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//===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Expr constant evaluator.
//
// Constant expression evaluation produces four main results:
//
// * A success/failure flag indicating whether constant folding was successful.
// This is the 'bool' return value used by most of the code in this file. A
// 'false' return value indicates that constant folding has failed, and any
// appropriate diagnostic has already been produced.
//
// * An evaluated result, valid only if constant folding has not failed.
//
// * A flag indicating if evaluation encountered (unevaluated) side-effects.
// These arise in cases such as (sideEffect(), 0) and (sideEffect() || 1),
// where it is possible to determine the evaluated result regardless.
//
// * A set of notes indicating why the evaluation was not a constant expression
// (under the C++11 rules only, at the moment), or, if folding failed too,
// why the expression could not be folded.
//
// If we are checking for a potential constant expression, failure to constant
// fold a potential constant sub-expression will be indicated by a 'false'
// return value (the expression could not be folded) and no diagnostic (the
// expression is not necessarily non-constant).
//
//===----------------------------------------------------------------------===//
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/TypeLoc.h"
#include "clang/AST/ASTDiagnostic.h"
#include "clang/AST/Expr.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/SmallString.h"
#include <cstring>
#include <functional>
using namespace clang;
using llvm::APSInt;
using llvm::APFloat;
static bool IsGlobalLValue(APValue::LValueBase B);
namespace {
struct LValue;
struct CallStackFrame;
struct EvalInfo;
static QualType getType(APValue::LValueBase B) {
if (!B) return QualType();
if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>())
return D->getType();
return B.get<const Expr*>()->getType();
}
/// Get an LValue path entry, which is known to not be an array index, as a
/// field or base class.
static
APValue::BaseOrMemberType getAsBaseOrMember(APValue::LValuePathEntry E) {
APValue::BaseOrMemberType Value;
Value.setFromOpaqueValue(E.BaseOrMember);
return Value;
}
/// Get an LValue path entry, which is known to not be an array index, as a
/// field declaration.
static const FieldDecl *getAsField(APValue::LValuePathEntry E) {
return dyn_cast<FieldDecl>(getAsBaseOrMember(E).getPointer());
}
/// Get an LValue path entry, which is known to not be an array index, as a
/// base class declaration.
static const CXXRecordDecl *getAsBaseClass(APValue::LValuePathEntry E) {
return dyn_cast<CXXRecordDecl>(getAsBaseOrMember(E).getPointer());
}
/// Determine whether this LValue path entry for a base class names a virtual
/// base class.
static bool isVirtualBaseClass(APValue::LValuePathEntry E) {
return getAsBaseOrMember(E).getInt();
}
/// Find the path length and type of the most-derived subobject in the given
/// path, and find the size of the containing array, if any.
static
unsigned findMostDerivedSubobject(ASTContext &Ctx, QualType Base,
ArrayRef<APValue::LValuePathEntry> Path,
uint64_t &ArraySize, QualType &Type) {
unsigned MostDerivedLength = 0;
Type = Base;
for (unsigned I = 0, N = Path.size(); I != N; ++I) {
if (Type->isArrayType()) {
const ConstantArrayType *CAT =
cast<ConstantArrayType>(Ctx.getAsArrayType(Type));
Type = CAT->getElementType();
ArraySize = CAT->getSize().getZExtValue();
MostDerivedLength = I + 1;
} else if (Type->isAnyComplexType()) {
const ComplexType *CT = Type->castAs<ComplexType>();
Type = CT->getElementType();
ArraySize = 2;
MostDerivedLength = I + 1;
} else if (const FieldDecl *FD = getAsField(Path[I])) {
Type = FD->getType();
ArraySize = 0;
MostDerivedLength = I + 1;
} else {
// Path[I] describes a base class.
ArraySize = 0;
}
}
return MostDerivedLength;
}
// The order of this enum is important for diagnostics.
enum CheckSubobjectKind {
CSK_Base, CSK_Derived, CSK_Field, CSK_ArrayToPointer, CSK_ArrayIndex,
CSK_This, CSK_Real, CSK_Imag
};
/// A path from a glvalue to a subobject of that glvalue.
struct SubobjectDesignator {
/// True if the subobject was named in a manner not supported by C++11. Such
/// lvalues can still be folded, but they are not core constant expressions
/// and we cannot perform lvalue-to-rvalue conversions on them.
bool Invalid : 1;
/// Is this a pointer one past the end of an object?
bool IsOnePastTheEnd : 1;
/// The length of the path to the most-derived object of which this is a
/// subobject.
unsigned MostDerivedPathLength : 30;
/// The size of the array of which the most-derived object is an element, or
/// 0 if the most-derived object is not an array element.
uint64_t MostDerivedArraySize;
/// The type of the most derived object referred to by this address.
QualType MostDerivedType;
typedef APValue::LValuePathEntry PathEntry;
/// The entries on the path from the glvalue to the designated subobject.
SmallVector<PathEntry, 8> Entries;
SubobjectDesignator() : Invalid(true) {}
explicit SubobjectDesignator(QualType T)
: Invalid(false), IsOnePastTheEnd(false), MostDerivedPathLength(0),
MostDerivedArraySize(0), MostDerivedType(T) {}
SubobjectDesignator(ASTContext &Ctx, const APValue &V)
: Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
MostDerivedPathLength(0), MostDerivedArraySize(0) {
if (!Invalid) {
IsOnePastTheEnd = V.isLValueOnePastTheEnd();
ArrayRef<PathEntry> VEntries = V.getLValuePath();
Entries.insert(Entries.end(), VEntries.begin(), VEntries.end());
if (V.getLValueBase())
MostDerivedPathLength =
findMostDerivedSubobject(Ctx, getType(V.getLValueBase()),
V.getLValuePath(), MostDerivedArraySize,
MostDerivedType);
}
}
void setInvalid() {
Invalid = true;
Entries.clear();
}
/// Determine whether this is a one-past-the-end pointer.
bool isOnePastTheEnd() const {
if (IsOnePastTheEnd)
return true;
if (MostDerivedArraySize &&
Entries[MostDerivedPathLength - 1].ArrayIndex == MostDerivedArraySize)
return true;
return false;
}
/// Check that this refers to a valid subobject.
bool isValidSubobject() const {
if (Invalid)
return false;
return !isOnePastTheEnd();
}
/// Check that this refers to a valid subobject, and if not, produce a
/// relevant diagnostic and set the designator as invalid.
bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK);
/// Update this designator to refer to the first element within this array.
void addArrayUnchecked(const ConstantArrayType *CAT) {
PathEntry Entry;
Entry.ArrayIndex = 0;
Entries.push_back(Entry);
// This is a most-derived object.
MostDerivedType = CAT->getElementType();
MostDerivedArraySize = CAT->getSize().getZExtValue();
MostDerivedPathLength = Entries.size();
}
/// Update this designator to refer to the given base or member of this
/// object.
void addDeclUnchecked(const Decl *D, bool Virtual = false) {
PathEntry Entry;
APValue::BaseOrMemberType Value(D, Virtual);
Entry.BaseOrMember = Value.getOpaqueValue();
Entries.push_back(Entry);
// If this isn't a base class, it's a new most-derived object.
if (const FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
MostDerivedType = FD->getType();
MostDerivedArraySize = 0;
MostDerivedPathLength = Entries.size();
}
}
/// Update this designator to refer to the given complex component.
void addComplexUnchecked(QualType EltTy, bool Imag) {
PathEntry Entry;
Entry.ArrayIndex = Imag;
Entries.push_back(Entry);
// This is technically a most-derived object, though in practice this
// is unlikely to matter.
MostDerivedType = EltTy;
MostDerivedArraySize = 2;
MostDerivedPathLength = Entries.size();
}
void diagnosePointerArithmetic(EvalInfo &Info, const Expr *E, uint64_t N);
/// Add N to the address of this subobject.
void adjustIndex(EvalInfo &Info, const Expr *E, uint64_t N) {
if (Invalid) return;
if (MostDerivedPathLength == Entries.size() && MostDerivedArraySize) {
Entries.back().ArrayIndex += N;
if (Entries.back().ArrayIndex > MostDerivedArraySize) {
diagnosePointerArithmetic(Info, E, Entries.back().ArrayIndex);
setInvalid();
}
return;
}
// [expr.add]p4: For the purposes of these operators, a pointer to a
// nonarray object behaves the same as a pointer to the first element of
// an array of length one with the type of the object as its element type.
if (IsOnePastTheEnd && N == (uint64_t)-1)
IsOnePastTheEnd = false;
else if (!IsOnePastTheEnd && N == 1)
IsOnePastTheEnd = true;
else if (N != 0) {
diagnosePointerArithmetic(Info, E, uint64_t(IsOnePastTheEnd) + N);
setInvalid();
}
}
};
/// A stack frame in the constexpr call stack.
struct CallStackFrame {
EvalInfo &Info;
/// Parent - The caller of this stack frame.
CallStackFrame *Caller;
/// CallLoc - The location of the call expression for this call.
SourceLocation CallLoc;
/// Callee - The function which was called.
const FunctionDecl *Callee;
/// Index - The call index of this call.
unsigned Index;
/// This - The binding for the this pointer in this call, if any.
const LValue *This;
/// ParmBindings - Parameter bindings for this function call, indexed by
/// parameters' function scope indices.
const APValue *Arguments;
typedef llvm::DenseMap<const Expr*, APValue> MapTy;
typedef MapTy::const_iterator temp_iterator;
/// Temporaries - Temporary lvalues materialized within this stack frame.
MapTy Temporaries;
CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
const FunctionDecl *Callee, const LValue *This,
const APValue *Arguments);
~CallStackFrame();
};
/// A partial diagnostic which we might know in advance that we are not going
/// to emit.
class OptionalDiagnostic {
PartialDiagnostic *Diag;
public:
explicit OptionalDiagnostic(PartialDiagnostic *Diag = 0) : Diag(Diag) {}
template<typename T>
OptionalDiagnostic &operator<<(const T &v) {
if (Diag)
*Diag << v;
return *this;
}
OptionalDiagnostic &operator<<(const APSInt &I) {
if (Diag) {
llvm::SmallVector<char, 32> Buffer;
I.toString(Buffer);
*Diag << StringRef(Buffer.data(), Buffer.size());
}
return *this;
}
OptionalDiagnostic &operator<<(const APFloat &F) {
if (Diag) {
llvm::SmallVector<char, 32> Buffer;
F.toString(Buffer);
*Diag << StringRef(Buffer.data(), Buffer.size());
}
return *this;
}
};
/// EvalInfo - This is a private struct used by the evaluator to capture
/// information about a subexpression as it is folded. It retains information
/// about the AST context, but also maintains information about the folded
/// expression.
