1 //=== UndefResultChecker.cpp ------------------------------------*- 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 UndefResultChecker, a builtin check in ExprEngine that
11 // performs checks for undefined results of non-assignment binary operators.
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 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
21 #include "llvm/ADT/SmallString.h"
22 #include "llvm/Support/raw_ostream.h"
23 
24 using namespace clang;
25 using namespace ento;
26 
27 namespace {
28 class UndefResultChecker
29   : public Checker< check::PostStmt<BinaryOperator> > {
30 
31   mutable OwningPtr<BugType> BT;
32 
33 public:
34   void checkPostStmt(const BinaryOperator *B, CheckerContext &C) const;
35 };
36 } // end anonymous namespace
37 
38 void UndefResultChecker::checkPostStmt(const BinaryOperator *B,
39                                        CheckerContext &C) const {
40   ProgramStateRef state = C.getState();
41   const LocationContext *LCtx = C.getLocationContext();
42   if (state->getSVal(B, LCtx).isUndef()) {
43     // Generate an error node.
44     ExplodedNode *N = C.generateSink();
45     if (!N)
46       return;
47 
48     if (!BT)
49       BT.reset(new BuiltinBug("Result of operation is garbage or undefined"));
50 
51     SmallString<256> sbuf;
52     llvm::raw_svector_ostream OS(sbuf);
53     const Expr *Ex = NULL;
54     bool isLeft = true;
55 
56     if (state->getSVal(B->getLHS(), LCtx).isUndef()) {
57       Ex = B->getLHS()->IgnoreParenCasts();
58       isLeft = true;
59     }
60     else if (state->getSVal(B->getRHS(), LCtx).isUndef()) {
61       Ex = B->getRHS()->IgnoreParenCasts();
62       isLeft = false;
63     }
64 
65     if (Ex) {
66       OS << "The " << (isLeft ? "left" : "right")
67          << " operand of '"
68          << BinaryOperator::getOpcodeStr(B->getOpcode())
69          << "' is a garbage value";
70     }
71     else {
72       // Neither operand was undefined, but the result is undefined.
73       OS << "The result of the '"
74          << BinaryOperator::getOpcodeStr(B->getOpcode())
75          << "' expression is undefined";
76     }
77     BugReport *report = new BugReport(*BT, OS.str(), N);
78     if (Ex) {
79       report->addRange(Ex->getSourceRange());
80       bugreporter::trackNullOrUndefValue(N, Ex, *report);
81     }
82     else
83       bugreporter::trackNullOrUndefValue(N, B, *report);
84 
85     C.emitReport(report);
86   }
87 }
88 
89 void ento::registerUndefResultChecker(CheckerManager &mgr) {
90   mgr.registerChecker<UndefResultChecker>();
91 }
92