[libc++] Remove <stddef.h> includes from the granularized <cstddef> headers #114788
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philnik777
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@llvm/pr-subscribers-libcxx Author: Nikolas Klauser (philnik777) ChangesWe can define some of these aliases without having to include the system <stddef.h> and there doesn't seem to be much of a reason we shouldn't do it this way. Full diff: https://github.com/llvm/llvm-project/pull/114788.diff 12 Files Affected:
diff --git a/libcxx/include/__cstddef/nullptr_t.h b/libcxx/include/__cstddef/nullptr_t.h
index de3f7d4ab5fa75..7eaae017539652 100644
--- a/libcxx/include/__cstddef/nullptr_t.h
+++ b/libcxx/include/__cstddef/nullptr_t.h
@@ -10,7 +10,6 @@
#define _LIBCPP___CSTDDEF_NULLPTR_T_H
#include <__config>
-#include <stddef.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -18,7 +17,7 @@
_LIBCPP_BEGIN_NAMESPACE_STD
-using ::nullptr_t;
+using nullptr_t = decltype(nullptr);
_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__cstddef/ptrdiff_t.h b/libcxx/include/__cstddef/ptrdiff_t.h
index f8b5cdaaff01c9..c53e999d73b019 100644
--- a/libcxx/include/__cstddef/ptrdiff_t.h
+++ b/libcxx/include/__cstddef/ptrdiff_t.h
@@ -10,7 +10,6 @@
#define _LIBCPP___CSTDDEF_PTRDIFF_T_H
#include <__config>
-#include <stddef.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -18,7 +17,7 @@
_LIBCPP_BEGIN_NAMESPACE_STD
-using ::ptrdiff_t _LIBCPP_USING_IF_EXISTS;
+using ptrdiff_t = __PTRDIFF_TYPE__;
_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__cstddef/size_t.h b/libcxx/include/__cstddef/size_t.h
index 91abbf01318953..9a6d921d0d1f2f 100644
--- a/libcxx/include/__cstddef/size_t.h
+++ b/libcxx/include/__cstddef/size_t.h
@@ -10,7 +10,6 @@
#define _LIBCPP___CSTDDEF_SIZE_T_H
#include <__config>
-#include <stddef.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -18,7 +17,7 @@
_LIBCPP_BEGIN_NAMESPACE_STD
-using ::size_t _LIBCPP_USING_IF_EXISTS;
+using size_t = __SIZE_TYPE__;
_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__exception/exception_ptr.h b/libcxx/include/__exception/exception_ptr.h
index 32c56fc5cc1263..c43c005603dd7a 100644
--- a/libcxx/include/__exception/exception_ptr.h
+++ b/libcxx/include/__exception/exception_ptr.h
@@ -10,6 +10,7 @@
#define _LIBCPP___EXCEPTION_EXCEPTION_PTR_H
#include <__config>
+#include <__cstddef/nullptr_t.h>
#include <__exception/operations.h>
#include <__memory/addressof.h>
#include <__memory/construct_at.h>
diff --git a/libcxx/include/__functional/function.h b/libcxx/include/__functional/function.h
index e3844f86dbd3f5..543be05f10f330 100644
--- a/libcxx/include/__functional/function.h
+++ b/libcxx/include/__functional/function.h
@@ -12,6 +12,7 @@
#include <__assert>
#include <__config>
+#include <__cstddef/nullptr_t.h>
#include <__exception/exception.h>
#include <__functional/binary_function.h>
#include <__functional/invoke.h>
diff --git a/libcxx/include/__functional/hash.h b/libcxx/include/__functional/hash.h
index 87009dfa62ef59..a33cba53c9309c 100644
--- a/libcxx/include/__functional/hash.h
+++ b/libcxx/include/__functional/hash.h
@@ -10,6 +10,7 @@
#define _LIBCPP___FUNCTIONAL_HASH_H
#include <__config>
+#include <__cstddef/nullptr_t.h>
#include <__functional/unary_function.h>
#include <__fwd/functional.h>
#include <__type_traits/conjunction.h>
diff --git a/libcxx/include/__memory/shared_ptr.h b/libcxx/include/__memory/shared_ptr.h
index 0722b3f3e6d543..f50dc272f64ae1 100644
--- a/libcxx/include/__memory/shared_ptr.h
+++ b/libcxx/include/__memory/shared_ptr.h
@@ -13,6 +13,7 @@
#include <__compare/compare_three_way.h>
#include <__compare/ordering.h>
#include <__config>
+#include <__cstddef/nullptr_t.h>
#include <__cstddef/ptrdiff_t.h>
#include <__exception/exception.h>
#include <__functional/binary_function.h>