///
/// If an expression could be evaluated, it is still possible it is not a C
/// "integer constant expression" or constant expression. If not, this struct
/// captures information about how and why not.
///
/// One bit of information passed *into* the request for constant folding
/// indicates whether the subexpression is "evaluated" or not according to C
/// rules. For example, the RHS of (0 && foo()) is not evaluated. We can
/// evaluate the expression regardless of what the RHS is, but C only allows
/// certain things in certain situations.
struct EvalInfo {
ASTContext &Ctx;
/// EvalStatus - Contains information about the evaluation.
Expr::EvalStatus &EvalStatus;
/// CurrentCall - The top of the constexpr call stack.
CallStackFrame *CurrentCall;
/// CallStackDepth - The number of calls in the call stack right now.
unsigned CallStackDepth;
/// NextCallIndex - The next call index to assign.
unsigned NextCallIndex;
typedef llvm::DenseMap<const OpaqueValueExpr*, APValue> MapTy;
/// OpaqueValues - Values used as the common expression in a
/// BinaryConditionalOperator.
MapTy OpaqueValues;
/// BottomFrame - The frame in which evaluation started. This must be
/// initialized after CurrentCall and CallStackDepth.
CallStackFrame BottomFrame;
/// EvaluatingDecl - This is the declaration whose initializer is being
/// evaluated, if any.
const VarDecl *EvaluatingDecl;
/// EvaluatingDeclValue - This is the value being constructed for the
/// declaration whose initializer is being evaluated, if any.
APValue *EvaluatingDeclValue;
/// HasActiveDiagnostic - Was the previous diagnostic stored? If so, further
/// notes attached to it will also be stored, otherwise they will not be.
bool HasActiveDiagnostic;
/// CheckingPotentialConstantExpression - Are we checking whether the
/// expression is a potential constant expression? If so, some diagnostics
/// are suppressed.
bool CheckingPotentialConstantExpression;
EvalInfo(const ASTContext &C, Expr::EvalStatus &S)
: Ctx(const_cast<ASTContext&>(C)), EvalStatus(S), CurrentCall(0),
CallStackDepth(0), NextCallIndex(1),
BottomFrame(*this, SourceLocation(), 0, 0, 0),
EvaluatingDecl(0), EvaluatingDeclValue(0), HasActiveDiagnostic(false),
CheckingPotentialConstantExpression(false) {}
const APValue *getOpaqueValue(const OpaqueValueExpr *e) const {
MapTy::const_iterator i = OpaqueValues.find(e);
if (i == OpaqueValues.end()) return 0;
return &i->second;
}
void setEvaluatingDecl(const VarDecl *VD, APValue &Value) {
EvaluatingDecl = VD;
EvaluatingDeclValue = &Value;
}
const LangOptions &getLangOpts() const { return Ctx.getLangOpts(); }
bool CheckCallLimit(SourceLocation Loc) {
// Don't perform any constexpr calls (other than the call we're checking)
// when checking a potential constant expression.
if (CheckingPotentialConstantExpression && CallStackDepth > 1)
return false;
if (NextCallIndex == 0) {
// NextCallIndex has wrapped around.
Diag(Loc, diag::note_constexpr_call_limit_exceeded);
return false;
}
if (CallStackDepth <= getLangOpts().ConstexprCallDepth)
return true;
Diag(Loc, diag::note_constexpr_depth_limit_exceeded)
<< getLangOpts().ConstexprCallDepth;
return false;
}
CallStackFrame *getCallFrame(unsigned CallIndex) {
assert(CallIndex && "no call index in getCallFrame");
// We will eventually hit BottomFrame, which has Index 1, so Frame can't
// be null in this loop.
CallStackFrame *Frame = CurrentCall;
while (Frame->Index > CallIndex)
Frame = Frame->Caller;
return (Frame->Index == CallIndex) ? Frame : 0;
}
private:
/// Add a diagnostic to the diagnostics list.
PartialDiagnostic &addDiag(SourceLocation Loc, diag::kind DiagId) {
PartialDiagnostic PD(DiagId, Ctx.getDiagAllocator());
EvalStatus.Diag->push_back(std::make_pair(Loc, PD));
return EvalStatus.Diag->back().second;
}
/// Add notes containing a call stack to the current point of evaluation.
void addCallStack(unsigned Limit);
public:
/// Diagnose that the evaluation cannot be folded.
OptionalDiagnostic Diag(SourceLocation Loc, diag::kind DiagId
= diag::note_invalid_subexpr_in_const_expr,
unsigned ExtraNotes = 0) {
// If we have a prior diagnostic, it will be noting that the expression
// isn't a constant expression. This diagnostic is more important.
// FIXME: We might want to show both diagnostics to the user.
if (EvalStatus.Diag) {
unsigned CallStackNotes = CallStackDepth - 1;
unsigned Limit = Ctx.getDiagnostics().getConstexprBacktraceLimit();
if (Limit)
CallStackNotes = std::min(CallStackNotes, Limit + 1);
if (CheckingPotentialConstantExpression)
CallStackNotes = 0;
HasActiveDiagnostic = true;
EvalStatus.Diag->clear();
EvalStatus.Diag->reserve(1 + ExtraNotes + CallStackNotes);
addDiag(Loc, DiagId);
if (!CheckingPotentialConstantExpression)
addCallStack(Limit);
return OptionalDiagnostic(&(*EvalStatus.Diag)[0].second);
}
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
OptionalDiagnostic Diag(const Expr *E, diag::kind DiagId
= diag::note_invalid_subexpr_in_const_expr,
unsigned ExtraNotes = 0) {
if (EvalStatus.Diag)
return Diag(E->getExprLoc(), DiagId, ExtraNotes);
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
/// Diagnose that the evaluation does not produce a C++11 core constant
/// expression.
template<typename LocArg>
OptionalDiagnostic CCEDiag(LocArg Loc, diag::kind DiagId
= diag::note_invalid_subexpr_in_const_expr,
unsigned ExtraNotes = 0) {
// Don't override a previous diagnostic.
if (!EvalStatus.Diag || !EvalStatus.Diag->empty()) {
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
return Diag(Loc, DiagId, ExtraNotes);
}
/// Add a note to a prior diagnostic.
OptionalDiagnostic Note(SourceLocation Loc, diag::kind DiagId) {
if (!HasActiveDiagnostic)
return OptionalDiagnostic();
return OptionalDiagnostic(&addDiag(Loc, DiagId));
}
/// Add a stack of notes to a prior diagnostic.
void addNotes(ArrayRef<PartialDiagnosticAt> Diags) {
if (HasActiveDiagnostic) {
EvalStatus.Diag->insert(EvalStatus.Diag->end(),
Diags.begin(), Diags.end());
}
}
/// Should we continue evaluation as much as possible after encountering a
/// construct which can't be folded?
bool keepEvaluatingAfterFailure() {
return CheckingPotentialConstantExpression &&
EvalStatus.Diag && EvalStatus.Diag->empty();
}
};
/// Object used to treat all foldable expressions as constant expressions.
struct FoldConstant {
bool Enabled;
explicit FoldConstant(EvalInfo &Info)
: Enabled(Info.EvalStatus.Diag && Info.EvalStatus.Diag->empty() &&
!Info.EvalStatus.HasSideEffects) {
}
// Treat the value we've computed since this object was created as constant.
void Fold(EvalInfo &Info) {
if (Enabled && !Info.EvalStatus.Diag->empty() &&
!Info.EvalStatus.HasSideEffects)
Info.EvalStatus.Diag->clear();
}
};
/// RAII object used to suppress diagnostics and side-effects from a
/// speculative evaluation.
class SpeculativeEvaluationRAII {
EvalInfo &Info;
Expr::EvalStatus Old;
public:
SpeculativeEvaluationRAII(EvalInfo &Info,
llvm::SmallVectorImpl<PartialDiagnosticAt>
*NewDiag = 0)
: Info(Info), Old(Info.EvalStatus) {
Info.EvalStatus.Diag = NewDiag;
}
~SpeculativeEvaluationRAII() {
Info.EvalStatus = Old;
}
};
}
bool SubobjectDesignator::checkSubobject(EvalInfo &Info, const Expr *E,
CheckSubobjectKind CSK) {
if (Invalid)
return false;
if (isOnePastTheEnd()) {
Info.CCEDiag(E, diag::note_constexpr_past_end_subobject)
<< CSK;
setInvalid();
return false;
}
return true;
}
void SubobjectDesignator::diagnosePointerArithmetic(EvalInfo &Info,
const Expr *E, uint64_t N) {
if (MostDerivedPathLength == Entries.size() && MostDerivedArraySize)
Info.CCEDiag(E, diag::note_constexpr_array_index)
<< static_cast<int>(N) << /*array*/ 0
<< static_cast<unsigned>(MostDerivedArraySize);
else
Info.CCEDiag(E, diag::note_constexpr_array_index)
<< static_cast<int>(N) << /*non-array*/ 1;
setInvalid();
}
CallStackFrame::CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
const FunctionDecl *Callee, const LValue *This,
const APValue *Arguments)
: Info(Info), Caller(Info.CurrentCall), CallLoc(CallLoc), Callee(Callee),
Index(Info.NextCallIndex++), This(This), Arguments(Arguments) {
Info.CurrentCall = this;
++Info.CallStackDepth;
}
CallStackFrame::~CallStackFrame() {
assert(Info.CurrentCall == this && "calls retired out of order");
--Info.CallStackDepth;
Info.CurrentCall = Caller;
}
/// Produce a string describing the given constexpr call.
static void describeCall(CallStackFrame *Frame, llvm::raw_ostream &Out) {
unsigned ArgIndex = 0;
bool IsMemberCall = isa<CXXMethodDecl>(Frame->Callee) &&
!isa<CXXConstructorDecl>(Frame->Callee) &&
cast<CXXMethodDecl>(Frame->Callee)->isInstance();
if (!IsMemberCall)
Out << *Frame->Callee << '(';
for (FunctionDecl::param_const_iterator I = Frame->Callee->param_begin(),
E = Frame->Callee->param_end(); I != E; ++I, ++ArgIndex) {
if (ArgIndex > (unsigned)IsMemberCall)
Out << ", ";
const ParmVarDecl *Param = *I;
const APValue &Arg = Frame->Arguments[ArgIndex];
Arg.printPretty(Out, Frame->Info.Ctx, Param->getType());
if (ArgIndex == 0 && IsMemberCall)
Out << "->" << *Frame->Callee << '(';
}
Out << ')';
}
void EvalInfo::addCallStack(unsigned Limit) {
// Determine which calls to skip, if any.
