[libcxx-commits] [libcxx] [libc++] P2747R2: `constexpr` placement new (library part) (PR #105768)
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libcxx-commits at lists.llvm.org
Thu Aug 22 19:09:14 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: A. Jiang (frederick-vs-ja)
<details>
<summary>Changes</summary>
Paper link: https://wg21.link/P2747R2
The library changes affect direct `operator new` and `operator new[]` calls even when the core language changes are absent. "Actual" placement new tests are not added yet as the core language changes haven't been implemented (pending on #<!-- -->97957).
Drive-by: Formatting the whole `new.pass.cpp` and `new_array.pass.cpp`.
Closes #<!-- -->105427.
---
Full diff: https://github.com/llvm/llvm-project/pull/105768.diff
12 Files Affected:
- (modified) libcxx/docs/FeatureTestMacroTable.rst (+1-1)
- (modified) libcxx/docs/ReleaseNotes/20.rst (+1-1)
- (modified) libcxx/docs/Status/Cxx2cPapers.csv (+1-1)
- (modified) libcxx/include/__config (+6)
- (modified) libcxx/include/new (+8-2)
- (modified) libcxx/include/version (+1-1)
- (modified) libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new.pass.cpp (+21-10)
- (modified) libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new_array.pass.cpp (+25-14)
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/new.version.compile.pass.cpp (+5-11)
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp (+5-11)
- (modified) libcxx/test/support/test_macros.h (+6)
- (modified) libcxx/utils/generate_feature_test_macro_components.py (-1)
``````````diff
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index a1506e115fe70f..8a429ddd476010 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -404,7 +404,7 @@ Status
---------------------------------------------------------- -----------------
``__cpp_lib_bitset`` ``202306L``
---------------------------------------------------------- -----------------
- ``__cpp_lib_constexpr_new`` *unimplemented*
+ ``__cpp_lib_constexpr_new`` ``202406L``
---------------------------------------------------------- -----------------
``__cpp_lib_constrained_equality`` *unimplemented*
---------------------------------------------------------- -----------------
diff --git a/libcxx/docs/ReleaseNotes/20.rst b/libcxx/docs/ReleaseNotes/20.rst
index fe9f4c1973cdb4..d048ab32d1f130 100644
--- a/libcxx/docs/ReleaseNotes/20.rst
+++ b/libcxx/docs/ReleaseNotes/20.rst
@@ -38,7 +38,7 @@ What's New in Libc++ 20.0.0?
Implemented Papers
------------------
-- TODO
+- P2747R2 - ``constexpr`` placement new
Improvements and New Features
diff --git a/libcxx/docs/Status/Cxx2cPapers.csv b/libcxx/docs/Status/Cxx2cPapers.csv
index dd62bcc2555ffc..bfb5e34da458d4 100644
--- a/libcxx/docs/Status/Cxx2cPapers.csv
+++ b/libcxx/docs/Status/Cxx2cPapers.csv
@@ -63,7 +63,7 @@
"`P2642R6 <https://wg21.link/P2642R6>`__","Padded ``mdspan`` layouts","2024-03 (Tokyo)","","",""
"`P3029R1 <https://wg21.link/P3029R1>`__","Better ``mdspan``'s CTAD","2024-03 (Tokyo)","|Complete|","19.0",""
"","","","","",""
-"`P2747R2 <https://wg21.link/P2747R2>`__","``constexpr`` placement new","2024-06 (St. Louis)","","",""
+"`P2747R2 <https://wg21.link/P2747R2>`__","``constexpr`` placement new","2024-06 (St. Louis)","|Complete|","20.0",""
"`P2997R1 <https://wg21.link/P2997R1>`__","Removing the common reference requirement from the indirectly invocable concepts","2024-06 (St. Louis)","|Complete| [#note-P2997R1]_","19.0",""
"`P2389R2 <https://wg21.link/P2389R2>`__","``dextents`` Index Type Parameter","2024-06 (St. Louis)","|Complete|","19.0",""
"`P3168R2 <https://wg21.link/P3168R2>`__","Give ``std::optional`` Range Support","2024-06 (St. Louis)","","","|ranges|"
