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//===--- ScopeInfo.h - Information about a semantic context -----*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file defines FunctionScopeInfo and its subclasses, which contain
// information about a single function, block, lambda, or method body.
#include "clang/AST/Expr.h"
#include "clang/AST/Type.h"
#include "clang/Basic/CapturedStmt.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "clang/Sema/CleanupInfo.h"
#include "clang/Sema/Ownership.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringSwitch.h"
#include <algorithm>
namespace clang {
class Decl;
class BlockDecl;
class CapturedDecl;
class CXXMethodDecl;
class FieldDecl;
class ObjCPropertyDecl;
class IdentifierInfo;
class ImplicitParamDecl;
class LabelDecl;
class ReturnStmt;
class Scope;
class SwitchStmt;
class TemplateTypeParmDecl;
class TemplateParameterList;
class VarDecl;
class ObjCIvarRefExpr;
class ObjCPropertyRefExpr;
class ObjCMessageExpr;
namespace sema {
/// \brief Contains information about the compound statement currently being
/// parsed.
class CompoundScopeInfo {
: HasEmptyLoopBodies(false) { }
/// \brief Whether this compound stamement contains `for' or `while' loops
/// with empty bodies.
bool HasEmptyLoopBodies;
void setHasEmptyLoopBodies() {
HasEmptyLoopBodies = true;
class PossiblyUnreachableDiag {
PartialDiagnostic PD;
SourceLocation Loc;
const Stmt *stmt;
PossiblyUnreachableDiag(const PartialDiagnostic &PD, SourceLocation Loc,
const Stmt *stmt)
: PD(PD), Loc(Loc), stmt(stmt) {}
/// \brief Retains information about a function, method, or block that is
/// currently being parsed.
class FunctionScopeInfo {
enum ScopeKind {
/// \brief What kind of scope we are describing.
ScopeKind Kind : 3;
/// \brief Whether this function contains a VLA, \@try, try, C++
/// initializer, or anything else that can't be jumped past.
bool HasBranchProtectedScope : 1;
/// \brief Whether this function contains any switches or direct gotos.
bool HasBranchIntoScope : 1;
/// \brief Whether this function contains any indirect gotos.
bool HasIndirectGoto : 1;
/// \brief Whether a statement was dropped because it was invalid.
bool HasDroppedStmt : 1;
/// \brief True if current scope is for OpenMP declare reduction combiner.
bool HasOMPDeclareReductionCombiner : 1;
/// \brief Whether there is a fallthrough statement in this function.
bool HasFallthroughStmt : 1;
/// \brief Whether we make reference to a declaration that could be
/// unavailable.
bool HasPotentialAvailabilityViolations : 1;
/// A flag that is set when parsing a method that must call super's
/// implementation, such as \c -dealloc, \c -finalize, or any method marked
/// with \c __attribute__((objc_requires_super)).
bool ObjCShouldCallSuper : 1;
/// True when this is a method marked as a designated initializer.
bool ObjCIsDesignatedInit : 1;
/// This starts true for a method marked as designated initializer and will
/// be set to false if there is an invocation to a designated initializer of
/// the super class.
bool ObjCWarnForNoDesignatedInitChain : 1;
/// True when this is an initializer method not marked as a designated
/// initializer within a class that has at least one initializer marked as a
/// designated initializer.
bool ObjCIsSecondaryInit : 1;
/// This starts true for a secondary initializer method and will be set to
/// false if there is an invocation of an initializer on 'self'.
bool ObjCWarnForNoInitDelegation : 1;
/// \brief True only when this function has not already built, or attempted
/// to build, the initial and final coroutine suspend points
bool NeedsCoroutineSuspends : 1;
/// \brief An enumeration represeting the kind of the first coroutine statement
/// in the function. One of co_return, co_await, or co_yield.
unsigned char FirstCoroutineStmtKind : 2;
/// First coroutine statement in the current function.
/// (ex co_return, co_await, co_yield)
SourceLocation FirstCoroutineStmtLoc;
/// First 'return' statement in the current function.
