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[Cxx1z] Implement Lambda Capture of *this by Value as [=,*this] (P0018R3) 

Implement lambda capture of *this by copy.
For e.g.:
struct A {

  int d = 10;
  auto foo() { return [*this] (auto a) mutable { d+=a; return d; }; }

};

auto L = A{}.foo(); // A{}'s lifetime is gone.

// Below is still ok, because *this was captured by value.
assert(L(10) == 20);
assert(L(100) == 120);

If the capture was implicit, or [this] (i.e. *this was captured by reference), this code would be otherwise undefined.

Implementation Strategy:
  - amend the parser to accept *this in the lambda introducer
  - add a new king of capture LCK_StarThis
  - teach Sema::CheckCXXThisCapture to handle by copy captures of the
    enclosing object (i.e. *this)
  - when CheckCXXThisCapture does capture by copy, the corresponding 
    initializer expression for the closure's data member 
    direct-initializes it thus making a copy of '*this'.
  - in codegen, when assigning to CXXThisValue, if *this was captured by 
    copy, make sure it points to the corresponding field member, and
    not, unlike when captured by reference, what the field member points
    to.
  - mark feature as implemented in svn

Much gratitude to Richard Smith for his carefully illuminating reviews!   

llvm-svn: 263921
This commit is contained in:
Faisal Vali 2016-03-21 09:25:37 +00:00
parent 2c8b5993be
commit dc6b596ebb
22 changed files with 379 additions and 88 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
clang/include/clang/AST/LambdaCapture.h
View File

@ -35,8 +35,18 @@ class LambdaCapture {
/// This includes the case of a non-reference init-capture.
Capture_ByCopy = 0x02
};
struct LLVM_ALIGNAS(4) OpaqueCapturedEntity {};
static OpaqueCapturedEntity ThisSentinel;
static OpaqueCapturedEntity VLASentinel;
// Captured Entity could represent:
// - a VarDecl* that represents the variable that was captured or the
// init-capture.
// - or, points to the ThisSentinel if this represents a capture of '*this'
// by value or reference.
// - or, points to the VLASentinel if this represents a capture of a VLA type.
llvm::PointerIntPair<void*, 2> CapturedEntityAndBits;
llvm::PointerIntPair<Decl *, 2> DeclAndBits;
SourceLocation Loc;
SourceLocation EllipsisLoc;
@ -69,20 +79,21 @@ public:
/// \brief Determine whether this capture handles the C++ \c this
/// pointer.
bool capturesThis() const {
return (DeclAndBits.getPointer() == nullptr) &&
!(DeclAndBits.getInt() & Capture_ByCopy);
return CapturedEntityAndBits.getPointer() == &ThisSentinel;
}
/// \brief Determine whether this capture handles a variable.
bool capturesVariable() const {
return dyn_cast_or_null<VarDecl>(DeclAndBits.getPointer());
void *Ptr = CapturedEntityAndBits.getPointer();
if (Ptr != &ThisSentinel && Ptr != &VLASentinel)
return dyn_cast_or_null<VarDecl>(static_cast<Decl *>(Ptr));
return false;
}
/// \brief Determine whether this captures a variable length array bound
/// expression.
bool capturesVLAType() const {
return (DeclAndBits.getPointer() == nullptr) &&
(DeclAndBits.getInt() & Capture_ByCopy);
return CapturedEntityAndBits.getPointer() == &VLASentinel;
}
/// \brief Retrieve the declaration of the local variable being
@ -91,13 +102,15 @@ public:
/// This operation is only valid if this capture is a variable capture
/// (other than a capture of \c this).
VarDecl *getCapturedVar() const {
assert(capturesVariable() && "No variable available for 'this' capture");
return cast<VarDecl>(DeclAndBits.getPointer());
assert(capturesVariable() && "No variable available for capture");
return static_cast<VarDecl *>(CapturedEntityAndBits.getPointer());
}
/// \brief Determine whether this was an implicit capture (not
/// written between the square brackets introducing the lambda).
bool isImplicit() const { return DeclAndBits.getInt() & Capture_Implicit; }
bool isImplicit() const {
return CapturedEntityAndBits.getInt() & Capture_Implicit;
}
/// \brief Determine whether this was an explicit capture (written
/// between the square brackets introducing the lambda).

