https://github.com/shafik created https://github.com/llvm/llvm-project/pull/70150
During constant evaluation when value-initializing a class if the base class was default-initialized it would undue the previously zero-initialized class members. This fixes the way we handle default initialization to avoid initializing over an already initialized member to an indeterminate value. Fixes: https://github.com/llvm/llvm-project/issues/69890 >From 54190bf0805df23037bbe2929282c958d609375f Mon Sep 17 00:00:00 2001 From: Shafik Yaghmour <shafik.yaghm...@intel.com> Date: Tue, 24 Oct 2023 16:21:30 -0700 Subject: [PATCH] [Clang] Ensure zero-init is not overridden when intializing a base class in a constant expression context During constant evaluation when value-initializing a class if the base class was default-initialized it would undue the previously zero-initialized class members. This fixes the way we handle default initialzation to avoid initializing over an already initialized member to an indeterminate value. Fixes: https://github.com/llvm/llvm-project/issues/69890 --- clang/docs/ReleaseNotes.rst | 4 +++ clang/lib/AST/ExprConstant.cpp | 33 +++++++++++-------- .../dcl.init/dcl.init.general/p16-cxx20.cpp | 18 ++++++++++ 3 files changed, 42 insertions(+), 13 deletions(-) create mode 100644 clang/test/CXX/dcl.decl/dcl.init/dcl.init.general/p16-cxx20.cpp diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index a063733e96cb74c..ae2f082ad323a78 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -622,6 +622,10 @@ Bug Fixes to C++ Support (`#46200 <https://github.com/llvm/llvm-project/issues/46200>`_) (`#57812 <https://github.com/llvm/llvm-project/issues/57812>`_) +- Fix bug where we were overriding zero-initialization of class members when + default initializing a base class in a constant expression context. Fixes: + (`#69890 <https://github.com/llvm/llvm-project/issues/69890>`_) + Bug Fixes to AST Handling ^^^^^^^^^^^^^^^^^^^^^^^^^ - Fixed an import failure of recursive friend class template. diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp index 6b47b8a1256477d..eea0827d6f7a8a1 100644 --- a/clang/lib/AST/ExprConstant.cpp +++ b/clang/lib/AST/ExprConstant.cpp @@ -4872,8 +4872,13 @@ static bool HandleBaseToDerivedCast(EvalInfo &Info, const CastExpr *E, /// Get the value to use for a default-initialized object of type T. /// Return false if it encounters something invalid. -static bool getDefaultInitValue(QualType T, APValue &Result) { +static bool handleDefaultInitValue(QualType T, APValue &Result) { bool Success = true; + + // If there is already a value present don't overwrite it. + if (!Result.isAbsent()) + return true; + if (auto *RD = T->getAsCXXRecordDecl()) { if (RD->isInvalidDecl()) { Result = APValue(); @@ -4890,13 +4895,14 @@ static bool getDefaultInitValue(QualType T, APValue &Result) { for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), End = RD->bases_end(); I != End; ++I, ++Index) - Success &= getDefaultInitValue(I->getType(), Result.getStructBase(Index)); + Success &= + handleDefaultInitValue(I->getType(), Result.getStructBase(Index)); for (const auto *I : RD->fields()) { if (I->isUnnamedBitfield()) continue; - Success &= getDefaultInitValue(I->getType(), - Result.getStructField(I->getFieldIndex())); + Success &= handleDefaultInitValue( + I->getType(), Result.getStructField(I->getFieldIndex())); } return Success; } @@ -4906,7 +4912,7 @@ static bool getDefaultInitValue(QualType T, APValue &Result) { Result = APValue(APValue::UninitArray(), 0, AT->getSize().getZExtValue()); if (Result.hasArrayFiller()) Success &= - getDefaultInitValue(AT->getElementType(), Result.getArrayFiller()); + handleDefaultInitValue(AT->getElementType(), Result.getArrayFiller()); return Success; } @@ -4947,7 +4953,7 @@ static bool EvaluateVarDecl(EvalInfo &Info, const VarDecl *VD) { if (!InitE) { if (VD->getType()->isDependentType()) return Info.noteSideEffect(); - return getDefaultInitValue(VD->getType(), Val); + return handleDefaultInitValue(VD->getType(), Val); } if (InitE->isValueDependent()) return false; @@ -6049,7 +6055,7 @@ struct StartLifetimeOfUnionMemberHandler { return false; } APValue Result; - Failed = !getDefaultInitValue(Field->getType(), Result); + Failed = !handleDefaultInitValue(Field->getType(), Result); Subobj.setUnion(Field, Result); return true; } @@ -6401,7 +6407,7 @@ static bool HandleConstructorCall(const Expr *E, const LValue &This, for (; !declaresSameEntity(*FieldIt, FD); ++FieldIt) { assert(FieldIt != RD->field_end() && "missing field?"); if (!FieldIt->isUnnamedBitfield()) - Success &= getDefaultInitValue( + Success &= handleDefaultInitValue( FieldIt->getType(), Result.getStructField(FieldIt->getFieldIndex())); } @@ -6458,7 +6464,8 @@ static bool HandleConstructorCall(const Expr *E, const LValue &This, // FIXME: This immediately starts the lifetime of all members of // an anonymous struct. It would be preferable to strictly start // member lifetime in initialization order. - Success &= getDefaultInitValue(Info.Ctx.getRecordType(CD), *Value); + Success &= + handleDefaultInitValue(Info.Ctx.getRecordType(CD), *Value); } // Store Subobject as its parent before updating it for the last element // in the chain. @@ -6510,7 +6517,7 @@ static bool HandleConstructorCall(const Expr *E, const LValue &This, if (!RD->isUnion()) { for (; FieldIt != RD->field_end(); ++FieldIt) { if (!FieldIt->isUnnamedBitfield()) - Success &= getDefaultInitValue( + Success &= handleDefaultInitValue( FieldIt->getType(), Result.getStructField(FieldIt->getFieldIndex())); } @@ -9823,7 +9830,7 @@ bool PointerExprEvaluator::VisitCXXNewExpr(const CXXNewExpr *E) { } else if (Init) { if (!EvaluateInPlace(*Val, Info, Result, Init)) return false; - } else if (!getDefaultInitValue(AllocType, *Val)) { + } else if (!handleDefaultInitValue(AllocType, *Val)) { return false; } @@ -10233,7 +10240,7 @@ bool RecordExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E, if (ZeroInit) return ZeroInitialization(E, T); - return getDefaultInitValue(T, Result); + return handleDefaultInitValue(T, Result); } const FunctionDecl *Definition = nullptr; @@ -15655,7 +15662,7 @@ bool VarDecl::evaluateDestruction( APValue DestroyedValue; if (getEvaluatedValue() && !getEvaluatedValue()->isAbsent()) DestroyedValue = *getEvaluatedValue(); - else if (!getDefaultInitValue(getType(), DestroyedValue)) + else if (!handleDefaultInitValue(getType(), DestroyedValue)) return false; if (!EvaluateDestruction(getASTContext(), this, std::move(DestroyedValue), diff --git a/clang/test/CXX/dcl.decl/dcl.init/dcl.init.general/p16-cxx20.cpp b/clang/test/CXX/dcl.decl/dcl.init/dcl.init.general/p16-cxx20.cpp new file mode 100644 index 000000000000000..1ad205d769c3895 --- /dev/null +++ b/clang/test/CXX/dcl.decl/dcl.init/dcl.init.general/p16-cxx20.cpp @@ -0,0 +1,18 @@ +// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s + +// If the initializer is (), the object is value-initialized. + +// expected-no-diagnostics +namespace GH69890 { +struct A { + constexpr A() {} + int x; +}; + +struct B : A { + int y; +}; + +static_assert(B().x == 0); +static_assert(B().y == 0); +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