SourceLocation FirstReturnLoc;
/// First C++ 'try' statement in the current function.
SourceLocation FirstCXXTryLoc;
/// First SEH '__try' statement in the current function.
SourceLocation FirstSEHTryLoc;
/// \brief Used to determine if errors occurred in this function or block.
DiagnosticErrorTrap ErrorTrap;
/// SwitchStack - This is the current set of active switch statements in the
/// block.
SmallVector<SwitchStmt*, 8> SwitchStack;
/// \brief The list of return statements that occur within the function or
/// block, if there is any chance of applying the named return value
/// optimization, or if we need to infer a return type.
SmallVector<ReturnStmt*, 4> Returns;
/// \brief The promise object for this coroutine, if any.
VarDecl *CoroutinePromise = nullptr;
/// \brief The initial and final coroutine suspend points.
std::pair<Stmt *, Stmt *> CoroutineSuspends;
/// \brief The stack of currently active compound stamement scopes in the
/// function.
SmallVector<CompoundScopeInfo, 4> CompoundScopes;
/// \brief A list of PartialDiagnostics created but delayed within the
/// current function scope. These diagnostics are vetted for reachability
/// prior to being emitted.
SmallVector<PossiblyUnreachableDiag, 4> PossiblyUnreachableDiags;
/// \brief A list of parameters which have the nonnull attribute and are
/// modified in the function.
llvm::SmallPtrSet<const ParmVarDecl*, 8> ModifiedNonNullParams;
/// Represents a simple identification of a weak object.
/// Part of the implementation of -Wrepeated-use-of-weak.
/// This is used to determine if two weak accesses refer to the same object.
/// Here are some examples of how various accesses are "profiled":
/// Access Expression | "Base" Decl | "Property" Decl
/// :---------------: | :-----------------: | :------------------------------:
/// | self (VarDecl) | property (ObjCPropertyDecl)
/// self.implicitProp | self (VarDecl) | -implicitProp (ObjCMethodDecl)
/// self->ivar.prop | ivar (ObjCIvarDecl) | prop (ObjCPropertyDecl)
/// cxxObj.obj.prop | obj (FieldDecl) | prop (ObjCPropertyDecl)
/// [self foo].prop | 0 (unknown) | prop (ObjCPropertyDecl)
/// self.prop1.prop2 | prop1 (ObjCPropertyDecl) | prop2 (ObjCPropertyDecl)
/// MyClass.prop | MyClass (ObjCInterfaceDecl) | -prop (ObjCMethodDecl)
/// | +foo (ObjCMethodDecl) | -prop (ObjCPropertyDecl)
/// weakVar | 0 (known) | weakVar (VarDecl)
/// self->weakIvar | self (VarDecl) | weakIvar (ObjCIvarDecl)
/// Objects are identified with only two Decls to make it reasonably fast to
/// compare them.
class WeakObjectProfileTy {
/// The base object decl, as described in the class documentation.
/// The extra flag is "true" if the Base and Property are enough to uniquely
/// identify the object in memory.
/// \sa isExactProfile()
typedef llvm::PointerIntPair<const NamedDecl *, 1, bool> BaseInfoTy;
BaseInfoTy Base;
/// The "property" decl, as described in the class documentation.
/// Note that this may not actually be an ObjCPropertyDecl, e.g. in the
/// case of "implicit" properties (regular methods accessed via dot syntax).
const NamedDecl *Property;
/// Used to find the proper base profile for a given base expression.
static BaseInfoTy getBaseInfo(const Expr *BaseE);
inline WeakObjectProfileTy();
static inline WeakObjectProfileTy getSentinel();
WeakObjectProfileTy(const ObjCPropertyRefExpr *RE);
WeakObjectProfileTy(const Expr *Base, const ObjCPropertyDecl *Property);
WeakObjectProfileTy(const DeclRefExpr *RE);
WeakObjectProfileTy(const ObjCIvarRefExpr *RE);
const NamedDecl *getBase() const { return Base.getPointer(); }
const NamedDecl *getProperty() const { return Property; }
/// Returns true if the object base specifies a known object in memory,
/// rather than, say, an instance variable or property of another object.
