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
checkPostStmt(const BinaryOperator * B,CheckerContext & C) const38 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
44 // Do not report assignments of uninitialized values inside swap functions.
45 // This should allow to swap partially uninitialized structs
46 // (radar://14129997)
47 if (const FunctionDecl *EnclosingFunctionDecl =
48 dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))
49 if (C.getCalleeName(EnclosingFunctionDecl) == "swap")
50 return;
51
52 // Generate an error node.
53 ExplodedNode *N = C.generateSink();
54 if (!N)
55 return;
56
57 if (!BT)
58 BT.reset(new BuiltinBug("Result of operation is garbage or undefined"));
59
60 SmallString<256> sbuf;
61 llvm::raw_svector_ostream OS(sbuf);
62 const Expr *Ex = NULL;
63 bool isLeft = true;
64
65 if (state->getSVal(B->getLHS(), LCtx).isUndef()) {
66 Ex = B->getLHS()->IgnoreParenCasts();
67 isLeft = true;
68 }
69 else if (state->getSVal(B->getRHS(), LCtx).isUndef()) {
70 Ex = B->getRHS()->IgnoreParenCasts();
71 isLeft = false;
72 }
73
74 if (Ex) {
75 OS << "The " << (isLeft ? "left" : "right")
76 << " operand of '"
77 << BinaryOperator::getOpcodeStr(B->getOpcode())
78 << "' is a garbage value";
79 }
80 else {
81 // Neither operand was undefined, but the result is undefined.
82 OS << "The result of the '"
83 << BinaryOperator::getOpcodeStr(B->getOpcode())
84 << "' expression is undefined";
85 }
86 BugReport *report = new BugReport(*BT, OS.str(), N);
87 if (Ex) {
88 report->addRange(Ex->getSourceRange());
89 bugreporter::trackNullOrUndefValue(N, Ex, *report);
90 }
91 else
92 bugreporter::trackNullOrUndefValue(N, B, *report);
93
94 C.emitReport(report);
95 }
96 }
97
registerUndefResultChecker(CheckerManager & mgr)98 void ento::registerUndefResultChecker(CheckerManager &mgr) {
99 mgr.registerChecker<UndefResultChecker>();
100 }
101