3
clang/include/clang/Basic/DiagnosticParseKinds.td
View File

@ -766,6 +766,9 @@ def warn_cxx98_compat_lambda : Warning<
def err_lambda_missing_parens : Error<
"lambda requires '()' before %select{'mutable'|return type|"
"attribute specifier}0">;
// C++1z lambda expressions
def err_expected_star_this_capture : Error<
"expected 'this' following '*' in lambda capture list">;
// Availability attribute
def err_expected_version : Error<

7
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -5991,6 +5991,13 @@ let CategoryName = "Lambda Issue" in {
"cannot deduce type for lambda capture %0 from initializer of type %2">;
def err_init_capture_deduction_failure_from_init_list : Error<
"cannot deduce type for lambda capture %0 from initializer list">;
// C++1z '*this' captures.
def warn_cxx14_compat_star_this_lambda_capture : Warning<
"by value capture of '*this' is incompatible with C++ standards before C++1z">,
InGroup<CXXPre1zCompat>, DefaultIgnore;
def ext_star_this_lambda_capture_cxx1z : ExtWarn<
"capture of '*this' by copy is a C++1z extension">, InGroup<CXX1z>;
}
def err_return_in_captured_stmt : Error<

3
clang/include/clang/Basic/Lambda.h
View File

@ -32,7 +32,8 @@ enum LambdaCaptureDefault {
/// by reference. C++1y also allows "init-capture", where the initializer
/// is an expression.
enum LambdaCaptureKind {
LCK_This, ///< Capturing the \c this pointer
LCK_This, ///< Capturing the \c *this object by reference
LCK_StarThis, /// < Capturing the \c *this object by copy
LCK_ByCopy, ///< Capturing by copy (a.k.a., by value)
LCK_ByRef, ///< Capturing by reference
LCK_VLAType ///< Capturing variable-length array type

51
clang/include/clang/Sema/ScopeInfo.h
View File

@ -420,18 +420,20 @@ public:
// variables of reference type are captured by reference, and other
// variables are captured by copy.
enum CaptureKind {
Cap_ByCopy, Cap_ByRef, Cap_Block, Cap_This
Cap_ByCopy, Cap_ByRef, Cap_Block, Cap_VLA
};
/// The variable being captured (if we are not capturing 'this') and whether
/// this is a nested capture.
llvm::PointerIntPair<VarDecl*, 1, bool> VarAndNested;
/// Expression to initialize a field of the given type, and the kind of
/// capture (if this is a capture and not an init-capture). The expression
/// is only required if we are capturing ByVal and the variable's type has
/// a non-trivial copy constructor.
llvm::PointerIntPair<void *, 2, CaptureKind> InitExprAndCaptureKind;
enum {
IsNestedCapture = 0x1,
IsThisCaptured = 0x2
};
/// The variable being captured (if we are not capturing 'this') and whether
/// this is a nested capture, and whether we are capturing 'this'
llvm::PointerIntPair<VarDecl*, 2> VarAndNestedAndThis;
/// \brief The source location at which the first capture occurred.
SourceLocation Loc;
@ -447,27 +449,28 @@ public:
Capture(VarDecl *Var, bool Block, bool ByRef, bool IsNested,
SourceLocation Loc, SourceLocation EllipsisLoc,
QualType CaptureType, Expr *Cpy)
: VarAndNested(Var, IsNested),
InitExprAndCaptureKind(Cpy, Block ? Cap_Block :
ByRef ? Cap_ByRef : Cap_ByCopy),
: VarAndNestedAndThis(Var, IsNested ? IsNestedCapture : 0),
InitExprAndCaptureKind(
Cpy, !Var ? Cap_VLA : Block ? Cap_Block : ByRef ? Cap_ByRef
: Cap_ByCopy),
Loc(Loc), EllipsisLoc(EllipsisLoc), CaptureType(CaptureType) {}
enum IsThisCapture { ThisCapture };
Capture(IsThisCapture, bool IsNested, SourceLocation Loc,
QualType CaptureType, Expr *Cpy)
: VarAndNested(nullptr, IsNested),
InitExprAndCaptureKind(Cpy, Cap_This),
QualType CaptureType, Expr *Cpy, const bool ByCopy)
: VarAndNestedAndThis(
nullptr, (IsThisCaptured | (IsNested ? IsNestedCapture : 0))),
InitExprAndCaptureKind(Cpy, ByCopy ? Cap_ByCopy : Cap_ByRef),
Loc(Loc), EllipsisLoc(), CaptureType(CaptureType) {}
bool isThisCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_This;
return VarAndNestedAndThis.getInt() & IsThisCaptured;
}
bool isVariableCapture() const {
return InitExprAndCaptureKind.getInt() != Cap_This && !isVLATypeCapture();
return !isThisCapture() && !isVLATypeCapture();
}
bool isCopyCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_ByCopy &&
!isVLATypeCapture();
return InitExprAndCaptureKind.getInt() == Cap_ByCopy;
}
bool isReferenceCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_ByRef;
@ -476,13 +479,14 @@ public:
return InitExprAndCaptureKind.getInt() == Cap_Block;
}
bool isVLATypeCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_ByCopy &&
getVariable() == nullptr;
return InitExprAndCaptureKind.getInt() == Cap_VLA;
}
bool isNested() const {
return VarAndNestedAndThis.getInt() & IsNestedCapture;
}
bool isNested() const { return VarAndNested.getInt(); }
VarDecl *getVariable() const {
return VarAndNested.getPointer();
return VarAndNestedAndThis.getPointer();
}
/// \brief Retrieve the location at which this variable was captured.
@ -542,7 +546,7 @@ public:
}
void addThisCapture(bool isNested, SourceLocation Loc, QualType CaptureType,
Expr *Cpy);
Expr *Cpy, bool ByCopy);
/// \brief Determine whether the C++ 'this' is captured.
bool isCXXThisCaptured() const { return CXXThisCaptureIndex != 0; }
@ -862,9 +866,10 @@ void FunctionScopeInfo::recordUseOfWeak(const ExprT *E, bool IsRead) {
inline void
CapturingScopeInfo::addThisCapture(bool isNested, SourceLocation Loc,
QualType CaptureType, Expr *Cpy) {
QualType CaptureType, Expr *Cpy,
const bool ByCopy) {
Captures.push_back(Capture(Capture::ThisCapture, isNested, Loc, CaptureType,
Cpy));
Cpy, ByCopy));
CXXThisCaptureIndex = Captures.size();
}

