1 files changed, 96 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Checkers/ObjCAtSyncChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/ObjCAtSyncChecker.cpp
new file mode 100644
index 000000000000..0e25817c8793
--- /dev/null
+++ b/clang/lib/StaticAnalyzer/Checkers/ObjCAtSyncChecker.cpp
@@ -0,0 +1,96 @@
+//== ObjCAtSyncChecker.cpp - nil mutex checker for @synchronized -*- 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 ObjCAtSyncChecker, a builtin check that checks for null pointers
+// used as mutexes for @synchronized.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/AST/StmtObjC.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/ExprEngine.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class ObjCAtSyncChecker
+    : public Checker< check::PreStmt<ObjCAtSynchronizedStmt> > {
+  mutable std::unique_ptr<BuiltinBug> BT_null;
+  mutable std::unique_ptr<BuiltinBug> BT_undef;
+
+public:
+  void checkPreStmt(const ObjCAtSynchronizedStmt *S, CheckerContext &C) const;
+};
+} // end anonymous namespace
+
+void ObjCAtSyncChecker::checkPreStmt(const ObjCAtSynchronizedStmt *S,
+                                     CheckerContext &C) const {
+
+  const Expr *Ex = S->getSynchExpr();
+  ProgramStateRef state = C.getState();
+  SVal V = C.getSVal(Ex);
+
+  // Uninitialized value used for the mutex?
+  if (V.getAs<UndefinedVal>()) {
+    if (ExplodedNode *N = C.generateErrorNode()) {
+      if (!BT_undef)
+        BT_undef.reset(new BuiltinBug(this, "Uninitialized value used as mutex "
+                                            "for @synchronized"));
+      auto report = std::make_unique<PathSensitiveBugReport>(
+          *BT_undef, BT_undef->getDescription(), N);
+      bugreporter::trackExpressionValue(N, Ex, *report);
+      C.emitReport(std::move(report));
+    }
+    return;
+  }
+
+  if (V.isUnknown())
+    return;
+
+  // Check for null mutexes.
+  ProgramStateRef notNullState, nullState;
+  std::tie(notNullState, nullState) = state->assume(V.castAs<DefinedSVal>());
+
+  if (nullState) {
+    if (!notNullState) {
+      // Generate an error node.  This isn't a sink since
+      // a null mutex just means no synchronization occurs.
+      if (ExplodedNode *N = C.generateNonFatalErrorNode(nullState)) {
+        if (!BT_null)
+          BT_null.reset(new BuiltinBug(
+              this, "Nil value used as mutex for @synchronized() "
+                    "(no synchronization will occur)"));
+        auto report = std::make_unique<PathSensitiveBugReport>(
+            *BT_null, BT_null->getDescription(), N);
+        bugreporter::trackExpressionValue(N, Ex, *report);
+
+        C.emitReport(std::move(report));
+        return;
+      }
+    }
+    // Don't add a transition for 'nullState'.  If the value is
+    // under-constrained to be null or non-null, assume it is non-null
+    // afterwards.
+  }
+
+  if (notNullState)
+    C.addTransition(notNullState);
+}
+
+void ento::registerObjCAtSyncChecker(CheckerManager &mgr) {
+  mgr.registerChecker<ObjCAtSyncChecker>();
+}
+
+bool ento::shouldRegisterObjCAtSyncChecker(const LangOptions &LO) {
+  return LO.ObjC;
+}