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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 / C++1y 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/ASTDiagnostic.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/Support/raw_ostream.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();
const Expr *Base = B.get<const Expr*>();
// For a materialized temporary, the type of the temporary we materialized
// may not be the type of the expression.
if (const MaterializeTemporaryExpr *MTE =
dyn_cast<MaterializeTemporaryExpr>(Base)) {
SmallVector<const Expr *, 2> CommaLHSs;
SmallVector<SubobjectAdjustment, 2> Adjustments;
const Expr *Temp = MTE->GetTemporaryExpr();
const Expr *Inner = Temp->skipRValueSubobjectAdjustments(CommaLHSs,
Adjustments);
// Keep any cv-qualifiers from the reference if we generated a temporary
// for it.
if (Inner != Temp)
return Inner->getType();
}
return Base->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,
bool &IsArray) {
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;
IsArray = true;
} else if (Type->isAnyComplexType()) {
const ComplexType *CT = Type->castAs<ComplexType>();
Type = CT->getElementType();
ArraySize = 2;
MostDerivedLength = I + 1;
IsArray = true;
} else if (const FieldDecl *FD = getAsField(Path[I])) {
Type = FD->getType();
ArraySize = 0;
MostDerivedLength = I + 1;
IsArray = false;
} else {
// Path[I] describes a base class.
ArraySize = 0;
IsArray = false;
}
}
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.
unsigned Invalid : 1;
/// Is this a pointer one past the end of an object?
unsigned IsOnePastTheEnd : 1;
/// Indicator of whether the most-derived object is an array element.
unsigned MostDerivedIsArrayElement : 1;
/// The length of the path to the most-derived object of which this is a
/// subobject.
unsigned MostDerivedPathLength : 29;
/// The size of the array of which the most-derived object is an element.
/// This will always be 0 if the most-derived object is not an array
/// element. 0 is not an indicator of whether or not the most-derived object
/// is an array, however, because 0-length arrays are allowed.
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),
MostDerivedIsArrayElement(false), MostDerivedPathLength(0),
MostDerivedArraySize(0), MostDerivedType(T) {}
SubobjectDesignator(ASTContext &Ctx, const APValue &V)
: Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
MostDerivedIsArrayElement(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()) {
bool IsArray = false;
MostDerivedPathLength =
findMostDerivedSubobject(Ctx, getType(V.getLValueBase()),
V.getLValuePath(), MostDerivedArraySize,
MostDerivedType, IsArray);
MostDerivedIsArrayElement = IsArray;
}
}
}
void setInvalid() {
Invalid = true;
Entries.clear();
}
/// Determine whether this is a one-past-the-end pointer.
bool isOnePastTheEnd() const {
assert(!Invalid);
if (IsOnePastTheEnd)
return true;
if (MostDerivedIsArrayElement &&
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();
MostDerivedIsArrayElement = true;
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();
MostDerivedIsArrayElement = false;
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;
MostDerivedIsArrayElement = true;
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() &&
MostDerivedIsArrayElement) {
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;
/// Arguments - Parameter bindings for this function call, indexed by
/// parameters' function scope indices.
APValue *Arguments;
// Note that we intentionally use std::map here so that references to
// values are stable.
typedef std::map<const void*, 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,
APValue *Arguments);
~CallStackFrame();
APValue *getTemporary(const void *Key) {
MapTy::iterator I = Temporaries.find(Key);
return I == Temporaries.end() ? nullptr : &I->second;
}
APValue &createTemporary(const void *Key, bool IsLifetimeExtended);
};
/// Temporarily override 'this'.
class ThisOverrideRAII {
public:
ThisOverrideRAII(CallStackFrame &Frame, const LValue *NewThis, bool Enable)
: Frame(Frame), OldThis(Frame.This) {
if (Enable)
Frame.This = NewThis;
}
~ThisOverrideRAII() {
Frame.This = OldThis;
}
private:
CallStackFrame &Frame;
const LValue *OldThis;
};
/// 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 = nullptr)
: Diag(Diag) {}
template<typename T>
OptionalDiagnostic &operator<<(const T &v) {
if (Diag)
*Diag << v;
return *this;
}
OptionalDiagnostic &operator<<(const APSInt &I) {
if (Diag) {
SmallVector<char, 32> Buffer;
I.toString(Buffer);
*Diag << StringRef(Buffer.data(), Buffer.size());
}
return *this;
}
OptionalDiagnostic &operator<<(const APFloat &F) {
if (Diag) {
// FIXME: Force the precision of the source value down so we don't
// print digits which are usually useless (we don't really care here if
// we truncate a digit by accident in edge cases). Ideally,
// APFloat::toString would automatically print the shortest
// representation which rounds to the correct value, but it's a bit
// tricky to implement.
unsigned precision =
llvm::APFloat::semanticsPrecision(F.getSemantics());
precision = (precision * 59 + 195) / 196;
SmallVector<char, 32> Buffer;
F.toString(Buffer, precision);
*Diag << StringRef(Buffer.data(), Buffer.size());
}
return *this;
}
};
/// A cleanup, and a flag indicating whether it is lifetime-extended.
class Cleanup {
llvm::PointerIntPair<APValue*, 1, bool> Value;
public:
Cleanup(APValue *Val, bool IsLifetimeExtended)
: Value(Val, IsLifetimeExtended) {}
bool isLifetimeExtended() const { return Value.getInt(); }
void endLifetime() {
*Value.getPointer() = APValue();
}
};
/// 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;
/// StepsLeft - The remaining number of evaluation steps we're permitted
/// to perform. This is essentially a limit for the number of statements
/// we will evaluate.
unsigned StepsLeft;
/// BottomFrame - The frame in which evaluation started. This must be
/// initialized after CurrentCall and CallStackDepth.
