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//===--- Ownership.h - Parser ownership helpers -----------------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file contains classes for managing ownership of Stmt and Expr nodes.
#include "clang/Basic/LLVM.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/PointerIntPair.h"
// OpaquePtr
namespace clang {
class Attr;
class CXXCtorInitializer;
class CXXBaseSpecifier;
class Decl;
class DeclGroupRef;
class Expr;
class NestedNameSpecifier;
class QualType;
class Sema;
class Stmt;
class TemplateName;
class TemplateParameterList;
/// OpaquePtr - This is a very simple POD type that wraps a pointer that the
/// Parser doesn't know about but that Sema or another client does. The UID
/// template argument is used to make sure that "Decl" pointers are not
/// compatible with "Type" pointers for example.
template <class PtrTy>
class OpaquePtr {
void *Ptr;
explicit OpaquePtr(void *Ptr) : Ptr(Ptr) {}
typedef llvm::PointerLikeTypeTraits<PtrTy> Traits;
OpaquePtr() : Ptr(0) {}
static OpaquePtr make(PtrTy P) { OpaquePtr OP; OP.set(P); return OP; }
template <typename T> T* getAs() const {
return get();
template <typename T> T getAsVal() const {
return get();
PtrTy get() const {
return Traits::getFromVoidPointer(Ptr);
void set(PtrTy P) {
Ptr = Traits::getAsVoidPointer(P);
operator bool() const { return Ptr != 0; }
void *getAsOpaquePtr() const { return Ptr; }
static OpaquePtr getFromOpaquePtr(void *P) { return OpaquePtr(P); }
/// UnionOpaquePtr - A version of OpaquePtr suitable for membership
/// in a union.
template <class T> struct UnionOpaquePtr {
void *Ptr;
static UnionOpaquePtr make(OpaquePtr<T> P) {
UnionOpaquePtr OP = { P.getAsOpaquePtr() };
return OP;
OpaquePtr<T> get() const { return OpaquePtr<T>::getFromOpaquePtr(Ptr); }
operator OpaquePtr<T>() const { return get(); }
UnionOpaquePtr &operator=(OpaquePtr<T> P) {
Ptr = P.getAsOpaquePtr();
return *this;
namespace llvm {
template <class T>
class PointerLikeTypeTraits<clang::OpaquePtr<T> > {
static inline void *getAsVoidPointer(clang::OpaquePtr<T> P) {
// FIXME: Doesn't work? return P.getAs< void >();
return P.getAsOpaquePtr();
static inline clang::OpaquePtr<T> getFromVoidPointer(void *P) {
return clang::OpaquePtr<T>::getFromOpaquePtr(P);
enum { NumLowBitsAvailable = 0 };
template <class T>
struct isPodLike<clang::OpaquePtr<T> > { static const bool value = true; };
// -------------------------- About Move Emulation -------------------------- //
// The smart pointer classes in this file attempt to emulate move semantics
// as they appear in C++0x with rvalue references. Since C++03 doesn't have
// rvalue references, some tricks are needed to get similar results.
// Move semantics in C++0x have the following properties:
// 1) "Moving" means transferring the value of an object to another object,
// similar to copying, but without caring what happens to the old object.
// In particular, this means that the new object can steal the old object's
// resources instead of creating a copy.
// 2) Since moving can modify the source object, it must either be explicitly
// requested by the user, or the modifications must be unnoticeable.
// 3) As such, C++0x moving is only allowed in three contexts:
// * By explicitly using std::move() to request it.
// * From a temporary object, since that object cannot be accessed
// afterwards anyway, thus making the state unobservable.
// * On function return, since the object is not observable afterwards.
// To sum up: moving from a named object should only be possible with an
// explicit std::move(), or on function return. Moving from a temporary should
// be implicitly done. Moving from a const object is forbidden.
// The emulation is not perfect, and has the following shortcomings:
// * move() is not in namespace std.
// * move() is required on function return.
