commit b1eacdf947a040d11cf7c1fe5d1a78889c75d36b Author: Richard Smith Date: Fri Dec 14 14:41:39 2018 -0800 Add distinct cast kind for an lvalue-to-rvalue conversion on nullptr_t. This represents in the AST the fact that such an lvalue-to-rvalue conversion is not like any others (it does not actually read a value from memory). diff --git a/include/clang/AST/OperationKinds.def b/include/clang/AST/OperationKinds.def index cd19091e31..2cc6ab8322 100644 --- a/include/clang/AST/OperationKinds.def +++ b/include/clang/AST/OperationKinds.def @@ -112,6 +112,14 @@ CAST_OPERATION(ArrayToPointerDecay) /// void(int) -> void(*)(int) CAST_OPERATION(FunctionToPointerDecay) +/// CK_NullptrLValueToRValue - An lvalue-to-rvalue conversion on an +/// lvalue of type std::nullptr_t. Unlike a regular lvalue-to-rvalue +/// conversion, this does not access the object. +/// std::nullptr_t a, b = a; +/// The semantics of this are largely the same as CK_NullToPointer, +/// but it still counts as an lvalue-to-rvalue conversion. +CAST_OPERATION(NullptrLValueToRValue) + /// CK_NullToPointer - Null pointer constant to pointer, ObjC /// pointer, or block pointer. /// (void*) 0 diff --git a/include/clang/AST/OperationKinds.h b/include/clang/AST/OperationKinds.h index ac512d721e..2a2461b80c 100644 --- a/include/clang/AST/OperationKinds.h +++ b/include/clang/AST/OperationKinds.h @@ -23,6 +23,13 @@ enum CastKind { #include "clang/AST/OperationKinds.def" }; +/// Determine whether this cast kind is any kind of lvalue-to-rvalue conversion, +/// including the oddball nullptr_t lvalue-to-rvalue conversion which doesn't +/// actually read from memory and so does not constitute an 'access'. +inline bool isLValueToRValue(CastKind CK) { + return CK == CK_LValueToRValue || CK == CK_NullptrLValueToRValue; +} + enum BinaryOperatorKind { #define BINARY_OPERATION(Name, Spelling) BO_##Name, #include "clang/AST/OperationKinds.def" diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp index 5a80016850..f02246423b 100644 --- a/lib/AST/Expr.cpp +++ b/lib/AST/Expr.cpp @@ -1629,6 +1629,7 @@ bool CastExpr::CastConsistency() const { case CK_ArrayToPointerDecay: case CK_NullToMemberPointer: case CK_NullToPointer: + case CK_NullptrLValueToRValue: case CK_ConstructorConversion: case CK_IntegralToPointer: case CK_PointerToIntegral: @@ -2613,7 +2614,7 @@ Expr *Expr::IgnoreParenLValueCasts() { while (true) { E = E->IgnoreParens(); if (CastExpr *P = dyn_cast(E)) { - if (P->getCastKind() == CK_LValueToRValue) { + if (isLValueToRValue(P->getCastKind())) { E = P->getSubExpr(); continue; } diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp index 837dc9c2a8..d9c3de77f0 100644 --- a/lib/AST/ExprConstant.cpp +++ b/lib/AST/ExprConstant.cpp @@ -5908,6 +5908,7 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) { return true; return HandleBaseToDerivedCast(Info, E, Result); + case CK_NullptrLValueToRValue: case CK_NullToPointer: VisitIgnoredValue(E->getSubExpr()); return ZeroInitialization(E); @@ -9699,6 +9700,7 @@ bool IntExprEvaluator::VisitCastExpr(const CastExpr *E) { case CK_ToUnion: case CK_ArrayToPointerDecay: case CK_FunctionToPointerDecay: + case CK_NullptrLValueToRValue: case CK_NullToPointer: case CK_NullToMemberPointer: case CK_BaseToDerivedMemberPointer: @@ -10231,6 +10233,7 @@ bool ComplexExprEvaluator::VisitCastExpr(const CastExpr *E) { case CK_ToUnion: case CK_ArrayToPointerDecay: case CK_FunctionToPointerDecay: + case CK_NullptrLValueToRValue: case CK_NullToPointer: case CK_NullToMemberPointer: case CK_BaseToDerivedMemberPointer: diff --git a/lib/Analysis/UninitializedValues.cpp b/lib/Analysis/UninitializedValues.cpp index 31c88a1095..51afd5d59f 100644 --- a/lib/Analysis/UninitializedValues.cpp +++ b/lib/Analysis/UninitializedValues.cpp @@ -490,6 +490,9 @@ void ClassifyRefs::VisitCallExpr(CallExpr *CE) { void ClassifyRefs::VisitCastExpr(CastExpr *CE) { if (CE->getCastKind() == CK_LValueToRValue) classify(CE->getSubExpr(), Use); + else if (CE->getCastKind() == CK_NullptrLValueToRValue) + // Objects of type 'nullptr_t' are never really used. + classify(CE->getSubExpr(), Ignore); else if (const auto *CSE = dyn_cast(CE)) { if (CSE->getType()->isVoidType()) { // Squelch any detected load of an uninitialized value if diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp index 6ef1091cc0..6271d0e16c 100644 --- a/lib/CodeGen/CGExpr.cpp +++ b/lib/CodeGen/CGExpr.cpp @@ -4137,6 +4137,7 @@ LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) { case CK_FunctionToPointerDecay: case CK_NullToMemberPointer: case CK_NullToPointer: + case CK_NullptrLValueToRValue: case CK_IntegralToPointer: case CK_PointerToIntegral: case CK_PointerToBoolean: diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp index db49b3f28a..d9ec72c430 100644 --- a/lib/CodeGen/CGExprAgg.cpp +++ b/lib/CodeGen/CGExprAgg.cpp @@ -813,6 +813,7 @@ void AggExprEmitter::VisitCastExpr(CastExpr *E) { case CK_BitCast: case CK_ArrayToPointerDecay: case CK_FunctionToPointerDecay: + case CK_NullptrLValueToRValue: case CK_NullToPointer: case CK_NullToMemberPointer: case CK_BaseToDerivedMemberPointer: diff --git a/lib/CodeGen/CGExprComplex.cpp b/lib/CodeGen/CGExprComplex.cpp index 2db693b44c..58a039026a 100644 --- a/lib/CodeGen/CGExprComplex.cpp +++ b/lib/CodeGen/CGExprComplex.cpp @@ -475,6 +475,7 @@ ComplexPairTy ComplexExprEmitter::EmitCast(CastKind CK, Expr *Op, case CK_ToUnion: case CK_ArrayToPointerDecay: case CK_FunctionToPointerDecay: + case CK_NullptrLValueToRValue: case CK_NullToPointer: case CK_NullToMemberPointer: case CK_BaseToDerivedMemberPointer: diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp index c9475840ae..68f6b6537a 100644 --- a/lib/CodeGen/CGExprConstant.cpp +++ b/lib/CodeGen/CGExprConstant.cpp @@ -865,6 +865,7 @@ public: case CK_PointerToIntegral: case CK_PointerToBoolean: case CK_NullToPointer: + case CK_NullptrLValueToRValue: case CK_IntegralCast: case CK_BooleanToSignedIntegral: case CK_IntegralToPointer: diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp index f53bb33e46..8b7f3086b5 100644 --- a/lib/CodeGen/CGExprScalar.cpp +++ b/lib/CodeGen/CGExprScalar.cpp @@ -2082,6 +2082,7 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) { return EmitLValue(E).getPointer(); case CK_NullToPointer: + case CK_NullptrLValueToRValue: if (MustVisitNullValue(E)) (void) Visit(E); diff --git a/lib/Edit/RewriteObjCFoundationAPI.cpp b/lib/Edit/RewriteObjCFoundationAPI.cpp index 7c9ab17009..b2bf0eecb2 100644 --- a/lib/Edit/RewriteObjCFoundationAPI.cpp +++ b/lib/Edit/RewriteObjCFoundationAPI.cpp @@ -1050,6 +1050,7 @@ static bool rewriteToNumericBoxedExpression(const ObjCMessageExpr *Msg, case CK_ToUnion: case CK_ArrayToPointerDecay: case CK_FunctionToPointerDecay: + case CK_NullptrLValueToRValue: case CK_NullToPointer: case CK_NullToMemberPointer: case CK_BaseToDerivedMemberPointer: diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp index a8e3b85fe0..a5e82efee5 100644 --- a/lib/Sema/Sema.cpp +++ b/lib/Sema/Sema.cpp @@ -482,6 +482,7 @@ ExprResult Sema::ImpCastExprToType(Expr *E, QualType Ty, llvm_unreachable("can't implicitly cast lvalue to rvalue with this cast " "kind"); case CK_LValueToRValue: + case CK_NullptrLValueToRValue: case CK_ArrayToPointerDecay: case CK_FunctionToPointerDecay: case CK_ToVoid: diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp index 4ba0fb12e7..fa7a412ccf 100644 --- a/lib/Sema/SemaExpr.cpp +++ b/lib/Sema/SemaExpr.cpp @@ -623,8 +623,12 @@ ExprResult