3
clang/include/clang/Sema/Sema.h
View File

@ -4623,7 +4623,8 @@ public:
/// \return returns 'true' if failed, 'false' if success.
bool CheckCXXThisCapture(SourceLocation Loc, bool Explicit = false,
bool BuildAndDiagnose = true,
const unsigned *const FunctionScopeIndexToStopAt = nullptr);
const unsigned *const FunctionScopeIndexToStopAt = nullptr,
bool ByCopy = false);
/// \brief Determine whether the given type is the type of *this that is used
/// outside of the body of a member function for a type that is currently

25
clang/lib/AST/ExprCXX.cpp
View File

@ -879,18 +879,25 @@ CXXConstructExpr::CXXConstructExpr(const ASTContext &C, StmtClass SC,
}
}
LambdaCapture::OpaqueCapturedEntity LambdaCapture::ThisSentinel;
LambdaCapture::OpaqueCapturedEntity LambdaCapture::VLASentinel;
LambdaCapture::LambdaCapture(SourceLocation Loc, bool Implicit,
LambdaCaptureKind Kind, VarDecl *Var,
SourceLocation EllipsisLoc)
: DeclAndBits(Var, 0), Loc(Loc), EllipsisLoc(EllipsisLoc)
: CapturedEntityAndBits(Var, 0), Loc(Loc), EllipsisLoc(EllipsisLoc)
{
unsigned Bits = 0;
if (Implicit)
Bits |= Capture_Implicit;
switch (Kind) {
case LCK_StarThis:
Bits |= Capture_ByCopy;
// Fall through
case LCK_This:
assert(!Var && "'this' capture cannot have a variable!");
CapturedEntityAndBits.setPointer(&ThisSentinel);
break;
case LCK_ByCopy:
@ -901,18 +908,20 @@ LambdaCapture::LambdaCapture(SourceLocation Loc, bool Implicit,
break;
case LCK_VLAType:
assert(!Var && "VLA type capture cannot have a variable!");
Bits |= Capture_ByCopy;
CapturedEntityAndBits.setPointer(&VLASentinel);
break;
}
DeclAndBits.setInt(Bits);
CapturedEntityAndBits.setInt(Bits);
}
LambdaCaptureKind LambdaCapture::getCaptureKind() const {
Decl *D = DeclAndBits.getPointer();
bool CapByCopy = DeclAndBits.getInt() & Capture_ByCopy;
if (!D)
return CapByCopy ? LCK_VLAType : LCK_This;
void *Ptr = CapturedEntityAndBits.getPointer();
if (Ptr == &VLASentinel)
return LCK_VLAType;
const unsigned Bits = CapturedEntityAndBits.getInt();
bool CapByCopy = Bits & Capture_ByCopy;
if (Ptr == &ThisSentinel)
return CapByCopy ? LCK_StarThis : LCK_This;
return CapByCopy ? LCK_ByCopy : LCK_ByRef;
}