// * There are difficulties with implicit conversions.
// * Microsoft's compiler must be given the /Za switch to successfully compile.
// -------------------------- Implementation -------------------------------- //
// The move emulation relies on the peculiar reference binding semantics of
// C++03: as a rule, a non-const reference may not bind to a temporary object,
// except for the implicit object parameter in a member function call, which
// can refer to a temporary even when not being const.
// The moveable object has five important functions to facilitate moving:
// * A private, unimplemented constructor taking a non-const reference to its
// own class. This constructor serves a two-fold purpose.
// - It prevents the creation of a copy constructor that takes a const
// reference. Temporaries would be able to bind to the argument of such a
// constructor, and that would be bad.
// - Named objects will bind to the non-const reference, but since it's
// private, this will fail to compile. This prevents implicit moving from
// named objects.
// There's also a copy assignment operator for the same purpose.
// * An implicit, non-const conversion operator to a special mover type. This
// type represents the rvalue reference of C++0x. Being a non-const member,
// its implicit this parameter can bind to temporaries.
// * A constructor that takes an object of this mover type. This constructor
// performs the actual move operation. There is an equivalent assignment
// operator.
// There is also a free move() function that takes a non-const reference to
// an object and returns a temporary. Internally, this function uses explicit
// constructor calls to move the value from the referenced object to the return
// value.
// There are now three possible scenarios of use.
// * Copying from a const object. Constructor overload resolution will find the
// non-const copy constructor, and the move constructor. The first is not
// viable because the const object cannot be bound to the non-const reference.
// The second fails because the conversion to the mover object is non-const.
// Moving from a const object fails as intended.
// * Copying from a named object. Constructor overload resolution will select
// the non-const copy constructor, but fail as intended, because this
// constructor is private.
// * Copying from a temporary. Constructor overload resolution cannot select
// the non-const copy constructor, because the temporary cannot be bound to
// the non-const reference. It thus selects the move constructor. The
// temporary can be bound to the implicit this parameter of the conversion
// operator, because of the special binding rule. Construction succeeds.
// Note that the Microsoft compiler, as an extension, allows binding
// temporaries against non-const references. The compiler thus selects the
// non-const copy constructor and fails, because the constructor is private.
// Passing /Za (disable extensions) disables this behaviour.
// The free move() function is used to move from a named object.
// Note that when passing an object of a different type (the classes below
// have OwningResult and OwningPtr, which should be mixable), you get a problem.
// Argument passing and function return use copy initialization rules. The
// effect of this is that, when the source object is not already of the target
// type, the compiler will first seek a way to convert the source object to the
// target type, and only then attempt to copy the resulting object. This means
// that when passing an OwningResult where an OwningPtr is expected, the
// compiler will first seek a conversion from OwningResult to OwningPtr, then
// copy the OwningPtr. The resulting conversion sequence is:
// OwningResult object -> ResultMover -> OwningResult argument to
// OwningPtr(OwningResult) -> OwningPtr -> PtrMover -> final OwningPtr
// This conversion sequence is too complex to be allowed. Thus the special
// move_* functions, which help the compiler out with some explicit
// conversions.
namespace clang {
// Basic
class DiagnosticBuilder;
// Determines whether the low bit of the result pointer for the
// given UID is always zero. If so, ActionResult will use that bit
// for it's "invalid" flag.
template<class Ptr>
struct IsResultPtrLowBitFree {
static const bool value = false;
/// ActionResult - This structure is used while parsing/acting on
/// expressions, stmts, etc. It encapsulates both the object returned by
/// the action, plus a sense of whether or not it is valid.
/// When CompressInvalid is true, the "invalid" flag will be
/// stored in the low bit of the Val pointer.
template<class PtrTy,
bool CompressInvalid = IsResultPtrLowBitFree<PtrTy>::value>
class ActionResult {
PtrTy Val;
bool Invalid;
ActionResult(bool Invalid = false)
: Val(PtrTy()), Invalid(Invalid) {}
ActionResult(PtrTy val) : Val(val), Invalid(false) {}
ActionResult(const DiagnosticBuilder &) : Val(PtrTy()), Invalid(true) {}
// These two overloads prevent void* -> bool conversions.
