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Diffstat (limited to 'clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp')
-rw-r--r-- | clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp new file mode 100644 index 000000000000..247cba7dc933 --- /dev/null +++ b/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp @@ -0,0 +1,115 @@ +//=== 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; +} |