RetainCountChecker.h

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//==--- RetainCountChecker.h - Checks for leaks and other issues -*- C++ -*--//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//  This file defines the methods for RetainCountChecker, which implements
//  a reference count checker for Core Foundation and Cocoa on (Mac OS X).
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_LIB_STATICANALYZER_CHECKERS_RETAINCOUNTCHECKER_H
#define LLVM_CLANG_LIB_STATICANALYZER_CHECKERS_RETAINCOUNTCHECKER_H
 
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "RetainCountDiagnostics.h"
#include "clang/AST/Attr.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/ParentMap.h"
#include "clang/Analysis/DomainSpecific/CocoaConventions.h"
#include "clang/Analysis/PathDiagnostic.h"
#include "clang/Analysis/RetainSummaryManager.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Analysis/SelectorExtras.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ImmutableList.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include <cstdarg>
#include <utility>
 
namespace clang {
namespace ento {
namespace retaincountchecker {
 
/// Metadata on reference.
class RefVal {
public:
  enum Kind {
    Owned = 0, // Owning reference.
    NotOwned,  // Reference is not owned by still valid (not freed).
    Released,  // Object has been released.
    ReturnedOwned, // Returned object passes ownership to caller.
    ReturnedNotOwned, // Return object does not pass ownership to caller.
    ERROR_START,
    ErrorDeallocNotOwned, // -dealloc called on non-owned object.
    ErrorUseAfterRelease, // Object used after released.
    ErrorReleaseNotOwned, // Release of an object that was not owned.
    ERROR_LEAK_START,
    ErrorLeak,  // A memory leak due to excessive reference counts.
    ErrorLeakReturned, // A memory leak due to the returning method not having
                       // the correct naming conventions.
    ErrorOverAutorelease,
    ErrorReturnedNotOwned
  };
 
  /// Tracks how an object referenced by an ivar has been used.
  ///
  /// This accounts for us not knowing if an arbitrary ivar is supposed to be
  /// stored at +0 or +1.
  enum class IvarAccessHistory {
    None,
    AccessedDirectly,
    ReleasedAfterDirectAccess
  };
 
private:
  /// The number of outstanding retains.
  unsigned Cnt;
  /// The number of outstanding autoreleases.
  unsigned ACnt;
  /// The (static) type of the object at the time we started tracking it.
  QualType T;
 
  /// The current state of the object.
  ///
  /// See the RefVal::Kind enum for possible values.
  unsigned RawKind : 5;
 
  /// The kind of object being tracked (CF or ObjC or OSObject), if known.
  ///
  /// See the ObjKind enum for possible values.
  unsigned RawObjectKind : 3;
 
  /// True if the current state and/or retain count may turn out to not be the
  /// best possible approximation of the reference counting state.
  ///
  /// If true, the checker may decide to throw away ("override") this state
  /// in favor of something else when it sees the object being used in new ways.
  ///
  /// This setting should not be propagated to state derived from this state.
  /// Once we start deriving new states, it would be inconsistent to override
  /// them.
  unsigned RawIvarAccessHistory : 2;
 
  RefVal(Kind k, ObjKind o, unsigned cnt, unsigned acnt, QualType t,
         IvarAccessHistory IvarAccess)
    : Cnt(cnt), ACnt(acnt), T(t), RawKind(static_cast<unsigned>(k)),
      RawObjectKind(static_cast<unsigned>(o)),
      RawIvarAccessHistory(static_cast<unsigned>(IvarAccess)) {
    assert(getKind() == k && "not enough bits for the kind");
    assert(getObjKind() == o && "not enough bits for the object kind");
    assert(getIvarAccessHistory() == IvarAccess && "not enough bits");
  }
 
public:
  Kind getKind() const { return static_cast<Kind>(RawKind); }
 
  ObjKind getObjKind() const {
    return static_cast<ObjKind>(RawObjectKind);
  }
 
  unsigned getCount() const { return Cnt; }
  unsigned getAutoreleaseCount() const { return ACnt; }
  unsigned getCombinedCounts() const { return Cnt + ACnt; }
  void clearCounts() {
    Cnt = 0;
    ACnt = 0;
  }
  void setCount(unsigned i) {
    Cnt = i;
  }
  void setAutoreleaseCount(unsigned i) {
    ACnt = i;
  }
 
