Implement DR1454. This allows all intermediate results in constant expressions
to be core constant expressions (including pointers and references to
temporaries), and makes constexpr calculations Turing-complete. A Turing machine
simulator is included as a testcase.
This opens up the possibilty of removing CCValue entirely, and removing some
copies from the constant evaluator in the process, but that cleanup is not part
of this change.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150557 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/APValue.h b/include/clang/AST/APValue.h
index f361f0f..f687fb7 100644
--- a/include/clang/AST/APValue.h
+++ b/include/clang/AST/APValue.h
@@ -138,14 +138,14 @@
APValue(const APValue &RHS) : Kind(Uninitialized) {
*this = RHS;
}
- APValue(LValueBase B, const CharUnits &O, NoLValuePath N)
+ APValue(LValueBase B, const CharUnits &O, NoLValuePath N, unsigned CallIndex)
: Kind(Uninitialized) {
- MakeLValue(); setLValue(B, O, N);
+ MakeLValue(); setLValue(B, O, N, CallIndex);
}
APValue(LValueBase B, const CharUnits &O, ArrayRef<LValuePathEntry> Path,
- bool OnePastTheEnd)
+ bool OnePastTheEnd, unsigned CallIndex)
: Kind(Uninitialized) {
- MakeLValue(); setLValue(B, O, Path, OnePastTheEnd);
+ MakeLValue(); setLValue(B, O, Path, OnePastTheEnd, CallIndex);
}
APValue(UninitArray, unsigned InitElts, unsigned Size) : Kind(Uninitialized) {
MakeArray(InitElts, Size);
@@ -246,6 +246,7 @@
bool isLValueOnePastTheEnd() const;
bool hasLValuePath() const;
ArrayRef<LValuePathEntry> getLValuePath() const;
+ unsigned getLValueCallIndex() const;
APValue &getVectorElt(unsigned I) {
assert(isVector() && "Invalid accessor");
@@ -365,9 +366,11 @@
((ComplexAPFloat*)(char*)Data)->Real = R;
((ComplexAPFloat*)(char*)Data)->Imag = I;
}
- void setLValue(LValueBase B, const CharUnits &O, NoLValuePath);
+ void setLValue(LValueBase B, const CharUnits &O, NoLValuePath,
+ unsigned CallIndex);
void setLValue(LValueBase B, const CharUnits &O,
- ArrayRef<LValuePathEntry> Path, bool OnePastTheEnd);
+ ArrayRef<LValuePathEntry> Path, bool OnePastTheEnd,
+ unsigned CallIndex);
void setUnion(const FieldDecl *Field, const APValue &Value) {
assert(isUnion() && "Invalid accessor");
((UnionData*)(char*)Data)->Field = Field;
diff --git a/include/clang/Basic/DiagnosticASTKinds.td b/include/clang/Basic/DiagnosticASTKinds.td
index f2154fb..2d6e498 100644
--- a/include/clang/Basic/DiagnosticASTKinds.td
+++ b/include/clang/Basic/DiagnosticASTKinds.td
@@ -35,9 +35,7 @@
"non-literal type %0 cannot be used in a constant expression">;
def note_constexpr_non_global : Note<
"%select{pointer|reference}0 to %select{|subobject of }1"
- "%select{temporary|%4}2 %select{is not a constant expression|"
- "cannot be returned from a constexpr function|"
- "cannot be used to initialize a member in a constant expression}3">;
+ "%select{temporary|%3}2 is not a constant expression">;
def note_constexpr_array_index : Note<"cannot refer to element %0 of "
"%select{array of %2 elements|non-array object}1 in a constant expression">;
def note_constexpr_float_arithmetic : Note<
@@ -76,6 +74,10 @@
def note_constexpr_temporary_here : Note<"temporary created here">;
def note_constexpr_depth_limit_exceeded : Note<
"constexpr evaluation exceeded maximum depth of %0 calls">;
+def note_constexpr_call_limit_exceeded : Note<
+ "constexpr evaluation hit maximum call limit">;
+def note_constexpr_lifetime_ended : Note<
+ "read of %select{temporary|variable}0 whose lifetime has ended">;
def note_constexpr_ltor_volatile_type : Note<
"read of volatile-qualified type %0 is not allowed in a constant expression">;
def note_constexpr_ltor_volatile_obj : Note<
diff --git a/lib/AST/APValue.cpp b/lib/AST/APValue.cpp
index b8942c3..4e17d3b 100644
--- a/lib/AST/APValue.cpp
+++ b/lib/AST/APValue.cpp
@@ -28,6 +28,7 @@
llvm::PointerIntPair<APValue::LValueBase, 1, bool> BaseAndIsOnePastTheEnd;
CharUnits Offset;
unsigned PathLength;
+ unsigned CallIndex;
};
}
@@ -166,9 +167,10 @@
else if (isLValue()) {
if (RHS.hasLValuePath())
setLValue(RHS.getLValueBase(), RHS.getLValueOffset(), RHS.getLValuePath(),
- RHS.isLValueOnePastTheEnd());
+ RHS.isLValueOnePastTheEnd(), RHS.getLValueCallIndex());
else
- setLValue(RHS.getLValueBase(), RHS.getLValueOffset(), NoLValuePath());
+ setLValue(RHS.getLValueBase(), RHS.getLValueOffset(), NoLValuePath(),
+ RHS.getLValueCallIndex());
} else if (isArray()) {
for (unsigned I = 0, N = RHS.getArrayInitializedElts(); I != N; ++I)
getArrayInitializedElt(I) = RHS.getArrayInitializedElt(I);
@@ -525,22 +527,31 @@
return ArrayRef<LValuePathEntry>(LVal.getPath(), LVal.PathLength);
}
-void APValue::setLValue(LValueBase B, const CharUnits &O, NoLValuePath) {
+unsigned APValue::getLValueCallIndex() const {
+ assert(isLValue() && "Invalid accessor");
+ return ((const LV*)(const char*)Data)->CallIndex;
+}
+
+void APValue::setLValue(LValueBase B, const CharUnits &O, NoLValuePath,
+ unsigned CallIndex) {
assert(isLValue() && "Invalid accessor");
LV &LVal = *((LV*)(char*)Data);
LVal.BaseAndIsOnePastTheEnd.setPointer(B);
LVal.BaseAndIsOnePastTheEnd.setInt(false);
LVal.Offset = O;
+ LVal.CallIndex = CallIndex;
LVal.resizePath((unsigned)-1);
}
void APValue::setLValue(LValueBase B, const CharUnits &O,
- ArrayRef<LValuePathEntry> Path, bool IsOnePastTheEnd) {
+ ArrayRef<LValuePathEntry> Path, bool IsOnePastTheEnd,
+ unsigned CallIndex) {
assert(isLValue() && "Invalid accessor");
LV &LVal = *((LV*)(char*)Data);
LVal.BaseAndIsOnePastTheEnd.setPointer(B);
LVal.BaseAndIsOnePastTheEnd.setInt(IsOnePastTheEnd);
LVal.Offset = O;
+ LVal.CallIndex = CallIndex;
LVal.resizePath(Path.size());
memcpy(LVal.getPath(), Path.data(), Path.size() * sizeof(LValuePathEntry));
}
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 6ad9938..9454895 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -51,26 +51,14 @@
using llvm::APSInt;
using llvm::APFloat;
-/// 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.
