1 files changed, 121 insertions, 0 deletions
diff --git a/contrib/llvm-project/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp b/contrib/llvm-project/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp
new file mode 100644
index 000000000000..b17b983f0345
--- /dev/null
+++ b/contrib/llvm-project/clang/lib/StaticAnalyzer/Checkers/UndefBranchChecker.cpp
@@ -0,0 +1,121 @@
+//=== 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/AST/StmtObjC.h"
+#include "clang/AST/Type.h"
+#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 <optional>
+#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;
+};
+
+} // namespace
+
+void UndefBranchChecker::checkBranchCondition(const Stmt *Condition,
+                                              CheckerContext &Ctx) const {
+  // ObjCForCollection is a loop, but has no actual condition.
+  if (isa<ObjCForCollectionStmt>(Condition))
+    return;
+  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 (std::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 CheckerManager &mgr) {
+  return true;
+}