1 //==- ObjCUnusedIVarsChecker.cpp - Check for unused ivars --------*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines a CheckObjCUnusedIvars, a checker that
11 // analyzes an Objective-C class's interface/implementation to determine if it
12 // has any ivars that are never accessed.
14 //===----------------------------------------------------------------------===//
16 #include "ClangSACheckers.h"
17 #include "clang/AST/Attr.h"
18 #include "clang/AST/DeclObjC.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/AST/ExprObjC.h"
21 #include "clang/Basic/LangOptions.h"
22 #include "clang/Basic/SourceManager.h"
23 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
24 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
25 #include "clang/StaticAnalyzer/Core/Checker.h"
27 using namespace clang;
30 enum IVarState { Unused, Used };
31 typedef llvm::DenseMap<const ObjCIvarDecl*,IVarState> IvarUsageMap;
33 static void Scan(IvarUsageMap& M, const Stmt *S) {
37 if (const ObjCIvarRefExpr *Ex = dyn_cast<ObjCIvarRefExpr>(S)) {
38 const ObjCIvarDecl *D = Ex->getDecl();
39 IvarUsageMap::iterator I = M.find(D);
45 // Blocks can reference an instance variable of a class.
46 if (const BlockExpr *BE = dyn_cast<BlockExpr>(S)) {
47 Scan(M, BE->getBody());
51 if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(S))
52 for (PseudoObjectExpr::const_semantics_iterator
53 i = POE->semantics_begin(), e = POE->semantics_end(); i != e; ++i) {
55 if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(sub))
56 sub = OVE->getSourceExpr();
60 for (const Stmt *SubStmt : S->children())
64 static void Scan(IvarUsageMap& M, const ObjCPropertyImplDecl *D) {
68 const ObjCIvarDecl *ID = D->getPropertyIvarDecl();
73 IvarUsageMap::iterator I = M.find(ID);
78 static void Scan(IvarUsageMap& M, const ObjCContainerDecl *D) {
79 // Scan the methods for accesses.
80 for (const auto *I : D->instance_methods())
81 Scan(M, I->getBody());
83 if (const ObjCImplementationDecl *ID = dyn_cast<ObjCImplementationDecl>(D)) {
84 // Scan for @synthesized property methods that act as setters/getters
86 for (const auto *I : ID->property_impls())
89 // Scan the associated categories as well.
90 for (const auto *Cat : ID->getClassInterface()->visible_categories()) {
91 if (const ObjCCategoryImplDecl *CID = Cat->getImplementation())
97 static void Scan(IvarUsageMap &M, const DeclContext *C, const FileID FID,
99 for (const auto *I : C->decls())
100 if (const auto *FD = dyn_cast<FunctionDecl>(I)) {
101 SourceLocation L = FD->getLocStart();
102 if (SM.getFileID(L) == FID)
103 Scan(M, FD->getBody());
107 static void checkObjCUnusedIvar(const ObjCImplementationDecl *D,
109 const CheckerBase *Checker) {
111 const ObjCInterfaceDecl *ID = D->getClassInterface();
114 // Iterate over the ivars.
115 for (const auto *Ivar : ID->ivars()) {
116 // Ignore ivars that...
117 // (a) aren't private
118 // (b) explicitly marked unused
120 // (d) are unnamed bitfields
121 if (Ivar->getAccessControl() != ObjCIvarDecl::Private ||
122 Ivar->hasAttr<UnusedAttr>() || Ivar->hasAttr<IBOutletAttr>() ||
123 Ivar->hasAttr<IBOutletCollectionAttr>() ||
124 Ivar->isUnnamedBitfield())
133 // Now scan the implementation declaration.
136 // Any potentially unused ivars?
137 bool hasUnused = false;
138 for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I)
139 if (I->second == Unused) {
147 // We found some potentially unused ivars. Scan the entire translation unit
148 // for functions inside the @implementation that reference these ivars.
149 // FIXME: In the future hopefully we can just use the lexical DeclContext
150 // to go from the ObjCImplementationDecl to the lexically "nested"
152 SourceManager &SM = BR.getSourceManager();
153 Scan(M, D->getDeclContext(), SM.getFileID(D->getLocation()), SM);
155 // Find ivars that are unused.
156 for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I)
157 if (I->second == Unused) {
159 llvm::raw_string_ostream os(sbuf);
160 os << "Instance variable '" << *I->first << "' in class '" << *ID
161 << "' is never used by the methods in its @implementation "
162 "(although it may be used by category methods).";
164 PathDiagnosticLocation L =
165 PathDiagnosticLocation::create(I->first, BR.getSourceManager());
166 BR.EmitBasicReport(D, Checker, "Unused instance variable", "Optimization",
171 //===----------------------------------------------------------------------===//
172 // ObjCUnusedIvarsChecker
173 //===----------------------------------------------------------------------===//
176 class ObjCUnusedIvarsChecker : public Checker<
177 check::ASTDecl<ObjCImplementationDecl> > {
179 void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr,
180 BugReporter &BR) const {
181 checkObjCUnusedIvar(D, BR, this);
186 void ento::registerObjCUnusedIvarsChecker(CheckerManager &mgr) {
187 mgr.registerChecker<ObjCUnusedIvarsChecker>();