+static bool IsGlobalLValue(APValue::LValueBase B);
+
namespace {
struct LValue;
struct CallStackFrame;
struct EvalInfo;
- QualType getType(APValue::LValueBase B) {
+ static QualType getType(APValue::LValueBase B) {
if (!B) return QualType();
if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>())
return D->getType();
@@ -79,6 +67,7 @@
/// 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);
@@ -87,17 +76,17 @@
/// Get an LValue path entry, which is known to not be an array index, as a
/// field declaration.
- const FieldDecl *getAsField(APValue::LValuePathEntry E) {
+ 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.
- const CXXRecordDecl *getAsBaseClass(APValue::LValuePathEntry E) {
+ 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.
- bool isVirtualBaseClass(APValue::LValuePathEntry E) {
+ static bool isVirtualBaseClass(APValue::LValuePathEntry E) {
return getAsBaseOrMember(E).getInt();
}
@@ -267,9 +256,6 @@
class CCValue : public APValue {
typedef llvm::APSInt APSInt;
typedef llvm::APFloat APFloat;
- /// If the value is a reference or pointer into a parameter or temporary,
- /// this is the corresponding call stack frame.
- CallStackFrame *CallFrame;
/// If the value is a reference or pointer, this is a description of how the
/// subobject was specified.
SubobjectDesignator Designator;
@@ -282,22 +268,19 @@
CCValue(const APValue *E, unsigned N) : APValue(E, N) {}
CCValue(const APSInt &R, const APSInt &I) : APValue(R, I) {}
CCValue(const APFloat &R, const APFloat &I) : APValue(R, I) {}
- CCValue(const CCValue &V) : APValue(V), CallFrame(V.CallFrame) {}
- CCValue(LValueBase B, const CharUnits &O, CallStackFrame *F,
+ CCValue(const CCValue &V) : APValue(V), Designator(V.Designator) {}
+ CCValue(LValueBase B, const CharUnits &O, unsigned I,
const SubobjectDesignator &D) :
- APValue(B, O, APValue::NoLValuePath()), CallFrame(F), Designator(D) {}
+ APValue(B, O, APValue::NoLValuePath(), I), Designator(D) {}
CCValue(ASTContext &Ctx, const APValue &V, GlobalValue) :
- APValue(V), CallFrame(0), Designator(Ctx, V) {}
+ APValue(V), Designator(Ctx, V) {
+ }
CCValue(const ValueDecl *D, bool IsDerivedMember,
ArrayRef<const CXXRecordDecl*> Path) :
APValue(D, IsDerivedMember, Path) {}
CCValue(const AddrLabelExpr* LHSExpr, const AddrLabelExpr* RHSExpr) :
APValue(LHSExpr, RHSExpr) {}
- CallStackFrame *getLValueFrame() const {
- assert(getKind() == LValue);
- return CallFrame;
- }
SubobjectDesignator &getLValueDesignator() {
assert(getKind() == LValue);
return Designator;
@@ -305,6 +288,21 @@
const SubobjectDesignator &getLValueDesignator() const {
return const_cast<CCValue*>(this)->getLValueDesignator();
}
+ APValue toAPValue() const {
+ if (!isLValue())
+ return *this;
+
+ if (Designator.Invalid) {
+ // This is not a core constant expression. An appropriate diagnostic
+ // will have already been produced.
+ return APValue(getLValueBase(), getLValueOffset(),
+ APValue::NoLValuePath(), getLValueCallIndex());
+ }
+
+ return APValue(getLValueBase(), getLValueOffset(),
+ Designator.Entries, Designator.IsOnePastTheEnd,
+ getLValueCallIndex());
+ }
};
/// A stack frame in the constexpr call stack.
@@ -320,6 +318,9 @@
/// 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;
@@ -372,6 +373,20 @@
}
};
+ /// 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;
@@ -384,6 +399,9 @@
/// 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*, CCValue> MapTy;
/// OpaqueValues - Values used as the common expression in a
/// BinaryConditionalOperator.
