NSErrorChecker.cpp revision 243830 
1//=- NSErrorChecker.cpp - Coding conventions for uses of NSError -*- C++ -*-==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//  This file defines a CheckNSError, a flow-insenstive check
11//  that determines if an Objective-C class interface correctly returns
12//  a non-void return type.
13//
14//  File under feature request PR 2600.
15//
16//===----------------------------------------------------------------------===//
17
18#include "ClangSACheckers.h"
19#include "clang/StaticAnalyzer/Core/Checker.h"
20#include "clang/StaticAnalyzer/Core/CheckerManager.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
23#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
24#include "clang/AST/DeclObjC.h"
25#include "clang/AST/Decl.h"
26#include "llvm/ADT/SmallVector.h"
27
28using namespace clang;
29using namespace ento;
30
31static bool IsNSError(QualType T, IdentifierInfo *II);
32static bool IsCFError(QualType T, IdentifierInfo *II);
33
34//===----------------------------------------------------------------------===//
35// NSErrorMethodChecker
36//===----------------------------------------------------------------------===//
37
38namespace {
39class NSErrorMethodChecker
40    : public Checker< check::ASTDecl<ObjCMethodDecl> > {
41  mutable IdentifierInfo *II;
42
43public:
44  NSErrorMethodChecker() : II(0) { }
45
46  void checkASTDecl(const ObjCMethodDecl *D,
47                    AnalysisManager &mgr, BugReporter &BR) const;
48};
49}
50
51void NSErrorMethodChecker::checkASTDecl(const ObjCMethodDecl *D,
52                                        AnalysisManager &mgr,
53                                        BugReporter &BR) const {
54  if (!D->isThisDeclarationADefinition())
55    return;
56  if (!D->getResultType()->isVoidType())
57    return;
58
59  if (!II)
60    II = &D->getASTContext().Idents.get("NSError");
61
62  bool hasNSError = false;
63  for (ObjCMethodDecl::param_const_iterator
64         I = D->param_begin(), E = D->param_end(); I != E; ++I)  {
65    if (IsNSError((*I)->getType(), II)) {
66      hasNSError = true;
67      break;
68    }
69  }
70
71  if (hasNSError) {
72    const char *err = "Method accepting NSError** "
73        "should have a non-void return value to indicate whether or not an "
74        "error occurred";
75    PathDiagnosticLocation L =
76      PathDiagnosticLocation::create(D, BR.getSourceManager());
77    BR.EmitBasicReport(D, "Bad return type when passing NSError**",
78                       "Coding conventions (Apple)", err, L);
79  }
80}
81
82//===----------------------------------------------------------------------===//
83// CFErrorFunctionChecker
84//===----------------------------------------------------------------------===//
85
86namespace {
87class CFErrorFunctionChecker
88    : public Checker< check::ASTDecl<FunctionDecl> > {
89  mutable IdentifierInfo *II;
90
91public:
92  CFErrorFunctionChecker() : II(0) { }
93
94  void checkASTDecl(const FunctionDecl *D,
95                    AnalysisManager &mgr, BugReporter &BR) const;
96};
97}
98
99void CFErrorFunctionChecker::checkASTDecl(const FunctionDecl *D,
100                                        AnalysisManager &mgr,
101                                        BugReporter &BR) const {
102  if (!D->doesThisDeclarationHaveABody())
103    return;
104  if (!D->getResultType()->isVoidType())
105    return;
106
107  if (!II)
108    II = &D->getASTContext().Idents.get("CFErrorRef");
109
110  bool hasCFError = false;
111  for (FunctionDecl::param_const_iterator
112         I = D->param_begin(), E = D->param_end(); I != E; ++I)  {
113    if (IsCFError((*I)->getType(), II)) {
114      hasCFError = true;
115      break;
116    }
117  }
118
119  if (hasCFError) {
120    const char *err = "Function accepting CFErrorRef* "
121        "should have a non-void return value to indicate whether or not an "
122        "error occurred";
123    PathDiagnosticLocation L =
124      PathDiagnosticLocation::create(D, BR.getSourceManager());
125    BR.EmitBasicReport(D, "Bad return type when passing CFErrorRef*",
126                       "Coding conventions (Apple)", err, L);
127  }
128}
129
130//===----------------------------------------------------------------------===//
131// NSOrCFErrorDerefChecker
132//===----------------------------------------------------------------------===//
133
134namespace {
135
136class NSErrorDerefBug : public BugType {
137public:
138  NSErrorDerefBug() : BugType("NSError** null dereference",
139                              "Coding conventions (Apple)") {}
140};
141
142class CFErrorDerefBug : public BugType {
143public:
144  CFErrorDerefBug() : BugType("CFErrorRef* null dereference",
145                              "Coding conventions (Apple)") {}
146};
147
148}
149
150namespace {
151class NSOrCFErrorDerefChecker
152    : public Checker< check::Location,
153                        check::Event<ImplicitNullDerefEvent> > {
154  mutable IdentifierInfo *NSErrorII, *CFErrorII;
155public:
156  bool ShouldCheckNSError, ShouldCheckCFError;
157  NSOrCFErrorDerefChecker() : NSErrorII(0), CFErrorII(0),
158                              ShouldCheckNSError(0), ShouldCheckCFError(0) { }
159
160  void checkLocation(SVal loc, bool isLoad, const Stmt *S,
161                     CheckerContext &C) const;
162  void checkEvent(ImplicitNullDerefEvent event) const;
163};
164}
165
166typedef llvm::ImmutableMap<SymbolRef, unsigned> ErrorOutFlag;
167REGISTER_TRAIT_WITH_PROGRAMSTATE(NSErrorOut, ErrorOutFlag)
168REGISTER_TRAIT_WITH_PROGRAMSTATE(CFErrorOut, ErrorOutFlag)
169
170template <typename T>
171static bool hasFlag(SVal val, ProgramStateRef state) {
172  if (SymbolRef sym = val.getAsSymbol())
173    if (const unsigned *attachedFlags = state->get<T>(sym))
174      return *attachedFlags;
175  return false;
176}
177
178template <typename T>
179static void setFlag(ProgramStateRef state, SVal val, CheckerContext &C) {
180  // We tag the symbol that the SVal wraps.
