| //=== UndefBranchChecker.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 file defines UndefBranchChecker, which checks for undefined branch |
| // condition. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #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 <utility> |
| |
| using namespace clang; |
| using namespace ento; |
| |
| namespace { |
| |
| class UndefBranchChecker : public Checker<check::BranchCondition> { |
| mutable std::unique_ptr<BuiltinBug> BT; |
| |
| struct FindUndefExpr { |
| ProgramStateRef St; |
| const LocationContext *LCtx; |
| |
| FindUndefExpr(ProgramStateRef S, const LocationContext *L) |
| : St(std::move(S)), LCtx(L) {} |
| |
| const Expr *FindExpr(const Expr *Ex) { |
| if (!MatchesCriteria(Ex)) |
| return nullptr; |
| |
| for (const Stmt *SubStmt : Ex->children()) |
| if (const Expr *ExI = dyn_cast_or_null<Expr>(SubStmt)) |
| if (const Expr *E2 = FindExpr(ExI)) |
| return E2; |
| |
| return Ex; |
| } |
| |
| bool MatchesCriteria(const Expr *Ex) { |
| return St->getSVal(Ex, LCtx).isUndef(); |
| } |
| }; |
| |
| public: |
| void checkBranchCondition(const Stmt *Condition, CheckerContext &Ctx) const; |
| }; |
| |
| } |
| |
| void UndefBranchChecker::checkBranchCondition(const Stmt *Condition, |
| CheckerContext &Ctx) const { |
| SVal X = Ctx.getSVal(Condition); |
| if (X.isUndef()) { |
| // Generate a sink node, which implicitly marks both outgoing branches as |
| // infeasible. |
| ExplodedNode *N = Ctx.generateErrorNode(); |
| if (N) { |
| if (!BT) |
| BT.reset(new BuiltinBug( |
| this, "Branch condition evaluates to a garbage value")); |
| |
| // What's going on here: we want to highlight the subexpression of the |
| // condition that is the most likely source of the "uninitialized |
| // branch condition." We do a recursive walk of the condition's |
| // subexpressions and roughly look for the most nested subexpression |
| // that binds to Undefined. We then highlight that expression's range. |
| |
| // Get the predecessor node and check if is a PostStmt with the Stmt |
| // being the terminator condition. We want to inspect the state |
| // of that node instead because it will contain main information about |
| // the subexpressions. |
| |
| // Note: any predecessor will do. They should have identical state, |
| // since all the BlockEdge did was act as an error sink since the value |
| // had to already be undefined. |
| assert (!N->pred_empty()); |
| const Expr *Ex = cast<Expr>(Condition); |
| ExplodedNode *PrevN = *N->pred_begin(); |
| ProgramPoint P = PrevN->getLocation(); |
| ProgramStateRef St = N->getState(); |
| |
| if (Optional<PostStmt> PS = P.getAs<PostStmt>()) |
| if (PS->getStmt() == Ex) |
| St = PrevN->getState(); |
| |
| FindUndefExpr FindIt(St, Ctx.getLocationContext()); |
| Ex = FindIt.FindExpr(Ex); |
| |
| // Emit the bug report. |
| auto R = std::make_unique<PathSensitiveBugReport>( |
| *BT, BT->getDescription(), N); |
| bugreporter::trackExpressionValue(N, Ex, *R); |
| R->addRange(Ex->getSourceRange()); |
| |
| Ctx.emitReport(std::move(R)); |
| } |
| } |
| } |
| |
| void ento::registerUndefBranchChecker(CheckerManager &mgr) { |
| mgr.registerChecker<UndefBranchChecker>(); |
| } |
| |
| bool ento::shouldRegisterUndefBranchChecker(const LangOptions &LO) { |
| return true; |
| } |