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-rw-r--r--clang/lib/AST/ExprConstant.cpp242
1 files changed, 220 insertions, 22 deletions
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index ea36072bd9c..2c4cad1fff4 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -37,6 +37,7 @@
#include "clang/AST/ASTDiagnostic.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/CharUnits.h"
+#include "clang/AST/CXXInheritance.h"
#include "clang/AST/Expr.h"
#include "clang/AST/OSLog.h"
#include "clang/AST/RecordLayout.h"
@@ -2485,6 +2486,21 @@ static bool HandleLValueBasePath(EvalInfo &Info, const CastExpr *E,
return true;
}
+/// Cast an lvalue referring to a derived class to a known base subobject.
+static bool CastToBaseClass(EvalInfo &Info, const Expr *E, LValue &Result,
+ const CXXRecordDecl *DerivedRD,
+ const CXXRecordDecl *BaseRD) {
+ CXXBasePaths Paths(/*FindAmbiguities=*/false,
+ /*RecordPaths=*/true, /*DetectVirtual=*/false);
+ if (!DerivedRD->isDerivedFrom(BaseRD, Paths))
+ llvm_unreachable("Class must be derived from the passed in base class!");
+
+ for (CXXBasePathElement &Elem : Paths.front())
+ if (!HandleLValueBase(Info, E, Result, Elem.Class, Elem.Base))
+ return false;
+ return true;
+}
+
/// Update LVal to refer to the given field, which must be a member of the type
/// currently described by LVal.
static bool HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
@@ -4461,16 +4477,19 @@ static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
}
// DR1872: An instantiated virtual constexpr function can't be called in a
- // constant expression.
- if (isa<CXXMethodDecl>(Declaration) &&
- cast<CXXMethodDecl>(Declaration)->isVirtual()) {
- Info.FFDiag(CallLoc, diag::note_constexpr_virtual_call);
+ // constant expression (prior to C++20). We can still constant-fold such a
+ // call.
+ if (!Info.Ctx.getLangOpts().CPlusPlus2a && isa<CXXMethodDecl>(Declaration) &&
+ cast<CXXMethodDecl>(Declaration)->isVirtual())
+ Info.CCEDiag(CallLoc, diag::note_constexpr_virtual_call);
+
+ if (Definition && Definition->isInvalidDecl()) {
+ Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
return false;
}
// Can we evaluate this function call?
- if (Definition && Definition->isConstexpr() &&
- !Definition->isInvalidDecl() && Body)
+ if (Definition && Definition->isConstexpr() && Body)
return true;
if (Info.getLangOpts().CPlusPlus11) {
@@ -4517,7 +4536,7 @@ const AccessKinds CheckMemberCallThisPointerHandler::AccessKind;
/// Check that the pointee of the 'this' pointer in a member function call is
/// either within its lifetime or in its period of construction or destruction.
static bool checkMemberCallThisPointer(EvalInfo &Info, const Expr *E,
- const LValue &This) {
+ const LValue &This, bool IsVirtual) {
if (This.Designator.Invalid)
return false;
@@ -4538,6 +4557,16 @@ static bool checkMemberCallThisPointer(EvalInfo &Info, const Expr *E,
: diag::note_constexpr_access_unsized_array)
<< AK_MemberCall;
return false;
+ } else if (IsVirtual) {
+ // Conservatively refuse to perform a virtual function call if we would
+ // not be able to read a notional 'vptr' value.
+ APValue Val;
+ This.moveInto(Val);
+ QualType StarThisType =
+ Info.Ctx.getLValueReferenceType(This.Designator.getType(Info.Ctx));
+ Info.FFDiag(E, diag::note_constexpr_virtual_out_of_lifetime)
+ << Val.getAsString(Info.Ctx, StarThisType);
+ return false;
}
return true;
}
@@ -4546,6 +4575,155 @@ static bool checkMemberCallThisPointer(EvalInfo &Info, const Expr *E,
return Obj && findSubobject(Info, E, Obj, This.Designator, Handler);
}
+struct DynamicType {
+ /// The dynamic class type of the object.
+ const CXXRecordDecl *Type;
+ /// The corresponding path length in the lvalue.
+ unsigned PathLength;
+};
+
+static const CXXRecordDecl *getBaseClassType(SubobjectDesignator &Designator,
+ unsigned PathLength) {
+ assert(PathLength >= Designator.MostDerivedPathLength && PathLength <=
+ Designator.Entries.size() && "invalid path length");
+ return (PathLength == Designator.MostDerivedPathLength)
+ ? Designator.MostDerivedType->getAsCXXRecordDecl()
+ : getAsBaseClass(Designator.Entries[PathLength - 1]);
+}
+
+/// Determine the dynamic type of an object.
+static Optional<DynamicType> ComputeDynamicType(EvalInfo &Info, LValue &This) {
+ // If we don't have an lvalue denoting an object of class type, there is no
+ // meaningful dynamic type. (We consider objects of non-class type to have no
+ // dynamic type.)