/// Note that this ignores the effects of aliasing; that is, \c is
/// considered an exact profile if \c foo is a local variable, even if
/// another variable \c foo2 refers to the same object as \c foo.
/// For increased precision, accesses with base variables that are
/// properties or ivars of 'self' (e.g. self.prop1.prop2) are considered to
/// be exact, though this is not true for arbitrary variables
/// (foo.prop1.prop2).
bool isExactProfile() const {
return Base.getInt();
bool operator==(const WeakObjectProfileTy &Other) const {
return Base == Other.Base && Property == Other.Property;
// For use in DenseMap.
// We can't specialize the usual llvm::DenseMapInfo at the end of the file
// because by that point the DenseMap in FunctionScopeInfo has already been
// instantiated.
class DenseMapInfo {
static inline WeakObjectProfileTy getEmptyKey() {
return WeakObjectProfileTy();
static inline WeakObjectProfileTy getTombstoneKey() {
return WeakObjectProfileTy::getSentinel();
static unsigned getHashValue(const WeakObjectProfileTy &Val) {
typedef std::pair<BaseInfoTy, const NamedDecl *> Pair;
return llvm::DenseMapInfo<Pair>::getHashValue(Pair(Val.Base,
static bool isEqual(const WeakObjectProfileTy &LHS,
const WeakObjectProfileTy &RHS) {
return LHS == RHS;
/// Represents a single use of a weak object.
/// Stores both the expression and whether the access is potentially unsafe
/// (i.e. it could potentially be warned about).
/// Part of the implementation of -Wrepeated-use-of-weak.
class WeakUseTy {
llvm::PointerIntPair<const Expr *, 1, bool> Rep;
WeakUseTy(const Expr *Use, bool IsRead) : Rep(Use, IsRead) {}
const Expr *getUseExpr() const { return Rep.getPointer(); }
bool isUnsafe() const { return Rep.getInt(); }
void markSafe() { Rep.setInt(false); }
bool operator==(const WeakUseTy &Other) const {
return Rep == Other.Rep;
/// Used to collect uses of a particular weak object in a function body.
/// Part of the implementation of -Wrepeated-use-of-weak.
typedef SmallVector<WeakUseTy, 4> WeakUseVector;
/// Used to collect all uses of weak objects in a function body.
/// Part of the implementation of -Wrepeated-use-of-weak.
typedef llvm::SmallDenseMap<WeakObjectProfileTy, WeakUseVector, 8,
/// Used to collect all uses of weak objects in this function body.
/// Part of the implementation of -Wrepeated-use-of-weak.
WeakObjectUseMap WeakObjectUses;
FunctionScopeInfo(const FunctionScopeInfo&) = default;
/// Record that a weak object was accessed.
/// Part of the implementation of -Wrepeated-use-of-weak.
template <typename ExprT>
inline void recordUseOfWeak(const ExprT *E, bool IsRead = true);
void recordUseOfWeak(const ObjCMessageExpr *Msg,
const ObjCPropertyDecl *Prop);
/// Record that a given expression is a "safe" access of a weak object (e.g.
/// assigning it to a strong variable.)
/// Part of the implementation of -Wrepeated-use-of-weak.
