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1 //===--- UndefinedAssignmentChecker.h ---------------------------*- C++ -*--==//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This defines UndefinedAssignmentChecker, a builtin check in ExprEngine that
11 // checks for assigning undefined values.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ClangSACheckers.h"
16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 
21 using namespace clang;
22 using namespace ento;
23 
24 namespace {
25 class UndefinedAssignmentChecker
26   : public Checker<check::Bind> {
27   mutable std::unique_ptr<BugType> BT;
28 
29 public:
30   void checkBind(SVal location, SVal val, const Stmt *S,
31                  CheckerContext &C) const;
32 };
33 }
34 
checkBind(SVal location,SVal val,const Stmt * StoreE,CheckerContext & C) const35 void UndefinedAssignmentChecker::checkBind(SVal location, SVal val,
36                                            const Stmt *StoreE,
37                                            CheckerContext &C) const {
38   if (!val.isUndef())
39     return;
40 
41   // Do not report assignments of uninitialized values inside swap functions.
42   // This should allow to swap partially uninitialized structs
43   // (radar://14129997)
44   if (const FunctionDecl *EnclosingFunctionDecl =
45       dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))
46     if (C.getCalleeName(EnclosingFunctionDecl) == "swap")
47       return;
48 
49   ExplodedNode *N = C.generateErrorNode();
50 
51   if (!N)
52     return;
53 
54   const char *str = "Assigned value is garbage or undefined";
55 
56   if (!BT)
57     BT.reset(new BuiltinBug(this, str));
58 
59   // Generate a report for this bug.
60   const Expr *ex = nullptr;
61 
62   while (StoreE) {
63     if (const BinaryOperator *B = dyn_cast<BinaryOperator>(StoreE)) {
64       if (B->isCompoundAssignmentOp()) {
65         ProgramStateRef state = C.getState();
66         if (state->getSVal(B->getLHS(), C.getLocationContext()).isUndef()) {
67           str = "The left expression of the compound assignment is an "
68                 "uninitialized value. The computed value will also be garbage";
69           ex = B->getLHS();
70           break;
71         }
72       }
73 
74       ex = B->getRHS();
75       break;
76     }
77 
78     if (const DeclStmt *DS = dyn_cast<DeclStmt>(StoreE)) {
79       const VarDecl *VD = dyn_cast<VarDecl>(DS->getSingleDecl());
80       ex = VD->getInit();
81     }
82 
83     break;
84   }
85 
86   auto R = llvm::make_unique<BugReport>(*BT, str, N);
87   if (ex) {
88     R->addRange(ex->getSourceRange());
89     bugreporter::trackNullOrUndefValue(N, ex, *R);
90   }
91   C.emitReport(std::move(R));
92 }
93 
registerUndefinedAssignmentChecker(CheckerManager & mgr)94 void ento::registerUndefinedAssignmentChecker(CheckerManager &mgr) {
95   mgr.registerChecker<UndefinedAssignmentChecker>();
96 }
97