is_lock_free());
- }
-}
-
-void run()
-{
-// structs and unions can't be defined in the template invocation.
-// Work around this with a typedef.
-#define CHECK_ALWAYS_LOCK_FREE(T) \
- do { \
- typedef T type; \
- checkAlwaysLockFree<type>(); \
- } while (0)
-
- CHECK_ALWAYS_LOCK_FREE(bool);
- CHECK_ALWAYS_LOCK_FREE(char);
- CHECK_ALWAYS_LOCK_FREE(signed char);
- CHECK_ALWAYS_LOCK_FREE(unsigned char);
-#if TEST_STD_VER > 17 && defined(__cpp_char8_t)
- CHECK_ALWAYS_LOCK_FREE(char8_t);
-#endif
- CHECK_ALWAYS_LOCK_FREE(char16_t);
- CHECK_ALWAYS_LOCK_FREE(char32_t);
- CHECK_ALWAYS_LOCK_FREE(wchar_t);
- CHECK_ALWAYS_LOCK_FREE(short);
- CHECK_ALWAYS_LOCK_FREE(unsigned short);
- CHECK_ALWAYS_LOCK_FREE(int);
- CHECK_ALWAYS_LOCK_FREE(unsigned int);
- CHECK_ALWAYS_LOCK_FREE(long);
- CHECK_ALWAYS_LOCK_FREE(unsigned long);
- CHECK_ALWAYS_LOCK_FREE(long long);
- CHECK_ALWAYS_LOCK_FREE(unsigned long long);
- CHECK_ALWAYS_LOCK_FREE(std::nullptr_t);
- CHECK_ALWAYS_LOCK_FREE(void*);
- CHECK_ALWAYS_LOCK_FREE(float);
- CHECK_ALWAYS_LOCK_FREE(double);
- CHECK_ALWAYS_LOCK_FREE(long double);
-#if __has_attribute(vector_size) && defined(_LIBCPP_VERSION)
- CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(1 * sizeof(int)))));
- CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(2 * sizeof(int)))));
- CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(4 * sizeof(int)))));
- CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(16 * sizeof(int)))));
- CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(32 * sizeof(int)))));
- CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(1 * sizeof(float)))));
- CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(2 * sizeof(float)))));
- CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(4 * sizeof(float)))));
- CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(16 * sizeof(float)))));
- CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(32 * sizeof(float)))));
- CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(1 * sizeof(double)))));
- CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(2 * sizeof(double)))));
- CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(4 * sizeof(double)))));
- CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(16 * sizeof(double)))));
- CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(32 * sizeof(double)))));
-#endif // __has_attribute(vector_size) && defined(_LIBCPP_VERSION)
- CHECK_ALWAYS_LOCK_FREE(struct Empty {});
- CHECK_ALWAYS_LOCK_FREE(struct OneInt { int i; });
- CHECK_ALWAYS_LOCK_FREE(struct IntArr2 { int i[2]; });
- CHECK_ALWAYS_LOCK_FREE(struct FloatArr3 { float i[3]; });
- CHECK_ALWAYS_LOCK_FREE(struct LLIArr2 { long long int i[2]; });
- CHECK_ALWAYS_LOCK_FREE(struct LLIArr4 { long long int i[4]; });
- CHECK_ALWAYS_LOCK_FREE(struct LLIArr8 { long long int i[8]; });
- CHECK_ALWAYS_LOCK_FREE(struct LLIArr16 { long long int i[16]; });
- CHECK_ALWAYS_LOCK_FREE(struct Padding { char c; /* padding */ long long int i; });
- CHECK_ALWAYS_LOCK_FREE(union IntFloat { int i; float f; });
- CHECK_ALWAYS_LOCK_FREE(enum class CharEnumClass : char { foo });
-
- // C macro and static constexpr must be consistent.