  QualType getType() const { return T; }
 
  /// Returns what the analyzer knows about direct accesses to a particular
  /// instance variable.
  ///
  /// If the object with this refcount wasn't originally from an Objective-C
  /// ivar region, this should always return IvarAccessHistory::None.
  IvarAccessHistory getIvarAccessHistory() const {
    return static_cast<IvarAccessHistory>(RawIvarAccessHistory);
  }
 
  bool isOwned() const {
    return getKind() == Owned;
  }
 
  bool isNotOwned() const {
    return getKind() == NotOwned;
  }
 
  bool isReturnedOwned() const {
    return getKind() == ReturnedOwned;
  }
 
  bool isReturnedNotOwned() const {
    return getKind() == ReturnedNotOwned;
  }
 
  /// Create a state for an object whose lifetime is the responsibility of the
  /// current function, at least partially.
  ///
  /// Most commonly, this is an owned object with a retain count of +1.
  static RefVal makeOwned(ObjKind o, QualType t) {
    return RefVal(Owned, o, /*Count=*/1, 0, t, IvarAccessHistory::None);
  }
 
  /// Create a state for an object whose lifetime is not the responsibility of
  /// the current function.
  ///
  /// Most commonly, this is an unowned object with a retain count of +0.
  static RefVal makeNotOwned(ObjKind o, QualType t) {
    return RefVal(NotOwned, o, /*Count=*/0, 0, t, IvarAccessHistory::None);
  }
 
  RefVal operator-(size_t i) const {
    return RefVal(getKind(), getObjKind(), getCount() - i,
                  getAutoreleaseCount(), getType(), getIvarAccessHistory());
  }
 
  RefVal operator+(size_t i) const {
    return RefVal(getKind(), getObjKind(), getCount() + i,
                  getAutoreleaseCount(), getType(), getIvarAccessHistory());
  }
 
  RefVal operator^(Kind k) const {
    return RefVal(k, getObjKind(), getCount(), getAutoreleaseCount(),
                  getType(), getIvarAccessHistory());
  }
 
  RefVal autorelease() const {
    return RefVal(getKind(), getObjKind(), getCount(), getAutoreleaseCount()+1,
                  getType(), getIvarAccessHistory());
  }
 
  RefVal withIvarAccess() const {
    assert(getIvarAccessHistory() == IvarAccessHistory::None);
    return RefVal(getKind(), getObjKind(), getCount(), getAutoreleaseCount(),
                  getType(), IvarAccessHistory::AccessedDirectly);
  }
 
  RefVal releaseViaIvar() const {
    assert(getIvarAccessHistory() == IvarAccessHistory::AccessedDirectly);
    return RefVal(getKind(), getObjKind(), getCount(), getAutoreleaseCount(),
                  getType(), IvarAccessHistory::ReleasedAfterDirectAccess);
  }
 
  // Comparison, profiling, and pretty-printing.
  bool hasSameState(const RefVal &X) const {
    return getKind() == X.getKind() && Cnt == X.Cnt && ACnt == X.ACnt &&
           getIvarAccessHistory() == X.getIvarAccessHistory();
  }
 
  bool operator==(const RefVal& X) const {
    return T == X.T && hasSameState(X) && getObjKind() == X.getObjKind();
  }
 
  void Profile(llvm::FoldingSetNodeID& ID) const {
    ID.Add(T);
    ID.AddInteger(RawKind);
    ID.AddInteger(Cnt);
    ID.AddInteger(ACnt);
    ID.AddInteger(RawObjectKind);
    ID.AddInteger(RawIvarAccessHistory);
  }
 
  void print(raw_ostream &Out) const;
};
 
class RetainCountChecker
    : public CheckerFamily<
          check::Bind, check::DeadSymbols, check::BeginFunction,
          check::EndFunction, check::PostStmt<BlockExpr>,
          check::PostStmt<CastExpr>, check::PostStmt<ObjCArrayLiteral>,
          check::PostStmt<ObjCDictionaryLiteral>,
          check::PostStmt<ObjCBoxedExpr>, check::PostStmt<ObjCIvarRefExpr>,
          check::PostCall, check::RegionChanges, eval::Assume, eval::Call> {
 
public:
  RefCountFrontend RetainCount;
  RefCountFrontend OSObjectRetainCount;
 
  mutable std::unique_ptr<RetainSummaryManager> Summaries;
 
  static std::unique_ptr<SimpleProgramPointTag> DeallocSentTag;
  static std::unique_ptr<SimpleProgramPointTag> CastFailTag;
 
  /// Track initial parameters (for the entry point) for NS/CF objects.
  bool TrackNSCFStartParam = false;
 
  StringRef getDebugTag() const override { return "RetainCountChecker"; }
 
  RetainSummaryManager &getSummaryManager(ASTContext &Ctx) const {
    if (!Summaries)
      Summaries = std::make_unique<RetainSummaryManager>(
          Ctx, RetainCount.isEnabled(), OSObjectRetainCount.isEnabled());
    return *Summaries;
  }
 