4
clang/lib/AST/StmtPrinter.cpp
View File

@ -2008,7 +2008,9 @@ void StmtPrinter::VisitLambdaExpr(LambdaExpr *Node) {
case LCK_This:
OS << "this";
break;
case LCK_StarThis:
OS << "*this";
break;
case LCK_ByRef:
if (Node->getCaptureDefault() != LCD_ByRef || Node->isInitCapture(C))
OS << '&';

1
clang/lib/AST/StmtProfile.cpp
View File

@ -1258,6 +1258,7 @@ StmtProfiler::VisitLambdaExpr(const LambdaExpr *S) {
C != CEnd; ++C) {
ID.AddInteger(C->getCaptureKind());
switch (C->getCaptureKind()) {
case LCK_StarThis:
case LCK_This:
break;
case LCK_ByRef:

20
clang/lib/CodeGen/CodeGenFunction.cpp
View File

@ -823,10 +823,22 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
MD->getParent()->getCaptureFields(LambdaCaptureFields,
LambdaThisCaptureField);
if (LambdaThisCaptureField) {
// If this lambda captures this, load it.
LValue ThisLValue = EmitLValueForLambdaField(LambdaThisCaptureField);
CXXThisValue = EmitLoadOfLValue(ThisLValue,
SourceLocation()).getScalarVal();
// If the lambda captures the object referred to by '*this' - either by
// value or by reference, make sure CXXThisValue points to the correct
// object.
// Get the lvalue for the field (which is a copy of the enclosing object
// or contains the address of the enclosing object).
LValue ThisFieldLValue = EmitLValueForLambdaField(LambdaThisCaptureField);
if (!LambdaThisCaptureField->getType()->isPointerType()) {
// If the enclosing object was captured by value, just use its address.
CXXThisValue = ThisFieldLValue.getAddress().getPointer();
} else {
// Load the lvalue pointed to by the field, since '*this' was captured
// by reference.
CXXThisValue =
EmitLoadOfLValue(ThisFieldLValue, SourceLocation()).getScalarVal();
}
}
for (auto *FD : MD->getParent()->fields()) {
if (FD->hasCapturedVLAType()) {

12
clang/lib/Parse/ParseExprCXX.cpp
View File

@ -846,8 +846,16 @@ Optional<unsigned> Parser::ParseLambdaIntroducer(LambdaIntroducer &Intro,
IdentifierInfo *Id = nullptr;
SourceLocation EllipsisLoc;
ExprResult Init;
if (Tok.is(tok::kw_this)) {
if (Tok.is(tok::star)) {
Loc = ConsumeToken();
if (Tok.is(tok::kw_this)) {
ConsumeToken();
Kind = LCK_StarThis;
} else {
return DiagResult(diag::err_expected_star_this_capture);
}
} else if (Tok.is(tok::kw_this)) {
Kind = LCK_This;
Loc = ConsumeToken();
} else {

3
clang/lib/Sema/SemaDecl.cpp
View File

@ -11010,7 +11010,8 @@ static void RebuildLambdaScopeInfo(CXXMethodDecl *CallOperator,
} else if (C.capturesThis()) {
LSI->addThisCapture(/*Nested*/ false, C.getLocation(),
S.getCurrentThisType(), /*Expr*/ nullptr);
S.getCurrentThisType(), /*Expr*/ nullptr,
C.getCaptureKind() == LCK_StarThis);
} else {
LSI->addVLATypeCapture(C.getLocation(), I->getType());
}

1
clang/lib/Sema/SemaExpr.cpp
View File

@ -13249,6 +13249,7 @@ static bool captureInCapturedRegion(CapturedRegionScopeInfo *RSI,
/// \brief Create a field within the lambda class for the variable
/// being captured.
// FIXME: Delete VarDecl *Var below, it is not used in the function.
static void addAsFieldToClosureType(Sema &S, LambdaScopeInfo *LSI, VarDecl *Var,
QualType FieldType, QualType DeclRefType,
SourceLocation Loc,

