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 std::unique_ptr<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.generateErrorNode();
54 if (!N)
55 return;
56
57 if (!BT)
58 BT.reset(
59 new BuiltinBug(this, "Result of operation is garbage or undefined"));
60
61 SmallString<256> sbuf;
62 llvm::raw_svector_ostream OS(sbuf);
63 const Expr *Ex = nullptr;
64 bool isLeft = true;
65
66 if (state->getSVal(B->getLHS(), LCtx).isUndef()) {
67 Ex = B->getLHS()->IgnoreParenCasts();
68 isLeft = true;
69 }
70 else if (state->getSVal(B->getRHS(), LCtx).isUndef()) {
71 Ex = B->getRHS()->IgnoreParenCasts();
72 isLeft = false;
73 }
74
75 if (Ex) {
76 OS << "The " << (isLeft ? "left" : "right")
77 << " operand of '"
78 << BinaryOperator::getOpcodeStr(B->getOpcode())
79 << "' is a garbage value";
80 }
81 else {
82 // Neither operand was undefined, but the result is undefined.
83 OS << "The result of the '"
84 << BinaryOperator::getOpcodeStr(B->getOpcode())
85 << "' expression is undefined";
86 }
87 auto report = llvm::make_unique<BugReport>(*BT, OS.str(), N);
88 if (Ex) {
89 report->addRange(Ex->getSourceRange());
90 bugreporter::trackNullOrUndefValue(N, Ex, *report);
91 }
92 else
93 bugreporter::trackNullOrUndefValue(N, B, *report);
94
95 C.emitReport(std::move(report));
96 }
97 }
98
registerUndefResultChecker(CheckerManager & mgr)99 void ento::registerUndefResultChecker(CheckerManager &mgr) {
100 mgr.registerChecker<UndefResultChecker>();
101 }
102