1 //==- ObjCMissingSuperCallChecker.cpp - Check missing super-calls in ObjC --==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 //  This file defines a ObjCMissingSuperCallChecker, a checker that
10 //  analyzes a UIViewController implementation to determine if it
11 //  correctly calls super in the methods where this is mandatory.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
16 #include "clang/Analysis/PathDiagnostic.h"
17 #include "clang/AST/DeclObjC.h"
18 #include "clang/AST/Expr.h"
19 #include "clang/AST/ExprObjC.h"
20 #include "clang/AST/RecursiveASTVisitor.h"
21 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
22 #include "clang/StaticAnalyzer/Core/Checker.h"
23 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
24 #include "llvm/ADT/SmallSet.h"
25 #include "llvm/ADT/SmallString.h"
26 #include "llvm/Support/raw_ostream.h"
27 
28 using namespace clang;
29 using namespace ento;
30 
31 namespace {
32 struct SelectorDescriptor {
33   const char *SelectorName;
34   unsigned ArgumentCount;
35 };
36 
37 //===----------------------------------------------------------------------===//
38 // FindSuperCallVisitor - Identify specific calls to the superclass.
39 //===----------------------------------------------------------------------===//
40 
41 class FindSuperCallVisitor : public RecursiveASTVisitor<FindSuperCallVisitor> {
42 public:
43   explicit FindSuperCallVisitor(Selector S) : DoesCallSuper(false), Sel(S) {}
44 
45   bool VisitObjCMessageExpr(ObjCMessageExpr *E) {
46     if (E->getSelector() == Sel)
47       if (E->getReceiverKind() == ObjCMessageExpr::SuperInstance)
48         DoesCallSuper = true;
49 
50     // Recurse if we didn't find the super call yet.
51     return !DoesCallSuper;
52   }
53 
54   bool DoesCallSuper;
55 
56 private:
57   Selector Sel;
58 };
59 
60 //===----------------------------------------------------------------------===//
61 // ObjCSuperCallChecker
62 //===----------------------------------------------------------------------===//
63 
64 class ObjCSuperCallChecker : public Checker<
65                                       check::ASTDecl<ObjCImplementationDecl> > {
66 public:
67   ObjCSuperCallChecker() : IsInitialized(false) {}
68 
69   void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager &Mgr,
70                     BugReporter &BR) const;
71 private:
72   bool isCheckableClass(const ObjCImplementationDecl *D,
73                         StringRef &SuperclassName) const;
74   void initializeSelectors(ASTContext &Ctx) const;
75   void fillSelectors(ASTContext &Ctx, ArrayRef<SelectorDescriptor> Sel,
76                      StringRef ClassName) const;
77   mutable llvm::StringMap<llvm::SmallSet<Selector, 16> > SelectorsForClass;
78   mutable bool IsInitialized;
79 };
80 
81 }
82 
83 /// Determine whether the given class has a superclass that we want
84 /// to check. The name of the found superclass is stored in SuperclassName.
85 ///
86 /// \param D The declaration to check for superclasses.
87 /// \param[out] SuperclassName On return, the found superclass name.
88 bool ObjCSuperCallChecker::isCheckableClass(const ObjCImplementationDecl *D,
89                                             StringRef &SuperclassName) const {
90   const ObjCInterfaceDecl *ID = D->getClassInterface()->getSuperClass();
91   for ( ; ID ; ID = ID->getSuperClass())
92   {
93     SuperclassName = ID->getIdentifier()->getName();
94     if (SelectorsForClass.count(SuperclassName))
95       return true;
96   }
97   return false;
98 }
99 
100 void ObjCSuperCallChecker::fillSelectors(ASTContext &Ctx,
101                                          ArrayRef<SelectorDescriptor> Sel,
102                                          StringRef ClassName) const {
103   llvm::SmallSet<Selector, 16> &ClassSelectors = SelectorsForClass[ClassName];
104   // Fill the Selectors SmallSet with all selectors we want to check.
105   for (ArrayRef<SelectorDescriptor>::iterator I = Sel.begin(), E = Sel.end();
106        I != E; ++I) {
107     SelectorDescriptor Descriptor = *I;
108     assert(Descriptor.ArgumentCount <= 1); // No multi-argument selectors yet.
109 
110     // Get the selector.
