clang/lib/StaticAnalyzer/Checkers/UndefinedAssignmentChecker.cpp

   1 //===--- UndefinedAssignmentChecker.h ---------------------------*- 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 defines UndefinedAssignmentChecker, a builtin check in ExprEngine that
  10 // checks for assigning undefined values.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
  15 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
  16 #include "clang/StaticAnalyzer/Core/Checker.h"
  17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
  18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
  19
  20 using namespace clang;
  21 using namespace ento;
  22
  23 namespace {
  24 class UndefinedAssignmentChecker
  25   : public Checker<check::Bind> {
  26   mutable std::unique_ptr<BugType> BT;
  27
  28 public:
  29   void checkBind(SVal location, SVal val, const Stmt *S,
  30                  CheckerContext &C) const;
  31 };
  32 }
  33
  34 void UndefinedAssignmentChecker::checkBind(SVal location, SVal val,
  35                                            const Stmt *StoreE,
  36                                            CheckerContext &C) const {
  37   if (!val.isUndef())
  38     return;
  39
  40   // Do not report assignments of uninitialized values inside swap functions.
  41   // This should allow to swap partially uninitialized structs
  42   if (const FunctionDecl *EnclosingFunctionDecl =
  43       dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))
  44     if (C.getCalleeName(EnclosingFunctionDecl) == "swap")
  45       return;
  46
  47   ExplodedNode *N = C.generateErrorNode();
  48
  49   if (!N)
  50     return;
  51
  52   static const char *const DefaultMsg =
  53       "Assigned value is garbage or undefined";
  54   if (!BT)
  55     BT.reset(new BugType(this, DefaultMsg));
  56
  57   // Generate a report for this bug.
  58   llvm::SmallString<128> Str;
  59   llvm::raw_svector_ostream OS(Str);
  60
  61   const Expr *ex = nullptr;
  62
  63   while (StoreE) {
  64     if (const UnaryOperator *U = dyn_cast<UnaryOperator>(StoreE)) {
  65       OS << "The expression is an uninitialized value. "
  66             "The computed value will also be garbage";
  67
  68       ex = U->getSubExpr();
  69       break;
  70     }
  71
  72     if (const BinaryOperator *B = dyn_cast<BinaryOperator>(StoreE)) {
  73       if (B->isCompoundAssignmentOp()) {
  74         if (C.getSVal(B->getLHS()).isUndef()) {
  75           OS << "The left expression of the compound assignment is an "
  76                 "uninitialized value. The computed value will also be garbage";
  77           ex = B->getLHS();
  78           break;
  79         }
  80       }
  81
  82       ex = B->getRHS();
  83       break;
  84     }
  85
  86     if (const DeclStmt *DS = dyn_cast<DeclStmt>(StoreE)) {
  87       const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());
  88       ex = VD->getInit();
  89     }
  90
  91     if (const auto *CD =
  92             dyn_cast<CXXConstructorDecl>(C.getStackFrame()->getDecl())) {
  93       if (CD->isImplicit()) {
  94         for (auto *I : CD->inits()) {
  95           if (I->getInit()->IgnoreImpCasts() == StoreE) {
  96             OS << "Value assigned to field '" << I->getMember()->getName()
  97                << "' in implicit constructor is garbage or undefined";
  98             break;
  99           }
 100         }
 101       }
 102     }
 103
 104     break;
 105   }
 106
 107   if (OS.str().empty())
 108     OS << DefaultMsg;
 109
 110   auto R = std::make_unique<PathSensitiveBugReport>(*BT, OS.str(), N);
 111   if (ex) {
 112     R->addRange(ex->getSourceRange());
 113     bugreporter::trackExpressionValue(N, ex, *R);
 114   }
 115   C.emitReport(std::move(R));
 116 }
 117
 118 void ento::registerUndefinedAssignmentChecker(CheckerManager &mgr) {
 119   mgr.registerChecker<UndefinedAssignmentChecker>();
 120 }
 121
 122 bool ento::shouldRegisterUndefinedAssignmentChecker(const CheckerManager &mgr) {
 123   return true;
 124 }