unsigned ActiveCalls = CallStackDepth - 1;
unsigned SkipStart = ActiveCalls, SkipEnd = SkipStart;
if (Limit && Limit < ActiveCalls) {
SkipStart = Limit / 2 + Limit % 2;
SkipEnd = ActiveCalls - Limit / 2;
}
// Walk the call stack and add the diagnostics.
unsigned CallIdx = 0;
for (CallStackFrame *Frame = CurrentCall; Frame != &BottomFrame;
Frame = Frame->Caller, ++CallIdx) {
// Skip this call?
if (CallIdx >= SkipStart && CallIdx < SkipEnd) {
if (CallIdx == SkipStart) {
// Note that we're skipping calls.
addDiag(Frame->CallLoc, diag::note_constexpr_calls_suppressed)
<< unsigned(ActiveCalls - Limit);
}
continue;
}
llvm::SmallVector<char, 128> Buffer;
llvm::raw_svector_ostream Out(Buffer);
describeCall(Frame, Out);
addDiag(Frame->CallLoc, diag::note_constexpr_call_here) << Out.str();
}
}
namespace {
struct ComplexValue {
private:
bool IsInt;
public:
APSInt IntReal, IntImag;
APFloat FloatReal, FloatImag;
ComplexValue() : FloatReal(APFloat::Bogus), FloatImag(APFloat::Bogus) {}
void makeComplexFloat() { IsInt = false; }
bool isComplexFloat() const { return !IsInt; }
APFloat &getComplexFloatReal() { return FloatReal; }
APFloat &getComplexFloatImag() { return FloatImag; }
void makeComplexInt() { IsInt = true; }
bool isComplexInt() const { return IsInt; }
APSInt &getComplexIntReal() { return IntReal; }
APSInt &getComplexIntImag() { return IntImag; }
void moveInto(APValue &v) const {
if (isComplexFloat())
v = APValue(FloatReal, FloatImag);
else
v = APValue(IntReal, IntImag);
}
void setFrom(const APValue &v) {
assert(v.isComplexFloat() || v.isComplexInt());
if (v.isComplexFloat()) {
makeComplexFloat();
FloatReal = v.getComplexFloatReal();
FloatImag = v.getComplexFloatImag();
} else {
makeComplexInt();
IntReal = v.getComplexIntReal();
IntImag = v.getComplexIntImag();
}
}
};
struct LValue {
APValue::LValueBase Base;
CharUnits Offset;
unsigned CallIndex;
SubobjectDesignator Designator;
const APValue::LValueBase getLValueBase() const { return Base; }
CharUnits &getLValueOffset() { return Offset; }
const CharUnits &getLValueOffset() const { return Offset; }
unsigned getLValueCallIndex() const { return CallIndex; }
SubobjectDesignator &getLValueDesignator() { return Designator; }
const SubobjectDesignator &getLValueDesignator() const { return Designator;}
void moveInto(APValue &V) const {
if (Designator.Invalid)
V = APValue(Base, Offset, APValue::NoLValuePath(), CallIndex);
else
V = APValue(Base, Offset, Designator.Entries,
Designator.IsOnePastTheEnd, CallIndex);
}
void setFrom(ASTContext &Ctx, const APValue &V) {
assert(V.isLValue());
Base = V.getLValueBase();
Offset = V.getLValueOffset();
CallIndex = V.getLValueCallIndex();
Designator = SubobjectDesignator(Ctx, V);
}
void set(APValue::LValueBase B, unsigned I = 0) {
Base = B;
Offset = CharUnits::Zero();
CallIndex = I;
Designator = SubobjectDesignator(getType(B));
}
// Check that this LValue is not based on a null pointer. If it is, produce
// a diagnostic and mark the designator as invalid.
bool checkNullPointer(EvalInfo &Info, const Expr *E,
CheckSubobjectKind CSK) {
if (Designator.Invalid)
return false;
if (!Base) {
Info.CCEDiag(E, diag::note_constexpr_null_subobject)
<< CSK;
Designator.setInvalid();
return false;
}
return true;
}
// Check this LValue refers to an object. If not, set the designator to be
// invalid and emit a diagnostic.
bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK) {
// Outside C++11, do not build a designator referring to a subobject of
// any object: we won't use such a designator for anything.
if (!Info.getLangOpts().CPlusPlus0x)
Designator.setInvalid();
return checkNullPointer(Info, E, CSK) &&
Designator.checkSubobject(Info, E, CSK);
}
void addDecl(EvalInfo &Info, const Expr *E,
const Decl *D, bool Virtual = false) {
if (checkSubobject(Info, E, isa<FieldDecl>(D) ? CSK_Field : CSK_Base))
Designator.addDeclUnchecked(D, Virtual);
}
void addArray(EvalInfo &Info, const Expr *E, const ConstantArrayType *CAT) {
if (checkSubobject(Info, E, CSK_ArrayToPointer))
Designator.addArrayUnchecked(CAT);
}
void addComplex(EvalInfo &Info, const Expr *E, QualType EltTy, bool Imag) {
if (checkSubobject(Info, E, Imag ? CSK_Imag : CSK_Real))
Designator.addComplexUnchecked(EltTy, Imag);
}
void adjustIndex(EvalInfo &Info, const Expr *E, uint64_t N) {
if (checkNullPointer(Info, E, CSK_ArrayIndex))
Designator.adjustIndex(Info, E, N);
}
};
struct MemberPtr {
MemberPtr() {}
explicit MemberPtr(const ValueDecl *Decl) :
DeclAndIsDerivedMember(Decl, false), Path() {}
/// The member or (direct or indirect) field referred to by this member
/// pointer, or 0 if this is a null member pointer.
const ValueDecl *getDecl() const {
return DeclAndIsDerivedMember.getPointer();
}
/// Is this actually a member of some type derived from the relevant class?
bool isDerivedMember() const {
return DeclAndIsDerivedMember.getInt();
}
/// Get the class which the declaration actually lives in.
const CXXRecordDecl *getContainingRecord() const {
return cast<CXXRecordDecl>(
DeclAndIsDerivedMember.getPointer()->getDeclContext());
}
void moveInto(APValue &V) const {
V = APValue(getDecl(), isDerivedMember(), Path);
}
void setFrom(const APValue &V) {
assert(V.isMemberPointer());
DeclAndIsDerivedMember.setPointer(V.getMemberPointerDecl());
DeclAndIsDerivedMember.setInt(V.isMemberPointerToDerivedMember());
Path.clear();
ArrayRef<const CXXRecordDecl*> P = V.getMemberPointerPath();
Path.insert(Path.end(), P.begin(), P.end());
}
/// DeclAndIsDerivedMember - The member declaration, and a flag indicating
/// whether the member is a member of some class derived from the class type
/// of the member pointer.
llvm::PointerIntPair<const ValueDecl*, 1, bool> DeclAndIsDerivedMember;
/// Path - The path of base/derived classes from the member declaration's
/// class (exclusive) to the class type of the member pointer (inclusive).
SmallVector<const CXXRecordDecl*, 4> Path;
/// Perform a cast towards the class of the Decl (either up or down the
/// hierarchy).
bool castBack(const CXXRecordDecl *Class) {
assert(!Path.empty());
const CXXRecordDecl *Expected;
if (Path.size() >= 2)
Expected = Path[Path.size() - 2];
else
Expected = getContainingRecord();
if (Expected->getCanonicalDecl() != Class->getCanonicalDecl()) {
// C++11 [expr.static.cast]p12: In a conversion from (D::*) to (B::*),
// if B does not contain the original member and is not a base or
// derived class of the class containing the original member, the result
// of the cast is undefined.
// C++11 [conv.mem]p2 does not cover this case for a cast from (B::*) to
// (D::*). We consider that to be a language defect.
return false;
}
Path.pop_back();
return true;
}
/// Perform a base-to-derived member pointer cast.
bool castToDerived(const CXXRecordDecl *Derived) {
if (!getDecl())
return true;
if (!isDerivedMember()) {
Path.push_back(Derived);
return true;
}
if (!castBack(Derived))
return false;
if (Path.empty())
DeclAndIsDerivedMember.setInt(false);
return true;
}
/// Perform a derived-to-base member pointer cast.
bool castToBase(const CXXRecordDecl *Base) {
if (!getDecl())
return true;
if (Path.empty())
DeclAndIsDerivedMember.setInt(true);
if (isDerivedMember()) {
Path.push_back(Base);
return true;
}
return castBack(Base);
}
};
/// Compare two member pointers, which are assumed to be of the same type.
static bool operator==(const MemberPtr &LHS, const MemberPtr &RHS) {
if (!LHS.getDecl() || !RHS.getDecl())
return !LHS.getDecl() && !RHS.getDecl();
if (LHS.getDecl()->getCanonicalDecl() != RHS.getDecl()->getCanonicalDecl())
return false;
return LHS.Path == RHS.Path;
}
/// Kinds of constant expression checking, for diagnostics.
enum CheckConstantExpressionKind {
CCEK_Constant, ///< A normal constant.
CCEK_ReturnValue, ///< A constexpr function return value.
CCEK_MemberInit ///< A constexpr constructor mem-initializer.
};
}
static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E);
static bool EvaluateInPlace(APValue &Result, EvalInfo &Info,
const LValue &This, const Expr *E,
CheckConstantExpressionKind CCEK = CCEK_Constant,
bool AllowNonLiteralTypes = false);
static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info);
static bool EvaluatePointer(const Expr *E, LValue &Result, EvalInfo &Info);
static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
EvalInfo &Info);
static bool EvaluateTemporary(const Expr *E, LValue &Result, EvalInfo &Info);
static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info);
static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
EvalInfo &Info);
static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
static bool EvaluateComplex(const Expr *E, ComplexValue &Res, EvalInfo &Info);
//===----------------------------------------------------------------------===//
// Misc utilities
//===----------------------------------------------------------------------===//
/// Should this call expression be treated as a string literal?
static bool IsStringLiteralCall(const CallExpr *E) {
unsigned Builtin = E->isBuiltinCall();
return (Builtin == Builtin::BI__builtin___CFStringMakeConstantString ||
Builtin == Builtin::BI__builtin___NSStringMakeConstantString);
}
static bool IsGlobalLValue(APValue::LValueBase B) {
// C++11 [expr.const]p3 An address constant expression is a prvalue core
// constant expression of pointer type that evaluates to...
