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-rw-r--r--clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp115
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diff --git a/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp
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+++ b/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp
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+//=== 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;
+}