1 //=== UndefResultChecker.cpp ------------------------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This defines UndefResultChecker, a builtin check in ExprEngine that
11 // performs checks for undefined results of non-assignment binary operators.
13 //===----------------------------------------------------------------------===//
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"
24 using namespace clang;
28 class UndefResultChecker
29 : public Checker< check::PostStmt<BinaryOperator> > {
31 mutable std::unique_ptr<BugType> BT;
34 void checkPostStmt(const BinaryOperator *B, CheckerContext &C) const;
36 } // end anonymous namespace
38 static bool isArrayIndexOutOfBounds(CheckerContext &C, const Expr *Ex) {
39 ProgramStateRef state = C.getState();
40 const LocationContext *LCtx = C.getLocationContext();
42 if (!isa<ArraySubscriptExpr>(Ex))
45 SVal Loc = state->getSVal(Ex, LCtx);
49 const MemRegion *MR = Loc.castAs<loc::MemRegionVal>().getRegion();
50 const ElementRegion *ER = dyn_cast<ElementRegion>(MR);
54 DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();
55 DefinedOrUnknownSVal NumElements = C.getStoreManager().getSizeInElements(
56 state, ER->getSuperRegion(), ER->getValueType());
57 ProgramStateRef StInBound = state->assumeInBound(Idx, NumElements, true);
58 ProgramStateRef StOutBound = state->assumeInBound(Idx, NumElements, false);
59 return StOutBound && !StInBound;
62 void UndefResultChecker::checkPostStmt(const BinaryOperator *B,
63 CheckerContext &C) const {
64 ProgramStateRef state = C.getState();
65 const LocationContext *LCtx = C.getLocationContext();
66 if (state->getSVal(B, LCtx).isUndef()) {
68 // Do not report assignments of uninitialized values inside swap functions.
69 // This should allow to swap partially uninitialized structs
71 if (const FunctionDecl *EnclosingFunctionDecl =
72 dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))
73 if (C.getCalleeName(EnclosingFunctionDecl) == "swap")
76 // Generate an error node.
77 ExplodedNode *N = C.generateErrorNode();
83 new BuiltinBug(this, "Result of operation is garbage or undefined"));
85 SmallString<256> sbuf;
86 llvm::raw_svector_ostream OS(sbuf);
87 const Expr *Ex = nullptr;
90 if (state->getSVal(B->getLHS(), LCtx).isUndef()) {
91 Ex = B->getLHS()->IgnoreParenCasts();
94 else if (state->getSVal(B->getRHS(), LCtx).isUndef()) {
95 Ex = B->getRHS()->IgnoreParenCasts();
100 OS << "The " << (isLeft ? "left" : "right")
102 << BinaryOperator::getOpcodeStr(B->getOpcode())
103 << "' is a garbage value";
104 if (isArrayIndexOutOfBounds(C, Ex))
105 OS << " due to array index out of bounds";
108 // Neither operand was undefined, but the result is undefined.
109 OS << "The result of the '"
110 << BinaryOperator::getOpcodeStr(B->getOpcode())
111 << "' expression is undefined";
113 auto report = llvm::make_unique<BugReport>(*BT, OS.str(), N);
115 report->addRange(Ex->getSourceRange());
116 bugreporter::trackNullOrUndefValue(N, Ex, *report);
119 bugreporter::trackNullOrUndefValue(N, B, *report);
121 C.emitReport(std::move(report));
125 void ento::registerUndefResultChecker(CheckerManager &mgr) {
126 mgr.registerChecker<UndefResultChecker>();