https://github.com/antoniofrighetto updated https://github.com/llvm/llvm-project/pull/127824
>From aebd5455e9cf583b9f5a29c68d5217f49c7a49b5 Mon Sep 17 00:00:00 2001 From: Antonio Frighetto <m...@antoniofrighetto.com> Date: Wed, 19 Feb 2025 16:47:18 +0100 Subject: [PATCH 1/3] [clang][Sema] Propagate qualifiers during derived-to-base conversion When accessing a field member through a derived-to-base conversion, ensure qualifiers are propagated to the base class subobject. Fixes: https://github.com/llvm/llvm-project/issues/127683. --- clang/docs/ReleaseNotes.rst | 2 ++ clang/lib/Sema/SemaExpr.cpp | 6 ++-- clang/test/CodeGenCXX/derived-to-base.cpp | 25 ++++++++++++++ .../SemaCXX/derived-to-base-cv-qualifiers.cpp | 34 +++++++++++++++++++ 4 files changed, 65 insertions(+), 2 deletions(-) create mode 100644 clang/test/SemaCXX/derived-to-base-cv-qualifiers.cpp diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 62a64ff57599d..c96c79c8e6d6c 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -171,6 +171,8 @@ Bug Fixes to C++ Support - The initialization kind of elements of structured bindings direct-list-initialized from an array is corrected to direct-initialization. - Clang no longer crashes when a coroutine is declared ``[[noreturn]]``. (#GH127327) +- Clang was previously coalescing volatile writes to members of volatile base class subobjects. + The issue has been addressed by propagating qualifiers during derived-to-base conversions in the AST. (#GH127824) Bug Fixes to AST Handling ^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp index fad15bf95c415..c4d18609316ab 100644 --- a/clang/lib/Sema/SemaExpr.cpp +++ b/clang/lib/Sema/SemaExpr.cpp @@ -3107,8 +3107,10 @@ Sema::PerformObjectMemberConversion(Expr *From, /*IgnoreAccess=*/true)) return ExprError(); - return ImpCastExprToType(From, DestType, CK_UncheckedDerivedToBase, - VK, &BasePath); + DestType = Context.getQualifiedType(DestType, FromType.getQualifiers()); + + return ImpCastExprToType(From, DestType, CK_UncheckedDerivedToBase, VK, + &BasePath); } bool Sema::UseArgumentDependentLookup(const CXXScopeSpec &SS, diff --git a/clang/test/CodeGenCXX/derived-to-base.cpp b/clang/test/CodeGenCXX/derived-to-base.cpp index c8dbd5bf5cb05..c09a12b728bbb 100644 --- a/clang/test/CodeGenCXX/derived-to-base.cpp +++ b/clang/test/CodeGenCXX/derived-to-base.cpp @@ -46,4 +46,29 @@ namespace test3 { } } +// Ensure volatile is preserved during derived-to-base conversion. +namespace PR127683 { + +struct Base { + int Val; +}; + +struct Derived : Base { }; + +volatile Derived Obj; + +// CHECK-LABEL: define void @_ZN8PR12768319test_volatile_storeEv() +// CHECK: store volatile i32 0, ptr @_ZN8PR1276833ObjE, align 4 +void test_volatile_store() { + Obj.Val = 0; +} + +// CHECK-LABEL: define void @_ZN8PR12768318test_volatile_loadEv() +// CHECK: %0 = load volatile i32, ptr @_ZN8PR1276833ObjE, align 4 +void test_volatile_load() { + [[maybe_unused]] int Val = Obj.Val; +} + +} + // CHECK: attributes [[NUW]] = { mustprogress noinline nounwind{{.