@@ -413,7 +431,8 @@
EvalInfo(const ASTContext &C, Expr::EvalStatus &S)
: Ctx(const_cast<ASTContext&>(C)), EvalStatus(S), CurrentCall(0),
- CallStackDepth(0), BottomFrame(*this, SourceLocation(), 0, 0, 0),
+ CallStackDepth(0), NextCallIndex(1),
+ BottomFrame(*this, SourceLocation(), 0, 0, 0),
EvaluatingDecl(0), EvaluatingDeclValue(0), HasActiveDiagnostic(false),
CheckingPotentialConstantExpression(false) {}
@@ -435,6 +454,11 @@
// 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)
@@ -442,6 +466,16 @@
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) {
@@ -560,7 +594,7 @@
const FunctionDecl *Callee, const LValue *This,
const CCValue *Arguments)
: Info(Info), Caller(Info.CurrentCall), CallLoc(CallLoc), Callee(Callee),
- This(This), Arguments(Arguments) {
+ Index(Info.NextCallIndex++), This(This), Arguments(Arguments) {
Info.CurrentCall = this;
++Info.CallStackDepth;
}
@@ -591,10 +625,11 @@
if (!Arg.isLValue() || Arg.getLValueDesignator().Invalid)
Arg.printPretty(Out, Frame->Info.Ctx, Param->getType());
else {
- // Deliberately slice off the frame to form an APValue we can print.
+ // Convert the CCValue to an APValue without checking for constantness.
APValue Value(Arg.getLValueBase(), Arg.getLValueOffset(),
Arg.getLValueDesignator().Entries,
- Arg.getLValueDesignator().IsOnePastTheEnd);
+ Arg.getLValueDesignator().IsOnePastTheEnd,
+ Arg.getLValueCallIndex());
Value.printPretty(Out, Frame->Info.Ctx, Param->getType());
}
@@ -679,31 +714,31 @@
struct LValue {
APValue::LValueBase Base;
CharUnits Offset;
- CallStackFrame *Frame;
+ unsigned CallIndex;
SubobjectDesignator Designator;
const APValue::LValueBase getLValueBase() const { return Base; }
CharUnits &getLValueOffset() { return Offset; }
const CharUnits &getLValueOffset() const { return Offset; }
- CallStackFrame *getLValueFrame() const { return Frame; }
+ unsigned getLValueCallIndex() const { return CallIndex; }
SubobjectDesignator &getLValueDesignator() { return Designator; }
const SubobjectDesignator &getLValueDesignator() const { return Designator;}
void moveInto(CCValue &V) const {
- V = CCValue(Base, Offset, Frame, Designator);
+ V = CCValue(Base, Offset, CallIndex, Designator);
}
void setFrom(const CCValue &V) {
assert(V.isLValue());
Base = V.getLValueBase();
Offset = V.getLValueOffset();
- Frame = V.getLValueFrame();
+ CallIndex = V.getLValueCallIndex();
Designator = V.getLValueDesignator();
}
- void set(APValue::LValueBase B, CallStackFrame *F = 0) {
+ void set(APValue::LValueBase B, unsigned I = 0) {
Base = B;
Offset = CharUnits::Zero();
- Frame = F;
+ CallIndex = I;
Designator = SubobjectDesignator(getType(B));
}
@@ -852,11 +887,10 @@
}
static bool Evaluate(CCValue &Result, EvalInfo &Info, const Expr *E);
-static bool EvaluateConstantExpression(APValue &Result, EvalInfo &Info,
- const LValue &This, const Expr *E,
- CheckConstantExpressionKind CCEK
- = CCEK_Constant,
- bool AllowNonLiteralTypes = false);
+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,
@@ -928,47 +962,43 @@
}
}
+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. Type T should be
/// either LValue or CCValue. Return true if we can fold this expression,
/// whether or not it's a constant expression.
-template<typename T>
-static bool CheckLValueConstantExpression(EvalInfo &Info, const Expr *E,
- const T &LVal, APValue &Value,
- CheckConstantExpressionKind CCEK) {
+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();
if (!IsGlobalLValue(Base)) {
if (Info.getLangOpts().CPlusPlus0x) {
const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
- Info.Diag(E->getExprLoc(), diag::note_constexpr_non_global, 1)
- << E->isGLValue() << !Designator.Entries.empty()
- << !!VD << CCEK << VD;
- if (VD)
- Info.Note(VD->getLocation(), diag::note_declared_at);
- else
- Info.Note(Base.dyn_cast<const Expr*>()->getExprLoc(),
- diag::note_constexpr_temporary_here);
+ Info.Diag(Loc, diag::note_constexpr_non_global, 1)
+ << IsReferenceType << !Designator.Entries.empty()
+ << !!VD << VD;
+ NoteLValueLocation(Info, Base);
} else {
- Info.Diag(E->getExprLoc());
+ Info.Diag(Loc);
}
// Don't allow references to temporaries to escape.
return false;
}
-
- bool IsReferenceType = E->isGLValue();
-
- if (Designator.Invalid) {
- // This is not a core constant expression. An appropriate diagnostic will
- // have already been produced.
- Value = APValue(LVal.getLValueBase(), LVal.getLValueOffset(),
- APValue::NoLValuePath());
- return true;
- }
-
- Value = APValue(LVal.getLValueBase(), LVal.getLValueOffset(),
- Designator.Entries, Designator.IsOnePastTheEnd);
+ 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.