ActionResult(const void *);
ActionResult(volatile void *);
bool isInvalid() const { return Invalid; }
bool isUsable() const { return !Invalid && Val; }
PtrTy get() const { return Val; }
PtrTy release() const { return Val; }
PtrTy take() const { return Val; }
template <typename T> T *takeAs() { return static_cast<T*>(get()); }
void set(PtrTy V) { Val = V; }
const ActionResult &operator=(PtrTy RHS) {
Val = RHS;
Invalid = false;
return *this;
// This ActionResult partial specialization places the "invalid"
// flag into the low bit of the pointer.
template<typename PtrTy>
class ActionResult<PtrTy, true> {
// A pointer whose low bit is 1 if this result is invalid, 0
// otherwise.
uintptr_t PtrWithInvalid;
typedef llvm::PointerLikeTypeTraits<PtrTy> PtrTraits;
ActionResult(bool Invalid = false)
: PtrWithInvalid(static_cast<uintptr_t>(Invalid)) { }
ActionResult(PtrTy V) {
void *VP = PtrTraits::getAsVoidPointer(V);
PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
ActionResult(const DiagnosticBuilder &) : PtrWithInvalid(0x01) { }
// These two overloads prevent void* -> bool conversions.
ActionResult(const void *);
ActionResult(volatile void *);
bool isInvalid() const { return PtrWithInvalid & 0x01; }
bool isUsable() const { return PtrWithInvalid > 0x01; }
PtrTy get() const {
void *VP = reinterpret_cast<void *>(PtrWithInvalid & ~0x01);
return PtrTraits::getFromVoidPointer(VP);
PtrTy take() const { return get(); }
PtrTy release() const { return get(); }
template <typename T> T *takeAs() { return static_cast<T*>(get()); }
void set(PtrTy V) {
void *VP = PtrTraits::getAsVoidPointer(V);
PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
const ActionResult &operator=(PtrTy RHS) {
void *VP = PtrTraits::getAsVoidPointer(RHS);
PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
return *this;
/// ASTMultiPtr - A moveable smart pointer to multiple AST nodes. Only owns
/// the individual pointers, not the array holding them.
template <typename PtrTy> class ASTMultiPtr;
template <class PtrTy>
class ASTMultiPtr {
PtrTy *Nodes;
unsigned Count;
// Normal copying implicitly defined
ASTMultiPtr() : Nodes(0), Count(0) {}
explicit ASTMultiPtr(Sema &) : Nodes(0), Count(0) {}
ASTMultiPtr(Sema &, PtrTy *nodes, unsigned count)
: Nodes(nodes), Count(count) {}
// Fake mover in Parse/AstGuard.h needs this:
ASTMultiPtr(PtrTy *nodes, unsigned count) : Nodes(nodes), Count(count) {}
/// Access to the raw pointers.
PtrTy *get() const { return Nodes; }
/// Access to the count.
unsigned size() const { return Count; }
PtrTy *release() {
return Nodes;
class ParsedTemplateArgument;
class ASTTemplateArgsPtr {
ParsedTemplateArgument *Args;
mutable unsigned Count;
ASTTemplateArgsPtr(Sema &actions, ParsedTemplateArgument *args,
unsigned count) :
Args(args), Count(count) { }
// FIXME: Lame, not-fully-type-safe emulation of 'move semantics'.
ASTTemplateArgsPtr(ASTTemplateArgsPtr &Other) :
Args(Other.Args), Count(Other.Count) {
// FIXME: Lame, not-fully-type-safe emulation of 'move semantics'.
