text: //=- NSAutoreleasePoolChecker.cpp --------------------------------*- 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 a NSAutoreleasePoolChecker, a small checker that warns
  //  about subpar uses of NSAutoreleasePool.  Note that while the check itself
  //  (in its current form) could be written as a flow-insensitive check, in
  //  can be potentially enhanced in the future with flow-sensitive information.
  //  It is also a good example of the CheckerVisitor interface. 
  //
  //===----------------------------------------------------------------------===//
  
  #include "ClangSACheckers.h"
  #include "clang/AST/Decl.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.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/ExprEngine.h"
  
  using namespace clang;
  using namespace ento;
  
  namespace {
  class NSAutoreleasePoolChecker
    : public Checker<check::PreObjCMessage> {
    mutable std::unique_ptr<BugType> BT;
    mutable Selector releaseS;
  
  public:
    void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
  };
  
  } // end anonymous namespace
  
  void NSAutoreleasePoolChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
                                                     CheckerContext &C) const {
    if (!msg.isInstanceMessage())
      return;
  
    const ObjCInterfaceDecl *OD = msg.getReceiverInterface();
    if (!OD)
      return;  
    if (!OD->getIdentifier()->isStr("NSAutoreleasePool"))
      return;
  
    if (releaseS.isNull())
      releaseS = GetNullarySelector("release", C.getASTContext());
    // Sending 'release' message?
    if (msg.getSelector() != releaseS)
      return;
  
    if (!BT)
      BT.reset(new BugType(this, "Use -drain instead of -release",
                           "API Upgrade (Apple)"));
  
    ExplodedNode *N = C.addTransition();
    if (!N) {
      assert(0);
      return;
    }
  
    auto Report = llvm::make_unique<BugReport>(
        *BT, "Use -drain instead of -release when using NSAutoreleasePool and "
             "garbage collection", N);
    Report->addRange(msg.getSourceRange());
    C.emitReport(std::move(Report));
  }
  
  void ento::registerNSAutoreleasePoolChecker(CheckerManager &mgr) {
    if (mgr.getLangOpts().getGC() != LangOptions::NonGC)
      mgr.registerChecker<NSAutoreleasePoolChecker>();
  }
  