| //==- 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; |
| } |