void markSafeWeakUse(const Expr *E);
const WeakObjectUseMap &getWeakObjectUses() const {
return WeakObjectUses;
void setHasBranchIntoScope() {
HasBranchIntoScope = true;
void setHasBranchProtectedScope() {
HasBranchProtectedScope = true;
void setHasIndirectGoto() {
HasIndirectGoto = true;
void setHasDroppedStmt() {
HasDroppedStmt = true;
void setHasOMPDeclareReductionCombiner() {
HasOMPDeclareReductionCombiner = true;
void setHasFallthroughStmt() {
HasFallthroughStmt = true;
void setHasCXXTry(SourceLocation TryLoc) {
FirstCXXTryLoc = TryLoc;
void setHasSEHTry(SourceLocation TryLoc) {
FirstSEHTryLoc = TryLoc;
bool NeedsScopeChecking() const {
return !HasDroppedStmt &&
(HasIndirectGoto ||
(HasBranchProtectedScope && HasBranchIntoScope));
bool isCoroutine() const { return !FirstCoroutineStmtLoc.isInvalid(); }
void setFirstCoroutineStmt(SourceLocation Loc, StringRef Keyword) {
assert(FirstCoroutineStmtLoc.isInvalid() &&
"first coroutine statement location already set");
FirstCoroutineStmtLoc = Loc;
FirstCoroutineStmtKind = llvm::StringSwitch<unsigned char>(Keyword)
.Case("co_return", 0)
.Case("co_await", 1)
.Case("co_yield", 2);
StringRef getFirstCoroutineStmtKeyword() const {
&& "no coroutine statement available");
switch (FirstCoroutineStmtKind) {
case 0: return "co_return";
case 1: return "co_await";
case 2: return "co_yield";
llvm_unreachable("FirstCoroutineStmtKind has an invalid value");
void setNeedsCoroutineSuspends(bool value = true) {
assert((!value || CoroutineSuspends.first == nullptr) &&
"we already have valid suspend points");
NeedsCoroutineSuspends = value;
bool hasInvalidCoroutineSuspends() const {
return !NeedsCoroutineSuspends && CoroutineSuspends.first == nullptr;
void setCoroutineSuspends(Stmt *Initial, Stmt *Final) {
assert(Initial && Final && "suspend points cannot be null");
assert(CoroutineSuspends.first == nullptr && "suspend points already set");
NeedsCoroutineSuspends = false;
CoroutineSuspends.first = Initial;
CoroutineSuspends.second = Final;
FunctionScopeInfo(DiagnosticsEngine &Diag)
: Kind(SK_Function),
ErrorTrap(Diag) { }
virtual ~FunctionScopeInfo();
/// \brief Clear out the information in this function scope, making it
/// suitable for reuse.
void Clear();
class CapturingScopeInfo : public FunctionScopeInfo {
CapturingScopeInfo(const CapturingScopeInfo&) = default;
enum ImplicitCaptureStyle {
ImpCap_None, ImpCap_LambdaByval, ImpCap_LambdaByref, ImpCap_Block,
ImplicitCaptureStyle ImpCaptureStyle;
class Capture {
// There are three categories of capture: capturing 'this', capturing
// local variables, and C++1y initialized captures (which can have an
// arbitrary initializer, and don't really capture in the traditional
// sense at all).
// There are three ways to capture a local variable:
// - capture by copy in the C++11 sense,
// - capture by reference in the C++11 sense, and
// - __block capture.
// Lambdas explicitly specify capture by copy or capture by reference.
// For blocks, __block capture applies to variables with that annotation,
// variables of reference type are captured by reference, and other
// variables are captured by copy.
enum CaptureKind {
Cap_ByCopy, Cap_ByRef, Cap_Block, Cap_VLA
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;
/// 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;
/// \brief The source location at which the first capture occurred.
SourceLocation Loc;
/// \brief The location of the ellipsis that expands a parameter pack.
SourceLocation EllipsisLoc;
/// \brief The type as it was captured, which is in effect the type of the
/// non-static data member that would hold the capture.
QualType CaptureType;
/// \brief Whether an explicit capture has been odr-used in the body of the
/// lambda.
bool ODRUsed;
/// \brief Whether an explicit capture has been non-odr-used in the body of
/// the lambda.