@@ -978,20 +1008,16 @@
// A reference constant expression must refer to an object.
if (!Base) {
// FIXME: diagnostic
- Info.CCEDiag(E->getExprLoc());
+ 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(E->getExprLoc(), diag::note_constexpr_past_end, 1)
+ Info.Diag(Loc, diag::note_constexpr_past_end, 1)
<< !Designator.Entries.empty() << !!VD << VD;
- if (VD)
- Info.Note(VD->getLocation(), diag::note_declared_at);
- else
- Info.Note(Base.dyn_cast<const Expr*>()->getExprLoc(),
- diag::note_constexpr_temporary_here);
+ NoteLValueLocation(Info, Base);
}
return true;
@@ -1013,18 +1039,58 @@
}
/// Check that this core constant expression value is a valid value for a
-/// constant expression, and if it is, produce the corresponding constant value.
-/// If not, report an appropriate diagnostic. Does not check that the expression
-/// is of literal type.
-static bool CheckConstantExpression(EvalInfo &Info, const Expr *E,
- const CCValue &CCValue, APValue &Value,
- CheckConstantExpressionKind CCEK
- = CCEK_Constant) {
- if (!CCValue.isLValue()) {
- Value = CCValue;
- return true;
+/// 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());
}
- return CheckLValueConstantExpression(Info, E, CCValue, Value, CCEK);
+ 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()) {
+ CCValue Val(Info.Ctx, Value, CCValue::GlobalValue());
+ LValue LVal;
+ LVal.setFrom(Val);
+ return CheckLValueConstantExpression(Info, DiagLoc, Type, LVal);
+ }
+
+ // Everything else is fine.
+ return true;
}
const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
@@ -1032,7 +1098,7 @@
}
static bool IsLiteralLValue(const LValue &Value) {
- return Value.Base.dyn_cast<const Expr*>() && !Value.Frame;
+ return Value.Base.dyn_cast<const Expr*>() && !Value.CallIndex;
}
static bool IsWeakLValue(const LValue &Value) {
@@ -1583,7 +1649,6 @@
return false;
const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
- CallStackFrame *Frame = LVal.Frame;
SourceLocation Loc = Conv->getExprLoc();
if (!LVal.Base) {
@@ -1592,6 +1657,16 @@
return false;
}
+ CallStackFrame *Frame = 0;
+ if (LVal.CallIndex) {
+ Frame = Info.getCallFrame(LVal.CallIndex);
+ if (!Frame) {
+ Info.Diag(Loc, 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'
@@ -1680,7 +1755,17 @@
assert(RVal.getLValueOffset().isZero() &&
"offset for lvalue init of non-reference");
Base = RVal.getLValueBase().get<const Expr*>();
- Frame = RVal.getLValueFrame();
+
+ if (unsigned CallIndex = RVal.getLValueCallIndex()) {
+ Frame = Info.getCallFrame(CallIndex);
+ if (!Frame) {
+ Info.Diag(Loc, 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.
@@ -1896,7 +1981,7 @@
}
// Evaluate a statement.
-static EvalStmtResult EvaluateStmt(APValue &Result, EvalInfo &Info,
+static EvalStmtResult EvaluateStmt(CCValue &Result, EvalInfo &Info,
const Stmt *S) {
switch (S->getStmtClass()) {
default:
@@ -1907,11 +1992,8 @@
return ESR_Succeeded;
case Stmt::ReturnStmtClass: {
- CCValue CCResult;
const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
- if (!Evaluate(CCResult, Info, RetExpr) ||
- !CheckConstantExpression(Info, RetExpr, CCResult, Result,
- CCEK_ReturnValue))
+ if (!Evaluate(Result, Info, RetExpr))
return ESR_Failed;
return ESR_Returned;
}
@@ -2010,7 +2092,7 @@
static bool HandleFunctionCall(SourceLocation CallLoc,
const FunctionDecl *Callee, const LValue *This,
ArrayRef<const Expr*> Args, const Stmt *Body,
- EvalInfo &Info, APValue &Result) {
+ EvalInfo &Info, CCValue &Result) {
ArgVector ArgValues(Args.size());
if (!EvaluateArgs(Args, ArgValues, Info))
return false;
@@ -2045,7 +2127,7 @@
// If it's a delegating constructor, just delegate.
if (Definition->isDelegatingConstructor()) {
CXXConstructorDecl::init_const_iterator I = Definition->init_begin();
- return EvaluateConstantExpression(Result, Info, This, (*I)->getInit());
+ return EvaluateInPlace(Result, Info, This, (*I)->getInit());
}
// For a trivial copy or move constructor, perform an APValue copy. This is
@@ -2137,8 +2219,8 @@
llvm_unreachable("unknown base initializer kind");
}
- if (!EvaluateConstantExpression(*Value, Info, Subobject, (*I)->getInit(),
- (*I)->isBaseInitializer()
+ 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.
@@ -2488,14 +2570,14 @@
const FunctionDecl *Definition = 0;
Stmt *Body = FD->getBody(Definition);
- APValue Result;
+ CCValue Result;
if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition) ||
!HandleFunctionCall(E->getExprLoc(), Definition, This, Args, Body,
Info, Result))
return false;
- return DerivedSuccess(CCValue(Info.Ctx, Result, CCValue::GlobalValue()), E);
+ return DerivedSuccess(Result, E);
}
RetTy VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
@@ -2706,8 +2788,8 @@
// * BlockExpr
// * CallExpr for a MakeStringConstant builtin
// - Locals and temporaries
-// * Any Expr, with a Frame indicating the function in which the temporary was
-// evaluated.
+// * Any Expr, with a CallIndex indicating the function in which the temporary
+// was evaluated.
// plus an offset in bytes.
