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   const BugType BT{this, "Assigned value is garbage or undefined"};
  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   // Generate a report for this bug.
  53   llvm::SmallString<128> Str;
  54   llvm::raw_svector_ostream OS(Str);
  55
  56   const Expr *ex = nullptr;
  57
  58   while (StoreE) {
  59     if (const UnaryOperator *U = dyn_cast<UnaryOperator>(StoreE)) {
  60       OS << "The expression is an uninitialized value. "
  61             "The computed value will also be garbage";
  62
  63       ex = U->getSubExpr();
  64       break;
  65     }
  66
  67     if (const BinaryOperator *B = dyn_cast<BinaryOperator>(StoreE)) {
  68       if (B->isCompoundAssignmentOp()) {
  69         if (C.getSVal(B->getLHS()).isUndef()) {
  70           OS << "The left expression of the compound assignment is an "
  71                 "uninitialized value. The computed value will also be garbage";
  72           ex = B->getLHS();
  73           break;
  74         }
  75       }
  76
  77       ex = B->getRHS();
  78       break;
  79     }
  80
  81     if (const DeclStmt *DS = dyn_cast<DeclStmt>(StoreE)) {
  82       const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());
  83       ex = VD->getInit();
  84     }
  85
  86     if (const auto *CD =
  87             dyn_cast<CXXConstructorDecl>(C.getStackFrame()->getDecl())) {
  88       if (CD->isImplicit()) {
  89         for (auto *I : CD->inits()) {
  90           if (I->getInit()->IgnoreImpCasts() == StoreE) {
  91             OS << "Value assigned to field '" << I->getMember()->getName()
  92                << "' in implicit constructor is garbage or undefined";
  93             break;
  94           }
  95         }
  96       }
  97     }
  98
  99     break;
 100   }
 101
 102   if (OS.str().empty())
 103     OS << BT.getDescription();
 104
 105   auto R = std::make_unique<PathSensitiveBugReport>(BT, OS.str(), N);
 106   if (ex) {
 107     R->addRange(ex->getSourceRange());
 108     bugreporter::trackExpressionValue(N, ex, *R);
 109   }
 110   C.emitReport(std::move(R));
 111 }
 112
 113 void ento::registerUndefinedAssignmentChecker(CheckerManager &mgr) {
 114   mgr.registerChecker<UndefinedAssignmentChecker>();
 115 }
 116
 117 bool ento::shouldRegisterUndefinedAssignmentChecker(const CheckerManager &mgr) {
 118   return true;
 119 }