bool NonODRUsed;
Capture(VarDecl *Var, bool Block, bool ByRef, bool IsNested,
SourceLocation Loc, SourceLocation EllipsisLoc,
QualType CaptureType, Expr *Cpy)
: VarAndNestedAndThis(Var, IsNested ? IsNestedCapture : 0),
Cpy, !Var ? Cap_VLA : Block ? Cap_Block : ByRef ? Cap_ByRef
: Cap_ByCopy),
Loc(Loc), EllipsisLoc(EllipsisLoc), CaptureType(CaptureType),
ODRUsed(false), NonODRUsed(false) {}
enum IsThisCapture { ThisCapture };
Capture(IsThisCapture, bool IsNested, SourceLocation Loc,
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), ODRUsed(false),
NonODRUsed(false) {}
bool isThisCapture() const {
return VarAndNestedAndThis.getInt() & IsThisCaptured;
bool isVariableCapture() const {
return !isThisCapture() && !isVLATypeCapture();
bool isCopyCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_ByCopy;
bool isReferenceCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_ByRef;
bool isBlockCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_Block;
bool isVLATypeCapture() const {
return InitExprAndCaptureKind.getInt() == Cap_VLA;
bool isNested() const {
return VarAndNestedAndThis.getInt() & IsNestedCapture;
bool isODRUsed() const { return ODRUsed; }
bool isNonODRUsed() const { return NonODRUsed; }
void markUsed(bool IsODRUse) { (IsODRUse ? ODRUsed : NonODRUsed) = true; }
VarDecl *getVariable() const {
return VarAndNestedAndThis.getPointer();
/// \brief Retrieve the location at which this variable was captured.
SourceLocation getLocation() const { return Loc; }
/// \brief Retrieve the source location of the ellipsis, whose presence
/// indicates that the capture is a pack expansion.
SourceLocation getEllipsisLoc() const { return EllipsisLoc; }
/// \brief Retrieve the capture type for this capture, which is effectively
/// the type of the non-static data member in the lambda/block structure
/// that would store this capture.
QualType getCaptureType() const {
return CaptureType;
Expr *getInitExpr() const {
assert(!isVLATypeCapture() && "no init expression for type capture");
return static_cast<Expr *>(InitExprAndCaptureKind.getPointer());
CapturingScopeInfo(DiagnosticsEngine &Diag, ImplicitCaptureStyle Style)
: FunctionScopeInfo(Diag), ImpCaptureStyle(Style), CXXThisCaptureIndex(0),
/// CaptureMap - A map of captured variables to (index+1) into Captures.
llvm::DenseMap<VarDecl*, unsigned> CaptureMap;
/// CXXThisCaptureIndex - The (index+1) of the capture of 'this';
/// zero if 'this' is not captured.
unsigned CXXThisCaptureIndex;
/// Captures - The captures.
SmallVector<Capture, 4> Captures;
/// \brief - Whether the target type of return statements in this context
/// is deduced (e.g. a lambda or block with omitted return type).
bool HasImplicitReturnType;
/// ReturnType - The target type of return statements in this context,
/// or null if unknown.
QualType ReturnType;
void addCapture(VarDecl *Var, bool isBlock, bool isByref, bool isNested,
SourceLocation Loc, SourceLocation EllipsisLoc,
QualType CaptureType, Expr *Cpy) {
Captures.push_back(Capture(Var, isBlock, isByref, isNested, Loc,
EllipsisLoc, CaptureType, Cpy));
CaptureMap[Var] = Captures.size();
void addVLATypeCapture(SourceLocation Loc, QualType CaptureType) {
Captures.push_back(Capture(/*Var*/ nullptr, /*isBlock*/ false,
/*isByref*/ false, /*isNested*/ false, Loc,
/*EllipsisLoc*/ SourceLocation(), CaptureType,
/*Cpy*/ nullptr));
// Note, we do not need to add the type of 'this' since that is always
// retrievable from Sema::getCurrentThisType - and is also encoded within the
// type of the corresponding FieldDecl.
void addThisCapture(bool isNested, SourceLocation Loc,
Expr *Cpy, bool ByCopy);
/// \brief Determine whether the C++ 'this' is captured.
bool isCXXThisCaptured() const { return CXXThisCaptureIndex != 0; }
/// \brief Retrieve the capture of C++ 'this', if it has been captured.