//===----------------------------------------------------------------------===//
namespace {
@@ -2777,7 +2859,7 @@
bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
if (!VD->getType()->isReferenceType()) {
if (isa<ParmVarDecl>(VD)) {
- Result.set(VD, Info.CurrentCall);
+ Result.set(VD, Info.CurrentCall->Index);
return true;
}
return Success(VD);
@@ -2795,9 +2877,9 @@
if (E->getType()->isRecordType())
return EvaluateTemporary(E->GetTemporaryExpr(), Result, Info);
- Result.set(E, Info.CurrentCall);
- return EvaluateConstantExpression(Info.CurrentCall->Temporaries[E], Info,
- Result, E->GetTemporaryExpr());
+ Result.set(E, Info.CurrentCall->Index);
+ return EvaluateInPlace(Info.CurrentCall->Temporaries[E], Info,
+ Result, E->GetTemporaryExpr());
}
// Materialization of an lvalue temporary occurs when we need to force a copy
@@ -2808,7 +2890,7 @@
if (!HandleLValueToRValueConversion(Info, E, E->getType(), Result,
Info.CurrentCall->Temporaries[E]))
return false;
- Result.set(E, Info.CurrentCall);
+ Result.set(E, Info.CurrentCall->Index);
return true;
}
@@ -3032,7 +3114,7 @@
uint64_t N = Value.getInt().extOrTrunc(Size).getZExtValue();
Result.Base = (Expr*)0;
Result.Offset = CharUnits::fromQuantity(N);
- Result.Frame = 0;
+ Result.CallIndex = 0;
Result.Designator.setInvalid();
return true;
} else {
@@ -3046,9 +3128,9 @@
if (!EvaluateLValue(SubExpr, Result, Info))
return false;
} else {
- Result.set(SubExpr, Info.CurrentCall);
- if (!EvaluateConstantExpression(Info.CurrentCall->Temporaries[SubExpr],
- Info, Result, SubExpr))
+ Result.set(SubExpr, Info.CurrentCall->Index);
+ if (!EvaluateInPlace(Info.CurrentCall->Temporaries[SubExpr],
+ Info, Result, SubExpr))
return false;
}
// The result is a pointer to the first element of the array.
@@ -3175,7 +3257,8 @@
: ExprEvaluatorBaseTy(info), This(This), Result(Result) {}
bool Success(const CCValue &V, const Expr *E) {
- return CheckConstantExpression(Info, E, V, Result);
+ Result = V;
+ return true;
}
bool ZeroInitialization(const Expr *E);
@@ -3225,7 +3308,7 @@
HandleLValueMember(Info, E, Subobject, *I, &Layout);
ImplicitValueInitExpr VIE((*I)->getType());
- if (!EvaluateConstantExpression(
+ if (!EvaluateInPlace(
Result.getStructField((*I)->getFieldIndex()), Info, Subobject, &VIE))
return false;
}
@@ -3248,8 +3331,7 @@
HandleLValueMember(Info, E, Subobject, *I);
Result = APValue(*I);
ImplicitValueInitExpr VIE((*I)->getType());
- return EvaluateConstantExpression(Result.getUnionValue(), Info,
- Subobject, &VIE);
+ return EvaluateInPlace(Result.getUnionValue(), Info, Subobject, &VIE);
}
return HandleClassZeroInitialization(Info, E, RD, This, Result);
@@ -3304,8 +3386,7 @@
LValue Subobject = This;
HandleLValueMember(Info, InitExpr, Subobject, Field, &Layout);
- return EvaluateConstantExpression(Result.getUnionValue(), Info,
- Subobject, InitExpr);
+ return EvaluateInPlace(Result.getUnionValue(), Info, Subobject, InitExpr);
}
assert((!isa<CXXRecordDecl>(RD) || !cast<CXXRecordDecl>(RD)->getNumBases()) &&
@@ -3334,7 +3415,7 @@
// the initializer list.
ImplicitValueInitExpr VIE(HaveInit ? Info.Ctx.IntTy : Field->getType());
- if (!EvaluateConstantExpression(
+ if (!EvaluateInPlace(
Result.getStructField((*Field)->getFieldIndex()),
Info, Subobject, HaveInit ? E->getInit(ElementNo++) : &VIE)) {
if (!Info.keepEvaluatingAfterFailure())
@@ -3410,9 +3491,8 @@
/// Visit an expression which constructs the value of this temporary.