CallStackFrame BottomFrame;
/// A stack of values whose lifetimes end at the end of some surrounding
/// evaluation frame.
llvm::SmallVector<Cleanup, 16> CleanupStack;
/// EvaluatingDecl - This is the declaration whose initializer is being
/// evaluated, if any.
APValue::LValueBase 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;
/// \brief Have we emitted a diagnostic explaining why we couldn't constant
/// fold (not just why it's not strictly a constant expression)?
bool HasFoldFailureDiagnostic;
/// \brief Whether or not we're currently speculatively evaluating.
bool IsSpeculativelyEvaluating;
enum EvaluationMode {
/// Evaluate as a constant expression. Stop if we find that the expression
/// is not a constant expression.
EM_ConstantExpression,
/// Evaluate as a potential constant expression. Keep going if we hit a
/// construct that we can't evaluate yet (because we don't yet know the
/// value of something) but stop if we hit something that could never be
/// a constant expression.
EM_PotentialConstantExpression,
/// Fold the expression to a constant. Stop if we hit a side-effect that
/// we can't model.
EM_ConstantFold,
/// Evaluate the expression looking for integer overflow and similar
/// issues. Don't worry about side-effects, and try to visit all
/// subexpressions.
EM_EvaluateForOverflow,
/// Evaluate in any way we know how. Don't worry about side-effects that
/// can't be modeled.
EM_IgnoreSideEffects,
/// Evaluate as a constant expression. Stop if we find that the expression
/// is not a constant expression. Some expressions can be retried in the
/// optimizer if we don't constant fold them here, but in an unevaluated
/// context we try to fold them immediately since the optimizer never
/// gets a chance to look at it.
EM_ConstantExpressionUnevaluated,
/// Evaluate as a potential constant expression. Keep going if we hit a
/// construct that we can't evaluate yet (because we don't yet know the
/// value of something) but stop if we hit something that could never be
/// a constant expression. Some expressions can be retried in the
/// optimizer if we don't constant fold them here, but in an unevaluated
/// context we try to fold them immediately since the optimizer never
/// gets a chance to look at it.
EM_PotentialConstantExpressionUnevaluated,
/// Evaluate as a constant expression. Continue evaluating if we find a
/// MemberExpr with a base that can't be evaluated.
EM_DesignatorFold,
} EvalMode;
/// Are we checking whether the expression is a potential constant
/// expression?
bool checkingPotentialConstantExpression() const {
return EvalMode == EM_PotentialConstantExpression ||
EvalMode == EM_PotentialConstantExpressionUnevaluated;
}
/// Are we checking an expression for overflow?
// FIXME: We should check for any kind of undefined or suspicious behavior
// in such constructs, not just overflow.
bool checkingForOverflow() { return EvalMode == EM_EvaluateForOverflow; }
EvalInfo(const ASTContext &C, Expr::EvalStatus &S, EvaluationMode Mode)
: Ctx(const_cast<ASTContext &>(C)), EvalStatus(S), CurrentCall(nullptr),
CallStackDepth(0), NextCallIndex(1),
StepsLeft(getLangOpts().ConstexprStepLimit),
BottomFrame(*this, SourceLocation(), nullptr, nullptr, nullptr),
EvaluatingDecl((const ValueDecl *)nullptr),
EvaluatingDeclValue(nullptr), HasActiveDiagnostic(false),
HasFoldFailureDiagnostic(false), IsSpeculativelyEvaluating(false),
EvalMode(Mode) {}
void setEvaluatingDecl(APValue::LValueBase Base, APValue &Value) {
EvaluatingDecl = Base;
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.
FFDiag(Loc, diag::note_constexpr_call_limit_exceeded);
return false;
}
if (CallStackDepth <= getLangOpts().ConstexprCallDepth)
return true;
FFDiag(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 : nullptr;
}
bool nextStep(const Stmt *S) {
if (!StepsLeft) {
FFDiag(S->getLocStart(), diag::note_constexpr_step_limit_exceeded);
return false;
}
--StepsLeft;
return true;
}
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);
private:
OptionalDiagnostic Diag(SourceLocation Loc, diag::kind DiagId,
unsigned ExtraNotes, bool IsCCEDiag) {
if (EvalStatus.Diag) {
// If we have a prior diagnostic, it will be noting that the expression
// isn't a constant expression. This diagnostic is more important,
// unless we require this evaluation to produce a constant expression.
//
// FIXME: We might want to show both diagnostics to the user in
// EM_ConstantFold mode.
if (!EvalStatus.Diag->empty()) {
switch (EvalMode) {
case EM_ConstantFold:
case EM_IgnoreSideEffects:
case EM_EvaluateForOverflow:
if (!HasFoldFailureDiagnostic)
break;
// We've already failed to fold something. Keep that diagnostic.
case EM_ConstantExpression:
case EM_PotentialConstantExpression:
case EM_ConstantExpressionUnevaluated:
case EM_PotentialConstantExpressionUnevaluated:
case EM_DesignatorFold:
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
}
unsigned CallStackNotes = CallStackDepth - 1;
unsigned Limit = Ctx.getDiagnostics().getConstexprBacktraceLimit();
if (Limit)
CallStackNotes = std::min(CallStackNotes, Limit + 1);
if (checkingPotentialConstantExpression())
CallStackNotes = 0;
HasActiveDiagnostic = true;
HasFoldFailureDiagnostic = !IsCCEDiag;
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();
}
public:
// Diagnose that the evaluation could not be folded (FF => FoldFailure)
OptionalDiagnostic
FFDiag(SourceLocation Loc,
diag::kind DiagId = diag::note_invalid_subexpr_in_const_expr,
unsigned ExtraNotes = 0) {
return Diag(Loc, DiagId, ExtraNotes, false);
}
OptionalDiagnostic FFDiag(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, /*IsCCEDiag*/false);
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
/// Diagnose that the evaluation does not produce a C++11 core constant
/// expression.
