https://github.com/Rajveer100 updated https://github.com/llvm/llvm-project/pull/96301
>From 751e630dbf54ef6f3a1209a5d09f99093ad84cae Mon Sep 17 00:00:00 2001 From: Rajveer <rajveer.develo...@icloud.com> Date: Fri, 21 Jun 2024 18:26:36 +0530 Subject: [PATCH] [clang] Allow class with anonymous union member to be const-default-constructible even if a union member has a default member initializer (#95854) Resolves #95854 Clang incorrectly considers a class with an anonymous union member to not be const-default-constructible even if a union member has a default member initializer. This is valid as per ``8.3`` in `Draft C++ Standard <https://eel.is/c++draft/dcl.init#general-8.3>`_. The ``allowConstDefaultInit`` member function in ``CXXRecordDecl`` needs special-case unions to handle the rule. (#GH95854). ``` struct A { union { int n = 0; int m; }; }; const A a; ``` -- As per https://eel.is/c++draft/dcl.init#general-8.3 --- clang/docs/ReleaseNotes.rst | 6 ++++++ clang/include/clang/AST/DeclCXX.h | 3 ++- clang/lib/AST/DeclCXX.cpp | 9 ++++++++- clang/test/SemaCXX/GH95854.cpp | 21 +++++++++++++++++++++ 4 files changed, 37 insertions(+), 2 deletions(-) create mode 100644 clang/test/SemaCXX/GH95854.cpp diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 36cf615a4287cc..35259760adc60f 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -756,6 +756,12 @@ Bug Fixes in This Version - ``__is_array`` and ``__is_bounded_array`` no longer return ``true`` for zero-sized arrays. Fixes (#GH54705). + +- Clang incorrectly considers a class with an anonymous union member to not be + const-default-constructible even if a union member has a default member initializer. + This is valid as per ``8.3`` in `Draft C++ Standard <https://eel.is/c++draft/dcl.init#general-8.3>`_. + The ``allowConstDefaultInit`` member function in ``CXXRecordDecl`` needs + special-case unions to handle the rule. (#GH95854). - Correctly reject declarations where a statement is required in C. Fixes #GH92775 diff --git a/clang/include/clang/AST/DeclCXX.h b/clang/include/clang/AST/DeclCXX.h index fb52ac804849d8..f4d90e19e0e05e 100644 --- a/clang/include/clang/AST/DeclCXX.h +++ b/clang/include/clang/AST/DeclCXX.h @@ -1392,7 +1392,8 @@ class CXXRecordDecl : public RecordDecl { bool allowConstDefaultInit() const { return !data().HasUninitializedFields || !(data().HasDefaultedDefaultConstructor || - needsImplicitDefaultConstructor()); + needsImplicitDefaultConstructor()) || + (isUnion() && isEmpty()); } /// Determine whether this class has a destructor which has no diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp index d5c140fd343895..16f0a2b4592ed0 100644 --- a/clang/lib/AST/DeclCXX.cpp +++ b/clang/lib/AST/DeclCXX.cpp @@ -1018,6 +1018,9 @@ void CXXRecordDecl::addedMember(Decl *D) { if (isUnion() && !Field->isAnonymousStructOrUnion()) data().HasVariantMembers = true; + if (isUnion() && IsFirstField) + data().HasUninitializedFields = true; + // C++0x [class]p9: // A POD struct is a class that is both a trivial class and a // standard-layout class, and has no non-static data members of type @@ -1086,7 +1089,11 @@ void CXXRecordDecl::addedMember(Decl *D) { data().DefaultedCopyConstructorIsDeleted = true; } - if (!Field->hasInClassInitializer() && !Field->isMutable()) { + if (isUnion() && !Field->isMutable()) { + if (Field->hasInClassInitializer()) { + data().HasUninitializedFields = false; + } + } else if (!Field->hasInClassInitializer() && !Field->isMutable()) { if (CXXRecordDecl *FieldType = T->getAsCXXRecordDecl()) { if (FieldType->hasDefinition() && !FieldType->allowConstDefaultInit()) data().HasUninitializedFields = true; diff --git a/clang/test/SemaCXX/GH95854.cpp b/clang/test/SemaCXX/GH95854.cpp new file mode 100644 index 00000000000000..62ae549f2496f0 --- /dev/null +++ b/clang/test/SemaCXX/GH95854.cpp @@ -0,0 +1,21 @@ +// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify %s +// +// -expected-no-diagnostics + +struct A { + union { + int n = 0; + int m; + }; +}; +const A a; + +struct B { + union { + struct { + int n = 5; + int m; + }; + }; +}; +const B b; // expected-error {{default initialization of an object of const type 'const B' without a user-provided default constructor}} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