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 392053a64a8dc1..9dd8d46b48d28f 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -788,6 +788,12 @@ typedef __char32_t char32_t;
# define _LIBCPP_CONSTEXPR_SINCE_CXX23
# endif
+# if _LIBCPP_STD_VER >= 26
+# define _LIBCPP_CONSTEXPR_SINCE_CXX26 constexpr
+# else
+# define _LIBCPP_CONSTEXPR_SINCE_CXX26
+# endif
+
# ifndef _LIBCPP_WEAK
# define _LIBCPP_WEAK __attribute__((__weak__))
# endif
diff --git a/libcxx/include/new b/libcxx/include/new
index 214dbc398530bb..dc48cf44a3e7a2 100644
--- a/libcxx/include/new
+++ b/libcxx/include/new
@@ -242,8 +242,14 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p, std::size_t __sz,
# endif
# endif
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI void* operator new(std::size_t, void* __p) _NOEXCEPT { return __p; }
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI void* operator new[](std::size_t, void* __p) _NOEXCEPT { return __p; }
+_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void*
+operator new(std::size_t, void* __p) _NOEXCEPT {
+ return __p;
+}
+_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void*
+operator new[](std::size_t, void* __p) _NOEXCEPT {
+ return __p;
+}
inline _LIBCPP_HIDE_FROM_ABI void operator delete(void*, void*) _NOEXCEPT {}
inline _LIBCPP_HIDE_FROM_ABI void operator delete[](void*, void*) _NOEXCEPT {}
diff --git a/libcxx/include/version b/libcxx/include/version
index fe64343eafbc9c..aeddda625fc960 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -510,7 +510,7 @@ __cpp_lib_void_t 201411L <type_traits>
# undef __cpp_lib_bind_front
# define __cpp_lib_bind_front 202306L
# define __cpp_lib_bitset 202306L
-// # define __cpp_lib_constexpr_new 202406L
+# define __cpp_lib_constexpr_new 202406L
// # define __cpp_lib_constrained_equality 202403L
// # define __cpp_lib_copyable_function 202306L
// # define __cpp_lib_debugging 202311L
diff --git a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new.pass.cpp b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new.pass.cpp
index b857b397fc83e4..3e48a3634533a5 100644
--- a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new.pass.cpp
+++ b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new.pass.cpp
@@ -15,19 +15,30 @@
int A_constructed = 0;
-struct A
-{
- A() {++A_constructed;}
- ~A() {--A_constructed;}
+struct A {
+ A() { ++A_constructed; }
+ ~A() { --A_constructed; }
};
-int main(int, char**)
-{
- char buf[sizeof(A)];
+TEST_CONSTEXPR_CXX26 void test_direct_call() {
+ assert(::operator new(sizeof(int), &A_constructed) == &A_constructed);
- A* ap = new(buf) A;
- assert((char*)ap == buf);
- assert(A_constructed == 1);
+ char ch = '*';
+ assert(::operator new(1, &ch) == &ch);
+ assert(ch == '*');
+}
+
+#if TEST_STD_VER >= 26
+static_assert((test_direct_call(), true));
+#endif
+
+int main(int, char**) {
+ char buf[sizeof(A)];
+
+ A* ap = new (buf) A;
+ assert((char*)ap == buf);
+ assert(A_constructed == 1);
+ test_direct_call();
return 0;
}
diff --git a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new_array.pass.cpp b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new_array.pass.cpp
index 99a5442b6fb1f8..d318e338185c7e 100644
--- a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new_array.pass.cpp
+++ b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.placement/new_array.pass.cpp
@@ -15,23 +15,34 @@
int A_constructed = 0;
-struct A
-{
- A() {++A_constructed;}
- ~A() {--A_constructed;}
+struct A {
+ A() { ++A_constructed; }
+ ~A() { --A_constructed; }
};
-int main(int, char**)
-{
- const std::size_t Size = 3;
- // placement new might require additional space.