142
clang/lib/Sema/SemaExprCXX.cpp
View File

@ -845,11 +845,34 @@ QualType Sema::getCurrentThisType() {
// within a default initializer - so use the enclosing class as 'this'.
// There is no enclosing member function to retrieve the 'this' pointer
// from.
// FIXME: This looks wrong. If we're in a lambda within a lambda within a
// default member initializer, we need to recurse up more parents to find
// the right context. Looks like we should be walking up to the parent of
// the closure type, checking whether that is itself a lambda, and if so,
// recursing, until we reach a class or a function that isn't a lambda
// call operator. And we should accumulate the constness of *this on the
// way.
QualType ClassTy = Context.getTypeDeclType(
cast<CXXRecordDecl>(CurContext->getParent()->getParent()));
// There are no cv-qualifiers for 'this' within default initializers,
// per [expr.prim.general]p4.
return Context.getPointerType(ClassTy);
ThisTy = Context.getPointerType(ClassTy);
}
}
// Add const for '* this' capture if not mutable.
if (isLambdaCallOperator(CurContext)) {
LambdaScopeInfo *LSI = getCurLambda();
assert(LSI);
if (LSI->isCXXThisCaptured()) {
auto C = LSI->getCXXThisCapture();
QualType BaseType = ThisTy->getPointeeType();
if ((C.isThisCapture() && C.isCopyCapture()) &&
LSI->CallOperator->isConst() && !BaseType.isConstQualified()) {
BaseType.addConst();
ThisTy = Context.getPointerType(BaseType);
}
}
}
return ThisTy;
@ -884,28 +907,70 @@ Sema::CXXThisScopeRAII::~CXXThisScopeRAII() {
}
}
static Expr *captureThis(ASTContext &Context, RecordDecl *RD,
QualType ThisTy, SourceLocation Loc) {
static Expr *captureThis(Sema &S, ASTContext &Context, RecordDecl *RD,
QualType ThisTy, SourceLocation Loc,
const bool ByCopy) {
QualType CaptureThisTy = ByCopy ? ThisTy->getPointeeType() : ThisTy;
FieldDecl *Field
= FieldDecl::Create(Context, RD, Loc, Loc, nullptr, ThisTy,
Context.getTrivialTypeSourceInfo(ThisTy, Loc),
= FieldDecl::Create(Context, RD, Loc, Loc, nullptr, CaptureThisTy,
Context.getTrivialTypeSourceInfo(CaptureThisTy, Loc),
nullptr, false, ICIS_NoInit);
Field->setImplicit(true);
Field->setAccess(AS_private);
RD->addDecl(Field);
return new (Context) CXXThisExpr(Loc, ThisTy, /*isImplicit*/true);
Expr *This = new (Context) CXXThisExpr(Loc, ThisTy, /*isImplicit*/true);
if (ByCopy) {
Expr *StarThis = S.CreateBuiltinUnaryOp(Loc,
UO_Deref,
This).get();
InitializedEntity Entity = InitializedEntity::InitializeLambdaCapture(
nullptr, CaptureThisTy, Loc);
InitializationKind InitKind = InitializationKind::CreateDirect(Loc, Loc, Loc);
InitializationSequence Init(S, Entity, InitKind, StarThis);
ExprResult ER = Init.Perform(S, Entity, InitKind, StarThis);
if (ER.isInvalid()) return nullptr;
return ER.get();
}
return This;
}
bool Sema::CheckCXXThisCapture(SourceLocation Loc, bool Explicit,
bool BuildAndDiagnose, const unsigned *const FunctionScopeIndexToStopAt) {
bool Sema::CheckCXXThisCapture(SourceLocation Loc, const bool Explicit,
bool BuildAndDiagnose, const unsigned *const FunctionScopeIndexToStopAt,
const bool ByCopy) {
// We don't need to capture this in an unevaluated context.
if (isUnevaluatedContext() && !Explicit)
return true;
assert((!ByCopy || Explicit) && "cannot implicitly capture *this by value");
const unsigned MaxFunctionScopesIndex = FunctionScopeIndexToStopAt ?
*FunctionScopeIndexToStopAt : FunctionScopes.size() - 1;
// Otherwise, check that we can capture 'this'.
unsigned NumClosures = 0;
*FunctionScopeIndexToStopAt : FunctionScopes.size() - 1;
// Check that we can capture the *enclosing object* (referred to by '*this')
// by the capturing-entity/closure (lambda/block/etc) at
// MaxFunctionScopesIndex-deep on the FunctionScopes stack.
// Note: The *enclosing object* can only be captured by-value by a
// closure that is a lambda, using the explicit notation:
// [*this] { ... }.
// Every other capture of the *enclosing object* results in its by-reference
// capture.
// For a closure 'L' (at MaxFunctionScopesIndex in the FunctionScopes
// stack), we can capture the *enclosing object* only if:
// - 'L' has an explicit byref or byval capture of the *enclosing object*