Capture &getCXXThisCapture() {
assert(isCXXThisCaptured() && "this has not been captured");
return Captures[CXXThisCaptureIndex - 1];
/// \brief Determine whether the given variable has been captured.
bool isCaptured(VarDecl *Var) const {
return CaptureMap.count(Var);
/// \brief Determine whether the given variable-array type has been captured.
bool isVLATypeCaptured(const VariableArrayType *VAT) const;
/// \brief Retrieve the capture of the given variable, if it has been
/// captured already.
Capture &getCapture(VarDecl *Var) {
assert(isCaptured(Var) && "Variable has not been captured");
return Captures[CaptureMap[Var] - 1];
const Capture &getCapture(VarDecl *Var) const {
llvm::DenseMap<VarDecl*, unsigned>::const_iterator Known
= CaptureMap.find(Var);
assert(Known != CaptureMap.end() && "Variable has not been captured");
return Captures[Known->second - 1];
static bool classof(const FunctionScopeInfo *FSI) {
return FSI->Kind == SK_Block || FSI->Kind == SK_Lambda
|| FSI->Kind == SK_CapturedRegion;
/// \brief Retains information about a block that is currently being parsed.
class BlockScopeInfo final : public CapturingScopeInfo {
BlockDecl *TheDecl;
/// TheScope - This is the scope for the block itself, which contains
/// arguments etc.
Scope *TheScope;
/// BlockType - The function type of the block, if one was given.
/// Its return type may be BuiltinType::Dependent.
QualType FunctionType;
BlockScopeInfo(DiagnosticsEngine &Diag, Scope *BlockScope, BlockDecl *Block)
: CapturingScopeInfo(Diag, ImpCap_Block), TheDecl(Block),
Kind = SK_Block;
~BlockScopeInfo() override;
static bool classof(const FunctionScopeInfo *FSI) {
return FSI->Kind == SK_Block;
/// \brief Retains information about a captured region.
class CapturedRegionScopeInfo final : public CapturingScopeInfo {
/// \brief The CapturedDecl for this statement.
CapturedDecl *TheCapturedDecl;
/// \brief The captured record type.
RecordDecl *TheRecordDecl;
/// \brief This is the enclosing scope of the captured region.
Scope *TheScope;
/// \brief The implicit parameter for the captured variables.
ImplicitParamDecl *ContextParam;
/// \brief The kind of captured region.
unsigned short CapRegionKind;
unsigned short OpenMPLevel;
CapturedRegionScopeInfo(DiagnosticsEngine &Diag, Scope *S, CapturedDecl *CD,
RecordDecl *RD, ImplicitParamDecl *Context,
CapturedRegionKind K, unsigned OpenMPLevel)
: CapturingScopeInfo(Diag, ImpCap_CapturedRegion),
TheCapturedDecl(CD), TheRecordDecl(RD), TheScope(S),
ContextParam(Context), CapRegionKind(K), OpenMPLevel(OpenMPLevel)
Kind = SK_CapturedRegion;
~CapturedRegionScopeInfo() override;
/// \brief A descriptive name for the kind of captured region this is.
StringRef getRegionName() const {
switch (CapRegionKind) {
case CR_Default:
return "default captured statement";
case CR_OpenMP:
return "OpenMP region";
llvm_unreachable("Invalid captured region kind!");
static bool classof(const FunctionScopeInfo *FSI) {
return FSI->Kind == SK_CapturedRegion;
class LambdaScopeInfo final : public CapturingScopeInfo {
/// \brief The class that describes the lambda.
CXXRecordDecl *Lambda;
/// \brief The lambda's compiler-generated \c operator().
CXXMethodDecl *CallOperator;
/// \brief Source range covering the lambda introducer [...].
SourceRange IntroducerRange;
/// \brief Source location of the '&' or '=' specifying the default capture
/// type, if any.
SourceLocation CaptureDefaultLoc;
/// \brief The number of captures in the \c Captures list that are
/// explicit captures.
unsigned NumExplicitCaptures;
/// \brief Whether this is a mutable lambda.
bool Mutable;
/// \brief Whether the (empty) parameter list is explicit.
bool ExplicitParams;
/// \brief Whether any of the capture expressions requires cleanups.