bool VisitConstructExpr(const Expr *E) {
- Result.set(E, Info.CurrentCall);
- return EvaluateConstantExpression(Info.CurrentCall->Temporaries[E], Info,
- Result, E);
+ Result.set(E, Info.CurrentCall->Index);
+ return EvaluateInPlace(Info.CurrentCall->Temporaries[E], Info, Result, E);
}
bool VisitCastExpr(const CastExpr *E) {
@@ -3658,8 +3738,7 @@
LValue Subobject = This;
Subobject.addArray(Info, E, CAT);
ImplicitValueInitExpr VIE(CAT->getElementType());
- return EvaluateConstantExpression(Result.getArrayFiller(), Info,
- Subobject, &VIE);
+ return EvaluateInPlace(Result.getArrayFiller(), Info, Subobject, &VIE);
}
bool VisitInitListExpr(const InitListExpr *E);
@@ -3693,10 +3772,10 @@
for (uint64_t I = 0; I < NumElements; ++I) {
CCValue Char;
if (!HandleLValueToRValueConversion(Info, E->getInit(0),
- CAT->getElementType(), LV, Char) ||
- !CheckConstantExpression(Info, E->getInit(0), Char,
- Result.getArrayInitializedElt(I)) ||
- !HandleLValueArrayAdjustment(Info, E->getInit(0), LV,
+ CAT->getElementType(), LV, Char))
+ return false;
+ Result.getArrayInitializedElt(I) = Char.toAPValue();
+ if (!HandleLValueArrayAdjustment(Info, E->getInit(0), LV,
CAT->getElementType(), 1))
return false;
}
@@ -3712,8 +3791,8 @@
unsigned Index = 0;
for (InitListExpr::const_iterator I = E->begin(), End = E->end();
I != End; ++I, ++Index) {
- if (!EvaluateConstantExpression(Result.getArrayInitializedElt(Index),
- Info, Subobject, cast<Expr>(*I)) ||
+ if (!EvaluateInPlace(Result.getArrayInitializedElt(Index),
+ Info, Subobject, cast<Expr>(*I)) ||
!HandleLValueArrayAdjustment(Info, cast<Expr>(*I), Subobject,
CAT->getElementType(), 1)) {
if (!Info.keepEvaluatingAfterFailure())
@@ -3728,8 +3807,8 @@
// but sometimes does:
// struct S { constexpr S() : p(&p) {} void *p; };
// S s[10] = {};
- return EvaluateConstantExpression(Result.getArrayFiller(), Info,
- Subobject, E->getArrayFiller()) && Success;
+ return EvaluateInPlace(Result.getArrayFiller(), Info,
+ Subobject, E->getArrayFiller()) && Success;
}
bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E) {
@@ -3754,8 +3833,7 @@
LValue Subobject = This;
Subobject.addArray(Info, E, CAT);
ImplicitValueInitExpr VIE(CAT->getElementType());
- return EvaluateConstantExpression(Result.getArrayFiller(), Info,
- Subobject, &VIE);
+ return EvaluateInPlace(Result.getArrayFiller(), Info, Subobject, &VIE);
}
const CXXRecordDecl *RD = FD->getParent();
@@ -3783,8 +3861,7 @@
if (ZeroInit && !HadZeroInit) {
ImplicitValueInitExpr VIE(CAT->getElementType());
- if (!EvaluateConstantExpression(Result.getArrayFiller(), Info, Subobject,
- &VIE))
+ if (!EvaluateInPlace(Result.getArrayFiller(), Info, Subobject, &VIE))
return false;
}
@@ -4257,7 +4334,7 @@
}
return IsGlobalLValue(A.getLValueBase()) ||
- A.getLValueFrame() == B.getLValueFrame();
+ A.getLValueCallIndex() == B.getLValueCallIndex();
}
/// Perform the given integer operation, which is known to need at most BitWidth
@@ -5807,13 +5884,13 @@
return true;
} else if (E->getType()->isArrayType()) {
LValue LV;
- LV.set(E, Info.CurrentCall);
+ LV.set(E, Info.CurrentCall->Index);
if (!EvaluateArray(E, LV, Info.CurrentCall->Temporaries[E], Info))
return false;
Result = Info.CurrentCall->Temporaries[E];
} else if (E->getType()->isRecordType()) {
LValue LV;
- LV.set(E, Info.CurrentCall);
+ LV.set(E, Info.CurrentCall->Index);
if (!EvaluateRecord(E, LV, Info.CurrentCall->Temporaries[E], Info))
return false;
Result = Info.CurrentCall->Temporaries[E];
@@ -5836,14 +5913,12 @@
return true;
}
-/// EvaluateConstantExpression - Evaluate an expression as a constant expression
-/// in-place in an APValue. In some cases, the in-place evaluation is essential,
-/// since later initializers for an object can indirectly refer to subobjects
-/// which were initialized earlier.
-static bool EvaluateConstantExpression(APValue &Result, EvalInfo &Info,
- const LValue &This, const Expr *E,
- CheckConstantExpressionKind CCEK,
- bool AllowNonLiteralTypes) {
+/// EvaluateInPlace - Evaluate an expression in-place in an APValue. In some
+/// cases, the in-place evaluation is essential, since later initializers for
+/// an object can indirectly refer to subobjects which were initialized earlier.
+static bool EvaluateInPlace(APValue &Result, EvalInfo &Info, const LValue &This,
+ const Expr *E, CheckConstantExpressionKind CCEK,
+ bool AllowNonLiteralTypes) {
if (!AllowNonLiteralTypes && !CheckLiteralType(Info, E))
return false;
@@ -5858,8 +5933,10 @@
// For any other type, in-place evaluation is unimportant.
CCValue CoreConstResult;
- return Evaluate(CoreConstResult, Info, E) &&
- CheckConstantExpression(Info, E, CoreConstResult, Result, CCEK);
+ if (!Evaluate(CoreConstResult, Info, E))
+ return false;
+ Result = CoreConstResult.toAPValue();
+ return true;
}
/// EvaluateAsRValue - Try to evaluate this expression, performing an implicit
@@ -5881,7 +5958,8 @@
// Check this core constant expression is a constant expression, and if so,
// convert it to one.
- return CheckConstantExpression(Info, E, Value, Result);
+ Result = Value.toAPValue();
+ return CheckConstantExpression(Info, E->getExprLoc(), E->getType(), Result);
}
/// EvaluateAsRValue - Return true if this is a constant which we can fold using
@@ -5935,9 +6013,15 @@
EvalInfo Info(Ctx, Result);
LValue LV;
- return EvaluateLValue(this, LV, Info) && !Result.HasSideEffects &&
- CheckLValueConstantExpression(Info, this, LV, Result.Val,
- CCEK_Constant);
+ if (!EvaluateLValue(this, LV, Info) || Result.HasSideEffects ||
+ !CheckLValueConstantExpression(Info, getExprLoc(),
+ Ctx.getLValueReferenceType(getType()), LV))
+ return false;
+
+ CCValue Tmp;
+ LV.moveInto(Tmp);
+ Result.Val = Tmp.toAPValue();
+ return true;
}
bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
@@ -5965,14 +6049,18 @@
if (Ctx.getLangOptions().CPlusPlus && !VD->hasLocalStorage() &&
!VD->getType()->isReferenceType()) {
ImplicitValueInitExpr VIE(VD->getType());
- if (!EvaluateConstantExpression(Value, InitInfo, LVal, &VIE, CCEK_Constant,
- /*AllowNonLiteralTypes=*/true))
+ if (!EvaluateInPlace(Value, InitInfo, LVal, &VIE, CCEK_Constant,
+ /*AllowNonLiteralTypes=*/true))
return false;
}
- return EvaluateConstantExpression(Value, InitInfo, LVal, this, CCEK_Constant,
- /*AllowNonLiteralTypes=*/true) &&
- !EStatus.HasSideEffects;
+ if (!EvaluateInPlace(Value, InitInfo, LVal, this, CCEK_Constant,
+ /*AllowNonLiteralTypes=*/true) ||
+ EStatus.HasSideEffects)
+ return false;
+
+ return CheckConstantExpression(InitInfo, VD->getLocation(), VD->getType(),
+ Value);
}
/// isEvaluatable - Call EvaluateAsRValue to see if this expression can be
@@ -6499,18 +6587,20 @@
// is a temporary being used as the 'this' pointer.