// - or, 'L' has an implicit capture.
// AND
// -- there is no enclosing closure
// -- or, there is some enclosing closure 'E' that has already captured the
// *enclosing object*, and every intervening closure (if any) between 'E'
// and 'L' can implicitly capture the *enclosing object*.
// -- or, every enclosing closure can implicitly capture the
// *enclosing object*
unsigned NumCapturingClosures = 0;
for (unsigned idx = MaxFunctionScopesIndex; idx != 0; idx--) {
if (CapturingScopeInfo *CSI =
dyn_cast<CapturingScopeInfo>(FunctionScopes[idx])) {
@ -917,44 +982,69 @@ bool Sema::CheckCXXThisCapture(SourceLocation Loc, bool Explicit,
if (LSI && isGenericLambdaCallOperatorSpecialization(LSI->CallOperator)) {
// This context can't implicitly capture 'this'; fail out.
if (BuildAndDiagnose)
Diag(Loc, diag::err_this_capture) << Explicit;
Diag(Loc, diag::err_this_capture)
<< (Explicit && idx == MaxFunctionScopesIndex);
return true;
}
if (CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_LambdaByref ||
CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_LambdaByval ||
CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_Block ||
CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_CapturedRegion ||
Explicit) {
(Explicit && idx == MaxFunctionScopesIndex)) {
// Regarding (Explicit && idx == MaxFunctionScopesIndex): only the first
// iteration through can be an explicit capture, all enclosing closures,
// if any, must perform implicit captures.
// This closure can capture 'this'; continue looking upwards.
NumClosures++;
Explicit = false;
NumCapturingClosures++;
continue;
}
// This context can't implicitly capture 'this'; fail out.
if (BuildAndDiagnose)
Diag(Loc, diag::err_this_capture) << Explicit;
Diag(Loc, diag::err_this_capture)
<< (Explicit && idx == MaxFunctionScopesIndex);
return true;
}
break;
}
if (!BuildAndDiagnose) return false;
// Mark that we're implicitly capturing 'this' in all the scopes we skipped.
// If we got here, then the closure at MaxFunctionScopesIndex on the
// FunctionScopes stack, can capture the *enclosing object*, so capture it
// (including implicit by-reference captures in any enclosing closures).
// In the loop below, respect the ByCopy flag only for the closure requesting
// the capture (i.e. first iteration through the loop below). Ignore it for
// all enclosing closure's upto NumCapturingClosures (since they must be
// implicitly capturing the *enclosing object* by reference (see loop
// above)).
assert((!ByCopy ||
dyn_cast<LambdaScopeInfo>(FunctionScopes[MaxFunctionScopesIndex])) &&
"Only a lambda can capture the enclosing object (referred to by "
"*this) by copy");
// FIXME: We need to delay this marking in PotentiallyPotentiallyEvaluated
// contexts.
for (unsigned idx = MaxFunctionScopesIndex; NumClosures;
--idx, --NumClosures) {
for (unsigned idx = MaxFunctionScopesIndex; NumCapturingClosures;
--idx, --NumCapturingClosures) {
CapturingScopeInfo *CSI = cast<CapturingScopeInfo>(FunctionScopes[idx]);
Expr *ThisExpr = nullptr;
QualType ThisTy = getCurrentThisType();
if (LambdaScopeInfo *LSI = dyn_cast<LambdaScopeInfo>(CSI))
// For lambda expressions, build a field and an initializing expression.
ThisExpr = captureThis(Context, LSI->Lambda, ThisTy, Loc);
else if (CapturedRegionScopeInfo *RSI
if (LambdaScopeInfo *LSI = dyn_cast<LambdaScopeInfo>(CSI)) {
// For lambda expressions, build a field and an initializing expression,
// and capture the *enclosing object* by copy only if this is the first
// iteration.
ThisExpr = captureThis(*this, Context, LSI->Lambda, ThisTy, Loc,
ByCopy && idx == MaxFunctionScopesIndex);
} else if (CapturedRegionScopeInfo *RSI
= dyn_cast<CapturedRegionScopeInfo>(FunctionScopes[idx]))
ThisExpr = captureThis(Context, RSI->TheRecordDecl, ThisTy, Loc);
ThisExpr =
captureThis(*this, Context, RSI->TheRecordDecl, ThisTy, Loc,
false/*ByCopy*/);
bool isNested = NumClosures > 1;
CSI->addThisCapture(isNested, Loc, ThisTy, ThisExpr);
bool isNested = NumCapturingClosures > 1;
CSI->addThisCapture(isNested, Loc, ThisTy, ThisExpr, ByCopy);
}
return false;
}