// ... a null pointer value, or a prvalue core constant expression of type
// std::nullptr_t.
if (!B) return true;
if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
// ... the address of an object with static storage duration,
if (const VarDecl *VD = dyn_cast<VarDecl>(D))
return VD->hasGlobalStorage();
// ... the address of a function,
return isa<FunctionDecl>(D);
}
const Expr *E = B.get<const Expr*>();
switch (E->getStmtClass()) {
default:
return false;
case Expr::CompoundLiteralExprClass: {
const CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
return CLE->isFileScope() && CLE->isLValue();
}
// A string literal has static storage duration.
case Expr::StringLiteralClass:
case Expr::PredefinedExprClass:
case Expr::ObjCStringLiteralClass:
case Expr::ObjCEncodeExprClass:
case Expr::CXXTypeidExprClass:
return true;
case Expr::CallExprClass:
return IsStringLiteralCall(cast<CallExpr>(E));
// For GCC compatibility, &&label has static storage duration.
case Expr::AddrLabelExprClass:
return true;
// A Block literal expression may be used as the initialization value for
// Block variables at global or local static scope.
case Expr::BlockExprClass:
return !cast<BlockExpr>(E)->getBlockDecl()->hasCaptures();
case Expr::ImplicitValueInitExprClass:
// FIXME:
// We can never form an lvalue with an implicit value initialization as its
// base through expression evaluation, so these only appear in one case: the
// implicit variable declaration we invent when checking whether a constexpr
// constructor can produce a constant expression. We must assume that such
// an expression might be a global lvalue.
return true;
}
}
static void NoteLValueLocation(EvalInfo &Info, APValue::LValueBase Base) {
assert(Base && "no location for a null lvalue");
const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
if (VD)
Info.Note(VD->getLocation(), diag::note_declared_at);
else
Info.Note(Base.dyn_cast<const Expr*>()->getExprLoc(),
diag::note_constexpr_temporary_here);
}
/// Check that this reference or pointer core constant expression is a valid
/// value for an address or reference constant expression. Return true if we
/// can fold this expression, whether or not it's a constant expression.
static bool CheckLValueConstantExpression(EvalInfo &Info, SourceLocation Loc,
QualType Type, const LValue &LVal) {
bool IsReferenceType = Type->isReferenceType();
APValue::LValueBase Base = LVal.getLValueBase();
const SubobjectDesignator &Designator = LVal.getLValueDesignator();
// Check that the object is a global. Note that the fake 'this' object we
// manufacture when checking potential constant expressions is conservatively
// assumed to be global here.
if (!IsGlobalLValue(Base)) {
if (Info.getLangOpts().CPlusPlus0x) {
const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
Info.Diag(Loc, diag::note_constexpr_non_global, 1)
<< IsReferenceType << !Designator.Entries.empty()
<< !!VD << VD;
NoteLValueLocation(Info, Base);
} else {
Info.Diag(Loc);
}
// Don't allow references to temporaries to escape.
return false;
}
assert((Info.CheckingPotentialConstantExpression ||
LVal.getLValueCallIndex() == 0) &&
"have call index for global lvalue");
// Allow address constant expressions to be past-the-end pointers. This is
// an extension: the standard requires them to point to an object.
if (!IsReferenceType)
return true;
// A reference constant expression must refer to an object.
if (!Base) {
// FIXME: diagnostic
Info.CCEDiag(Loc);
return true;
}
// Does this refer one past the end of some object?
if (Designator.isOnePastTheEnd()) {
const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
Info.Diag(Loc, diag::note_constexpr_past_end, 1)
<< !Designator.Entries.empty() << !!VD << VD;
NoteLValueLocation(Info, Base);
}
return true;
}
/// Check that this core constant expression is of literal type, and if not,
/// produce an appropriate diagnostic.
static bool CheckLiteralType(EvalInfo &Info, const Expr *E) {
if (!E->isRValue() || E->getType()->isLiteralType())
return true;
// Prvalue constant expressions must be of literal types.
if (Info.getLangOpts().CPlusPlus0x)
Info.Diag(E, diag::note_constexpr_nonliteral)
<< E->getType();
else
Info.Diag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
/// Check that this core constant expression value is a valid value for a
/// constant expression. If not, report an appropriate diagnostic. Does not
/// check that the expression is of literal type.
static bool CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc,
QualType Type, const APValue &Value) {
// Core issue 1454: For a literal constant expression of array or class type,
// each subobject of its value shall have been initialized by a constant
// expression.
if (Value.isArray()) {
QualType EltTy = Type->castAsArrayTypeUnsafe()->getElementType();
for (unsigned I = 0, N = Value.getArrayInitializedElts(); I != N; ++I) {
if (!CheckConstantExpression(Info, DiagLoc, EltTy,
Value.getArrayInitializedElt(I)))
return false;
}
if (!Value.hasArrayFiller())
return true;
return CheckConstantExpression(Info, DiagLoc, EltTy,
Value.getArrayFiller());
}
if (Value.isUnion() && Value.getUnionField()) {
return CheckConstantExpression(Info, DiagLoc,
Value.getUnionField()->getType(),
Value.getUnionValue());
}
if (Value.isStruct()) {
RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
unsigned BaseIndex = 0;
for (CXXRecordDecl::base_class_const_iterator I = CD->bases_begin(),
End = CD->bases_end(); I != End; ++I, ++BaseIndex) {
if (!CheckConstantExpression(Info, DiagLoc, I->getType(),
Value.getStructBase(BaseIndex)))
return false;
}
}
for (RecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
I != E; ++I) {
if (!CheckConstantExpression(Info, DiagLoc, (*I)->getType(),
Value.getStructField((*I)->getFieldIndex())))
return false;
}
}
if (Value.isLValue()) {
LValue LVal;
LVal.setFrom(Info.Ctx, Value);
return CheckLValueConstantExpression(Info, DiagLoc, Type, LVal);
}
// Everything else is fine.
return true;
}
const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
return LVal.Base.dyn_cast<const ValueDecl*>();
}
static bool IsLiteralLValue(const LValue &Value) {
return Value.Base.dyn_cast<const Expr*>() && !Value.CallIndex;
}
static bool IsWeakLValue(const LValue &Value) {
const ValueDecl *Decl = GetLValueBaseDecl(Value);
return Decl && Decl->isWeak();
}
static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
// A null base expression indicates a null pointer. These are always
// evaluatable, and they are false unless the offset is zero.
if (!Value.getLValueBase()) {
Result = !Value.getLValueOffset().isZero();
return true;
}
// We have a non-null base. These are generally known to be true, but if it's
// a weak declaration it can be null at runtime.
Result = true;
const ValueDecl *Decl = Value.getLValueBase().dyn_cast<const ValueDecl*>();
return !Decl || !Decl->isWeak();
}
static bool HandleConversionToBool(const APValue &Val, bool &Result) {
switch (Val.getKind()) {
case APValue::Uninitialized:
return false;
case APValue::Int:
Result = Val.getInt().getBoolValue();
return true;
case APValue::Float:
Result = !Val.getFloat().isZero();
return true;
case APValue::ComplexInt:
Result = Val.getComplexIntReal().getBoolValue() ||
Val.getComplexIntImag().getBoolValue();
return true;
case APValue::ComplexFloat:
Result = !Val.getComplexFloatReal().isZero() ||
!Val.getComplexFloatImag().isZero();
return true;
case APValue::LValue:
return EvalPointerValueAsBool(Val, Result);
case APValue::MemberPointer:
Result = Val.getMemberPointerDecl();
return true;
case APValue::Vector:
case APValue::Array:
case APValue::Struct:
case APValue::Union:
case APValue::AddrLabelDiff:
return false;
}
llvm_unreachable("unknown APValue kind");
}
static bool EvaluateAsBooleanCondition(const Expr *E, bool &Result,
EvalInfo &Info) {
assert(E->isRValue() && "missing lvalue-to-rvalue conv in bool condition");
APValue Val;
if (!Evaluate(Val, Info, E))
return false;
return HandleConversionToBool(Val, Result);
}
template<typename T>
static bool HandleOverflow(EvalInfo &Info, const Expr *E,
const T &SrcValue, QualType DestType) {
Info.Diag(E, diag::note_constexpr_overflow)
<< SrcValue << DestType;
return false;
}
static bool HandleFloatToIntCast(EvalInfo &Info, const Expr *E,
QualType SrcType, const APFloat &Value,
QualType DestType, APSInt &Result) {
unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
// Determine whether we are converting to unsigned or signed.
bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
Result = APSInt(DestWidth, !DestSigned);
bool ignored;
if (Value.convertToInteger(Result, llvm::APFloat::rmTowardZero, &ignored)
& APFloat::opInvalidOp)
return HandleOverflow(Info, E, Value, DestType);
return true;
}
static bool HandleFloatToFloatCast(EvalInfo &Info, const Expr *E,
QualType SrcType, QualType DestType,
APFloat &Result) {
APFloat Value = Result;
bool ignored;
if (Result.convert(Info.Ctx.getFloatTypeSemantics(DestType),
APFloat::rmNearestTiesToEven, &ignored)
& APFloat::opOverflow)
return HandleOverflow(Info, E, Value, DestType);
return true;
}
static APSInt HandleIntToIntCast(EvalInfo &Info, const Expr *E,
QualType DestType, QualType SrcType,
APSInt &Value) {
unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
APSInt Result = Value;
// Figure out if this is a truncate, extend or noop cast.
// If the input is signed, do a sign extend, noop, or truncate.
Result = Result.extOrTrunc(DestWidth);
Result.setIsUnsigned(DestType->isUnsignedIntegerOrEnumerationType());
return Result;
}
static bool HandleIntToFloatCast(EvalInfo &Info, const Expr *E,
QualType SrcType, const APSInt &Value,
QualType DestType, APFloat &Result) {
Result = APFloat(Info.Ctx.getFloatTypeSemantics(DestType), 1);
if (Result.convertFromAPInt(Value, Value.isSigned(),
APFloat::rmNearestTiesToEven)
& APFloat::opOverflow)
return HandleOverflow(Info, E, Value, DestType);
return true;
}
static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
llvm::APInt &Res) {
APValue SVal;
if (!Evaluate(SVal, Info, E))
return false;
if (SVal.isInt()) {
Res = SVal.getInt();
return true;
}
if (SVal.isFloat()) {
Res = SVal.getFloat().bitcastToAPInt();
return true;
}
if (SVal.isVector()) {
QualType VecTy = E->getType();
unsigned VecSize = Info.Ctx.getTypeSize(VecTy);
QualType EltTy = VecTy->castAs<VectorType>()->getElementType();
unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
Res = llvm::APInt::getNullValue(VecSize);
for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
APValue &Elt = SVal.getVectorElt(i);
llvm::APInt EltAsInt;
if (Elt.isInt()) {
EltAsInt = Elt.getInt();
} else if (Elt.isFloat()) {
EltAsInt = Elt.getFloat().bitcastToAPInt();
} else {
// Don't try to handle vectors of anything other than int or float
// (not sure if it's possible to hit this case).