ASTTemplateArgsPtr& operator=(ASTTemplateArgsPtr &Other) {
Args = Other.Args;
Count = Other.Count;
return *this;
ParsedTemplateArgument *getArgs() const { return Args; }
unsigned size() const { return Count; }
void reset(ParsedTemplateArgument *args, unsigned count) {
Args = args;
Count = count;
const ParsedTemplateArgument &operator[](unsigned Arg) const;
ParsedTemplateArgument *release() const {
return Args;
/// \brief A small vector that owns a set of AST nodes.
template <class PtrTy, unsigned N = 8>
class ASTOwningVector : public SmallVector<PtrTy, N> {
ASTOwningVector(ASTOwningVector &); // do not implement
ASTOwningVector &operator=(ASTOwningVector &); // do not implement
explicit ASTOwningVector(Sema &Actions)
{ }
PtrTy *take() {
return &this->front();
template<typename T> T **takeAs() { return reinterpret_cast<T**>(take()); }
/// An opaque type for threading parsed type information through the
/// parser.
typedef OpaquePtr<QualType> ParsedType;
typedef UnionOpaquePtr<QualType> UnionParsedType;
/// A SmallVector of statements, with stack size 32 (as that is the only one
/// used.)
typedef ASTOwningVector<Stmt*, 32> StmtVector;
/// A SmallVector of expressions, with stack size 12 (the maximum used.)
typedef ASTOwningVector<Expr*, 12> ExprVector;
/// A SmallVector of types.
typedef ASTOwningVector<ParsedType, 12> TypeVector;
template <class T, unsigned N> inline
ASTMultiPtr<T> move_arg(ASTOwningVector<T, N> &vec) {
return ASTMultiPtr<T>(vec.take(), vec.size());
// These versions are hopefully no-ops.
template <class T, bool C>
inline ActionResult<T,C> move(ActionResult<T,C> &ptr) {
return ptr;
template <class T> inline
ASTMultiPtr<T>& move(ASTMultiPtr<T> &ptr) {
return ptr;
// We can re-use the low bit of expression, statement, base, and
// member-initializer pointers for the "invalid" flag of
// ActionResult.
template<> struct IsResultPtrLowBitFree<Expr*> {
static const bool value = true;
template<> struct IsResultPtrLowBitFree<Stmt*> {
static const bool value = true;
template<> struct IsResultPtrLowBitFree<CXXBaseSpecifier*> {
static const bool value = true;
template<> struct IsResultPtrLowBitFree<CXXCtorInitializer*> {
static const bool value = true;
typedef ActionResult<Expr*> ExprResult;
typedef ActionResult<Stmt*> StmtResult;
typedef ActionResult<ParsedType> TypeResult;
typedef ActionResult<CXXBaseSpecifier*> BaseResult;
typedef ActionResult<CXXCtorInitializer*> MemInitResult;
typedef ActionResult<Decl*> DeclResult;
typedef OpaquePtr<TemplateName> ParsedTemplateTy;
inline Expr *move(Expr *E) { return E; }
inline Stmt *move(Stmt *S) { return S; }
typedef ASTMultiPtr<Expr*> MultiExprArg;
typedef ASTMultiPtr<Stmt*> MultiStmtArg;
typedef ASTMultiPtr<ParsedType> MultiTypeArg;
typedef ASTMultiPtr<TemplateParameterList*> MultiTemplateParamsArg;
inline ExprResult ExprError() { return ExprResult(true); }
inline StmtResult StmtError() { return StmtResult(true); }
inline ExprResult ExprError(const DiagnosticBuilder&) { return ExprError(); }
inline StmtResult StmtError(const DiagnosticBuilder&) { return StmtError(); }
inline ExprResult ExprEmpty() { return ExprResult(false); }
inline StmtResult StmtEmpty() { return StmtResult(false); }
inline Expr *AssertSuccess(ExprResult R) {
assert(!R.isInvalid() && "operation was asserted to never fail!");
return R.get();
inline Stmt *AssertSuccess(StmtResult R) {
assert(!R.isInvalid() && "operation was asserted to never fail!");
return R.get();