https://github.com/antoniofrighetto updated https://github.com/llvm/llvm-project/pull/127824
>From e9988c36ed788b2d1ce00b028bed51169bd8b02c Mon Sep 17 00:00:00 2001 From: Antonio Frighetto <m...@antoniofrighetto.com> Date: Wed, 19 Mar 2025 09:04:29 +0100 Subject: [PATCH] [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 | 11 ++++- clang/test/CodeGenCXX/derived-to-base.cpp | 25 ++++++++++ .../derived-to-base-propagate-qualifiers.cpp | 46 +++++++++++++++++++ 4 files changed, 82 insertions(+), 2 deletions(-) create mode 100644 clang/test/SemaCXX/derived-to-base-propagate-qualifiers.cpp diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index ce4336acb806a..1c0504d831e3f 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -340,6 +340,8 @@ Bug Fixes to C++ Support - Fixed an assertion failure affecting code that uses C++23 "deducing this". (#GH130272) - Clang now properly instantiates destructors for initialized members within non-delegating constructors. (#GH93251) - Correctly diagnoses if unresolved using declarations shadows template paramters (#GH129411) +- 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 3ff372bdc9d0c..a03acb5fbd273 100644 --- a/clang/lib/Sema/SemaExpr.cpp +++ b/clang/lib/Sema/SemaExpr.cpp @@ -3113,8 +3113,15 @@ Sema::PerformObjectMemberConversion(Expr *From, /*IgnoreAccess=*/true)) return ExprError(); - return ImpCastExprToType(From, DestType, CK_UncheckedDerivedToBase, - VK, &BasePath); + // 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); + + 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-propagate-qualifiers.cpp b/clang/test/SemaCXX/derived-to-base-propagate-qualifiers.cpp new file mode 100644 index 0000000000000..8a3b944ab1cb6 --- /dev/null +++ b/clang/test/SemaCXX/derived-to-base-propagate-qualifiers.cpp @@ -0,0 +1,46 @@ +// RUN: %clang_cc1 -std=c++20 -fsyntax-only -ast-dump -verify %s | FileCheck %s + +// Ensure qualifiers are preserved during derived-to-base conversion. +namespace PR127683 { + +struct Base { + int Val; +}; + +struct Derived : Base { }; + +// Value-initialize base class subobjects with type qualifiers. +volatile Derived VObj; +const Derived CObj{}; // expected-note{{variable 'CObj' declared const here}} +const volatile Derived CVObj{}; // expected-note{{variable 'CVObj' declared const here}} +__attribute__((address_space(1))) Derived AddrSpaceObj{}; + +void test_store() { + // CHECK: `-ImplicitCastExpr {{.*}} 'volatile PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + VObj.Val = 0; + + // CHECK: `-ImplicitCastExpr {{.*}} 'const PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + CObj.Val = 1; // expected-error {{cannot assign to variable 'CObj' with const-qualified type 'const Derived'}} + + // CHECK: `-ImplicitCastExpr {{.*}} 'const volatile PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + CVObj.Val = 1; // expected-error {{cannot assign to variable 'CVObj' with const-qualified type 'const volatile Derived'}} + + // CHECK: `-ImplicitCastExpr {{.*}} '__attribute__((address_space(1))) PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + AddrSpaceObj.Val = 1; +} + +void test_load() { + // CHECK: `-ImplicitCastExpr {{.*}} <col:30> 'volatile PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + [[maybe_unused]] int Val = VObj.Val; + + // CHECK: `-ImplicitCastExpr {{.*}} 'const PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + Val = CObj.Val; + + // CHECK: `-ImplicitCastExpr {{.*}} 'const volatile PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + Val = CVObj.Val; + + // CHECK: `-ImplicitCastExpr {{.*}} '__attribute__((address_space(1))) PR127683::Base' lvalue <UncheckedDerivedToBase (Base)> + Val = AddrSpaceObj.Val; +} + +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