LValue This;
ImplicitValueInitExpr VIE(RD ? Info.Ctx.getRecordType(RD) : Info.Ctx.IntTy);
- This.set(&VIE, Info.CurrentCall);
+ This.set(&VIE, Info.CurrentCall->Index);
- APValue Scratch;
ArrayRef<const Expr*> Args;
SourceLocation Loc = FD->getLocation();
if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD)) {
+ APValue Scratch;
HandleConstructorCall(Loc, This, Args, CD, Info, Scratch);
- } else
+ } else {
+ CCValue Scratch;
HandleFunctionCall(Loc, FD, (MD && MD->isInstance()) ? &This : 0,
Args, FD->getBody(), Info, Scratch);
+ }
return Diags.empty();
}
diff --git a/test/CXX/expr/expr.const/p2-0x.cpp b/test/CXX/expr/expr.const/p2-0x.cpp
index a22d1e4..8d3638f 100644
--- a/test/CXX/expr/expr.const/p2-0x.cpp
+++ b/test/CXX/expr/expr.const/p2-0x.cpp
@@ -49,25 +49,23 @@
};
// - an invocation of a constexpr function with arguments that, when substituted
-// by function invocation substitution (7.1.5), do not produce a constant
+// by function invocation substitution (7.1.5), do not produce a core constant
// expression;
namespace NonConstExprReturn {
static constexpr const int &id_ref(const int &n) {
- return n; // expected-note {{reference to temporary cannot be returned from a constexpr function}}
+ return n;
}
struct NonConstExprFunction {
- int n : id_ref( // expected-error {{constant expression}} expected-note {{in call to 'id_ref(16)'}}
- 16 // expected-note {{temporary created here}}
- );
+ int n : id_ref(16); // ok
};
constexpr const int *address_of(const int &a) {
- return &a; // expected-note {{pointer to 'n' cannot be returned from a constexpr function}}
+ return &a;
}
constexpr const int *return_param(int n) { // expected-note {{declared here}}
- return address_of(n); // expected-note {{in call to 'address_of(n)'}}
+ return address_of(n);
}
struct S {
- int n : *return_param(0); // expected-error {{constant expression}} expected-note {{in call to 'return_param(0)'}}
+ int n : *return_param(0); // expected-error {{constant expression}} expected-note {{read of variable whose lifetime has ended}}
};
}
@@ -78,16 +76,16 @@
namespace NonConstExprCtor {
struct T {
constexpr T(const int &r) :
- r(r) { // expected-note 2{{reference to temporary cannot be used to initialize a member in a constant expression}}
+ r(r) {
}
const int &r;
};
constexpr int n = 0;
constexpr T t1(n); // ok
- constexpr T t2(0); // expected-error {{must be initialized by a constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'T(0)'}}
+ constexpr T t2(0); // expected-error {{must be initialized by a constant expression}} expected-note {{temporary created here}} expected-note {{reference to temporary is not a constant expression}}
struct S {
- int n : T(4).r; // expected-error {{constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'T(4)'}}
+ int n : T(4).r; // ok
};
}
@@ -176,12 +174,12 @@
struct S {
int m;
};
- constexpr S s = { 5 }; // expected-note {{declared here}}
+ constexpr S s = { 5 };
constexpr const int *p = &s.m + 1;
constexpr const int &f(const int *q) {
- return q[0]; // expected-note {{dereferenced pointer past the end of subobject of 's' is not a constant expression}}
+ return q[0];
}
- constexpr int n = (f(p), 0); // expected-error {{constant expression}} expected-note {{in call to 'f(&s.m + 1)'}}
+ constexpr int n = (f(p), 0); // ok
struct T {
int n : f(p); // expected-error {{not an integral constant expression}} expected-note {{read of dereferenced one-past-the-end pointer}}
};
diff --git a/test/SemaCXX/constant-expression-cxx11.cpp b/test/SemaCXX/constant-expression-cxx11.cpp
index 58f36fd..aa40311 100644
--- a/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/test/SemaCXX/constant-expression-cxx11.cpp
@@ -190,26 +190,21 @@
namespace ParameterScopes {
const int k = 42;
- constexpr const int &ObscureTheTruth(const int &a) { return a; } // expected-note 3{{reference to 'a' cannot be returned from a constexpr function}}
+ constexpr const int &ObscureTheTruth(const int &a) { return a; }
constexpr const int &MaybeReturnJunk(bool b, const int a) { // expected-note 2{{declared here}}
- return ObscureTheTruth(b ? a : k); // expected-note 2{{in call to 'ObscureTheTruth(a)'}}
+ return ObscureTheTruth(b ? a : k);
}
static_assert(MaybeReturnJunk(false, 0) == 42, ""); // ok
- constexpr int a = MaybeReturnJunk(true, 0); // expected-error {{constant expression}} expected-note {{in call to 'MaybeReturnJunk(1, 0)'}}
+ constexpr int a = MaybeReturnJunk(true, 0); // expected-error {{constant expression}} expected-note {{read of variable whose lifetime has ended}}
- constexpr const int MaybeReturnNonstaticRef(bool b, const int a) { // expected-note {{here}}
- // If ObscureTheTruth returns a reference to 'a', the result is not a
- // constant expression even though 'a' is still in scope.