- const std::size_t ExtraSize = 64;
- char buf[Size*sizeof(A) + ExtraSize];
+TEST_CONSTEXPR_CXX26 void test_direct_call() {
+ assert(::operator new[](sizeof(int), &A_constructed) == &A_constructed);
- A* ap = new(buf) A[Size];
- assert((char*)ap >= buf);
- assert((char*)ap < (buf + ExtraSize));
- assert(A_constructed == Size);
+ char ch = '*';
+ assert(::operator new[](1, &ch) == &ch);
+ assert(ch == '*');
+}
+
+#if TEST_STD_VER >= 26
+static_assert((test_direct_call(), true));
+#endif
+
+int main(int, char**) {
+ const std::size_t Size = 3;
+ // placement new might require additional space.
+ const std::size_t ExtraSize = 64;
+ char buf[Size * sizeof(A) + ExtraSize];
+
+ A* ap = new (buf) A[Size];
+ assert((char*)ap >= buf);
+ assert((char*)ap < (buf + ExtraSize));
+ assert(A_constructed == Size);
+ test_direct_call();
return 0;
}
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.compile.pass.cpp
index 17c1bd71eee675..e6308ae36085ca 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.compile.pass.cpp
@@ -171,17 +171,11 @@
#elif TEST_STD_VER > 23
-# if !defined(_LIBCPP_VERSION)
-# ifndef __cpp_lib_constexpr_new
-# error "__cpp_lib_constexpr_new should be defined in c++26"
-# endif
-# if __cpp_lib_constexpr_new != 202406L
-# error "__cpp_lib_constexpr_new should have the value 202406L in c++26"
-# endif
-# else // _LIBCPP_VERSION
-# ifdef __cpp_lib_constexpr_new
-# error "__cpp_lib_constexpr_new should not be defined because it is unimplemented in libc++!"
-# endif
+# ifndef __cpp_lib_constexpr_new
+# error "__cpp_lib_constexpr_new should be defined in c++26"
+# endif
+# if __cpp_lib_constexpr_new != 202406L
+# error "__cpp_lib_constexpr_new should have the value 202406L in c++26"
# endif
# if TEST_STD_VER > 17 && defined(__cpp_impl_destroying_delete) && __cpp_impl_destroying_delete >= 201806L
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
index b8bad696f1bae0..4ddd35ddff23f1 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
@@ -6554,17 +6554,11 @@
# error "__cpp_lib_constexpr_memory should have the value 202202L in c++26"
# endif
-# if !defined(_LIBCPP_VERSION)
-# ifndef __cpp_lib_constexpr_new
-# error "__cpp_lib_constexpr_new should be defined in c++26"
-# endif
-# if __cpp_lib_constexpr_new != 202406L
-# error "__cpp_lib_constexpr_new should have the value 202406L in c++26"
-# endif
-# else // _LIBCPP_VERSION
-# ifdef __cpp_lib_constexpr_new
-# error "__cpp_lib_constexpr_new should not be defined because it is unimplemented in libc++!"
-# endif
+# ifndef __cpp_lib_constexpr_new
+# error "__cpp_lib_constexpr_new should be defined in c++26"
+# endif
+# if __cpp_lib_constexpr_new != 202406L
+# error "__cpp_lib_constexpr_new should have the value 202406L in c++26"
# endif
# ifndef __cpp_lib_constexpr_numeric
diff --git a/libcxx/test/support/test_macros.h b/libcxx/test/support/test_macros.h
index e96208c85d1d24..b52baaeaf139a9 100644
--- a/libcxx/test/support/test_macros.h
+++ b/libcxx/test/support/test_macros.h
@@ -184,6 +184,12 @@
# define TEST_CONSTEXPR_CXX23
#endif
+#if TEST_STD_VER >= 26
+# define TEST_CONSTEXPR_CXX26 constexpr
+#else
+# define TEST_CONSTEXPR_CXX26
+#endif
+
#define TEST_ALIGNAS_TYPE(...) TEST_ALIGNAS(TEST_ALIGNOF(__VA_ARGS__))
#if !TEST_HAS_FEATURE(cxx_rtti) && !defined(__cpp_rtti) \
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
index b041b08f02aac5..a4404380851578 100755
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -363,7 +363,6 @@ def add_version_header(tc):
"name": "__cpp_lib_constexpr_new",
"values": {"c++26": 202406}, # P2747R2 constexpr placement new
"headers": ["new"],
- "unimplemented": True,
},
{
"name": "__cpp_lib_constexpr_numeric",
``````````
</details>
https://github.com/llvm/llvm-project/pull/105768
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