28
clang/lib/Sema/SemaLambda.cpp
View File

@ -924,7 +924,12 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
= Intro.Default == LCD_None? Intro.Range.getBegin() : Intro.DefaultLoc;
for (auto C = Intro.Captures.begin(), E = Intro.Captures.end(); C != E;
PrevCaptureLoc = C->Loc, ++C) {
if (C->Kind == LCK_This) {
if (C->Kind == LCK_This || C->Kind == LCK_StarThis) {
if (C->Kind == LCK_StarThis)
Diag(C->Loc, !getLangOpts().CPlusPlus1z
? diag::ext_star_this_lambda_capture_cxx1z
: diag::warn_cxx14_compat_star_this_lambda_capture);
// C++11 [expr.prim.lambda]p8:
// An identifier or this shall not appear more than once in a
// lambda-capture.
@ -936,10 +941,12 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
continue;
}
// C++11 [expr.prim.lambda]p8:
// If a lambda-capture includes a capture-default that is =, the
// lambda-capture shall not contain this [...].
if (Intro.Default == LCD_ByCopy) {
// C++1z [expr.prim.lambda]p8:
// If a lambda-capture includes a capture-default that is =, each
// simple-capture of that lambda-capture shall be of the form "&
// identifier" or "* this". [ Note: The form [&,this] is redundant but
// accepted for compatibility with ISO C++14. --end note ]
if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis) {
Diag(C->Loc, diag::err_this_capture_with_copy_default)
<< FixItHint::CreateRemoval(
SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc));
@ -955,7 +962,9 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
continue;
}
CheckCXXThisCapture(C->Loc, /*Explicit=*/true);
CheckCXXThisCapture(C->Loc, /*Explicit=*/true, /*BuildAndDiagnose*/ true,
/*FunctionScopeIndexToStopAtPtr*/ nullptr,
C->Kind == LCK_StarThis);
continue;
}
@ -1529,10 +1538,9 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
// Handle 'this' capture.
if (From.isThisCapture()) {
Captures.push_back(
LambdaCapture(From.getLocation(), IsImplicit, LCK_This));
CaptureInits.push_back(new (Context) CXXThisExpr(From.getLocation(),
getCurrentThisType(),
/*isImplicit=*/true));
LambdaCapture(From.getLocation(), IsImplicit,
From.isCopyCapture() ? LCK_StarThis : LCK_This));
CaptureInits.push_back(From.getInitExpr());
ArrayIndexStarts.push_back(ArrayIndexVars.size());
continue;
}

4
clang/lib/Sema/TreeTransform.h
View File

@ -10089,7 +10089,9 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
// Capturing 'this' is trivial.
if (C->capturesThis()) {
getSema().CheckCXXThisCapture(C->getLocation(), C->isExplicit());
getSema().CheckCXXThisCapture(C->getLocation(), C->isExplicit(),
/*BuildAndDiagnose*/ true, nullptr,
C->getCaptureKind() == LCK_StarThis);
continue;
}
// Captured expression will be recaptured during captured variables

1
clang/lib/Serialization/ASTReaderDecl.cpp
View File

@ -1497,6 +1497,7 @@ void ASTDeclReader::ReadCXXDefinitionData(
bool IsImplicit = Record[Idx++];
LambdaCaptureKind Kind = static_cast<LambdaCaptureKind>(Record[Idx++]);
switch (Kind) {
case LCK_StarThis:
case LCK_This:
case LCK_VLAType:
*ToCapture++ = Capture(Loc, IsImplicit, Kind, nullptr,SourceLocation());

1
clang/lib/Serialization/ASTWriter.cpp
View File

@ -5631,6 +5631,7 @@ void ASTWriter::AddCXXDefinitionData(const CXXRecordDecl *D, RecordDataImpl &Rec
Record.push_back(Capture.isImplicit());
Record.push_back(Capture.getCaptureKind());
switch (Capture.getCaptureKind()) {
case LCK_StarThis:
case LCK_This:
case LCK_VLAType:
break;

22
clang/test/CXX/expr/expr.prim/expr.prim.lambda/p15-star-this-capture.cpp Normal file
View File

@ -0,0 +1,22 @@
// RUN: %clang_cc1 -fsyntax-only -std=c++1z %s -verify
class NonCopyable {
NonCopyable(const NonCopyable&) = delete; //expected-note3{{explicitly marked deleted here}}
int x = 10;
void foo() {
auto L = [this] { return x; };
const auto &M = [*this] { return x; };//expected-error{{call to deleted}}
const auto &M2 = [this] () -> auto&& {
++x;
return [*this] { //expected-error{{call to deleted}} expected-warning{{reference to local}}
return ++x; //expected-error{{read-only}}
};
};
const auto &M3 = [*this] () mutable -> auto&& { //expected-error{{call to deleted}}
++x;
return [this] { // expected-warning{{reference to local}}
return x;
};
};
}
};