CleanupInfo Cleanup;
/// \brief Whether the lambda contains an unexpanded parameter pack.
bool ContainsUnexpandedParameterPack;
/// \brief If this is a generic lambda, use this as the depth of
/// each 'auto' parameter, during initial AST construction.
unsigned AutoTemplateParameterDepth;
/// \brief Store the list of the auto parameters for a generic lambda.
/// If this is a generic lambda, store the list of the auto
/// parameters converted into TemplateTypeParmDecls into a vector
/// that can be used to construct the generic lambda's template
/// parameter list, during initial AST construction.
SmallVector<TemplateTypeParmDecl*, 4> AutoTemplateParams;
/// If this is a generic lambda, and the template parameter
/// list has been created (from the AutoTemplateParams) then
/// store a reference to it (cache it to avoid reconstructing it).
TemplateParameterList *GLTemplateParameterList;
/// \brief Contains all variable-referring-expressions (i.e. DeclRefExprs
/// or MemberExprs) that refer to local variables in a generic lambda
/// or a lambda in a potentially-evaluated-if-used context.
/// Potentially capturable variables of a nested lambda that might need
/// to be captured by the lambda are housed here.
/// This is specifically useful for generic lambdas or
/// lambdas within a a potentially evaluated-if-used context.
/// If an enclosing variable is named in an expression of a lambda nested
/// within a generic lambda, we don't always know know whether the variable
/// will truly be odr-used (i.e. need to be captured) by that nested lambda,
/// until its instantiation. But we still need to capture it in the
/// enclosing lambda if all intervening lambdas can capture the variable.
llvm::SmallVector<Expr*, 4> PotentiallyCapturingExprs;
/// \brief Contains all variable-referring-expressions that refer
/// to local variables that are usable as constant expressions and
/// do not involve an odr-use (they may still need to be captured
/// if the enclosing full-expression is instantiation dependent).
llvm::SmallSet<Expr *, 8> NonODRUsedCapturingExprs;
/// Contains all of the variables defined in this lambda that shadow variables
/// that were defined in parent contexts. Used to avoid warnings when the
/// shadowed variables are uncaptured by this lambda.
struct ShadowedOuterDecl {
const VarDecl *VD;
const VarDecl *ShadowedDecl;
llvm::SmallVector<ShadowedOuterDecl, 4> ShadowingDecls;
SourceLocation PotentialThisCaptureLocation;
LambdaScopeInfo(DiagnosticsEngine &Diag)
: CapturingScopeInfo(Diag, ImpCap_None), Lambda(nullptr),
CallOperator(nullptr), NumExplicitCaptures(0), Mutable(false),
ExplicitParams(false), Cleanup{},
ContainsUnexpandedParameterPack(false), AutoTemplateParameterDepth(0),
GLTemplateParameterList(nullptr) {
Kind = SK_Lambda;
/// \brief Note when all explicit captures have been added.
void finishedExplicitCaptures() {
NumExplicitCaptures = Captures.size();
static bool classof(const FunctionScopeInfo *FSI) {
return FSI->Kind == SK_Lambda;
/// Is this scope known to be for a generic lambda? (This will be false until
/// we parse the first 'auto'-typed parameter.
bool isGenericLambda() const {
return !AutoTemplateParams.empty() || GLTemplateParameterList;
/// \brief Add a variable that might potentially be captured by the
/// lambda and therefore the enclosing lambdas.
/// This is also used by enclosing lambda's to speculatively capture
/// variables that nested lambda's - depending on their enclosing
/// specialization - might need to capture.
/// Consider:
/// void f(int, int); <-- don't capture
/// void f(const int&, double); <-- capture
/// void foo() {
/// const int x = 10;
/// auto L = [=](auto a) { // capture 'x'
/// return [=](auto b) {
/// f(x, a); // we may or may not need to capture 'x'
/// };
/// };
/// }
void addPotentialCapture(Expr *VarExpr) {
assert(isa<DeclRefExpr>(VarExpr) || isa<MemberExpr>(VarExpr));
void addPotentialThisCapture(SourceLocation Loc) {
PotentialThisCaptureLocation = Loc;
bool hasPotentialThisCapture() const {
return PotentialThisCaptureLocation.isValid();
/// \brief Mark a variable's reference in a lambda as non-odr using.