///
/// FIXME: Stop evaluating if we're in EM_ConstantExpression or
/// EM_PotentialConstantExpression mode and we produce one of these.
OptionalDiagnostic CCEDiag(SourceLocation Loc, diag::kind DiagId
= diag::note_invalid_subexpr_in_const_expr,
unsigned ExtraNotes = 0) {
// Don't override a previous diagnostic. Don't bother collecting
// diagnostics if we're evaluating for overflow.
if (!EvalStatus.Diag || !EvalStatus.Diag->empty()) {
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
return Diag(Loc, DiagId, ExtraNotes, true);
}
OptionalDiagnostic CCEDiag(const Expr *E, diag::kind DiagId
= diag::note_invalid_subexpr_in_const_expr,
unsigned ExtraNotes = 0) {
return CCEDiag(E->getExprLoc(), 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 after encountering a side-effect that we
/// couldn't model?
bool keepEvaluatingAfterSideEffect() {
switch (EvalMode) {
case EM_PotentialConstantExpression:
case EM_PotentialConstantExpressionUnevaluated:
case EM_EvaluateForOverflow:
case EM_IgnoreSideEffects:
return true;
case EM_ConstantExpression:
case EM_ConstantExpressionUnevaluated:
case EM_ConstantFold:
case EM_DesignatorFold:
return false;
}
llvm_unreachable("Missed EvalMode case");
}
/// Note that we have had a side-effect, and determine whether we should
/// keep evaluating.
bool noteSideEffect() {
EvalStatus.HasSideEffects = true;
return keepEvaluatingAfterSideEffect();
}
/// Should we continue evaluation after encountering undefined behavior?
bool keepEvaluatingAfterUndefinedBehavior() {
switch (EvalMode) {
case EM_EvaluateForOverflow:
case EM_IgnoreSideEffects:
case EM_ConstantFold:
case EM_DesignatorFold:
return true;
case EM_PotentialConstantExpression:
case EM_PotentialConstantExpressionUnevaluated:
case EM_ConstantExpression:
case EM_ConstantExpressionUnevaluated:
return false;
}
llvm_unreachable("Missed EvalMode case");
}
/// Note that we hit something that was technically undefined behavior, but
/// that we can evaluate past it (such as signed overflow or floating-point
/// division by zero.)
bool noteUndefinedBehavior() {
EvalStatus.HasUndefinedBehavior = true;
return keepEvaluatingAfterUndefinedBehavior();
}
/// Should we continue evaluation as much as possible after encountering a
/// construct which can't be reduced to a value?
bool keepEvaluatingAfterFailure() {
if (!StepsLeft)
return false;
switch (EvalMode) {
case EM_PotentialConstantExpression:
case EM_PotentialConstantExpressionUnevaluated:
case EM_EvaluateForOverflow:
return true;
case EM_ConstantExpression:
case EM_ConstantExpressionUnevaluated:
case EM_ConstantFold:
case EM_IgnoreSideEffects:
case EM_DesignatorFold:
return false;
}
llvm_unreachable("Missed EvalMode case");
}
/// Notes that we failed to evaluate an expression that other expressions
/// directly depend on, and determine if we should keep evaluating. This
/// should only be called if we actually intend to keep evaluating.
///
/// Call noteSideEffect() instead if we may be able to ignore the value that
/// we failed to evaluate, e.g. if we failed to evaluate Foo() in:
///
/// (Foo(), 1) // use noteSideEffect
/// (Foo() || true) // use noteSideEffect
/// Foo() + 1 // use noteFailure
LLVM_ATTRIBUTE_UNUSED_RESULT bool noteFailure() {
// Failure when evaluating some expression often means there is some
// subexpression whose evaluation was skipped. Therefore, (because we
// don't track whether we skipped an expression when unwinding after an
// evaluation failure) every evaluation failure that bubbles up from a
// subexpression implies that a side-effect has potentially happened. We
// skip setting the HasSideEffects flag to true until we decide to
// continue evaluating after that point, which happens here.
bool KeepGoing = keepEvaluatingAfterFailure();
EvalStatus.HasSideEffects |= KeepGoing;
return KeepGoing;
}
bool allowInvalidBaseExpr() const {
return EvalMode == EM_DesignatorFold;
}
};
/// Object used to treat all foldable expressions as constant expressions.
struct FoldConstant {
EvalInfo &Info;
bool Enabled;
bool HadNoPriorDiags;
EvalInfo::EvaluationMode OldMode;
explicit FoldConstant(EvalInfo &Info, bool Enabled)
: Info(Info),
Enabled(Enabled),
HadNoPriorDiags(Info.EvalStatus.Diag &&
Info.EvalStatus.Diag->empty() &&
!Info.EvalStatus.HasSideEffects),
OldMode(Info.EvalMode) {
if (Enabled &&
(Info.EvalMode == EvalInfo::EM_ConstantExpression ||
Info.EvalMode == EvalInfo::EM_ConstantExpressionUnevaluated))
Info.EvalMode = EvalInfo::EM_ConstantFold;
}
void keepDiagnostics() { Enabled = false; }
~FoldConstant() {
if (Enabled && HadNoPriorDiags && !Info.EvalStatus.Diag->empty() &&
!Info.EvalStatus.HasSideEffects)
Info.EvalStatus.Diag->clear();
Info.EvalMode = OldMode;
}
};
/// RAII object used to treat the current evaluation as the correct pointer
/// offset fold for the current EvalMode
struct FoldOffsetRAII {
EvalInfo &Info;
EvalInfo::EvaluationMode OldMode;
explicit FoldOffsetRAII(EvalInfo &Info, bool Subobject)
: Info(Info), OldMode(Info.EvalMode) {
if (!Info.checkingPotentialConstantExpression())
Info.EvalMode = Subobject ? EvalInfo::EM_DesignatorFold
: EvalInfo::EM_ConstantFold;
}
~FoldOffsetRAII() { Info.EvalMode = OldMode; }
};
/// RAII object used to optionally suppress diagnostics and side-effects from
/// a speculative evaluation.