diff --git a/libcxx/include/forward_list b/libcxx/include/forward_list
index 04466d9a673fc6..a511fef31bc5d1 100644
--- a/libcxx/include/forward_list
+++ b/libcxx/include/forward_list
@@ -200,6 +200,7 @@ template <class T, class Allocator, class Predicate>
#include <__algorithm/lexicographical_compare_three_way.h>
#include <__algorithm/min.h>
#include <__config>
+#include <__cstddef/nullptr_t.h>
#include <__iterator/distance.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/move_iterator.h>
diff --git a/libcxx/include/new b/libcxx/include/new
index 290ad9e97f8ded..dc5aabe6a97ef3 100644
--- a/libcxx/include/new
+++ b/libcxx/include/new
@@ -87,6 +87,7 @@ void operator delete[](void* ptr, void*) noexcept;
*/
#include <__config>
+#include <__cstddef/max_align_t.h>
#include <__cstddef/size_t.h>
#include <__exception/exception.h>
#include <__type_traits/is_function.h>
diff --git a/libcxx/include/string_view b/libcxx/include/string_view
index 0edda7aeb1a77c..db1f42523a13a3 100644
--- a/libcxx/include/string_view
+++ b/libcxx/include/string_view
@@ -208,6 +208,7 @@ namespace std {
#include <__algorithm/min.h>
#include <__assert>
#include <__config>
+#include <__cstddef/nullptr_t.h>
#include <__cstddef/ptrdiff_t.h>
#include <__cstddef/size_t.h>
#include <__functional/hash.h>
diff --git a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.cmp/cmp_nullptr.pass.cpp b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.cmp/cmp_nullptr.pass.cpp
index 4ca83ddff78e5b..e0aea76561e3a2 100644
--- a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.cmp/cmp_nullptr.pass.cpp
+++ b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.cmp/cmp_nullptr.pass.cpp
@@ -37,8 +37,9 @@
// template<class T>
// strong_ordering operator<=>(shared_ptr<T> const& x, nullptr_t) noexcept; // C++20
-#include <memory>
#include <cassert>
+#include <cstddef>
+#include <memory>
#include "test_macros.h"
#include "test_comparisons.h"
diff --git a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp
index 6f0ba2e756196c..5ef9c4b044c681 100644
--- a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp
+++ b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.special/cmp_nullptr.pass.cpp
@@ -39,9 +39,9 @@
// constexpr compare_three_way_result_t<typename unique_ptr<T, D>::pointer>
// operator<=>(const unique_ptr<T, D>& x, nullptr_t); // C++20
-#include <memory>
#include <cassert>
-#include <type_traits>
+#include <cstddef>
+#include <memory>
#include "test_macros.h"
#include "test_comparisons.h"
|
ldionne
requested changes
Nov 5, 2024
|
|
||
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) | ||
| # pragma GCC system_header | ||
| #endif | ||
|
|
||
| _LIBCPP_BEGIN_NAMESPACE_STD | ||
|
|
||
| using ::nullptr_t; | ||
| using nullptr_t = decltype(nullptr); |
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The big difference is that if the system headers and the compiler disagree about what those types should be, we'll now favour the compiler's definitions whereas we would have previously favoured the system headers (or the Clang builtin headers, depending on which one comes first).
I can't imagine why it would make sense for the compiler and the system library to disagree, but I'm fairly certain there are setups in which they disagree (those setups are probably brittle to the point of being arguably wrong).
So TLDR, it's probably possible for this patch to introduce a behavior change in some weird setups, but I don't think that's something we should take into account beyond recognizing that possibility.
philnik777
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ldionne
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We can define some of these aliases without having to include the system <stddef.h> and there doesn't seem to be much of a reason we shouldn't do it this way.