ObjCPropertyChecker.cpp

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//==- ObjCPropertyChecker.cpp - Check ObjC properties ------------*- 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 checker finds issues with Objective-C properties.
//  Currently finds only one kind of issue:
//  - Find synthesized properties with copy attribute of mutable NS collection
//    types. Calling -copy on such collections produces an immutable copy,
//    which contradicts the type of the property.
//
//===----------------------------------------------------------------------===//
 
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
 
using namespace clang;
using namespace ento;
 
namespace {
class ObjCPropertyChecker
    : public Checker<check::ASTDecl<ObjCPropertyDecl>> {
  void checkCopyMutable(const ObjCPropertyDecl *D, BugReporter &BR) const;
 
public:
  void checkASTDecl(const ObjCPropertyDecl *D, AnalysisManager &Mgr,
                    BugReporter &BR) const;
};
} // end anonymous namespace.
 
void ObjCPropertyChecker::checkASTDecl(const ObjCPropertyDecl *D,
                                       AnalysisManager &Mgr,
                                       BugReporter &BR) const {
  checkCopyMutable(D, BR);
}
 
void ObjCPropertyChecker::checkCopyMutable(const ObjCPropertyDecl *D,
                                           BugReporter &BR) const {
  if (D->isReadOnly() || D->getSetterKind() != ObjCPropertyDecl::Copy)
    return;
 
  QualType T = D->getType();
  if (!T->isObjCObjectPointerType())
    return;
 
  const std::string &PropTypeName(T->getPointeeType().getCanonicalType()
                                                     .getUnqualifiedType()
                                                     .getAsString());
  if (!StringRef(PropTypeName).starts_with("NSMutable"))
    return;
 
  const ObjCImplDecl *ImplD = nullptr;
  if (const ObjCInterfaceDecl *IntD =
          dyn_cast<ObjCInterfaceDecl>(D->getDeclContext())) {
    ImplD = IntD->getImplementation();
  } else if (auto *CatD = dyn_cast<ObjCCategoryDecl>(D->getDeclContext())) {
    ImplD = CatD->getClassInterface()->getImplementation();
  }
 
  if (!ImplD || ImplD->HasUserDeclaredSetterMethod(D))
    return;
 
  SmallString<128> Str;
  llvm::raw_svector_ostream OS(Str);
  OS << "Property of mutable type '" << PropTypeName
     << "' has 'copy' attribute; an immutable object will be stored instead";
 
  BR.EmitBasicReport(
      D, this, "Objective-C property misuse", "Logic error", OS.str(),
      PathDiagnosticLocation::createBegin(D, BR.getSourceManager()),
      D->getSourceRange());
}
 
void ento::registerObjCPropertyChecker(CheckerManager &Mgr) {
  Mgr.registerChecker<ObjCPropertyChecker>();
}
 
bool ento::shouldRegisterObjCPropertyChecker(const CheckerManager &mgr) {
  return true;
}