*}} } diff --git a/clang/test/SemaCXX/derived-to-base-cv-qualifiers.cpp b/clang/test/SemaCXX/derived-to-base-cv-qualifiers.cpp new file mode 100644 index 0000000000000..02a5bf8f6cecf --- /dev/null +++ b/clang/test/SemaCXX/derived-to-base-cv-qualifiers.cpp @@ -0,0 +1,34 @@ +// RUN: %clang_cc1 -std=c++20 -fsyntax-only -ast-dump %s | FileCheck %s + +// Ensure volatile is preserved during derived-to-base conversion. +namespace PR127683 { + +struct Base { + int Val; +}; + +struct Derived : Base { }; + +volatile Derived Obj; + +// CHECK: |-FunctionDecl {{.*}} test_volatile_store 'void ()' +// CHECK-NEXT: `-CompoundStmt {{.*}} +// CHECK-NEXT: `-BinaryOperator {{.*}} 'volatile int' lvalue '=' +// CHECK-NEXT: |-MemberExpr {{.*}} 'volatile int' lvalue .Val +// CHECK-NEXT: | `-ImplicitCastExpr {{.*}} 'volatile PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> +void test_volatile_store() { + Obj.Val = 0; +} + +// CHECK: `-FunctionDecl {{.*}} test_volatile_load 'void ()' +// CHECK-NEXT: `-CompoundStmt {{.*}} +// CHECK-NEXT: `-DeclStmt {{.*}} +// CHECK-NEXT: `-VarDecl {{.*}} Val 'int' cinit +// CHECK-NEXT: |-ImplicitCastExpr {{.*}} 'int' <LValueToRValue> +// CHECK-NEXT: | `-MemberExpr {{.*}} 'volatile int' lvalue .Val +// CHECK-NEXT: | `-ImplicitCastExpr {{.*}} 'volatile PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> +void test_volatile_load() { + [[maybe_unused]] int Val = Obj.Val; +} + +} >From 8646973726cc1639794f42f696e8d8af27c4bfa0 Mon Sep 17 00:00:00 2001 From: Antonio Frighetto <m...@antoniofrighetto.com> Date: Sat, 22 Feb 2025 16:42:36 +0100 Subject: [PATCH 2/3] !fixup fix ci issue --- clang/lib/Sema/SemaExpr.cpp | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp index c4d18609316ab..f16feb215d533 100644 --- a/clang/lib/Sema/SemaExpr.cpp +++ b/clang/lib/Sema/SemaExpr.cpp @@ -3107,7 +3107,9 @@ Sema::PerformObjectMemberConversion(Expr *From, /*IgnoreAccess=*/true)) return ExprError(); - DestType = Context.getQualifiedType(DestType, FromType.getQualifiers()); + Qualifiers FromTypeQuals = FromType.getQualifiers(); + FromTypeQuals.setAddressSpace(DestType.getAddressSpace()); + DestType = Context.getQualifiedType(DestType, FromTypeQuals); return ImpCastExprToType(From, DestType, CK_UncheckedDerivedToBase, VK, &BasePath); >From 6f68dff985b87ce9d4229a20924d2c06c164d90b Mon Sep 17 00:00:00 2001 From: Antonio Frighetto <m...@antoniofrighetto.com> Date: Thu, 27 Feb 2025 12:42:47 +0100 Subject: [PATCH 3/3] !fixup add quote from standard --- clang/lib/Sema/SemaExpr.cpp | 3 +++ 1 file changed, 3 insertions(+) diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp index f16feb215d533..a34e1735ca954 100644 --- a/clang/lib/Sema/SemaExpr.cpp +++ b/clang/lib/Sema/SemaExpr.cpp @@ -3107,6 +3107,9 @@ Sema::PerformObjectMemberConversion(Expr *From, /*IgnoreAccess=*/true)) return ExprError(); + // Propagate qualifiers to base subobjects as per: + // C++ [basic.type.qualifier]p1.2: + // A volatile object is [...] a subobject of a volatile object. Qualifiers FromTypeQuals = FromType.getQualifiers(); FromTypeQuals.setAddressSpace(DestType.getAddressSpace()); DestType = Context.getQualifiedType(DestType, FromTypeQuals); _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
