[clang] Implement CWG2759 "[[no_unique_address] and common initial sequence"
#82607
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…sequence" This patch implements said defect report resolution by adding additional check to common initial sequence evaluation. Consequently, this fixes CWG2759. No special handling of `[[msvc::no_unique_address]]` is performed, so it should follow `[[no_unique_address]]` behavior.
llvmbot
added
clang
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@llvm/pr-subscribers-clang Author: Vlad Serebrennikov (Endilll) ChangesThis patch implements said defect report resolution by adding additional check to common initial sequence evaluation. Consequently, this fixes CWG2759. No special handling of Full diff: https://github.com/llvm/llvm-project/pull/82607.diff 5 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index bac166e6c35627..a7c0f2fbbe7604 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -83,8 +83,6 @@ C++20 Feature Support
- Implemented the `__is_layout_compatible` intrinsic to support
`P0466R5: Layout-compatibility and Pointer-interconvertibility Traits <https://wg21.link/P0466R5>`_.
- Note: `CWG2759: [[no_unique_address] and common initial sequence <https://cplusplus.github.io/CWG/issues/2759.html>`_
- is not yet implemented.
C++23 Feature Support
^^^^^^^^^^^^^^^^^^^^^
@@ -108,6 +106,10 @@ Resolutions to C++ Defect Reports
of two types.
(`CWG1719: Layout compatibility and cv-qualification revisited <https://cplusplus.github.io/CWG/issues/1719.html>`_).
+- ``[[no_unique_address]]`` is now respected when evaluating layout
+ compatibility of two types.
+ (`CWG2759: [[no_unique_address] and common initial sequence <https://cplusplus.github.io/CWG/issues/2759.html>`_).
+
C Language Changes
------------------
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index e8bfb215a5b4c5..aba8852f6cfca4 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -19033,6 +19033,11 @@ static bool isLayoutCompatible(ASTContext &C, FieldDecl *Field1,
return false;
}
+ if (Field1->hasAttr<clang::NoUniqueAddressAttr>() ||
+ Field2->hasAttr<clang::NoUniqueAddressAttr>()) {
+ return false;
+ }
+
return true;
}
diff --git a/clang/test/CXX/drs/dr27xx.cpp b/clang/test/CXX/drs/dr27xx.cpp
index dd3fd5a20163fa..3fdf384bef27a7 100644
--- a/clang/test/CXX/drs/dr27xx.cpp
+++ b/clang/test/CXX/drs/dr27xx.cpp
@@ -10,6 +10,89 @@
// expected-no-diagnostics
#endif
+namespace dr2759 { // dr2759: 19
+#if __cplusplus >= 201103L
+
+struct CStruct {
+ int one;
+ int two;
+};
+
+struct CEmptyStruct {};
+struct CEmptyStruct2 {};
+
+struct CStructNoUniqueAddress {
+ int one;
+ [[no_unique_address]] int two;
+};
+
+struct CStructNoUniqueAddress2 {
+ int one;
+ [[no_unique_address]] int two;
+};
+
+union UnionLayout {
+ int a;
+ double b;
+ CStruct c;
+ [[no_unique_address]] CEmptyStruct d;
+ [[no_unique_address]] CEmptyStruct2 e;
+};
+
+union UnionLayout2 {
+ CStruct c;
+ int a;
+ CEmptyStruct2 e;
+ double b;
+ [[no_unique_address]] CEmptyStruct d;
+};
+
+union UnionLayout3 {
+ CStruct c;
+ int a;
+ double b;
+ [[no_unique_address]] CEmptyStruct d;
+};
+
+struct StructWithAnonUnion {
+ union {
+ int a;
+ double b;
+ CStruct c;
+ [[no_unique_address]] CEmptyStruct d;
+ [[no_unique_address]] CEmptyStruct2 e;
+ };
+};
+
+struct StructWithAnonUnion2 {
+ union {
+ CStruct c;
+ int a;
+ CEmptyStruct2 e;
+ double b;
+ [[no_unique_address]] CEmptyStruct d;
+ };
+};
+
+struct StructWithAnonUnion3 {
+ union {
+ CStruct c;
+ int a;
+ CEmptyStruct2 e;
+ double b;
+ [[no_unique_address]] CEmptyStruct d;
+ } u;
+};
+
+static_assert(__is_layout_compatible(CStruct, CStructNoUniqueAddress) != bool(__has_cpp_attribute(no_unique_address)), "");
+static_assert(__is_layout_compatible(CStructNoUniqueAddress, CStructNoUniqueAddress2) != bool(__has_cpp_attribute(no_unique_address)), "");
+static_assert(!__is_layout_compatible(UnionLayout, UnionLayout2), "");
+static_assert(!__is_layout_compatible(UnionLayout, UnionLayout3), "");
+static_assert(!__is_layout_compatible(StructWithAnonUnion, StructWithAnonUnion2), "");