+ if (This.Designator.IsOnePastTheEnd || This.Designator.Invalid ||
+ !This.Designator.MostDerivedType->getAsCXXRecordDecl())
+ return None;
+
+ // FIXME: For very deep class hierarchies, it might be beneficial to use a
+ // binary search here instead. But the overwhelmingly common case is that
+ // we're not in the middle of a constructor, so it probably doesn't matter
+ // in practice.
+ ArrayRef<APValue::LValuePathEntry> Path = This.Designator.Entries;
+ for (unsigned PathLength = This.Designator.MostDerivedPathLength;
+ PathLength <= Path.size(); ++PathLength) {
+ switch (Info.isEvaluatingConstructor(This.getLValueBase(),
+ Path.slice(0, PathLength))) {
+ case ConstructionPhase::Bases:
+ // We're constructing a base class. This is not the dynamic type.
+ break;
+
+ case ConstructionPhase::None:
+ case ConstructionPhase::AfterBases:
+ // We've finished constructing the base classes, so this is the dynamic
+ // type.
+ return DynamicType{getBaseClassType(This.Designator, PathLength),
+ PathLength};
+ }
+ }
+
+ // CWG issue 1517: we're constructing a base class of the object described by
+ // 'This', so that object has not yet begun its period of construction and
+ // any polymorphic operation on it results in undefined behavior.
+ return None;
+}
+
+/// Perform virtual dispatch.
+static const CXXMethodDecl *HandleVirtualDispatch(
+ EvalInfo &Info, const Expr *E, LValue &This, const CXXMethodDecl *Found,
+ llvm::SmallVectorImpl<QualType> &CovariantAdjustmentPath) {
+ Optional<DynamicType> DynType = ComputeDynamicType(Info, This);
+ if (!DynType) {
+ Info.FFDiag(E);
+ return nullptr;
+ }
+
+ // Find the final overrider. It must be declared in one of the classes on the
+ // path from the dynamic type to the static type.
+ // FIXME: If we ever allow literal types to have virtual base classes, that
+ // won't be true.
+ const CXXMethodDecl *Callee = Found;
+ unsigned PathLength = DynType->PathLength;
+ for (/**/; PathLength <= This.Designator.Entries.size(); ++PathLength) {
+ const CXXRecordDecl *Class = getBaseClassType(This.Designator, PathLength);
+ if (Class->getNumVBases()) {
+ Info.FFDiag(E);
+ return nullptr;
+ }
+
+ const CXXMethodDecl *Overrider =
+ Found->getCorrespondingMethodDeclaredInClass(Class, false);
+ if (Overrider) {
+ Callee = Overrider;
+ break;
+ }
+ }
+
+ // C++2a [class.abstract]p6:
+ // the effect of making a virtual call to a pure virtual function [...] is
+ // undefined
+ if (Callee->isPure()) {
+ Info.FFDiag(E, diag::note_constexpr_pure_virtual_call, 1) << Callee;
+ Info.Note(Callee->getLocation(), diag::note_declared_at);
+ return nullptr;
+ }
+
+ // If necessary, walk the rest of the path to determine the sequence of
+ // covariant adjustment steps to apply.
+ if (!Info.Ctx.hasSameUnqualifiedType(Callee->getReturnType(),
+ Found->getReturnType())) {
+ CovariantAdjustmentPath.push_back(Callee->getReturnType());
+ for (unsigned CovariantPathLength = PathLength + 1;
+ CovariantPathLength != This.Designator.Entries.size();
+ ++CovariantPathLength) {
+ const CXXRecordDecl *NextClass =
+ getBaseClassType(This.Designator, CovariantPathLength);
+ const CXXMethodDecl *Next =
+ Found->getCorrespondingMethodDeclaredInClass(NextClass, false);
+ if (Next && !Info.Ctx.hasSameUnqualifiedType(
+ Next->getReturnType(), CovariantAdjustmentPath.back()))
+ CovariantAdjustmentPath.push_back(Next->getReturnType());
+ }
+ if (!Info.Ctx.hasSameUnqualifiedType(Found->getReturnType(),
+ CovariantAdjustmentPath.back()))
+ CovariantAdjustmentPath.push_back(Found->getReturnType());
+ }
+
+ // Perform 'this' adjustment.
+ if (!CastToDerivedClass(Info, E, This, Callee->getParent(), PathLength))
+ return nullptr;
+
+ return Callee;
+}
+
+/// Perform the adjustment from a value returned by a virtual function to
+/// a value of the statically expected type, which may be a pointer or
+/// reference to a base class of the returned type.
