| //=== UndefResultChecker.cpp ------------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This defines UndefResultChecker, a builtin check in ExprEngine that |
| // performs checks for undefined results of non-assignment binary operators. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" |
| #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" |
| #include "clang/StaticAnalyzer/Core/Checker.h" |
| #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/Support/raw_ostream.h" |
| |
| using namespace clang; |
| using namespace ento; |
| |
| namespace { |
| class UndefResultChecker |
| : public Checker< check::PostStmt<BinaryOperator> > { |
| |
| const BugType BT{this, "Result of operation is garbage or undefined"}; |
| |
| public: |
| void checkPostStmt(const BinaryOperator *B, CheckerContext &C) const; |
| }; |
| } // end anonymous namespace |
| |
| static bool isArrayIndexOutOfBounds(CheckerContext &C, const Expr *Ex) { |
| ProgramStateRef state = C.getState(); |
| |
| if (!isa<ArraySubscriptExpr>(Ex)) |
| return false; |
| |
| SVal Loc = C.getSVal(Ex); |
| if (!Loc.isValid()) |
| return false; |
| |
| const MemRegion *MR = Loc.castAs<loc::MemRegionVal>().getRegion(); |
| const ElementRegion *ER = dyn_cast<ElementRegion>(MR); |
| if (!ER) |
| return false; |
| |
| DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>(); |
| DefinedOrUnknownSVal ElementCount = getDynamicElementCount( |
| state, ER->getSuperRegion(), C.getSValBuilder(), ER->getValueType()); |
| ProgramStateRef StInBound, StOutBound; |
| std::tie(StInBound, StOutBound) = state->assumeInBoundDual(Idx, ElementCount); |
| return StOutBound && !StInBound; |
| } |
| |
| void UndefResultChecker::checkPostStmt(const BinaryOperator *B, |
| CheckerContext &C) const { |
| if (C.getSVal(B).isUndef()) { |
| |
| // Do not report assignments of uninitialized values inside swap functions. |
| // This should allow to swap partially uninitialized structs |
| if (const FunctionDecl *EnclosingFunctionDecl = |
| dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl())) |
| if (C.getCalleeName(EnclosingFunctionDecl) == "swap") |
| return; |
| |
| // Generate an error node. |
| ExplodedNode *N = C.generateErrorNode(); |
| if (!N) |
| return; |
| |
| SmallString<256> sbuf; |
| llvm::raw_svector_ostream OS(sbuf); |
| const Expr *Ex = nullptr; |
| bool isLeft = true; |
| |
| if (C.getSVal(B->getLHS()).isUndef()) { |
| Ex = B->getLHS()->IgnoreParenCasts(); |
| isLeft = true; |
| } |
| else if (C.getSVal(B->getRHS()).isUndef()) { |
| Ex = B->getRHS()->IgnoreParenCasts(); |
| isLeft = false; |
| } |
| |
| if (Ex) { |
| OS << "The " << (isLeft ? "left" : "right") << " operand of '" |
| << BinaryOperator::getOpcodeStr(B->getOpcode()) |
| << "' is a garbage value"; |
| if (isArrayIndexOutOfBounds(C, Ex)) |
| OS << " due to array index out of bounds"; |
| } else { |
| // Neither operand was undefined, but the result is undefined. |
| OS << "The result of the '" |
| << BinaryOperator::getOpcodeStr(B->getOpcode()) |
| << "' expression is undefined"; |
| } |
| auto report = std::make_unique<PathSensitiveBugReport>(BT, OS.str(), N); |
| if (Ex) { |
| report->addRange(Ex->getSourceRange()); |
| bugreporter::trackExpressionValue(N, Ex, *report); |
| } |
| else |
| bugreporter::trackExpressionValue(N, B, *report); |
| |
| C.emitReport(std::move(report)); |
| } |
| } |
| |
| void ento::registerUndefResultChecker(CheckerManager &mgr) { |
| mgr.registerChecker<UndefResultChecker>(); |
| } |
| |
| bool ento::shouldRegisterUndefResultChecker(const CheckerManager &mgr) { |
| return true; |
| } |