class SpeculativeEvaluationRAII {
/// Pair of EvalInfo, and a bit that stores whether or not we were
/// speculatively evaluating when we created this RAII.
llvm::PointerIntPair<EvalInfo *, 1, bool> InfoAndOldSpecEval;
Expr::EvalStatus Old;
void moveFromAndCancel(SpeculativeEvaluationRAII &&Other) {
InfoAndOldSpecEval = Other.InfoAndOldSpecEval;
Old = Other.Old;
Other.InfoAndOldSpecEval.setPointer(nullptr);
}
void maybeRestoreState() {
EvalInfo *Info = InfoAndOldSpecEval.getPointer();
if (!Info)
return;
Info->EvalStatus = Old;
Info->IsSpeculativelyEvaluating = InfoAndOldSpecEval.getInt();
}
public:
SpeculativeEvaluationRAII() = default;
SpeculativeEvaluationRAII(
EvalInfo &Info, SmallVectorImpl<PartialDiagnosticAt> *NewDiag = nullptr)
: InfoAndOldSpecEval(&Info, Info.IsSpeculativelyEvaluating),
Old(Info.EvalStatus) {
Info.EvalStatus.Diag = NewDiag;
Info.IsSpeculativelyEvaluating = true;
}
SpeculativeEvaluationRAII(const SpeculativeEvaluationRAII &Other) = delete;
SpeculativeEvaluationRAII(SpeculativeEvaluationRAII &&Other) {
moveFromAndCancel(std::move(Other));
}
SpeculativeEvaluationRAII &operator=(SpeculativeEvaluationRAII &&Other) {
maybeRestoreState();
moveFromAndCancel(std::move(Other));
return *this;
}
~SpeculativeEvaluationRAII() { maybeRestoreState(); }
};
/// RAII object wrapping a full-expression or block scope, and handling
/// the ending of the lifetime of temporaries created within it.
template<bool IsFullExpression>
class ScopeRAII {
EvalInfo &Info;
unsigned OldStackSize;
public:
ScopeRAII(EvalInfo &Info)
: Info(Info), OldStackSize(Info.CleanupStack.size()) {}
~ScopeRAII() {
// Body moved to a static method to encourage the compiler to inline away
// instances of this class.
cleanup(Info, OldStackSize);
}
private:
static void cleanup(EvalInfo &Info, unsigned OldStackSize) {
unsigned NewEnd = OldStackSize;
for (unsigned I = OldStackSize, N = Info.CleanupStack.size();
I != N; ++I) {
if (IsFullExpression && Info.CleanupStack[I].isLifetimeExtended()) {
// Full-expression cleanup of a lifetime-extended temporary: nothing
// to do, just move this cleanup to the right place in the stack.
std::swap(Info.CleanupStack[I], Info.CleanupStack[NewEnd]);
++NewEnd;
} else {
// End the lifetime of the object.
Info.CleanupStack[I].endLifetime();
}
}
Info.CleanupStack.erase(Info.CleanupStack.begin() + NewEnd,
Info.CleanupStack.end());
}
};
typedef ScopeRAII<false> BlockScopeRAII;
typedef ScopeRAII<true> FullExpressionRAII;
}
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() && MostDerivedIsArrayElement)
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,
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;
}
APValue &CallStackFrame::createTemporary(const void *Key,
bool IsLifetimeExtended) {
APValue &Result = Temporaries[Key];
assert(Result.isUninit() && "temporary created multiple times");
Info.CleanupStack.push_back(Cleanup(&Result, IsLifetimeExtended));
return Result;
}
static void describeCall(CallStackFrame *Frame, raw_ostream &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;
}
// Use a different note for an inheriting constructor, because from the
// user's perspective it's not really a function at all.
if (auto *CD = dyn_cast_or_null<CXXConstructorDecl>(Frame->Callee)) {
if (CD->isInheritingConstructor()) {
addDiag(Frame->CallLoc, diag::note_constexpr_inherited_ctor_call_here)
<< CD->getParent();
continue;
}
}
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 InvalidBase : 1;
unsigned CallIndex : 31;
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();
InvalidBase = false;
CallIndex = V.getLValueCallIndex();
Designator = SubobjectDesignator(Ctx, V);
}
void set(APValue::LValueBase B, unsigned I = 0, bool BInvalid = false) {
Base = B;
Offset = CharUnits::Zero();
InvalidBase = BInvalid;
CallIndex = I;
Designator = SubobjectDesignator(getType(B));
}
void setInvalid(APValue::LValueBase B, unsigned I = 0) {
set(B, I, true);
}
// 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) {
return (CSK == CSK_ArrayToPointer || 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 (N && 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;
}
}
static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E);
static bool EvaluateInPlace(APValue &Result, EvalInfo &Info,
const LValue &This, const Expr *E,
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);
static bool EvaluateAtomic(const Expr *E, APValue &Result, EvalInfo &Info);
static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result);
//===----------------------------------------------------------------------===//
// Misc utilities
//===----------------------------------------------------------------------===//
/// Produce a string describing the given constexpr call.
static void describeCall(CallStackFrame *Frame, 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 << '(';
if (Frame->This && IsMemberCall) {
APValue Val;
Frame->This->moveInto(Val);
Val.printPretty(Out, Frame->Info.Ctx,
Frame->This->Designator.MostDerivedType);
// FIXME: Add parens around Val if needed.