+static bool HandleCovariantReturnAdjustment(EvalInfo &Info, const Expr *E,
+ APValue &Result,
+ ArrayRef<QualType> Path) {
+ assert(Result.isLValue() &&
+ "unexpected kind of APValue for covariant return");
+ if (Result.isNullPointer())
+ return true;
+
+ LValue LVal;
+ LVal.setFrom(Info.Ctx, Result);
+
+ const CXXRecordDecl *OldClass = Path[0]->getPointeeCXXRecordDecl();
+ for (unsigned I = 1; I != Path.size(); ++I) {
+ const CXXRecordDecl *NewClass = Path[I]->getPointeeCXXRecordDecl();
+ assert(OldClass && NewClass && "unexpected kind of covariant return");
+ if (OldClass != NewClass &&
+ !CastToBaseClass(Info, E, LVal, OldClass, NewClass))
+ return false;
+ OldClass = NewClass;
+ }
+
+ LVal.moveInto(Result);
+ return true;
+}
+
/// Determine if a class has any fields that might need to be copied by a
/// trivial copy or move operation.
static bool hasFields(const CXXRecordDecl *RD) {
@@ -4735,11 +4913,6 @@ static bool HandleConstructorCall(const Expr *E, const LValue &This,
BaseType->getAsCXXRecordDecl(), &Layout))
return false;
Value = &Result.getStructBase(BasesSeen++);
-
- // This is the point at which the dynamic type of the object becomes this
- // class type.
- if (BasesSeen == RD->getNumBases())
- EvalObj.finishedConstructingBases();
} else if ((FD = I->getMember())) {
if (!HandleLValueMember(Info, I->getInit(), Subobject, FD, &Layout))
return false;
@@ -4800,6 +4973,11 @@ static bool HandleConstructorCall(const Expr *E, const LValue &This,
return false;
Success = false;
}
+
+ // This is the point at which the dynamic type of the object becomes this
+ // class type.
+ if (I->isBaseInitializer() && BasesSeen == RD->getNumBases())
+ EvalObj.finishedConstructingBases();
}
return Success &&
@@ -5040,27 +5218,30 @@ public:
const FunctionDecl *FD = nullptr;
LValue *This = nullptr, ThisVal;
auto Args = llvm::makeArrayRef(E->getArgs(), E->getNumArgs());
+ bool HasQualifier = false;
// Extract function decl and 'this' pointer from the callee.
if (CalleeType->isSpecificBuiltinType(BuiltinType::BoundMember)) {
- const ValueDecl *Member = nullptr;
+ const CXXMethodDecl *Member = nullptr;
if (const MemberExpr *ME = dyn_cast<MemberExpr>(Callee)) {
// Explicit bound member calls, such as x.f() or p->g();
if (!EvaluateObjectArgument(Info, ME->getBase(), ThisVal))
return false;
- Member = ME->getMemberDecl();
+ Member = dyn_cast<CXXMethodDecl>(ME->getMemberDecl());
+ if (!Member)
+ return Error(Callee);
This = &ThisVal;
+ HasQualifier = ME->hasQualifier();
} else if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(Callee)) {
// Indirect bound member calls ('.*' or '->*').
- Member = HandleMemberPointerAccess(Info, BE, ThisVal, false);
- if (!Member) return false;
+ Member = dyn_cast_or_null<CXXMethodDecl>(
+ HandleMemberPointerAccess(Info, BE, ThisVal, false));
+ if (!Member)
+ return Error(Callee);
This = &ThisVal;
} else
return Error(Callee);
-
- FD = dyn_cast<FunctionDecl>(Member);
- if (!FD)
- return Error(Callee);
+ FD = Member;
} else if (CalleeType->isFunctionPointerType()) {
LValue Call;
if (!EvaluatePointer(Callee, Call, Info))
@@ -5130,8 +5311,20 @@ public:
} else
return Error(E);
- if (This && !checkMemberCallThisPointer(Info, E, *This))
- return false;
+ SmallVector<QualType, 4> CovariantAdjustmentPath;
+ if (This) {
+ auto *NamedMember = dyn_cast<CXXMethodDecl>(FD);
+ bool IsVirtual = NamedMember && NamedMember->isVirtual() && !HasQualifier;
+
+ // Check that the 'this' pointer points to an object of the right type.
+ if (!checkMemberCallThisPointer(Info, E, *This, IsVirtual))
+ return false;
+
+ // Perform virtual dispatch, if necessary.
+ if (IsVirtual && !(FD = HandleVirtualDispatch(Info, E, *This, NamedMember,
+ CovariantAdjustmentPath)))
+ return true;
+ }
const FunctionDecl *Definition = nullptr;
Stmt *Body = FD->getBody(Definition);
@@ -5141,6 +5334,11 @@ public:
Result, ResultSlot))
return false;
+ if (!CovariantAdjustmentPath.empty() &&
+ !HandleCovariantReturnAdjustment(Info, E, Result,
+ CovariantAdjustmentPath))
+ return false;
+
return true;
}
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