31
clang/test/CodeGenCXX/cxx1z-lambda-star-this.cpp Normal file
View File

@ -0,0 +1,31 @@
// RUN: %clang_cc1 -std=c++1y -triple i686-pc-windows-msvc -emit-llvm %s -o - | FileCheck %s
//CHECK: %[[A_LAMBDA:.*]] = type { %struct.A }
//CHECK: %[[B_LAMBDA:.*]] = type { %struct.B* }
struct A {
double a = 111;
auto foo() { return [*this] { return a; }; }
};
namespace ns1 {
int X = A{}.foo()();
} //end ns1
//CHECK: @"\01?foo@A@@QAE?A?<auto>@@XZ"(%struct.A* %this, %class.anon* noalias sret %[[A_LAMBDA_RETVAL:.*]])
// get the first object with the closure type, which is of type 'struct.A'
//CHECK: %0 = getelementptr inbounds %[[A_LAMBDA]], %[[A_LAMBDA]]* %[[A_LAMBDA_RETVAL]], i32 0, i32 0
//CHECK: %1 = bitcast %struct.A* %0 to i8*
//CHECK: %2 = bitcast %struct.A* %this1 to i8*
// copy the contents ...
//CHECK: call void @llvm.memcpy.p0i8.p0i8.i32(i8* %1, i8* %2, i32 8, i32 8, i1 false)
struct B {
double b = 222;
auto bar() { return [this] { return b; }; };
};
namespace ns2 {
int X = B{}.bar()();
}
//CHECK: @"\01?bar@B@@QAE?A?<auto>@@XZ"(%struct.B* %this, %class.anon.0* noalias sret %agg.result)
//CHECK: %0 = getelementptr inbounds %class.anon.0, %class.anon.0* %agg.result, i32 0, i32 0
//CHECK: store %struct.B* %this1, %struct.B** %0, align 4

72
clang/test/SemaCXX/cxx1z-lambda-star-this.cpp Normal file
View File

@ -0,0 +1,72 @@
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -emit-llvm-only %s
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s -DDELAYED_TEMPLATE_PARSING
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fms-extensions %s -DMS_EXTENSIONS
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing -fms-extensions %s -DMS_EXTENSIONS -DDELAYED_TEMPLATE_PARSING
namespace test_star_this {
namespace ns1 {
class A {
int x = 345;
auto foo() {
(void) [*this, this] { }; //expected-error{{'this' can appear only once}}
(void) [this] { ++x; };
(void) [*this] { ++x; }; //expected-error{{read-only variable}}
(void) [*this] () mutable { ++x; };
(void) [=] { return x; };
(void) [&, this] { return x; };
(void) [=, *this] { return x; };
(void) [&, *this] { return x; };
}
};
} // end ns1
namespace ns2 {
class B {
B(const B&) = delete; //expected-note{{deleted here}}
int *x = (int *) 456;
void foo() {
(void)[this] { return x; };
(void)[*this] { return x; }; //expected-error{{call to deleted}}
}
};
} // end ns2
namespace ns3 {
class B {
B(const B&) = delete; //expected-note2{{deleted here}}
int *x = (int *) 456;
public:
template<class T = int>
void foo() {
(void)[this] { return x; };
(void)[*this] { return x; }; //expected-error2{{call to deleted}}
}
B() = default;
} b;
B *c = (b.foo(), nullptr); //expected-note{{in instantiation}}
} // end ns3
namespace ns4 {
template<class U>
class B {
B(const B&) = delete; //expected-note{{deleted here}}
double d = 3.14;
public:
template<class T = int>
auto foo() {
const auto &L = [*this] (auto a) mutable { //expected-error{{call to deleted}}
d += a;
return [this] (auto b) { return d +=b; };
};
}
B() = default;
};
void main() {
B<int*> b;
b.foo(); //expected-note{{in instantiation}}
} // end main
} // end ns4
} //end ns test_star_this

2
clang/www/cxx_status.html
View File

@ -659,7 +659,7 @@ as the draft C++1z standard evolves.</p>
<tr>
<td>Lambda capture of <tt>*this</tt></td>
<td><a href="http://wg21.link/p0018r3">P0018R3</a></td>
<td class="none" align="center">No</td>
<td class="svn" align="center">SVN</td>
</tr>
<tr>
<td>Direct-list-initialization of <tt>enum</tt>s</td>