1 files changed, 191 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Checkers/ObjCUnusedIVarsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/ObjCUnusedIVarsChecker.cpp
new file mode 100644
index 000000000000..cb4770451572
--- /dev/null
+++ b/clang/lib/StaticAnalyzer/Checkers/ObjCUnusedIVarsChecker.cpp
@@ -0,0 +1,191 @@
+//==- ObjCUnusedIVarsChecker.cpp - Check for unused ivars --------*- 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 a CheckObjCUnusedIvars, a checker that
+//  analyzes an Objective-C class's interface/implementation to determine if it
+//  has any ivars that are never accessed.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/Analysis/PathDiagnostic.h"
+#include "clang/AST/Attr.h"
+#include "clang/AST/DeclObjC.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprObjC.h"
+#include "clang/Basic/LangOptions.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+
+using namespace clang;
+using namespace ento;
+
+enum IVarState { Unused, Used };
+typedef llvm::DenseMap<const ObjCIvarDecl*,IVarState> IvarUsageMap;
+
+static void Scan(IvarUsageMap& M, const Stmt *S) {
+  if (!S)
+    return;
+
+  if (const ObjCIvarRefExpr *Ex = dyn_cast<ObjCIvarRefExpr>(S)) {
+    const ObjCIvarDecl *D = Ex->getDecl();
+    IvarUsageMap::iterator I = M.find(D);
+    if (I != M.end())
+      I->second = Used;
+    return;
+  }
+
+  // Blocks can reference an instance variable of a class.
+  if (const BlockExpr *BE = dyn_cast<BlockExpr>(S)) {
+    Scan(M, BE->getBody());
+    return;
+  }
+
+  if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(S))
+    for (PseudoObjectExpr::const_semantics_iterator
+        i = POE->semantics_begin(), e = POE->semantics_end(); i != e; ++i) {
+      const Expr *sub = *i;
+      if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(sub))
+        sub = OVE->getSourceExpr();
+      Scan(M, sub);
+    }
+
+  for (const Stmt *SubStmt : S->children())
+    Scan(M, SubStmt);
+}
+
+static void Scan(IvarUsageMap& M, const ObjCPropertyImplDecl *D) {
+  if (!D)
+    return;
+
+  const ObjCIvarDecl *ID = D->getPropertyIvarDecl();
+
+  if (!ID)
+    return;
+
+  IvarUsageMap::iterator I = M.find(ID);
+  if (I != M.end())
+    I->second = Used;
+}
+
+static void Scan(IvarUsageMap& M, const ObjCContainerDecl *D) {
+  // Scan the methods for accesses.
+  for (const auto *I : D->instance_methods())
+    Scan(M, I->getBody());
+
+  if (const ObjCImplementationDecl *ID = dyn_cast<ObjCImplementationDecl>(D)) {
+    // Scan for @synthesized property methods that act as setters/getters
+    // to an ivar.
+    for (const auto *I : ID->property_impls())
+      Scan(M, I);
+
+    // Scan the associated categories as well.
+    for (const auto *Cat : ID->getClassInterface()->visible_categories()) {
+      if (const ObjCCategoryImplDecl *CID = Cat->getImplementation())
+        Scan(M, CID);
+    }
+  }
+}
+
+static void Scan(IvarUsageMap &M, const DeclContext *C, const FileID FID,
+                 const SourceManager &SM) {
+  for (const auto *I : C->decls())
+    if (const auto *FD = dyn_cast<FunctionDecl>(I)) {
+      SourceLocation L = FD->getBeginLoc();
+      if (SM.getFileID(L) == FID)
+        Scan(M, FD->getBody());
+    }
+}
+
+static void checkObjCUnusedIvar(const ObjCImplementationDecl *D,
+                                BugReporter &BR,
+                                const CheckerBase *Checker) {
+
+  const ObjCInterfaceDecl *ID = D->getClassInterface();
+  IvarUsageMap M;
+
+  // Iterate over the ivars.
+  for (const auto *Ivar : ID->ivars()) {
+    // Ignore ivars that...
+    // (a) aren't private
+    // (b) explicitly marked unused
+    // (c) are iboutlets
+    // (d) are unnamed bitfields
+    if (Ivar->getAccessControl() != ObjCIvarDecl::Private ||
+        Ivar->hasAttr<UnusedAttr>() || Ivar->hasAttr<IBOutletAttr>() ||
+        Ivar->hasAttr<IBOutletCollectionAttr>() ||
+        Ivar->isUnnamedBitfield())
+      continue;
+
+    M[Ivar] = Unused;
+  }
+
+  if (M.empty())
+    return;
+
+  // Now scan the implementation declaration.
+  Scan(M, D);
+
+  // Any potentially unused ivars?
+  bool hasUnused = false;
+  for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I)
+    if (I->second == Unused) {
+      hasUnused = true;
+      break;
+    }
+
+  if (!hasUnused)
+    return;
+
+  // We found some potentially unused ivars.  Scan the entire translation unit
+  // for functions inside the @implementation that reference these ivars.
+  // FIXME: In the future hopefully we can just use the lexical DeclContext
+  // to go from the ObjCImplementationDecl to the lexically "nested"
+  // C functions.
+  const SourceManager &SM = BR.getSourceManager();
+  Scan(M, D->getDeclContext(), SM.getFileID(D->getLocation()), SM);
+
+  // Find ivars that are unused.
+  for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I)
+    if (I->second == Unused) {
+      std::string sbuf;
+      llvm::raw_string_ostream os(sbuf);
+      os << "Instance variable '" << *I->first << "' in class '" << *ID
+         << "' is never used by the methods in its @implementation "
+            "(although it may be used by category methods).";
+
+      PathDiagnosticLocation L =
+        PathDiagnosticLocation::create(I->first, BR.getSourceManager());
+      BR.EmitBasicReport(D, Checker, "Unused instance variable", "Optimization",
+                         os.str(), L);
+    }
+}
+
+//===----------------------------------------------------------------------===//
+// ObjCUnusedIvarsChecker
+//===----------------------------------------------------------------------===//
+
+namespace {
+class ObjCUnusedIvarsChecker : public Checker<
+                                      check::ASTDecl<ObjCImplementationDecl> > {
+public:
+  void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr,
+                    BugReporter &BR) const {
+    checkObjCUnusedIvar(D, BR, this);
+  }
+};
+}
+
+void ento::registerObjCUnusedIvarsChecker(CheckerManager &mgr) {
+  mgr.registerChecker<ObjCUnusedIvarsChecker>();
+}
+
+bool ento::shouldRegisterObjCUnusedIvarsChecker(const LangOptions &LO) {
+  return true;
+}