Sema::DefaultLvalueConversion(Expr *E) { if (E->getType().getObjCLifetime() == Qualifiers::OCL_Weak) Cleanup.setExprNeedsCleanups(true); - ExprResult Res = ImplicitCastExpr::Create(Context, T, CK_LValueToRValue, E, - nullptr, VK_RValue); + // C++ [conv.lval]p3: + // If T is cv std::nullptr_t, the result is a null pointer constant. + CastKind CK = + T->isNullPtrType() ? CK_NullptrLValueToRValue : CK_LValueToRValue; + ExprResult Res = + ImplicitCastExpr::Create(Context, T, CK, E, nullptr, VK_RValue); // C11 6.3.2.1p2: // ... if the lvalue has atomic type, the value has the non-atomic version @@ -15899,7 +15903,7 @@ namespace { void VisitImplicitCastExpr(ImplicitCastExpr *E) { Inherited::VisitImplicitCastExpr(E); - if (E->getCastKind() == CK_LValueToRValue) + if (isLValueToRValue(E->getCastKind())) S.UpdateMarkingForLValueToRValue(E->getSubExpr()); } }; diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp index 57277f6e82..d71c632420 100644 --- a/lib/Sema/SemaInit.cpp +++ b/lib/Sema/SemaInit.cpp @@ -7686,9 +7686,12 @@ ExprResult InitializationSequence::Perform(Sema &S, case SK_LValueToRValue: { assert(CurInit.get()->isGLValue() && "cannot load from a prvalue"); - CurInit = ImplicitCastExpr::Create(S.Context, Step->Type, - CK_LValueToRValue, CurInit.get(), - /*BasePath=*/nullptr, VK_RValue); + CurInit = S.DefaultLvalueConversion(CurInit.get()); + if (!CurInit.isInvalid()) { + assert(CurInit.get()->isRValue() && "lvalue-to-rvalue failed"); + assert(S.Context.hasSameType(CurInit.get()->getType(), Step->Type) && + "lvalue-to-rvalue produced unexpected type"); + } break; } diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp index cc3c25cfb5..fe05e145bf 100644 --- a/lib/Sema/SemaStmt.cpp +++ b/lib/Sema/SemaStmt.cpp @@ -1458,7 +1458,7 @@ namespace { } void VisitCastExpr(CastExpr *E) { - if (E->getCastKind() == CK_LValueToRValue) + if (isLValueToRValue(E->getCastKind())) CheckLValueToRValueCast(E->getSubExpr()); else Visit(E->getSubExpr()); @@ -2766,7 +2766,7 @@ static void DiagnoseForRangeConstVariableCopies(Sema &SemaRef, if (!CE->getConstructor()->isCopyConstructor()) return; } else if (const CastExpr *CE = dyn_cast(InitExpr)) { - if (CE->getCastKind() != CK_LValueToRValue) + if (isLValueToRValue(CE->getCastKind())) return; } else { return; diff --git a/lib/Sema/SemaStmtAsm.cpp b/lib/Sema/SemaStmtAsm.cpp index d209266049..439d5c056c 100644 --- a/lib/Sema/SemaStmtAsm.cpp +++ b/lib/Sema/SemaStmtAsm.cpp @@ -48,7 +48,7 @@ static void removeLValueToRValueCast(Expr *E) { return; if (auto *CastE = dyn_cast(Child)) - if (CastE->getCastKind() == CK_LValueToRValue) { + if (isLValueToRValue(CastE->getCastKind())) { ExprUnderCast = CastE->getSubExpr(); // LValueToRValue cast inside GCCAsmStmt requires an explicit cast. ParentCast->setSubExpr(ExprUnderCast); diff --git a/lib/StaticAnalyzer/Core/ExprEngineC.cpp b/lib/StaticAnalyzer/Core/ExprEngineC.cpp index 7d47cf4f33..e95bed6b2b 100644 --- a/lib/StaticAnalyzer/Core/ExprEngineC.cpp +++ b/lib/StaticAnalyzer/Core/ExprEngineC.cpp @@ -379,7 +379,6 @@ void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex, case CK_BitCast: case CK_AddressSpaceConversion: case CK_BooleanToSignedIntegral: - case CK_NullToPointer: case CK_IntegralToPointer: case CK_PointerToIntegral: { SVal V = state->getSVal(Ex, LCtx); @@ -502,6 +501,13 @@ void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex, Bldr.generateNode(CastE, Pred, state); continue; } + case CK_NullptrLValueToRValue: + case CK_NullToPointer: { + SVal V = svalBuilder.makeNull(); + state = state->BindExpr(CastE, LCtx, V); + Bldr.generateNode(CastE, Pred, state); + continue; + } case CK_NullToMemberPointer: { SVal V = svalBuilder.getMemberPointer(nullptr); state = state->BindExpr(CastE, LCtx, V);