Out << "->" << *Frame->Callee << '(';
IsMemberCall = false;
}
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 << ')';
}
/// Evaluate an expression to see if it had side-effects, and discard its
/// result.
/// \return \c true if the caller should keep evaluating.
static bool EvaluateIgnoredValue(EvalInfo &Info, const Expr *E) {
APValue Scratch;
if (!Evaluate(Scratch, Info, E))
// We don't need the value, but we might have skipped a side effect here.
return Info.noteSideEffect();
return true;
}
/// Sign- or zero-extend a value to 64 bits. If it's already 64 bits, just
/// return its existing value.
static int64_t getExtValue(const APSInt &Value) {
return Value.isSigned() ? Value.getSExtValue()
: static_cast<int64_t>(Value.getZExtValue());
}
/// Should this call expression be treated as a string literal?
static bool IsStringLiteralCall(const CallExpr *E) {
unsigned Builtin = E->getBuiltinCallee();
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();
}
case Expr::MaterializeTemporaryExprClass:
// A materialized temporary might have been lifetime-extended to static
// storage duration.
return cast<MaterializeTemporaryExpr>(E)->getStorageDuration() == SD_Static;
// A string literal has static storage duration.
case Expr::StringLiteralClass:
case Expr::PredefinedExprClass:
case Expr::ObjCStringLiteralClass:
case Expr::ObjCEncodeExprClass:
case Expr::CXXTypeidExprClass:
case Expr::CXXUuidofExprClass:
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.get<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().CPlusPlus11) {
const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
Info.FFDiag(Loc, diag::note_constexpr_non_global, 1)
<< IsReferenceType << !Designator.Entries.empty()
<< !!VD << VD;
NoteLValueLocation(Info, Base);
} else {
Info.FFDiag(Loc);
}
// Don't allow references to temporaries to escape.
return false;
}
assert((Info.checkingPotentialConstantExpression() ||
LVal.getLValueCallIndex() == 0) &&
"have call index for global lvalue");
if (const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>()) {
if (const VarDecl *Var = dyn_cast<const VarDecl>(VD)) {
// Check if this is a thread-local variable.
if (Var->getTLSKind())
return false;
// A dllimport variable never acts like a constant.
if (Var->hasAttr<DLLImportAttr>())
return false;
}
if (const auto *FD = dyn_cast<const FunctionDecl>(VD)) {
// __declspec(dllimport) must be handled very carefully:
// We must never initialize an expression with the thunk in C++.
// Doing otherwise would allow the same id-expression to yield
// different addresses for the same function in different translation
// units. However, this means that we must dynamically initialize the
// expression with the contents of the import address table at runtime.
//
// The C language has no notion of ODR; furthermore, it has no notion of
// dynamic initialization. This means that we are permitted to
// perform initialization with the address of the thunk.
if (Info.getLangOpts().CPlusPlus && FD->hasAttr<DLLImportAttr>())
return false;
}
}
// 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.Invalid && Designator.isOnePastTheEnd()) {
const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
Info.FFDiag(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,
const LValue *This = nullptr) {
if (!E->isRValue() || E->getType()->isLiteralType(Info.Ctx))
return true;
// C++1y: A constant initializer for an object o [...] may also invoke
// constexpr constructors for o and its subobjects even if those objects
// are of non-literal class types.
if (Info.getLangOpts().CPlusPlus14 && This &&
Info.EvaluatingDecl == This->getLValueBase())
return true;
// Prvalue constant expressions must be of literal types.
if (Info.getLangOpts().CPlusPlus11)
Info.FFDiag(E, diag::note_constexpr_nonliteral)
<< E->getType();
else
Info.FFDiag(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) {
if (Value.isUninit()) {
Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
<< true << Type;
return false;
}
// We allow _Atomic(T) to be initialized from anything that T can be
// initialized from.
if (const AtomicType *AT = Type->getAs<AtomicType>())
Type = AT->getValueType();
// 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 (const auto *I : RD->fields()) {
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;
}
static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
return LVal.Base.dyn_cast<const ValueDecl*>();
}
static bool IsLiteralLValue(const LValue &Value) {
if (Value.CallIndex)
return false;
const Expr *E = Value.Base.dyn_cast<const Expr*>();
return E && !isa<MaterializeTemporaryExpr>(E);
}
static bool IsWeakLValue(const LValue &Value) {
const ValueDecl *Decl = GetLValueBaseDecl(Value);
return Decl && Decl->isWeak();
}
static bool isZeroSized(const LValue &Value) {
const ValueDecl *Decl = GetLValueBaseDecl(Value);
if (Decl && isa<VarDecl>(Decl)) {
QualType Ty = Decl->getType();
if (Ty->isArrayType())
return Ty->isIncompleteType() ||
Decl->getASTContext().getTypeSize(Ty) == 0;
}
return false;
}
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.CCEDiag(E, diag::note_constexpr_overflow)
<< SrcValue << DestType;
return Info.noteUndefinedBehavior();
}
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,
const 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 truncateBitfieldValue(EvalInfo &Info, const Expr *E,
APValue &Value, const FieldDecl *FD) {
assert(FD->isBitField() && "truncateBitfieldValue on non-bitfield");
if (!Value.isInt()) {
// Trying to store a pointer-cast-to-integer into a bitfield.
