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//==- ObjCUnusedIVarsChecker.cpp - Check for unused ivars --------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/Checker/Checkers/LocalCheckers.h"
#include "clang/Checker/BugReporter/PathDiagnostic.h"
#include "clang/Checker/BugReporter/BugReporter.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/Expr.h"
#include "clang/AST/DeclObjC.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SourceManager.h"
using namespace clang;
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;
}
for (Stmt::const_child_iterator I=S->child_begin(),E=S->child_end(); I!=E;++I)
Scan(M, *I);
}
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 (ObjCContainerDecl::instmeth_iterator I = D->instmeth_begin(),
E = D->instmeth_end(); I!=E; ++I)
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 (ObjCImplementationDecl::propimpl_iterator I = ID->propimpl_begin(),
E = ID->propimpl_end(); I!=E; ++I)
Scan(M, *I);
// Scan the associated categories as well.
for (const ObjCCategoryDecl *CD =
ID->getClassInterface()->getCategoryList(); CD ;
CD = CD->getNextClassCategory()) {
if (const ObjCCategoryImplDecl *CID = CD->getImplementation())
Scan(M, CID);
}
}
}
static void Scan(IvarUsageMap &M, const DeclContext *C, const FileID FID,
SourceManager &SM) {
for (DeclContext::decl_iterator I=C->decls_begin(), E=C->decls_end();
I!=E; ++I)
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(*I)) {
SourceLocation L = FD->getLocStart();
if (SM.getFileID(L) == FID)
Scan(M, FD->getBody());
}
}
void clang::CheckObjCUnusedIvar(const ObjCImplementationDecl *D,
BugReporter &BR) {
const ObjCInterfaceDecl* ID = D->getClassInterface();
IvarUsageMap M;
// Iterate over the ivars.
for (ObjCInterfaceDecl::ivar_iterator I=ID->ivar_begin(),
E=ID->ivar_end(); I!=E; ++I) {
const ObjCIvarDecl* ID = *I;
// Ignore ivars that...
// (a) aren't private
// (b) explicitly marked unused
// (c) are iboutlets
if (ID->getAccessControl() != ObjCIvarDecl::Private ||
ID->getAttr<UnusedAttr>() || ID->getAttr<IBOutletAttr>())
continue;
M[ID] = 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.
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).";
BR.EmitBasicReport("Unused instance variable", "Optimization",
os.str(), I->first->getLocation());
}
}
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