+static_assert(!__is_layout_compatible(StructWithAnonUnion, StructWithAnonUnion3), "");
+#endif
+} // namespace dr2759
+
namespace dr2789 { // dr2789: 18
#if __cplusplus >= 202302L
template <typename T = int>
diff --git a/clang/test/SemaCXX/type-traits.cpp b/clang/test/SemaCXX/type-traits.cpp
index 2c35d5ee19a4c6..23c339ebdf0826 100644
--- a/clang/test/SemaCXX/type-traits.cpp
+++ b/clang/test/SemaCXX/type-traits.cpp
@@ -1768,8 +1768,8 @@ void is_layout_compatible(int n)
static_assert(!__is_layout_compatible(CppStructNonStandardBySameBase, CppStructNonStandardBySameBase2), "");
static_assert(!__is_layout_compatible(CppStructNonStandardBy2ndVirtBase, CppStructNonStandardBy2ndVirtBase2), "");
static_assert(__is_layout_compatible(CStruct, CStructWithQualifiers), "");
- static_assert(__is_layout_compatible(CStruct, CStructNoUniqueAddress) == bool(__has_cpp_attribute(no_unique_address)), ""); // FIXME: this is CWG2759
- static_assert(__is_layout_compatible(CStructNoUniqueAddress, CStructNoUniqueAddress2) == bool(__has_cpp_attribute(no_unique_address)), ""); // FIXME: this is CWG2759
+ static_assert(__is_layout_compatible(CStruct, CStructNoUniqueAddress) != bool(__has_cpp_attribute(no_unique_address)), "");
+ static_assert(__is_layout_compatible(CStructNoUniqueAddress, CStructNoUniqueAddress2) != bool(__has_cpp_attribute(no_unique_address)), "");
static_assert(__is_layout_compatible(CStruct, CStructAlignment), "");
static_assert(__is_layout_compatible(CStruct, CStructAlignedMembers), ""); // FIXME: alignment of members impact common initial sequence
static_assert(__is_layout_compatible(CStructWithBitfelds, CStructWithBitfelds), "");
@@ -1782,10 +1782,10 @@ void is_layout_compatible(int n)
static_assert(!__is_layout_compatible(void(CStruct2::*)(int), void(CStruct2::*)(char)), "");
static_assert(__is_layout_compatible(CStructNested, CStructNested2), "");
static_assert(__is_layout_compatible(UnionLayout, UnionLayout), "");
- static_assert(__is_layout_compatible(UnionLayout, UnionLayout2), "");
+ static_assert(!__is_layout_compatible(UnionLayout, UnionLayout2), "");
static_assert(!__is_layout_compatible(UnionLayout, UnionLayout3), "");
- static_assert(__is_layout_compatible(StructWithAnonUnion, StructWithAnonUnion2), "");
- static_assert(__is_layout_compatible(StructWithAnonUnion, StructWithAnonUnion3), "");
+ static_assert(!__is_layout_compatible(StructWithAnonUnion, StructWithAnonUnion2), "");
+ static_assert(!__is_layout_compatible(StructWithAnonUnion, StructWithAnonUnion3), "");
static_assert(__is_layout_compatible(EnumLayout, EnumClassLayout), "");
static_assert(__is_layout_compatible(EnumForward, EnumForward), "");
static_assert(__is_layout_compatible(EnumForward, EnumClassForward), "");
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 38e2cb63142662..8b638e06f4aab6 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16362,7 +16362,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
<td><a href="https://cplusplus.github.io/CWG/issues/2759.html">2759</a></td>
<td>DR</td>
<td>[[no_unique_address] and common initial sequence</td>
- <td class="unknown" align="center">Unknown</td>
+ <td class="unreleased" align="center">Clang 19</td>
</tr>
<tr id="2760">
<td><a href="https://cplusplus.github.io/CWG/issues/2760.html">2760</a></td>
|
I do not think the code does that. At the very least, a type with msvc::no_unique_address should not be layout compatible with an equivalent declaration using no_unique_address. Whether two msvc::no_unique_address are layout compatible is less important, because the intent of msvc::no_unique_address is not documented and/or msvc does not implement CWG2759 |
tbaederr
reviewed
Feb 22, 2024
AaronBallman
approved these changes
Feb 22, 2024
Co-authored-by: Timm Baeder <[email protected]>
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
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This patch implements said defect report resolution by adding additional check to common initial sequence evaluation. Consequently, this fixes CWG2759.
No special handling of
[[msvc::no_unique_address]]is performed, so it should follow[[no_unique_address]]behavior.