// FIXME: In this case, we should provide the diagnostic for casting
// a pointer to an integer.
assert(Value.isLValue() && "integral value neither int nor lvalue?");
Info.FFDiag(E);
return false;
}
APSInt &Int = Value.getInt();
unsigned OldBitWidth = Int.getBitWidth();
unsigned NewBitWidth = FD->getBitWidthValue(Info.Ctx);
if (NewBitWidth < OldBitWidth)
Int = Int.trunc(NewBitWidth).extend(OldBitWidth);
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.FFDiag(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.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
/// Perform the given integer operation, which is known to need at most BitWidth
/// bits, and check for overflow in the original type (if that type was not an
/// unsigned type).
template<typename Operation>
static bool CheckedIntArithmetic(EvalInfo &Info, const Expr *E,
const APSInt &LHS, const APSInt &RHS,
unsigned BitWidth, Operation Op,
APSInt &Result) {
if (LHS.isUnsigned()) {
Result = Op(LHS, RHS);
return true;
}
APSInt Value(Op(LHS.extend(BitWidth), RHS.extend(BitWidth)), false);
Result = Value.trunc(LHS.getBitWidth());
if (Result.extend(BitWidth) != Value) {
if (Info.checkingForOverflow())
Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
diag::warn_integer_constant_overflow)
<< Result.toString(10) << E->getType();
else
return HandleOverflow(Info, E, Value, E->getType());
}
return true;
}
/// Perform the given binary integer operation.
static bool handleIntIntBinOp(EvalInfo &Info, const Expr *E, const APSInt &LHS,
BinaryOperatorKind Opcode, APSInt RHS,
APSInt &Result) {
switch (Opcode) {
default:
Info.FFDiag(E);
return false;
case BO_Mul:
return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() * 2,
std::multiplies<APSInt>(), Result);
case BO_Add:
return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
std::plus<APSInt>(), Result);
case BO_Sub:
return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
std::minus<APSInt>(), Result);
case BO_And: Result = LHS & RHS; return true;
case BO_Xor: Result = LHS ^ RHS; return true;
case BO_Or: Result = LHS | RHS; return true;
case BO_Div:
case BO_Rem:
if (RHS == 0) {
Info.FFDiag(E, diag::note_expr_divide_by_zero);
return false;
}
Result = (Opcode == BO_Rem ? LHS % RHS : LHS / RHS);
// Check for overflow case: INT_MIN / -1 or INT_MIN % -1. APSInt supports
// this operation and gives the two's complement result.
if (RHS.isNegative() && RHS.isAllOnesValue() &&
LHS.isSigned() && LHS.isMinSignedValue())
return HandleOverflow(Info, E, -LHS.extend(LHS.getBitWidth() + 1),
E->getType());
return true;
case BO_Shl: {
if (Info.getLangOpts().OpenCL)
// OpenCL 6.3j: shift values are effectively % word size of LHS.
RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
static_cast<uint64_t>(LHS.getBitWidth() - 1)),
RHS.isUnsigned());
else if (RHS.isSigned() && RHS.isNegative()) {
// During constant-folding, a negative shift is an opposite shift. Such
// a shift is not a constant expression.
Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
RHS = -RHS;
goto shift_right;
}
shift_left:
// C++11 [expr.shift]p1: Shift width must be less than the bit width of
// the shifted type.
unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
if (SA != RHS) {
Info.CCEDiag(E, diag::note_constexpr_large_shift)
<< RHS << E->getType() << LHS.getBitWidth();
} else if (LHS.isSigned()) {
// C++11 [expr.shift]p2: A signed left shift must have a non-negative
// operand, and must not overflow the corresponding unsigned type.
if (LHS.isNegative())
Info.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS;
else if (LHS.countLeadingZeros() < SA)
Info.CCEDiag(E, diag::note_constexpr_lshift_discards);
}
Result = LHS << SA;
return true;
}
case BO_Shr: {
if (Info.getLangOpts().OpenCL)
// OpenCL 6.3j: shift values are effectively % word size of LHS.
RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
static_cast<uint64_t>(LHS.getBitWidth() - 1)),
RHS.isUnsigned());
else if (RHS.isSigned() && RHS.isNegative()) {
// During constant-folding, a negative shift is an opposite shift. Such a
// shift is not a constant expression.
Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
RHS = -RHS;
goto shift_left;
}
shift_right:
// C++11 [expr.shift]p1: Shift width must be less than the bit width of the
// shifted type.
unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
if (SA != RHS)
Info.CCEDiag(E, diag::note_constexpr_large_shift)
<< RHS << E->getType() << LHS.getBitWidth();
Result = LHS >> SA;
return true;
}
case BO_LT: Result = LHS < RHS; return true;
case BO_GT: Result = LHS > RHS; return true;
case BO_LE: Result = LHS <= RHS; return true;
case BO_GE: Result = LHS >= RHS; return true;
case BO_EQ: Result = LHS == RHS; return true;
case BO_NE: Result = LHS != RHS; return true;
}
}
/// Perform the given binary floating-point operation, in-place, on LHS.
