1 // SmartPtrModeling.cpp - Model behavior of C++ smart pointers - C++ ------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines a checker that models various aspects of
10 // C++ smart pointer behavior.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "Move.h"
15 
16 #include "clang/AST/ExprCXX.h"
17 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19 #include "clang/StaticAnalyzer/Core/Checker.h"
20 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
22 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
23 
24 using namespace clang;
25 using namespace ento;
26 
27 namespace {
28 class SmartPtrModeling : public Checker<eval::Call> {
29   bool isNullAfterMoveMethod(const CallEvent &Call) const;
30 
31 public:
32   bool evalCall(const CallEvent &Call, CheckerContext &C) const;
33 };
34 } // end of anonymous namespace
35 
36 bool SmartPtrModeling::isNullAfterMoveMethod(const CallEvent &Call) const {
37   // TODO: Update CallDescription to support anonymous calls?
38   // TODO: Handle other methods, such as .get() or .release().
39   // But once we do, we'd need a visitor to explain null dereferences
40   // that are found via such modeling.
41   const auto *CD = dyn_cast_or_null<CXXConversionDecl>(Call.getDecl());
42   return CD && CD->getConversionType()->isBooleanType();
43 }
44 
45 bool SmartPtrModeling::evalCall(const CallEvent &Call,
46                                 CheckerContext &C) const {
47   if (!isNullAfterMoveMethod(Call))
48     return false;
49 
50   ProgramStateRef State = C.getState();
51   const MemRegion *ThisR =
52       cast<CXXInstanceCall>(&Call)->getCXXThisVal().getAsRegion();
53 
54   if (!move::isMovedFrom(State, ThisR)) {
55     // TODO: Model this case as well. At least, avoid invalidation of globals.
56     return false;
57   }
58 
59   // TODO: Add a note to bug reports describing this decision.
60   C.addTransition(
61       State->BindExpr(Call.getOriginExpr(), C.getLocationContext(),
62                       C.getSValBuilder().makeZeroVal(Call.getResultType())));
63   return true;
64 }
65 
66 void ento::registerSmartPtrModeling(CheckerManager &Mgr) {
67   Mgr.registerChecker<SmartPtrModeling>();
68 }
69 
70 bool ento::shouldRegisterSmartPtrModeling(const LangOptions &LO) {
71   return LO.CPlusPlus;
72 }
73