Info.Diag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
unsigned BaseEltSize = EltAsInt.getBitWidth();
if (BigEndian)
Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i*EltSize+BaseEltSize);
else
Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i*EltSize);
}
return true;
}
// Give up if the input isn't an int, float, or vector. For example, we
// reject "(v4i16)(intptr_t)&a".
Info.Diag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
/// Cast an lvalue referring to a base subobject to a derived class, by
/// truncating the lvalue's path to the given length.
static bool CastToDerivedClass(EvalInfo &Info, const Expr *E, LValue &Result,
const RecordDecl *TruncatedType,
unsigned TruncatedElements) {
SubobjectDesignator &D = Result.Designator;
// Check we actually point to a derived class object.
if (TruncatedElements == D.Entries.size())
return true;
assert(TruncatedElements >= D.MostDerivedPathLength &&
"not casting to a derived class");
if (!Result.checkSubobject(Info, E, CSK_Derived))
return false;
// Truncate the path to the subobject, and remove any derived-to-base offsets.
const RecordDecl *RD = TruncatedType;
for (unsigned I = TruncatedElements, N = D.Entries.size(); I != N; ++I) {
const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
const CXXRecordDecl *Base = getAsBaseClass(D.Entries[I]);
if (isVirtualBaseClass(D.Entries[I]))
Result.Offset -= Layout.getVBaseClassOffset(Base);
else
Result.Offset -= Layout.getBaseClassOffset(Base);
RD = Base;
}
D.Entries.resize(TruncatedElements);
return true;
}
static void HandleLValueDirectBase(EvalInfo &Info, const Expr *E, LValue &Obj,
const CXXRecordDecl *Derived,
const CXXRecordDecl *Base,
const ASTRecordLayout *RL = 0) {
if (!RL) RL = &Info.Ctx.getASTRecordLayout(Derived);
Obj.getLValueOffset() += RL->getBaseClassOffset(Base);
Obj.addDecl(Info, E, Base, /*Virtual*/ false);
}
static bool HandleLValueBase(EvalInfo &Info, const Expr *E, LValue &Obj,
const CXXRecordDecl *DerivedDecl,
const CXXBaseSpecifier *Base) {
const CXXRecordDecl *BaseDecl = Base->getType()->getAsCXXRecordDecl();
if (!Base->isVirtual()) {
HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);
return true;
}
SubobjectDesignator &D = Obj.Designator;
if (D.Invalid)
return false;
// Extract most-derived object and corresponding type.
DerivedDecl = D.MostDerivedType->getAsCXXRecordDecl();
if (!CastToDerivedClass(Info, E, Obj, DerivedDecl, D.MostDerivedPathLength))
return false;
// Find the virtual base class.
const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
Obj.getLValueOffset() += Layout.getVBaseClassOffset(BaseDecl);
Obj.addDecl(Info, E, BaseDecl, /*Virtual*/ true);
return true;
}
/// Update LVal to refer to the given field, which must be a member of the type
/// currently described by LVal.
static void HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
const FieldDecl *FD,
const ASTRecordLayout *RL = 0) {
if (!RL)
RL = &Info.Ctx.getASTRecordLayout(FD->getParent());
unsigned I = FD->getFieldIndex();
LVal.Offset += Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I));
LVal.addDecl(Info, E, FD);
}
/// Update LVal to refer to the given indirect field.
static void HandleLValueIndirectMember(EvalInfo &Info, const Expr *E,
LValue &LVal,
const IndirectFieldDecl *IFD) {
for (IndirectFieldDecl::chain_iterator C = IFD->chain_begin(),
CE = IFD->chain_end(); C != CE; ++C)
HandleLValueMember(Info, E, LVal, cast<FieldDecl>(*C));
}
/// Get the size of the given type in char units.
static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,
QualType Type, CharUnits &Size) {
// sizeof(void), __alignof__(void), sizeof(function) = 1 as a gcc
// extension.
if (Type->isVoidType() || Type->isFunctionType()) {
Size = CharUnits::One();
return true;
}
if (!Type->isConstantSizeType()) {
// sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
// FIXME: Better diagnostic.
Info.Diag(Loc);
return false;
}
Size = Info.Ctx.getTypeSizeInChars(Type);
return true;
}
/// Update a pointer value to model pointer arithmetic.
/// \param Info - Information about the ongoing evaluation.
/// \param E - The expression being evaluated, for diagnostic purposes.
/// \param LVal - The pointer value to be updated.
/// \param EltTy - The pointee type represented by LVal.
/// \param Adjustment - The adjustment, in objects of type EltTy, to add.
static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
LValue &LVal, QualType EltTy,
int64_t Adjustment) {
CharUnits SizeOfPointee;
if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
return false;
// Compute the new offset in the appropriate width.
LVal.Offset += Adjustment * SizeOfPointee;
LVal.adjustIndex(Info, E, Adjustment);
return true;
}
/// Update an lvalue to refer to a component of a complex number.
/// \param Info - Information about the ongoing evaluation.
/// \param LVal - The lvalue to be updated.
/// \param EltTy - The complex number's component type.
/// \param Imag - False for the real component, true for the imaginary.
static bool HandleLValueComplexElement(EvalInfo &Info, const Expr *E,
LValue &LVal, QualType EltTy,
bool Imag) {
if (Imag) {
CharUnits SizeOfComponent;
if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfComponent))
return false;
LVal.Offset += SizeOfComponent;
}
LVal.addComplex(Info, E, EltTy, Imag);
return true;
}
/// Try to evaluate the initializer for a variable declaration.
static bool EvaluateVarDeclInit(EvalInfo &Info, const Expr *E,
const VarDecl *VD,
CallStackFrame *Frame, APValue &Result) {
// If this is a parameter to an active constexpr function call, perform
// argument substitution.
if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD)) {
// Assume arguments of a potential constant expression are unknown
// constant expressions.
if (Info.CheckingPotentialConstantExpression)
return false;
if (!Frame || !Frame->Arguments) {
Info.Diag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
Result = Frame->Arguments[PVD->getFunctionScopeIndex()];
return true;
}
// Dig out the initializer, and use the declaration which it's attached to.
const Expr *Init = VD->getAnyInitializer(VD);
if (!Init || Init->isValueDependent()) {
// If we're checking a potential constant expression, the variable could be
// initialized later.
if (!Info.CheckingPotentialConstantExpression)
Info.Diag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
// If we're currently evaluating the initializer of this declaration, use that
// in-flight value.
if (Info.EvaluatingDecl == VD) {
Result = *Info.EvaluatingDeclValue;
return !Result.isUninit();
}
// Never evaluate the initializer of a weak variable. We can't be sure that
// this is the definition which will be used.
if (VD->isWeak()) {
Info.Diag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
// Check that we can fold the initializer. In C++, we will have already done
// this in the cases where it matters for conformance.
llvm::SmallVector<PartialDiagnosticAt, 8> Notes;
if (!VD->evaluateValue(Notes)) {
Info.Diag(E, diag::note_constexpr_var_init_non_constant,
Notes.size() + 1) << VD;
Info.Note(VD->getLocation(), diag::note_declared_at);
Info.addNotes(Notes);
return false;
} else if (!VD->checkInitIsICE()) {
Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant,
Notes.size() + 1) << VD;
Info.Note(VD->getLocation(), diag::note_declared_at);
Info.addNotes(Notes);
}
Result = *VD->getEvaluatedValue();
return true;
}
static bool IsConstNonVolatile(QualType T) {
Qualifiers Quals = T.getQualifiers();
return Quals.hasConst() && !Quals.hasVolatile();
}
/// Get the base index of the given base class within an APValue representing
/// the given derived class.
static unsigned getBaseIndex(const CXXRecordDecl *Derived,
const CXXRecordDecl *Base) {
Base = Base->getCanonicalDecl();
unsigned Index = 0;
for (CXXRecordDecl::base_class_const_iterator I = Derived->bases_begin(),
E = Derived->bases_end(); I != E; ++I, ++Index) {
if (I->getType()->getAsCXXRecordDecl()->getCanonicalDecl() == Base)
return Index;
}
llvm_unreachable("base class missing from derived class's bases list");
}
/// Extract the value of a character from a string literal.
static APSInt ExtractStringLiteralCharacter(EvalInfo &Info, const Expr *Lit,
uint64_t Index) {
// FIXME: Support PredefinedExpr, ObjCEncodeExpr, MakeStringConstant
const StringLiteral *S = dyn_cast<StringLiteral>(Lit);
assert(S && "unexpected string literal expression kind");
APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
Lit->getType()->getArrayElementTypeNoTypeQual()->isUnsignedIntegerType());
if (Index < S->getLength())
Value = S->getCodeUnit(Index);
return Value;
}
/// Extract the designated sub-object of an rvalue.
static bool ExtractSubobject(EvalInfo &Info, const Expr *E,
APValue &Obj, QualType ObjType,
const SubobjectDesignator &Sub, QualType SubType) {
if (Sub.Invalid)
// A diagnostic will have already been produced.
return false;
if (Sub.isOnePastTheEnd()) {
Info.Diag(E, Info.getLangOpts().CPlusPlus0x ?
(unsigned)diag::note_constexpr_read_past_end :
(unsigned)diag::note_invalid_subexpr_in_const_expr);
return false;
}
if (Sub.Entries.empty())
return true;
if (Info.CheckingPotentialConstantExpression && Obj.isUninit())
// This object might be initialized later.
return false;
APValue *O = &Obj;
// Walk the designator's path to find the subobject.
for (unsigned I = 0, N = Sub.Entries.size(); I != N; ++I) {
if (ObjType->isArrayType()) {
// Next subobject is an array element.
const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(ObjType);
assert(CAT && "vla in literal type?");
uint64_t Index = Sub.Entries[I].ArrayIndex;
if (CAT->getSize().ule(Index)) {
// Note, it should not be possible to form a pointer with a valid
// designator which points more than one past the end of the array.