static bool handleFloatFloatBinOp(EvalInfo &Info, const Expr *E,
APFloat &LHS, BinaryOperatorKind Opcode,
const APFloat &RHS) {
switch (Opcode) {
default:
Info.FFDiag(E);
return false;
case BO_Mul:
LHS.multiply(RHS, APFloat::rmNearestTiesToEven);
break;
case BO_Add:
LHS.add(RHS, APFloat::rmNearestTiesToEven);
break;
case BO_Sub:
LHS.subtract(RHS, APFloat::rmNearestTiesToEven);
break;
case BO_Div:
LHS.divide(RHS, APFloat::rmNearestTiesToEven);
break;
}
if (LHS.isInfinity() || LHS.isNaN()) {
Info.CCEDiag(E, diag::note_constexpr_float_arithmetic) << LHS.isNaN();
return Info.noteUndefinedBehavior();
}
return true;
}
/// 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) {
if (RD->isInvalidDecl()) return false;
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 bool HandleLValueDirectBase(EvalInfo &Info, const Expr *E, LValue &Obj,
const CXXRecordDecl *Derived,
const CXXRecordDecl *Base,
const ASTRecordLayout *RL = nullptr) {
if (!RL) {
if (Derived->isInvalidDecl()) return false;
RL = &Info.Ctx.getASTRecordLayout(Derived);
}
Obj.getLValueOffset() += RL->getBaseClassOffset(Base);
Obj.addDecl(Info, E, Base, /*Virtual*/ false);
return true;
}
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())
return HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);
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.
if (DerivedDecl->isInvalidDecl()) return false;
const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
Obj.getLValueOffset() += Layout.getVBaseClassOffset(BaseDecl);
Obj.addDecl(Info, E, BaseDecl, /*Virtual*/ true);
return true;
}
static bool HandleLValueBasePath(EvalInfo &Info, const CastExpr *E,
QualType Type, LValue &Result) {
for (CastExpr::path_const_iterator PathI = E->path_begin(),
PathE = E->path_end();
PathI != PathE; ++PathI) {
if (!HandleLValueBase(Info, E, Result, Type->getAsCXXRecordDecl(),
*PathI))
return false;
Type = (*PathI)->getType();
}
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,
const FieldDecl *FD,
const ASTRecordLayout *RL = nullptr) {
if (!RL) {
if (FD->getParent()->isInvalidDecl()) return false;
RL = &Info.Ctx.getASTRecordLayout(FD->getParent());
}
unsigned I = FD->getFieldIndex();
LVal.Offset += Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I));
LVal.addDecl(Info, E, FD);
return true;
}
/// Update LVal to refer to the given indirect field.
static bool HandleLValueIndirectMember(EvalInfo &Info, const Expr *E,
LValue &LVal,
const IndirectFieldDecl *IFD) {
for (const auto *C : IFD->chain())
if (!HandleLValueMember(Info, E, LVal, cast<FieldDecl>(C)))
return false;
return true;
}
/// 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->isDependentType()) {
Info.FFDiag(Loc);
return false;
}
if (!Type->isConstantSizeType()) {
// sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
// FIXME: Better diagnostic.
Info.FFDiag(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.
///
/// \param Info Information about the ongoing evaluation.
/// \param E An expression to be used when printing diagnostics.
/// \param VD The variable whose initializer should be obtained.
/// \param Frame The frame in which the variable was created. Must be null
/// if this variable is not local to the evaluation.
/// \param Result Filled in with a pointer to the value of the variable.
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.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
return false;
}
Result = &Frame->Arguments[PVD->getFunctionScopeIndex()];
return true;
}
// If this is a local variable, dig out its value.
if (Frame) {
Result = Frame->getTemporary(VD);
if (!Result) {
// Assume variables referenced within a lambda's call operator that were
// not declared within the call operator are captures and during checking
// of a potential constant expression, assume they are unknown constant
// expressions.
assert(isLambdaCallOperator(Frame->Callee) &&
(VD->getDeclContext() != Frame->Callee || VD->isInitCapture()) &&
"missing value for local variable");
if (Info.checkingPotentialConstantExpression())
return false;
// FIXME: implement capture evaluation during constant expr evaluation.
Info.FFDiag(E->getLocStart(),
diag::note_unimplemented_constexpr_lambda_feature_ast)
<< "captures not currently allowed";
return false;
}
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.FFDiag(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.dyn_cast<const ValueDecl*>() == VD) {
Result = Info.EvaluatingDeclValue;
return true;
}
// 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.FFDiag(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.
SmallVector<PartialDiagnosticAt, 8> Notes;
if (!VD->evaluateValue(Notes)) {
Info.FFDiag(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 ObjCEncodeExpr, MakeStringConstant
if (auto PE = dyn_cast<PredefinedExpr>(Lit))
Lit = PE->getFunctionName();
const StringLiteral *S = cast<StringLiteral>(Lit);
const ConstantArrayType *CAT =
Info.Ctx.getAsConstantArrayType(S->getType());
assert(CAT && "string literal isn't an array");
QualType CharType = CAT->getElementType();
assert(CharType->isIntegerType() && "unexpected character type");
APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
CharType->isUnsignedIntegerType());
if (Index < S->getLength())
Value = S->getCodeUnit(Index);
return Value;
}
// Expand a string literal into an array of characters.
static void expandStringLiteral(EvalInfo &Info, const Expr *Lit,
APValue &Result) {
const StringLiteral *S = cast<StringLiteral>(Lit);
const ConstantArrayType *CAT =
Info.Ctx.getAsConstantArrayType(S->getType());
assert(CAT && "string literal isn't an array");
QualType CharType = CAT->getElementType();
assert(CharType->isIntegerType() && "unexpected character type");
unsigned Elts = CAT->getSize().getZExtValue();
Result = APValue(APValue::UninitArray(),
std::min(S->getLength(), Elts), Elts);
APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
CharType->isUnsignedIntegerType());
if (Result.hasArrayFiller())
Result.getArrayFiller() = APValue(Value);
for (unsigned I = 0, N = Result.getArrayInitializedElts(); I != N; ++I) {
Value = S->getCodeUnit(I);
Result.getArrayInitializedElt(I) = APValue(Value);
}
}
// Expand an array so that it has more than Index filled elements.
static void expandArray(APValue &Array, unsigned Index) {
unsigned Size = Array.getArraySize();
assert(Index < Size);
// Always at least double the number of elements for which we store a value.
unsigned OldElts = Array.getArrayInitializedElts();
unsigned NewElts = std::max(Index+1, OldElts * 2);
NewElts = std::min(Size, std::max(NewElts, 8u));
// Copy the data across.