181  if (SymbolRef sym = val.getAsSymbol())
182    C.addTransition(state->set<T>(sym, true));
183}
184
185static QualType parameterTypeFromSVal(SVal val, CheckerContext &C) {
186  const StackFrameContext *
187    SFC = C.getLocationContext()->getCurrentStackFrame();
188  if (const loc::MemRegionVal* X = dyn_cast<loc::MemRegionVal>(&val)) {
189    const MemRegion* R = X->getRegion();
190    if (const VarRegion *VR = R->getAs<VarRegion>())
191      if (const StackArgumentsSpaceRegion *
192          stackReg = dyn_cast<StackArgumentsSpaceRegion>(VR->getMemorySpace()))
193        if (stackReg->getStackFrame() == SFC)
194          return VR->getValueType();
195  }
196
197  return QualType();
198}
199
200void NSOrCFErrorDerefChecker::checkLocation(SVal loc, bool isLoad,
201                                            const Stmt *S,
202                                            CheckerContext &C) const {
203  if (!isLoad)
204    return;
205  if (loc.isUndef() || !isa<Loc>(loc))
206    return;
207
208  ASTContext &Ctx = C.getASTContext();
209  ProgramStateRef state = C.getState();
210
211  // If we are loading from NSError**/CFErrorRef* parameter, mark the resulting
212  // SVal so that we can later check it when handling the
213  // ImplicitNullDerefEvent event.
214  // FIXME: Cumbersome! Maybe add hook at construction of SVals at start of
215  // function ?
216
217  QualType parmT = parameterTypeFromSVal(loc, C);
218  if (parmT.isNull())
219    return;
220
221  if (!NSErrorII)
222    NSErrorII = &Ctx.Idents.get("NSError");
223  if (!CFErrorII)
224    CFErrorII = &Ctx.Idents.get("CFErrorRef");
225
226  if (ShouldCheckNSError && IsNSError(parmT, NSErrorII)) {
227    setFlag<NSErrorOut>(state, state->getSVal(cast<Loc>(loc)), C);
228    return;
229  }
230
231  if (ShouldCheckCFError && IsCFError(parmT, CFErrorII)) {
232    setFlag<CFErrorOut>(state, state->getSVal(cast<Loc>(loc)), C);
233    return;
234  }
235}
236
237void NSOrCFErrorDerefChecker::checkEvent(ImplicitNullDerefEvent event) const {
238  if (event.IsLoad)
239    return;
240
241  SVal loc = event.Location;
242  ProgramStateRef state = event.SinkNode->getState();
243  BugReporter &BR = *event.BR;
244
245  bool isNSError = hasFlag<NSErrorOut>(loc, state);
246  bool isCFError = false;
247  if (!isNSError)
248    isCFError = hasFlag<CFErrorOut>(loc, state);
249
250  if (!(isNSError || isCFError))
251    return;
252
253  // Storing to possible null NSError/CFErrorRef out parameter.
254
255  // Emit an error.
256  std::string err;
257  llvm::raw_string_ostream os(err);
258    os << "Potential null dereference.  According to coding standards ";
259
260  if (isNSError)
261    os << "in 'Creating and Returning NSError Objects' the parameter '";
262  else
263    os << "documented in CoreFoundation/CFError.h the parameter '";
264
265  os  << "' may be null.";
266
267  BugType *bug = 0;
268  if (isNSError)
269    bug = new NSErrorDerefBug();
270  else
271    bug = new CFErrorDerefBug();
272  BugReport *report = new BugReport(*bug, os.str(),
273                                                    event.SinkNode);
274  BR.emitReport(report);
275}
276
277static bool IsNSError(QualType T, IdentifierInfo *II) {
278
279  const PointerType* PPT = T->getAs<PointerType>();
280  if (!PPT)
281    return false;
282
283  const ObjCObjectPointerType* PT =
284    PPT->getPointeeType()->getAs<ObjCObjectPointerType>();
285
286  if (!PT)
287    return false;
288
289  const ObjCInterfaceDecl *ID = PT->getInterfaceDecl();
290
291  // FIXME: Can ID ever be NULL?
292  if (ID)
293    return II == ID->getIdentifier();
294
295  return false;
296}
297
298static bool IsCFError(QualType T, IdentifierInfo *II) {
299  const PointerType* PPT = T->getAs<PointerType>();
300  if (!PPT) return false;
301
302  const TypedefType* TT = PPT->getPointeeType()->getAs<TypedefType>();
303  if (!TT) return false;
304
305  return TT->getDecl()->getIdentifier() == II;
306}
307
308void ento::registerNSErrorChecker(CheckerManager &mgr) {
309  mgr.registerChecker<NSErrorMethodChecker>();
310  NSOrCFErrorDerefChecker *
311    checker = mgr.registerChecker<NSOrCFErrorDerefChecker>();
312  checker->ShouldCheckNSError = true;
313}
314
315void ento::registerCFErrorChecker(CheckerManager &mgr) {
316  mgr.registerChecker<CFErrorFunctionChecker>();
317  NSOrCFErrorDerefChecker *
318    checker = mgr.registerChecker<NSOrCFErrorDerefChecker>();
319  checker->ShouldCheckCFError = true;
320}
321