Info.Diag(E, Info.getLangOpts().CPlusPlus0x ?
(unsigned)diag::note_constexpr_read_past_end :
(unsigned)diag::note_invalid_subexpr_in_const_expr);
return false;
}
// An array object is represented as either an Array APValue or as an
// LValue which refers to a string literal.
if (O->isLValue()) {
assert(I == N - 1 && "extracting subobject of character?");
assert(!O->hasLValuePath() || O->getLValuePath().empty());
Obj = APValue(ExtractStringLiteralCharacter(
Info, O->getLValueBase().get<const Expr*>(), Index));
return true;
} else if (O->getArrayInitializedElts() > Index)
O = &O->getArrayInitializedElt(Index);
else
O = &O->getArrayFiller();
ObjType = CAT->getElementType();
} else if (ObjType->isAnyComplexType()) {
// Next subobject is a complex number.
uint64_t Index = Sub.Entries[I].ArrayIndex;
if (Index > 1) {
Info.Diag(E, Info.getLangOpts().CPlusPlus0x ?
(unsigned)diag::note_constexpr_read_past_end :
(unsigned)diag::note_invalid_subexpr_in_const_expr);
return false;
}
assert(I == N - 1 && "extracting subobject of scalar?");
if (O->isComplexInt()) {
Obj = APValue(Index ? O->getComplexIntImag()
: O->getComplexIntReal());
} else {
assert(O->isComplexFloat());
Obj = APValue(Index ? O->getComplexFloatImag()
: O->getComplexFloatReal());
}
return true;
} else if (const FieldDecl *Field = getAsField(Sub.Entries[I])) {
if (Field->isMutable()) {
Info.Diag(E, diag::note_constexpr_ltor_mutable, 1)
<< Field;
Info.Note(Field->getLocation(), diag::note_declared_at);
return false;
}
// Next subobject is a class, struct or union field.
RecordDecl *RD = ObjType->castAs<RecordType>()->getDecl();
if (RD->isUnion()) {
const FieldDecl *UnionField = O->getUnionField();
if (!UnionField ||
UnionField->getCanonicalDecl() != Field->getCanonicalDecl()) {
Info.Diag(E, diag::note_constexpr_read_inactive_union_member)
<< Field << !UnionField << UnionField;
return false;
}
O = &O->getUnionValue();
} else
O = &O->getStructField(Field->getFieldIndex());
ObjType = Field->getType();
if (ObjType.isVolatileQualified()) {
if (Info.getLangOpts().CPlusPlus) {
// FIXME: Include a description of the path to the volatile subobject.
Info.Diag(E, diag::note_constexpr_ltor_volatile_obj, 1)
<< 2 << Field;
Info.Note(Field->getLocation(), diag::note_declared_at);
} else {
Info.Diag(E, diag::note_invalid_subexpr_in_const_expr);
}
return false;
}
} else {
// Next subobject is a base class.
const CXXRecordDecl *Derived = ObjType->getAsCXXRecordDecl();
const CXXRecordDecl *Base = getAsBaseClass(Sub.Entries[I]);
O = &O->getStructBase(getBaseIndex(Derived, Base));
ObjType = Info.Ctx.getRecordType(Base);
}
if (O->isUninit()) {
if (!Info.CheckingPotentialConstantExpression)
Info.Diag(E, diag::note_constexpr_read_uninit);
return false;
}
}
// This may look super-stupid, but it serves an important purpose: if we just
// swapped Obj and *O, we'd create an object which had itself as a subobject.
// To avoid the leak, we ensure that Tmp ends up owning the original complete
// object, which is destroyed by Tmp's destructor.
APValue Tmp;
O->swap(Tmp);
Obj.swap(Tmp);
return true;
}
/// Find the position where two subobject designators diverge, or equivalently
/// the length of the common initial subsequence.
static unsigned FindDesignatorMismatch(QualType ObjType,
const SubobjectDesignator &A,
const SubobjectDesignator &B,
bool &WasArrayIndex) {
unsigned I = 0, N = std::min(A.Entries.size(), B.Entries.size());
for (/**/; I != N; ++I) {
if (!ObjType.isNull() &&
(ObjType->isArrayType() || ObjType->isAnyComplexType())) {
// Next subobject is an array element.
if (A.Entries[I].ArrayIndex != B.Entries[I].ArrayIndex) {
WasArrayIndex = true;
return I;
}
if (ObjType->isAnyComplexType())
ObjType = ObjType->castAs<ComplexType>()->getElementType();
else
ObjType = ObjType->castAsArrayTypeUnsafe()->getElementType();
} else {
if (A.Entries[I].BaseOrMember != B.Entries[I].BaseOrMember) {
WasArrayIndex = false;
return I;
}
if (const FieldDecl *FD = getAsField(A.Entries[I]))
// Next subobject is a field.
ObjType = FD->getType();
else
// Next subobject is a base class.
ObjType = QualType();
}
}
WasArrayIndex = false;
return I;
}
/// Determine whether the given subobject designators refer to elements of the
/// same array object.
static bool AreElementsOfSameArray(QualType ObjType,
const SubobjectDesignator &A,
const SubobjectDesignator &B) {
if (A.Entries.size() != B.Entries.size())
return false;
bool IsArray = A.MostDerivedArraySize != 0;
if (IsArray && A.MostDerivedPathLength != A.Entries.size())
// A is a subobject of the array element.
return false;
// If A (and B) designates an array element, the last entry will be the array
// index. That doesn't have to match. Otherwise, we're in the 'implicit array
// of length 1' case, and the entire path must match.
bool WasArrayIndex;
unsigned CommonLength = FindDesignatorMismatch(ObjType, A, B, WasArrayIndex);
return CommonLength >= A.Entries.size() - IsArray;
}
/// HandleLValueToRValueConversion - Perform an lvalue-to-rvalue conversion on
/// the given lvalue. This can also be used for 'lvalue-to-lvalue' conversions
/// for looking up the glvalue referred to by an entity of reference type.
///
/// \param Info - Information about the ongoing evaluation.
/// \param Conv - The expression for which we are performing the conversion.
/// Used for diagnostics.
/// \param Type - The type we expect this conversion to produce, before
/// stripping cv-qualifiers in the case of a non-clas type.
/// \param LVal - The glvalue on which we are attempting to perform this action.
/// \param RVal - The produced value will be placed here.
static bool HandleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
QualType Type,
const LValue &LVal, APValue &RVal) {
if (LVal.Designator.Invalid)
// A diagnostic will have already been produced.
return false;
const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
if (!LVal.Base) {
// FIXME: Indirection through a null pointer deserves a specific diagnostic.
Info.Diag(Conv, diag::note_invalid_subexpr_in_const_expr);
return false;
}
CallStackFrame *Frame = 0;
if (LVal.CallIndex) {
Frame = Info.getCallFrame(LVal.CallIndex);
if (!Frame) {
Info.Diag(Conv, diag::note_constexpr_lifetime_ended, 1) << !Base;
NoteLValueLocation(Info, LVal.Base);
return false;
}
}
// C++11 DR1311: An lvalue-to-rvalue conversion on a volatile-qualified type
// is not a constant expression (even if the object is non-volatile). We also
// apply this rule to C++98, in order to conform to the expected 'volatile'
// semantics.
if (Type.isVolatileQualified()) {
if (Info.getLangOpts().CPlusPlus)
Info.Diag(Conv, diag::note_constexpr_ltor_volatile_type) << Type;
else
Info.Diag(Conv);
return false;
}
if (const ValueDecl *D = LVal.Base.dyn_cast<const ValueDecl*>()) {
// In C++98, const, non-volatile integers initialized with ICEs are ICEs.
// In C++11, constexpr, non-volatile variables initialized with constant
// expressions are constant expressions too. Inside constexpr functions,
// parameters are constant expressions even if they're non-const.
// In C, such things can also be folded, although they are not ICEs.
const VarDecl *VD = dyn_cast<VarDecl>(D);
if (VD) {
if (const VarDecl *VDef = VD->getDefinition(Info.Ctx))
VD = VDef;
}
if (!VD || VD->isInvalidDecl()) {
Info.Diag(Conv);
return false;
}
// DR1313: If the object is volatile-qualified but the glvalue was not,
// behavior is undefined so the result is not a constant expression.
QualType VT = VD->getType();
if (VT.isVolatileQualified()) {
if (Info.getLangOpts().CPlusPlus) {
Info.Diag(Conv, diag::note_constexpr_ltor_volatile_obj, 1) << 1 << VD;
Info.Note(VD->getLocation(), diag::note_declared_at);
} else {
Info.Diag(Conv);
}
return false;
}
if (!isa<ParmVarDecl>(VD)) {
if (VD->isConstexpr()) {
// OK, we can read this variable.
} else if (VT->isIntegralOrEnumerationType()) {
if (!VT.isConstQualified()) {
if (Info.getLangOpts().CPlusPlus) {
Info.Diag(Conv, diag::note_constexpr_ltor_non_const_int, 1) << VD;
Info.Note(VD->getLocation(), diag::note_declared_at);
} else {
Info.Diag(Conv);
}
return false;
}
} else if (VT->isFloatingType() && VT.isConstQualified()) {
// We support folding of const floating-point types, in order to make
// static const data members of such types (supported as an extension)
// more useful.
if (Info.getLangOpts().CPlusPlus0x) {
Info.CCEDiag(Conv, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
Info.Note(VD->getLocation(), diag::note_declared_at);
} else {
Info.CCEDiag(Conv);
}
} else {
// FIXME: Allow folding of values of any literal type in all languages.
if (Info.getLangOpts().CPlusPlus0x) {
Info.Diag(Conv, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
Info.Note(VD->getLocation(), diag::note_declared_at);
} else {
Info.Diag(Conv);
}
return false;
}
}
if (!EvaluateVarDeclInit(Info, Conv, VD, Frame, RVal))
return false;
if (isa<ParmVarDecl>(VD) || !VD->getAnyInitializer()->isLValue())
return ExtractSubobject(Info, Conv, RVal, VT, LVal.Designator, Type);
// The declaration was initialized by an lvalue, with no lvalue-to-rvalue
// conversion. This happens when the declaration and the lvalue should be
// considered synonymous, for instance when initializing an array of char
// from a string literal. Continue as if the initializer lvalue was the
// value we were originally given.
assert(RVal.getLValueOffset().isZero() &&
"offset for lvalue init of non-reference");
Base = RVal.getLValueBase().get<const Expr*>();
if (unsigned CallIndex = RVal.getLValueCallIndex()) {
Frame = Info.getCallFrame(CallIndex);
if (!Frame) {
Info.Diag(Conv, diag::note_constexpr_lifetime_ended, 1) << !Base;
NoteLValueLocation(Info, RVal.getLValueBase());
return false;
}
} else {
Frame = 0;
}
}
// Volatile temporary objects cannot be read in constant expressions.
if (Base->getType().isVolatileQualified()) {
if (Info.getLangOpts().CPlusPlus) {
Info.Diag(Conv, diag::note_constexpr_ltor_volatile_obj, 1) << 0;
Info.Note(Base->getExprLoc(), diag::note_constexpr_temporary_here);
} else {
Info.Diag(Conv);
}
return false;
}
if (Frame) {
// If this is a temporary expression with a nontrivial initializer, grab the
// value from the relevant stack frame.