APValue NewValue(APValue::UninitArray(), NewElts, Size);
for (unsigned I = 0; I != OldElts; ++I)
NewValue.getArrayInitializedElt(I).swap(Array.getArrayInitializedElt(I));
for (unsigned I = OldElts; I != NewElts; ++I)
NewValue.getArrayInitializedElt(I) = Array.getArrayFiller();
if (NewValue.hasArrayFiller())
NewValue.getArrayFiller() = Array.getArrayFiller();
Array.swap(NewValue);
}
/// Determine whether a type would actually be read by an lvalue-to-rvalue
/// conversion. If it's of class type, we may assume that the copy operation
/// is trivial. Note that this is never true for a union type with fields
/// (because the copy always "reads" the active member) and always true for
/// a non-class type.
static bool isReadByLvalueToRvalueConversion(QualType T) {
CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
if (!RD || (RD->isUnion() && !RD->field_empty()))
return true;
if (RD->isEmpty())
return false;
for (auto *Field : RD->fields())
if (isReadByLvalueToRvalueConversion(Field->getType()))
return true;
for (auto &BaseSpec : RD->bases())
if (isReadByLvalueToRvalueConversion(BaseSpec.getType()))
return true;
return false;
}
/// Diagnose an attempt to read from any unreadable field within the specified
/// type, which might be a class type.
static bool diagnoseUnreadableFields(EvalInfo &Info, const Expr *E,
QualType T) {
CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
if (!RD)
return false;
if (!RD->hasMutableFields())
return false;
for (auto *Field : RD->fields()) {
// If we're actually going to read this field in some way, then it can't
// be mutable. If we're in a union, then assigning to a mutable field
// (even an empty one) can change the active member, so that's not OK.
// FIXME: Add core issue number for the union case.
if (Field->isMutable() &&
(RD->isUnion() || isReadByLvalueToRvalueConversion(Field->getType()))) {
Info.FFDiag(E, diag::note_constexpr_ltor_mutable, 1) << Field;
Info.Note(Field->getLocation(), diag::note_declared_at);
return true;
}
if (diagnoseUnreadableFields(Info, E, Field->getType()))
return true;
}
for (auto &BaseSpec : RD->bases())
if (diagnoseUnreadableFields(Info, E, BaseSpec.getType()))
return true;
// All mutable fields were empty, and thus not actually read.
return false;
}
/// Kinds of access we can perform on an object, for diagnostics.
enum AccessKinds {
AK_Read,
AK_Assign,
AK_Increment,
AK_Decrement
};
namespace {
/// A handle to a complete object (an object that is not a subobject of
/// another object).
struct CompleteObject {
/// The value of the complete object.
APValue *Value;
/// The type of the complete object.
QualType Type;
CompleteObject() : Value(nullptr) {}
CompleteObject(APValue *Value, QualType Type)
: Value(Value), Type(Type) {
assert(Value && "missing value for complete object");
}
explicit operator bool() const { return Value; }
};
} // end anonymous namespace
/// Find the designated sub-object of an rvalue.
template<typename SubobjectHandler>
typename SubobjectHandler::result_type
findSubobject(EvalInfo &Info, const Expr *E, const CompleteObject &Obj,
const SubobjectDesignator &Sub, SubobjectHandler &handler) {
if (Sub.Invalid)
// A diagnostic will have already been produced.
return handler.failed();
if (Sub.isOnePastTheEnd()) {
if (Info.getLangOpts().CPlusPlus11)
Info.FFDiag(E, diag::note_constexpr_access_past_end)
<< handler.AccessKind;
else
Info.FFDiag(E);
return handler.failed();
}
APValue *O = Obj.Value;
QualType ObjType = Obj.Type;
const FieldDecl *LastField = nullptr;
// Walk the designator's path to find the subobject.
for (unsigned I = 0, N = Sub.Entries.size(); /**/; ++I) {
if (O->isUninit()) {
if (!Info.checkingPotentialConstantExpression())
Info.FFDiag(E, diag::note_constexpr_access_uninit) << handler.AccessKind;
return handler.failed();
}
if (I == N) {
// If we are reading an object of class type, there may still be more
// things we need to check: if there are any mutable subobjects, we
// cannot perform this read. (This only happens when performing a trivial
// copy or assignment.)
if (ObjType->isRecordType() && handler.AccessKind == AK_Read &&
diagnoseUnreadableFields(Info, E, ObjType))
return handler.failed();
if (!handler.found(*O, ObjType))
return false;
// If we modified a bit-field, truncate it to the right width.
if (handler.AccessKind != AK_Read &&
LastField && LastField->isBitField() &&
!truncateBitfieldValue(Info, E, *O, LastField))
return false;
return true;
}
LastField = nullptr;
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.
if (Info.getLangOpts().CPlusPlus11)
Info.FFDiag(E, diag::note_constexpr_access_past_end)
<< handler.AccessKind;
else
Info.FFDiag(E);
return handler.failed();
}
ObjType = CAT->getElementType();
// 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());
if (handler.AccessKind != AK_Read)
expandStringLiteral(Info, O->getLValueBase().get<