/// For generic lambdas, if a variable is named in a potentially evaluated
/// expression, where the enclosing full expression is dependent then we
/// must capture the variable (given a default capture).
/// This is accomplished by recording all references to variables
/// (DeclRefExprs or MemberExprs) within said nested lambda in its array of
/// PotentialCaptures. All such variables have to be captured by that lambda,
/// except for as described below.
/// If that variable is usable as a constant expression and is named in a
/// manner that does not involve its odr-use (e.g. undergoes
/// lvalue-to-rvalue conversion, or discarded) record that it is so. Upon the
/// act of analyzing the enclosing full expression (ActOnFinishFullExpr)
/// if we can determine that the full expression is not instantiation-
/// dependent, then we can entirely avoid its capture.
/// const int n = 0;
/// [&] (auto x) {
/// (void)+n + x;
/// };
/// Interestingly, this strategy would involve a capture of n, even though
/// it's obviously not odr-used here, because the full-expression is
/// instantiation-dependent. It could be useful to avoid capturing such
/// variables, even when they are referred to in an instantiation-dependent
/// expression, if we can unambiguously determine that they shall never be
/// odr-used. This would involve removal of the variable-referring-expression
/// from the array of PotentialCaptures during the lvalue-to-rvalue
/// conversions. But per the working draft N3797, (post-chicago 2013) we must
/// capture such variables.
/// Before anyone is tempted to implement a strategy for not-capturing 'n',
/// consider the insightful warning in:
/// /cfe-commits/Week-of-Mon-20131104/092596.html
/// "The problem is that the set of captures for a lambda is part of the ABI
/// (since lambda layout can be made visible through inline functions and the
/// like), and there are no guarantees as to which cases we'll manage to build
/// an lvalue-to-rvalue conversion in, when parsing a template -- some
/// seemingly harmless change elsewhere in Sema could cause us to start or stop
/// building such a node. So we need a rule that anyone can implement and get
/// exactly the same result".
void markVariableExprAsNonODRUsed(Expr *CapturingVarExpr) {
|| isa<MemberExpr>(CapturingVarExpr));
bool isVariableExprMarkedAsNonODRUsed(Expr *CapturingVarExpr) const {
|| isa<MemberExpr>(CapturingVarExpr));
return NonODRUsedCapturingExprs.count(CapturingVarExpr);
void removePotentialCapture(Expr *E) {
PotentiallyCapturingExprs.end(), E),
void clearPotentialCaptures() {
PotentialThisCaptureLocation = SourceLocation();
unsigned getNumPotentialVariableCaptures() const {
return PotentiallyCapturingExprs.size();
bool hasPotentialCaptures() const {
return getNumPotentialVariableCaptures() ||
// When passed the index, returns the VarDecl and Expr associated
// with the index.
void getPotentialVariableCapture(unsigned Idx, VarDecl *&VD, Expr *&E) const;
: Base(nullptr, false), Property(nullptr) {}
FunctionScopeInfo::WeakObjectProfileTy::getSentinel() {
FunctionScopeInfo::WeakObjectProfileTy Result;
return Result;
template <typename ExprT>
void FunctionScopeInfo::recordUseOfWeak(const ExprT *E, bool IsRead) {
WeakUseVector &Uses = WeakObjectUses[WeakObjectProfileTy(E)];
Uses.push_back(WeakUseTy(E, IsRead));
inline void
CapturingScopeInfo::addThisCapture(bool isNested, SourceLocation Loc,
Expr *Cpy,
const bool ByCopy) {
Captures.push_back(Capture(Capture::ThisCapture, isNested, Loc, QualType(),
Cpy, ByCopy));
CXXThisCaptureIndex = Captures.size();
} // end namespace sema
} // end namespace clang