RVal = Frame->Temporaries[Base];
} else if (const CompoundLiteralExpr *CLE
= dyn_cast<CompoundLiteralExpr>(Base)) {
// In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
// initializer until now for such expressions. Such an expression can't be
// an ICE in C, so this only matters for fold.
assert(!Info.getLangOpts().CPlusPlus && "lvalue compound literal in c++?");
if (!Evaluate(RVal, Info, CLE->getInitializer()))
return false;
} else if (isa<StringLiteral>(Base)) {
// We represent a string literal array as an lvalue pointing at the
// corresponding expression, rather than building an array of chars.
// FIXME: Support PredefinedExpr, ObjCEncodeExpr, MakeStringConstant
RVal = APValue(Base, CharUnits::Zero(), APValue::NoLValuePath(), 0);
} else {
Info.Diag(Conv, diag::note_invalid_subexpr_in_const_expr);
return false;
}
return ExtractSubobject(Info, Conv, RVal, Base->getType(), LVal.Designator,
Type);
}
/// Build an lvalue for the object argument of a member function call.
static bool EvaluateObjectArgument(EvalInfo &Info, const Expr *Object,
LValue &This) {
if (Object->getType()->isPointerType())
return EvaluatePointer(Object, This, Info);
if (Object->isGLValue())
return EvaluateLValue(Object, This, Info);
if (Object->getType()->isLiteralType())
return EvaluateTemporary(Object, This, Info);
return false;
}
/// HandleMemberPointerAccess - Evaluate a member access operation and build an
/// lvalue referring to the result.
///
/// \param Info - Information about the ongoing evaluation.
/// \param BO - The member pointer access operation.
/// \param LV - Filled in with a reference to the resulting object.
/// \param IncludeMember - Specifies whether the member itself is included in
/// the resulting LValue subobject designator. This is not possible when
/// creating a bound member function.
/// \return The field or method declaration to which the member pointer refers,
/// or 0 if evaluation fails.
static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
const BinaryOperator *BO,
LValue &LV,
bool IncludeMember = true) {
assert(BO->getOpcode() == BO_PtrMemD || BO->getOpcode() == BO_PtrMemI);
bool EvalObjOK = EvaluateObjectArgument(Info, BO->getLHS(), LV);
if (!EvalObjOK && !Info.keepEvaluatingAfterFailure())
return 0;
MemberPtr MemPtr;
if (!EvaluateMemberPointer(BO->getRHS(), MemPtr, Info))
return 0;
// C++11 [expr.mptr.oper]p6: If the second operand is the null pointer to
// member value, the behavior is undefined.
if (!MemPtr.getDecl())
return 0;
if (!EvalObjOK)
return 0;
if (MemPtr.isDerivedMember()) {
// This is a member of some derived class. Truncate LV appropriately.
// The end of the derived-to-base path for the base object must match the
// derived-to-base path for the member pointer.
if (LV.Designator.MostDerivedPathLength + MemPtr.Path.size() >
LV.Designator.Entries.size())
return 0;
unsigned PathLengthToMember =
LV.Designator.Entries.size() - MemPtr.Path.size();
for (unsigned I = 0, N = MemPtr.Path.size(); I != N; ++I) {
const CXXRecordDecl *LVDecl = getAsBaseClass(
LV.Designator.Entries[PathLengthToMember + I]);
const CXXRecordDecl *MPDecl = MemPtr.Path[I];
if (LVDecl->getCanonicalDecl() != MPDecl->getCanonicalDecl())
return 0;
}
// Truncate the lvalue to the appropriate derived class.
if (!CastToDerivedClass(Info, BO, LV, MemPtr.getContainingRecord(),
PathLengthToMember))
return 0;
} else if (!MemPtr.Path.empty()) {
// Extend the LValue path with the member pointer's path.
LV.Designator.Entries.reserve(LV.Designator.Entries.size() +
MemPtr.Path.size() + IncludeMember);
// Walk down to the appropriate base class.
QualType LVType = BO->getLHS()->getType();
if (const PointerType *PT = LVType->getAs<PointerType>())
LVType = PT->getPointeeType();
const CXXRecordDecl *RD = LVType->getAsCXXRecordDecl();
assert(RD && "member pointer access on non-class-type expression");
// The first class in the path is that of the lvalue.
for (unsigned I = 1, N = MemPtr.Path.size(); I != N; ++I) {
const CXXRecordDecl *Base = MemPtr.Path[N - I - 1];
HandleLValueDirectBase(Info, BO, LV, RD, Base);
RD = Base;
}
// Finally cast to the class containing the member.
HandleLValueDirectBase(Info, BO, LV, RD, MemPtr.getContainingRecord());
}
// Add the member. Note that we cannot build bound member functions here.
if (IncludeMember) {
if (const FieldDecl *FD = dyn_cast<FieldDecl>(MemPtr.getDecl()))
HandleLValueMember(Info, BO, LV, FD);
else if (const IndirectFieldDecl *IFD =
dyn_cast<IndirectFieldDecl>(MemPtr.getDecl()))
HandleLValueIndirectMember(Info, BO, LV, IFD);
else
llvm_unreachable("can't construct reference to bound member function");
}
return MemPtr.getDecl();
}
/// HandleBaseToDerivedCast - Apply the given base-to-derived cast operation on
/// the provided lvalue, which currently refers to the base object.
static bool HandleBaseToDerivedCast(EvalInfo &Info, const CastExpr *E,
LValue &Result) {
SubobjectDesignator &D = Result.Designator;
if (D.Invalid || !Result.checkNullPointer(Info, E, CSK_Derived))
return false;
QualType TargetQT = E->getType();
if (const PointerType *PT = TargetQT->getAs<PointerType>())
TargetQT = PT->getPointeeType();
// Check this cast lands within the final derived-to-base subobject path.
if (D.MostDerivedPathLength + E->path_size() > D.Entries.size()) {
Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
<< D.MostDerivedType << TargetQT;
return false;
}
// Check the type of the final cast. We don't need to check the path,
// since a cast can only be formed if the path is unique.
unsigned NewEntriesSize = D.Entries.size() - E->path_size();
const CXXRecordDecl *TargetType = TargetQT->getAsCXXRecordDecl();
const CXXRecordDecl *FinalType;
if (NewEntriesSize == D.MostDerivedPathLength)
FinalType = D.MostDerivedType->getAsCXXRecordDecl();
else
FinalType = getAsBaseClass(D.Entries[NewEntriesSize - 1]);
if (FinalType->getCanonicalDecl() != TargetType->getCanonicalDecl()) {
Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
<< D.MostDerivedType << TargetQT;
return false;
}
// Truncate the lvalue to the appropriate derived class.
return CastToDerivedClass(Info, E, Result, TargetType, NewEntriesSize);
}
namespace {
enum EvalStmtResult {
/// Evaluation failed.
ESR_Failed,
/// Hit a 'return' statement.
ESR_Returned,
/// Evaluation succeeded.
ESR_Succeeded
};
}
// Evaluate a statement.
static EvalStmtResult EvaluateStmt(APValue &Result, EvalInfo &Info,
const Stmt *S) {
switch (S->getStmtClass()) {
default:
return ESR_Failed;
case Stmt::NullStmtClass:
case Stmt::DeclStmtClass:
return ESR_Succeeded;
case Stmt::ReturnStmtClass: {
const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
if (!Evaluate(Result, Info, RetExpr))
return ESR_Failed;
return ESR_Returned;
}
case Stmt::CompoundStmtClass: {
const CompoundStmt *CS = cast<CompoundStmt>(S);
for (CompoundStmt::const_body_iterator BI = CS->body_begin(),
BE = CS->body_end(); BI != BE; ++BI) {
EvalStmtResult ESR = EvaluateStmt(Result, Info, *BI);
if (ESR != ESR_Succeeded)
return ESR;
}
return ESR_Succeeded;
}
}
}
/// CheckTrivialDefaultConstructor - Check whether a constructor is a trivial
/// default constructor. If so, we'll fold it whether or not it's marked as
/// constexpr. If it is marked as constexpr, we will never implicitly define it,
/// so we need special handling.
static bool CheckTrivialDefaultConstructor(EvalInfo &Info, SourceLocation Loc,
const CXXConstructorDecl *CD,
bool IsValueInitialization) {
if (!CD->isTrivial() || !CD->isDefaultConstructor())
return false;
// Value-initialization does not call a trivial default constructor, so such a
// call is a core constant expression whether or not the constructor is
// constexpr.
if (!CD->isConstexpr() && !IsValueInitialization) {
if (Info.getLangOpts().CPlusPlus0x) {
// FIXME: If DiagDecl is an implicitly-declared special member function,
// we should be much more explicit about why it's not constexpr.
Info.CCEDiag(Loc, diag::note_constexpr_invalid_function, 1)
<< /*IsConstexpr*/0 << /*IsConstructor*/1 << CD;
Info.Note(CD->getLocation(), diag::note_declared_at);
} else {
Info.CCEDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
}
}
return true;
}
/// CheckConstexprFunction - Check that a function can be called in a constant
/// expression.
static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
const FunctionDecl *Declaration,
const FunctionDecl *Definition) {
// Potential constant expressions can contain calls to declared, but not yet
// defined, constexpr functions.
if (Info.CheckingPotentialConstantExpression && !Definition &&
Declaration->isConstexpr())
return false;
// Can we evaluate this function call?
if (Definition && Definition->isConstexpr() && !Definition->isInvalidDecl())
return true;
if (Info.getLangOpts().CPlusPlus0x) {
const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;
// FIXME: If DiagDecl is an implicitly-declared special member function, we
// should be much more explicit about why it's not constexpr.