111     IdentifierInfo *II = &Ctx.Idents.get(Descriptor.SelectorName);
112 
113     Selector Sel = Ctx.Selectors.getSelector(Descriptor.ArgumentCount, &II);
114     ClassSelectors.insert(Sel);
115   }
116 }
117 
118 void ObjCSuperCallChecker::initializeSelectors(ASTContext &Ctx) const {
119 
120   { // Initialize selectors for: UIViewController
121     const SelectorDescriptor Selectors[] = {
122       { "addChildViewController", 1 },
123       { "viewDidAppear", 1 },
124       { "viewDidDisappear", 1 },
125       { "viewWillAppear", 1 },
126       { "viewWillDisappear", 1 },
127       { "removeFromParentViewController", 0 },
128       { "didReceiveMemoryWarning", 0 },
129       { "viewDidUnload", 0 },
130       { "viewDidLoad", 0 },
131       { "viewWillUnload", 0 },
132       { "updateViewConstraints", 0 },
133       { "encodeRestorableStateWithCoder", 1 },
134       { "restoreStateWithCoder", 1 }};
135 
136     fillSelectors(Ctx, Selectors, "UIViewController");
137   }
138 
139   { // Initialize selectors for: UIResponder
140     const SelectorDescriptor Selectors[] = {
141       { "resignFirstResponder", 0 }};
142 
143     fillSelectors(Ctx, Selectors, "UIResponder");
144   }
145 
146   { // Initialize selectors for: NSResponder
147     const SelectorDescriptor Selectors[] = {
148       { "encodeRestorableStateWithCoder", 1 },
149       { "restoreStateWithCoder", 1 }};
150 
151     fillSelectors(Ctx, Selectors, "NSResponder");
152   }
153 
154   { // Initialize selectors for: NSDocument
155     const SelectorDescriptor Selectors[] = {
156       { "encodeRestorableStateWithCoder", 1 },
157       { "restoreStateWithCoder", 1 }};
158 
159     fillSelectors(Ctx, Selectors, "NSDocument");
160   }
161 
162   IsInitialized = true;
163 }
164 
165 void ObjCSuperCallChecker::checkASTDecl(const ObjCImplementationDecl *D,
166                                         AnalysisManager &Mgr,
167                                         BugReporter &BR) const {
168   ASTContext &Ctx = BR.getContext();
169 
170   // We need to initialize the selector table once.
171   if (!IsInitialized)
172     initializeSelectors(Ctx);
173 
174   // Find out whether this class has a superclass that we are supposed to check.
175   StringRef SuperclassName;
176   if (!isCheckableClass(D, SuperclassName))
177     return;
178 
179 
180   // Iterate over all instance methods.
181   for (auto *MD : D->instance_methods()) {
182     Selector S = MD->getSelector();
183     // Find out whether this is a selector that we want to check.
184     if (!SelectorsForClass[SuperclassName].count(S))
185       continue;
186 
187     // Check if the method calls its superclass implementation.
188     if (MD->getBody())
189     {
190       FindSuperCallVisitor Visitor(S);
191       Visitor.TraverseDecl(MD);
192 
193       // It doesn't call super, emit a diagnostic.
194       if (!Visitor.DoesCallSuper) {
195         PathDiagnosticLocation DLoc =
196           PathDiagnosticLocation::createEnd(MD->getBody(),
197                                             BR.getSourceManager(),
198                                             Mgr.getAnalysisDeclContext(D));
199 
200         const char *Name = "Missing call to superclass";
201         SmallString<320> Buf;
202         llvm::raw_svector_ostream os(Buf);
203 
204         os << "The '" << S.getAsString()
205            << "' instance method in " << SuperclassName.str() << " subclass '"
206            << *D << "' is missing a [super " << S.getAsString() << "] call";
207 
208         BR.EmitBasicReport(MD, this, Name, categories::CoreFoundationObjectiveC,
209                            os.str(), DLoc);
210       }
211     }
212   }
213 }
214 
215 
216 //===----------------------------------------------------------------------===//
217 // Check registration.
218 //===----------------------------------------------------------------------===//
219 
220 void ento::registerObjCSuperCallChecker(CheckerManager &Mgr) {
221   Mgr.registerChecker<ObjCSuperCallChecker>();
222 }
223 
224 bool ento::shouldRegisterObjCSuperCallChecker(const LangOptions &LO) {
225   return true;
226 }
227 
228 /*
229  ToDo list for expanding this check in the future, the list is not exhaustive.
230  There are also cases where calling super is suggested but not "mandatory".
231  In addition to be able to check the classes and methods below, architectural
232  improvements like being able to allow for the super-call to be done in a called
233  method would be good too.
234 
235 UIDocument subclasses
236 - finishedHandlingError:recovered: (is multi-arg)
237 - finishedHandlingError:recovered: (is multi-arg)
238 
239 UIViewController subclasses
240 - loadView (should *never* call super)
241 - transitionFromViewController:toViewController:
242          duration:options:animations:completion: (is multi-arg)
243 
244 UICollectionViewController subclasses
245 - loadView (take care because UIViewController subclasses should NOT call super
246             in loadView, but UICollectionViewController subclasses should)
247 
248 NSObject subclasses
249 - doesNotRecognizeSelector (it only has to call super if it doesn't throw)
250 
251 UIPopoverBackgroundView subclasses (some of those are class methods)
252 - arrowDirection (should *never* call super)
253 - arrowOffset (should *never* call super)
254 - arrowBase (should *never* call super)
255 - arrowHeight (should *never* call super)
256 - contentViewInsets (should *never* call super)
257 
258 UITextSelectionRect subclasses (some of those are properties)
259 - rect (should *never* call super)
260 - range (should *never* call super)
261 - writingDirection (should *never* call super)
262 - isVertical (should *never* call super)
263 - containsStart (should *never* call super)
264 - containsEnd (should *never* call super)
265 */
266