path: root/include/clang/Sema/ScopeInfo.h

//===--- 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.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_SEMA_SCOPE_INFO_H
#define LLVM_CLANG_SEMA_SCOPE_INFO_H

#include "clang/AST/Type.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"

namespace clang {

class Decl;
class BlockDecl;
class CapturedDecl;
class CXXMethodDecl;
class ObjCPropertyDecl;
class IdentifierInfo;
class LabelDecl;
class ReturnStmt;
class Scope;
class SwitchStmt;
class VarDecl;
class DeclRefExpr;
class ObjCIvarRefExpr;
class ObjCPropertyRefExpr;
class ObjCMessageExpr;

namespace sema {

/// \brief Contains information about the compound statement currently being
/// parsed.
class CompoundScopeInfo {
public:
  CompoundScopeInfo()
    : HasEmptyLoopBodies(false) { }

  /// \brief Whether this compound stamement contains `for' or `while' loops
  /// with empty bodies.
  bool HasEmptyLoopBodies;

  void setHasEmptyLoopBodies() {
    HasEmptyLoopBodies = true;
  }
};

class PossiblyUnreachableDiag {
public:
  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 {
protected:
  enum ScopeKind {
    SK_Function,
    SK_Block,
    SK_Lambda,
    SK_CapturedRegion
  };
  
public:
  /// \brief What kind of scope we are describing.
  ///
  ScopeKind Kind;

  /// \brief Whether this function contains a VLA, \@try, try, C++
  /// initializer, or anything else that can't be jumped past.
  bool HasBranchProtectedScope;

  /// \brief Whether this function contains any switches or direct gotos.
  bool HasBranchIntoScope;

  /// \brief Whether this function contains any indirect gotos.
  bool HasIndirectGoto;

  /// \brief Whether a statement was dropped because it was invalid.
  bool HasDroppedStmt;

  /// 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;

  /// \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 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;

public:
  /// 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.property     | 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)
  /// 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);

    // For use in DenseMap.
    friend class DenseMapInfo;
    inline WeakObjectProfileTy();
    static inline WeakObjectProfileTy getSentinel();

  public:
    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 foo.bar 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 {
    public:
      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,
                                                           Val.Property));
      }

      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;
  public:
    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,
                              WeakObjectProfileTy::DenseMapInfo>
          WeakObjectUseMap;

private:
  /// Used to collect all uses of weak objects in this function body.
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  WeakObjectUseMap WeakObjectUses;

public:
  /// 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 stro