Info.Diag(CallLoc, diag::note_constexpr_invalid_function, 1)
<< DiagDecl->isConstexpr() << isa<CXXConstructorDecl>(DiagDecl)
<< DiagDecl;
Info.Note(DiagDecl->getLocation(), diag::note_declared_at);
} else {
Info.Diag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
}
return false;
}
namespace {
typedef SmallVector<APValue, 8> ArgVector;
}
/// EvaluateArgs - Evaluate the arguments to a function call.
static bool EvaluateArgs(ArrayRef<const Expr*> Args, ArgVector &ArgValues,
EvalInfo &Info) {
bool Success = true;
for (ArrayRef<const Expr*>::iterator I = Args.begin(), E = Args.end();
I != E; ++I) {
if (!Evaluate(ArgValues[I - Args.begin()], Info, *I)) {
// If we're checking for a potential constant expression, evaluate all
// initializers even if some of them fail.
if (!Info.keepEvaluatingAfterFailure())
return false;
Success = false;
}
}
return Success;
}
/// Evaluate a function call.
static bool HandleFunctionCall(SourceLocation CallLoc,
const FunctionDecl *Callee, const LValue *This,
ArrayRef<const Expr*> Args, const Stmt *Body,
EvalInfo &Info, APValue &Result) {
ArgVector ArgValues(Args.size());
if (!EvaluateArgs(Args, ArgValues, Info))
return false;
if (!Info.CheckCallLimit(CallLoc))
return false;
CallStackFrame Frame(Info, CallLoc, Callee, This, ArgValues.data());
return EvaluateStmt(Result, Info, Body) == ESR_Returned;
}
/// Evaluate a constructor call.
static bool HandleConstructorCall(SourceLocation CallLoc, const LValue &This,
ArrayRef<const Expr*> Args,
const CXXConstructorDecl *Definition,
EvalInfo &Info, APValue &Result) {
ArgVector ArgValues(Args.size());
if (!EvaluateArgs(Args, ArgValues, Info))
return false;
if (!Info.CheckCallLimit(CallLoc))
return false;
const CXXRecordDecl *RD = Definition->getParent();
if (RD->getNumVBases()) {
Info.Diag(CallLoc, diag::note_constexpr_virtual_base) << RD;
return false;
}
CallStackFrame Frame(Info, CallLoc, Definition, &This, ArgValues.data());
// If it's a delegating constructor, just delegate.
if (Definition->isDelegatingConstructor()) {
CXXConstructorDecl::init_const_iterator I = Definition->init_begin();
return EvaluateInPlace(Result, Info, This, (*I)->getInit());
}
// For a trivial copy or move constructor, perform an APValue copy. This is
// essential for unions, where the operations performed by the constructor
// cannot be represented by ctor-initializers.
if (Definition->isDefaulted() &&
((Definition->isCopyConstructor() && Definition->isTrivial()) ||
(Definition->isMoveConstructor() && Definition->isTrivial()))) {
LValue RHS;
RHS.setFrom(Info.Ctx, ArgValues[0]);
return HandleLValueToRValueConversion(Info, Args[0], Args[0]->getType(),
RHS, Result);
}
// Reserve space for the struct members.
if (!RD->isUnion() && Result.isUninit())
Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
std::distance(RD->field_begin(), RD->field_end()));
const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
bool Success = true;
unsigned BasesSeen = 0;
#ifndef NDEBUG
CXXRecordDecl::base_class_const_iterator BaseIt = RD->bases_begin();
#endif
for (CXXConstructorDecl::init_const_iterator I = Definition->init_begin(),
E = Definition->init_end(); I != E; ++I) {
LValue Subobject = This;
APValue *Value = &Result;
// Determine the subobject to initialize.
if ((*I)->isBaseInitializer()) {
QualType BaseType((*I)->getBaseClass(), 0);
#ifndef NDEBUG
// Non-virtual base classes are initialized in the order in the class
// definition. We have already checked for virtual base classes.
assert(!BaseIt->isVirtual() && "virtual base for literal type");
assert(Info.Ctx.hasSameType(BaseIt->getType(), BaseType) &&
"base class initializers not in expected order");
++BaseIt;
#endif
HandleLValueDirectBase(Info, (*I)->getInit(), Subobject, RD,
BaseType->getAsCXXRecordDecl(), &Layout);
Value = &Result.getStructBase(BasesSeen++);
} else if (FieldDecl *FD = (*I)->getMember()) {
HandleLValueMember(Info, (*I)->getInit(), Subobject, FD, &Layout);
if (RD->isUnion()) {
Result = APValue(FD);
Value = &Result.getUnionValue();
} else {
Value = &Result.getStructField(FD->getFieldIndex());
}
} else if (IndirectFieldDecl *IFD = (*I)->getIndirectMember()) {
// Walk the indirect field decl's chain to find the object to initialize,
// and make sure we've initialized every step along it.
for (IndirectFieldDecl::chain_iterator C = IFD->chain_begin(),
CE = IFD->chain_end();
C != CE; ++C) {
FieldDecl *FD = cast<FieldDecl>(*C);
CXXRecordDecl *CD = cast<CXXRecordDecl>(FD->getParent());
// Switch the union field if it differs. This happens if we had
// preceding zero-initialization, and we're now initializing a union
// subobject other than the first.
// FIXME: In this case, the values of the other subobjects are
// specified, since zero-initialization sets all padding bits to zero.
if (Value->isUninit() ||
(Value->isUnion() && Value->getUnionField() != FD)) {
if (CD->isUnion())
*Value = APValue(FD);
else
*Value = APValue(APValue::UninitStruct(), CD->getNumBases(),
std::distance(CD->field_begin(), CD->field_end()));
}
HandleLValueMember(Info, (*I)->getInit(), Subobject, FD);
if (CD->isUnion())
Value = &Value->getUnionValue();
else
Value = &Value->getStructField(FD->getFieldIndex());
}
} else {
llvm_unreachable("unknown base initializer kind");
}
if (!EvaluateInPlace(*Value, Info, Subobject, (*I)->getInit(),
(*I)->isBaseInitializer()
? CCEK_Constant : CCEK_MemberInit)) {
// If we're checking for a potential constant expression, evaluate all
// initializers even if some of them fail.
if (!Info.keepEvaluatingAfterFailure())
return false;
Success = false;
}
}
return Success;
}
namespace {
class HasSideEffect
: public ConstStmtVisitor<HasSideEffect, bool> {
const ASTContext &Ctx;
public:
HasSideEffect(const ASTContext &C) : Ctx(C) {}
// Unhandled nodes conservatively default to having side effects.
bool VisitStmt(const Stmt *S) {
return true;
}
bool VisitParenExpr(const ParenExpr *E) { return Visit(E->getSubExpr()); }
bool VisitGenericSelectionExpr(const GenericSelectionExpr *E) {
return Visit(E->getResultExpr());
}
bool VisitDeclRefExpr(const DeclRefExpr *E) {
if (Ctx.getCanonicalType(E->getType()).isVolatileQualified())
return true;
return false;
}
bool VisitObjCIvarRefExpr(const ObjCIvarRefExpr *E) {
if (Ctx.getCanonicalType(E->getType()).isVolatileQualified())
return true;
return false;
}
// We don't want to evaluate BlockExprs multiple times, as they generate
// a ton of code.
bool VisitBlockExpr(const BlockExpr *E) { return true; }
bool VisitPredefinedExpr(const PredefinedExpr *E) { return false; }
bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E)
{ return Visit(E->getInitializer()); }
bool VisitMemberExpr(const MemberExpr *E) { return Visit(E->getBase()); }
bool VisitIntegerLiteral(const IntegerLiteral *E) { return false; }
bool VisitFloatingLiteral(const FloatingLiteral *E) { return false; }
bool VisitStringLiteral(const StringLiteral *E) { return false; }
bool VisitCharacterLiteral(const CharacterLiteral *E) { return false; }
bool VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E)
{ return false; }
bool VisitArraySubscriptExpr(const ArraySubscriptExpr *E)
{ return Visit(E->getLHS()) || Visit(E->getRHS()); }
bool VisitChooseExpr(const ChooseExpr *E)
{ return Visit(E->getChosenSubExpr(Ctx)); }
bool VisitCastExpr(const CastExpr *E) { return Visit(E->getSubExpr()); }
bool VisitBinAssign(const BinaryOperator *E) { return true; }
bool VisitCompoundAssignOperator(const BinaryOperator *E) { return true; }
bool VisitBinaryOperator(const BinaryOperator *E)
{ return Visit(E->getLHS()) || Visit(E->getRHS()); }
bool VisitUnaryPreInc(const UnaryOperator *E) { return true; }
bool VisitUnaryPostInc(const UnaryOperator *E) { return true; }
bool VisitUnaryPreDec(const UnaryOperator *E) { return true; }
bool VisitUnaryPostDec(const UnaryOperator *E) { return true; }
bool VisitUnaryDeref(const UnaryOperator *E) {
if (Ctx.getCanonicalType(E->getType()).isVolatileQualified())
return true;
return Visit(E->getSubExpr());
}
bool VisitUnaryOperator(const UnaryOperator *E) { return Visit(E->getSubExpr()); }
// Has side effects if any element does.
bool VisitInitListExpr(const InitListExpr *E) {
for (unsigned i = 0, e = E->getNumInits(); i != e; ++i)
if (Visit(E->getInit(i))) return true;
if (const Expr *filler = E->getArrayFiller())
return Visit(filler);
return false;
}
bool VisitSizeOfPackExpr(const SizeOfPackExpr *) { return false; }
};
class OpaqueValueEvaluation {
EvalInfo &info;
OpaqueValueExpr *opaqueValue;
public:
OpaqueValueEvaluation(EvalInfo &info, OpaqueValueExpr *opaqueValue,
Expr *value)
: info(info), opaqueValue(opaqueValue) {
// If evaluation fails, fail immediately.
if (!Evaluate(info.OpaqueValues[opaqueValue], info, value)) {
this->opaqueValue = 0;
return;
}
}
bool hasError() const { return opaqueValue == 0; }
~OpaqueValueEvaluation() {
// FIXME: For a recursive constexpr call, an outer stack frame might have
// been using this opaque value too, and will now have to re-evaluate the
// source expression.
if (opaqueValue) info.OpaqueValues.erase(opaqueValue);
}
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Generic Evaluation
//===----------------------------------------------------------------------===//
namespace {
// FIXME: RetTy is always bool. Remove it.
template <class Derived, typename RetTy=bool>
class ExprEvaluatorBase