- enum class CharEnumClass : char { foo };
- static_assert(std::atomic<bool>::is_always_lock_free == (2 == ATOMIC_BOOL_LOCK_FREE), "");
- static_assert(std::atomic<char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
- static_assert(std::atomic<CharEnumClass>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
- static_assert(std::atomic<signed char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
- static_assert(std::atomic<unsigned char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE), "");
-#if TEST_STD_VER > 17 && defined(__cpp_char8_t)
- static_assert(std::atomic<char8_t>::is_always_lock_free == (2 == ATOMIC_CHAR8_T_LOCK_FREE), "");
-#endif
- static_assert(std::atomic<char16_t>::is_always_lock_free == (2 == ATOMIC_CHAR16_T_LOCK_FREE), "");
- static_assert(std::atomic<char32_t>::is_always_lock_free == (2 == ATOMIC_CHAR32_T_LOCK_FREE), "");
- static_assert(std::atomic<wchar_t>::is_always_lock_free == (2 == ATOMIC_WCHAR_T_LOCK_FREE), "");
- static_assert(std::atomic<short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE), "");
- static_assert(std::atomic<unsigned short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE), "");
- static_assert(std::atomic<int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE), "");
- static_assert(std::atomic<unsigned int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE), "");
- static_assert(std::atomic<long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE), "");
- static_assert(std::atomic<unsigned long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE), "");
- static_assert(std::atomic<long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
- static_assert(std::atomic<unsigned long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
- static_assert(std::atomic<void*>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE), "");
- static_assert(std::atomic<std::nullptr_t>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE), "");
-
-#if TEST_STD_VER >= 20
- static_assert(std::atomic_signed_lock_free::is_always_lock_free, "");
- static_assert(std::atomic_unsigned_lock_free::is_always_lock_free, "");
-#endif
-}
-
-int main(int, char**) { run(); return 0; }
diff --git a/libcxx/test/std/atomics/atomics.ref/is_always_lock_free.pass.cpp b/libcxx/test/std/atomics/atomics.ref/is_always_lock_free.pass.cpp
index 94f65e3b4b669..acdbf63a24d85 100644
--- a/libcxx/test/std/atomics/atomics.ref/is_always_lock_free.pass.cpp
+++ b/libcxx/test/std/atomics/atomics.ref/is_always_lock_free.pass.cpp
@@ -9,7 +9,10 @@
// UNSUPPORTED: c++03, c++11, c++14, c++17
// <atomic>
-
+//
+// template <class T>
+// class atomic_ref;
+//
// static constexpr bool is_always_lock_free;
// bool is_lock_free() const noexcept;
@@ -18,10 +21,29 @@
#include <concepts>
#include "test_macros.h"
+#include "atomic_helpers.h"
template <typename T>
-void check_always_lock_free(std::atomic_ref<T> const a) {
- std::same_as<const bool> decltype(auto) is_always_lock_free = std::atomic_ref<T>::is_always_lock_free;
+void check_always_lock_free(std::atomic_ref<T> const& a) {
+ using InfoT = LockFreeStatusInfo<T>;
+
+ constexpr std::same_as<const bool> decltype(auto) is_always_lock_free = std::atomic_ref<T>::is_always_lock_free;
+
+ // If we know the status of T for sure, validate the exact result of the function.
+ if constexpr (InfoT::status_known) {
+ constexpr LockFreeStatus known_status = InfoT::value;
+ if constexpr (known_status == LockFreeStatus::always) {
+ static_assert(is_always_lock_free, "is_always_lock_free is inconsistent with known lock-free status");
+ assert(a.is_lock_free() && "is_lock_free() is inconsistent with known lock-free status");
+ } else if constexpr (known_status == LockFreeStatus::never) {
+ static_assert(!is_always_lock_free, "is_always_lock_free is inconsistent with known lock-free status");
+ assert(!a.is_lock_free() && "is_lock_free() is inconsistent with known lock-free status");
+ } else {
+ assert(a.is_lock_free() || !a.is_lock_free()); // This is kinda dumb, but we might as well call the function once.
+ }
+ }
+
+ // In all cases, also sanity-check it based on the implication always-lock-free => lock-free.
if (is_always_lock_free) {
std::same_as<bool> decltype(auto) is_lock_free = a.is_lock_free();
assert(is_lock_free);
@@ -33,10 +55,14 @@ void check_always_lock_free(std::atomic_ref<T> const a) {
do { \
typedef T type; \
type obj{}; \
- check_always_lock_free(std::atomic_ref<type>(obj)); \
+ std::atomic_ref<type> a(obj); \
+ check_always_lock_free(a); \
} while (0)
void test() {
+ char c = 'x';
+ check_always_lock_free(std::atomic_ref<char>(c));
+
int i = 0;
check_always_lock_free(std::atomic_ref<int>(i));
diff --git a/libcxx/test/support/atomic_helpers.h b/libcxx/test/support/atomic_helpers.h
index 0266a0961067b..d2f2b751cb47d 100644
--- a/libcxx/test/support/atomic_helpers.h
+++ b/libcxx/test/support/atomic_helpers.h
@@ -11,9 +11,112 @@
#include <cassert>
#include <cstdint>
+#include <cstddef>
+#include <type_traits>
#include "test_macros.h"
+#if defined(TEST_COMPILER_CLANG)
+# define TEST_ATOMIC_CHAR_LOCK_FREE __CLANG_ATOMIC_CHAR_LOCK_FREE
+# def...
[truncated]
|
dalg24
approved these changes
Jul 26, 2024
…99570) The builtin __atomic_always_lock_free takes into account the type of the pointer provided as the second argument. Because we were passing void*, rather than T*, the calculation failed. This meant that atomic_ref<T>::is_always_lock_free was only true for char & bool. This bug exists elsewhere in the atomic library (when using GCC, we fail to pass a pointer at all, and we fail to correctly align the atomic like _Atomic would). This change also attempts to start sorting out testing difficulties with this function that caused the bug to exist by using the __GCC_ATOMIC_(CHAR|SHORT|INT|LONG|LLONG|POINTER)_IS_LOCK_FREE predefined macros to establish an expected value for `is_always_lock_free` and `is_lock_free` for the respective types, as well as types with matching sizes and compatible alignment values. Using these compiler pre-defines we can actually validate that certain types, like char and int, are actually always lock free like they are on every platform in the wild. Note that this patch was actually authored by Eric Fiselier but I picked up the patch and GitHub won't let me set Eric as the primary author. Co-authored-by: Eric Fiselier <eric@efcs.ca> (cherry picked from commit cc1dfb3)
|
@ldionne (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR. |
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Backport cc1dfb3
Requested by: @ldionne