- return ObscureTheTruth(b ? a : k); // expected-note {{in call to 'ObscureTheTruth(a)'}}
+ constexpr const int MaybeReturnNonstaticRef(bool b, const int a) {
+ return ObscureTheTruth(b ? a : k);
}
static_assert(MaybeReturnNonstaticRef(false, 0) == 42, ""); // ok
- constexpr int b = MaybeReturnNonstaticRef(true, 0); // expected-error {{constant expression}} expected-note {{in call to 'MaybeReturnNonstaticRef(1, 0)'}}
+ constexpr int b = MaybeReturnNonstaticRef(true, 0); // ok
constexpr int InternalReturnJunk(int n) {
- // TODO: We could reject this: it never produces a constant expression.
- // However, we currently don't evaluate function calls while testing for
- // potential constant expressions, for performance.
- return MaybeReturnJunk(true, n); // expected-note {{in call to 'MaybeReturnJunk(1, 0)'}}
+ return MaybeReturnJunk(true, n); // expected-note {{read of variable whose lifetime has ended}}
}
constexpr int n3 = InternalReturnJunk(0); // expected-error {{must be initialized by a constant expression}} expected-note {{in call to 'InternalReturnJunk(0)'}}
@@ -528,10 +523,10 @@
static_assert(D().c.n == 42, "");
struct E {
- constexpr E() : p(&p) {} // expected-note {{pointer to subobject of temporary cannot be used to initialize a member in a constant expression}}
+ constexpr E() : p(&p) {}
void *p;
};
-constexpr const E &e1 = E(); // expected-error {{constant expression}} expected-note {{in call to 'E()'}} expected-note {{temporary created here}}
+constexpr const E &e1 = E(); // expected-error {{constant expression}} expected-note {{reference to temporary is not a constant expression}} expected-note {{temporary created here}}
// This is a constant expression if we elide the copy constructor call, and
// is not a constant expression if we don't! But we do, so it is.
constexpr E e2 = E();
@@ -1158,3 +1153,19 @@
#undef fold
}
+
+namespace DR1454 {
+
+constexpr const int &f(const int &n) { return n; }
+constexpr int k1 = f(0); // ok
+
+struct Wrap {
+ const int &value;
+};
+constexpr const Wrap &g(const Wrap &w) { return w; }
+constexpr int k2 = g({0}).value; // ok
+
+constexpr const int &i = 0; // expected-error {{constant expression}} expected-note {{temporary}} expected-note 2{{here}}
+constexpr const int j = i; // expected-error {{constant expression}} expected-note {{initializer of 'i' is not a constant expression}}
+
+}
diff --git a/test/SemaCXX/constexpr-turing.cpp b/test/SemaCXX/constexpr-turing.cpp
new file mode 100644
index 0000000..c515378
--- /dev/null
+++ b/test/SemaCXX/constexpr-turing.cpp
@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -verify -std=c++11 %s
+
+// A direct proof that constexpr is Turing-complete, once DR1454 is implemented.
+
+const unsigned halt = (unsigned)-1;
+
+enum Dir { L, R };
+struct Action {
+ bool tape;
+ Dir dir;
+ unsigned next;
+};
+using State = Action[2];
+
+// An infinite tape!
+struct Tape {
+ constexpr Tape() : l(0), val(false), r(0) {}
+ constexpr Tape(const Tape &old, bool write) :
+ l(old.l), val(write), r(old.r) {}
+ constexpr Tape(const Tape &old, Dir dir) :
+ l(dir == L ? old.l ? old.l->l : 0 : &old),
+ val(dir == L ? old.l ? old.l->val : false
+ : old.r ? old.r->val : false),
+ r(dir == R ? old.r ? old.r->r : 0 : &old) {}
+ const Tape *l;
+ bool val;
+ const Tape *r;
+};
+constexpr Tape update(const Tape &old, bool write) { return Tape(old, write); }
+constexpr Tape move(const Tape &old, Dir dir) { return Tape(old, dir); }
+
+// Run turing machine 'tm' on tape 'tape' from state 'state'. Return number of
+// steps taken until halt.
+constexpr unsigned run(const State *tm, const Tape &tape, unsigned state) {
+ return state == halt ? 1 :
+ run(tm, move(update(tape, tm[state][tape.val].tape),
+ tm[state][tape.val].dir),
+ tm[state][tape.val].next) + 1;
+}
+
+// 3-state busy beaver. 14 steps.
+constexpr State bb3[] = {
+ { { true, R, 1 }, { true, L, 2 } },
+ { { true, L, 0 }, { true, R, 1 } },
+ { { true, L, 1 }, { true, R, halt } }
+};
+static_assert(run(bb3, Tape(), 0) == 14, "");
+
+// 4-state busy beaver. 108 steps.
+constexpr State bb4[] = {
+ { { true, R, 1 }, { true, L, 1 } },
+ { { true, L, 0 }, { false, L, 2 } },
+ { { true, R, halt }, { true, L, 3 } },
+ { { true, R, 3 }, { false, R, 0 } } };
+static_assert(run(bb4, Tape(), 0) == 108, "");