  RetainSummaryManager &getSummaryManager(CheckerContext &C) const {
    return getSummaryManager(C.getASTContext());
  }
 
  const RefCountFrontend &getPreferredFrontend() const {
    // FIXME: The two frontends of this checker family are in an unusual
    // relationship: if they are both enabled, then all bug reports are
    // reported by RetainCount (i.e. `osx.cocoa.RetainCount`), even the bugs
    // that "belong to" OSObjectRetainCount (i.e. `osx.OSObjectRetainCount`).
    // This is counter-intuitive and should be fixed to avoid confusion.
    return RetainCount.isEnabled() ? RetainCount : OSObjectRetainCount;
  }
 
  void printState(raw_ostream &Out, ProgramStateRef State,
                  const char *NL, const char *Sep) const override;
 
  void checkBind(SVal loc, SVal val, const Stmt *S, bool AtDeclInit,
                 CheckerContext &C) const;
  void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
  void checkPostStmt(const CastExpr *CE, CheckerContext &C) const;
 
  void checkPostStmt(const ObjCArrayLiteral *AL, CheckerContext &C) const;
  void checkPostStmt(const ObjCDictionaryLiteral *DL, CheckerContext &C) const;
  void checkPostStmt(const ObjCBoxedExpr *BE, CheckerContext &C) const;
 
  void checkPostStmt(const ObjCIvarRefExpr *IRE, CheckerContext &C) const;
 
  void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
 
  void checkSummary(const RetainSummary &Summ, const CallEvent &Call,
                    CheckerContext &C) const;
 
  void processSummaryOfInlined(const RetainSummary &Summ,
                               const CallEvent &Call,
                               CheckerContext &C) const;
 
  bool evalCall(const CallEvent &Call, CheckerContext &C) const;
 
  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
                                 bool Assumption) const;
 
  ProgramStateRef
  checkRegionChanges(ProgramStateRef state,
                     const InvalidatedSymbols *invalidated,
                     ArrayRef<const MemRegion *> ExplicitRegions,
                     ArrayRef<const MemRegion *> Regions, const StackFrame *SF,
                     const CallEvent *Call) const;
 
  ExplodedNode* checkReturnWithRetEffect(const ReturnStmt *S, CheckerContext &C,
                                ExplodedNode *Pred, RetEffect RE, RefVal X,
                                SymbolRef Sym, ProgramStateRef state) const;
 
  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
  void checkBeginFunction(CheckerContext &C) const;
  void checkEndFunction(const ReturnStmt *RS, CheckerContext &C) const;
 
  ProgramStateRef updateSymbol(ProgramStateRef state, SymbolRef sym,
                               RefVal V, ArgEffect E, RefVal::Kind &hasErr,
                               CheckerContext &C) const;
 
  const RefCountBug &errorKindToBugKind(RefVal::Kind ErrorKind,
                                        SymbolRef Sym) const;
 
  bool isReleaseUnownedError(RefVal::Kind ErrorKind) const;
 
  void processNonLeakError(ProgramStateRef St, SourceRange ErrorRange,
                           RefVal::Kind ErrorKind, SymbolRef Sym,
                           CheckerContext &C) const;
 
  void processObjCLiterals(CheckerContext &C, const Expr *Ex) const;
 
  ProgramStateRef handleSymbolDeath(ProgramStateRef state,
                                    SymbolRef sid, RefVal V,
                                    SmallVectorImpl<SymbolRef> &Leaked) const;
 
  ProgramStateRef handleAutoreleaseCounts(ProgramStateRef state,
                                          ExplodedNode *Pred,
                                          CheckerContext &Ctx, SymbolRef Sym,
                                          RefVal V,
                                          const ReturnStmt *S = nullptr) const;
 
  ExplodedNode *processLeaks(ProgramStateRef state,
                             SmallVectorImpl<SymbolRef> &Leaked,
                             CheckerContext &Ctx,
                             ExplodedNode *Pred = nullptr) const;
 
  static const SimpleProgramPointTag &getDeallocSentTag() {
    return *DeallocSentTag;
  }
 
  static const SimpleProgramPointTag &getCastFailTag() { return *CastFailTag; }
 
private:
  /// Perform the necessary checks and state adjustments at the end of the
  /// function.
  /// \p S Return statement, may be null.
  ExplodedNode * processReturn(const ReturnStmt *S, CheckerContext &C) const;
};
 
//===----------------------------------------------------------------------===//
// RefBindings - State used to track object reference counts.
//===----------------------------------------------------------------------===//
 
const RefVal *getRefBinding(ProgramStateRef State, SymbolRef Sym);
 
/// Returns true if this stack frame is for an Objective-C method that is a
/// property getter or setter whose body has been synthesized by the analyzer.
inline bool isSynthesizedAccessor(const StackFrame *SF) {
  auto Method = dyn_cast_or_null<ObjCMethodDecl>(SF->getDecl());
  if (!Method || !Method->isPropertyAccessor())
    return false;
 
  return SF->getAnalysisDeclContext()->isBodyAutosynthesized();
}
 
} // end namespace retaincountchecker
} // end namespace ento
} // end namespace clang
 
#endif