NSErrorChecker.cpp revision dc84cd5efdd3430efb22546b4ac656aa0540b210 
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/AST/Decl.h"
20#include "clang/AST/DeclObjC.h"
21#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
22#include "clang/StaticAnalyzer/Core/Checker.h"
23#include "clang/StaticAnalyzer/Core/CheckerManager.h"
24#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
25#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
26#include "llvm/ADT/SmallString.h"
27#include "llvm/Support/raw_ostream.h"
28
29using namespace clang;
30using namespace ento;
31
32static bool IsNSError(QualType T, IdentifierInfo *II);
33static bool IsCFError(QualType T, IdentifierInfo *II);
34
35//===----------------------------------------------------------------------===//
36// NSErrorMethodChecker
37//===----------------------------------------------------------------------===//
38
39namespace {
40class NSErrorMethodChecker
41    : public Checker< check::ASTDecl<ObjCMethodDecl> > {
42  mutable IdentifierInfo *II;
43
44public:
45  NSErrorMethodChecker() : II(0) { }
46
47  void checkASTDecl(const ObjCMethodDecl *D,
48                    AnalysisManager &mgr, BugReporter &BR) const;
49};
50}
51
52void NSErrorMethodChecker::checkASTDecl(const ObjCMethodDecl *D,
53                                        AnalysisManager &mgr,
54                                        BugReporter &BR) const {
55  if (!D->isThisDeclarationADefinition())
56    return;
57  if (!D->getResultType()->isVoidType())
58    return;
59
60  if (!II)
61    II = &D->getASTContext().Idents.get("NSError");
62
63  bool hasNSError = false;
64  for (ObjCMethodDecl::param_const_iterator
65         I = D->param_begin(), E = D->param_end(); I != E; ++I)  {
66    if (IsNSError((*I)->getType(), II)) {
67      hasNSError = true;
68      break;
69    }
70  }
71
72  if (hasNSError) {
73    const char *err = "Method accepting NSError** "
74        "should have a non-void return value to indicate whether or not an "
75        "error occurred";
76    PathDiagnosticLocation L =
77      PathDiagnosticLocation::create(D, BR.getSourceManager());
78    BR.EmitBasicReport(D, "Bad return type when passing NSError**",
79                       "Coding conventions (Apple)", err, L);
80  }
81}
82
83//===----------------------------------------------------------------------===//
84// CFErrorFunctionChecker
85//===----------------------------------------------------------------------===//
86
87namespace {
88class CFErrorFunctionChecker
89    : public Checker< check::ASTDecl<FunctionDecl> > {
90  mutable IdentifierInfo *II;
91
92public:
93  CFErrorFunctionChecker() : II(0) { }
94
95  void checkASTDecl(const FunctionDecl *D,
96                    AnalysisManager &mgr, BugReporter &BR) const;
97};
98}
99
100void CFErrorFunctionChecker::checkASTDecl(const FunctionDecl *D,
101                                        AnalysisManager &mgr,
102                                        BugReporter &BR) const {
103  if (!D->doesThisDeclarationHaveABody())
104    return;
105  if (!D->getResultType()->isVoidType())
106    return;
107
108  if (!II)
109    II = &D->getASTContext().Idents.get("CFErrorRef");
110
111  bool hasCFError = false;
112  for (FunctionDecl::param_const_iterator
113         I = D->param_begin(), E = D->param_end(); I != E; ++I)  {
114    if (IsCFError((*I)->getType(), II)) {
115      hasCFError = true;
116      break;
117    }
118  }
119
120  if (hasCFError) {
121    const char *err = "Function accepting CFErrorRef* "
122        "should have a non-void return value to indicate whether or not an "
123        "error occurred";
124    PathDiagnosticLocation L =
125      PathDiagnosticLocation::create(D, BR.getSourceManager());
126    BR.EmitBasicReport(D, "Bad return type when passing CFErrorRef*",
127                       "Coding conventions (Apple)", err, L);
128  }
129}
130
131//===----------------------------------------------------------------------===//
132// NSOrCFErrorDerefChecker
133//===----------------------------------------------------------------------===//
134
135namespace {
136
137class NSErrorDerefBug : public BugType {
138public:
139  NSErrorDerefBug() : BugType("NSError** null dereference",
140                              "Coding conventions (Apple)") {}
141};
142
143class CFErrorDerefBug : public BugType {
144public:
145  CFErrorDerefBug() : BugType("CFErrorRef* null dereference",
146                              "Coding conventions (Apple)") {}
147};
148
149}
150
151namespace {
152class NSOrCFErrorDerefChecker
153    : public Checker< check::Location,
154                        check::Event<ImplicitNullDerefEvent> > {
155  mutable IdentifierInfo *NSErrorII, *CFErrorII;
156public:
157  bool ShouldCheckNSError, ShouldCheckCFError;
158  NSOrCFErrorDerefChecker() : NSErrorII(0), CFErrorII(0),
159                              ShouldCheckNSError(0), ShouldCheckCFError(0) { }
160
161  void checkLocation(SVal loc, bool isLoad, const Stmt *S,
162                     CheckerContext &C) const;
163  void checkEvent(ImplicitNullDerefEvent event) const;
164};
165}
166
167typedef llvm::ImmutableMap<SymbolRef, unsigned> ErrorOutFlag;
168REGISTER_TRAIT_WITH_PROGRAMSTATE(NSErrorOut, ErrorOutFlag)
169REGISTER_TRAIT_WITH_PROGRAMSTATE(CFErrorOut, ErrorOutFlag)
170
171template <typename T>
172static bool hasFlag(SVal val, ProgramStateRef state) {
173  if (SymbolRef sym = val.getAsSymbol())
174    if (const unsigned *attachedFlags = state->get<T>(sym))
175      return *attachedFlags;
176  return false;
177}
178
179template <typename T>
180static void setFlag(ProgramStateRef state, SVal val, CheckerContext &C) {
181  // We tag the symbol that the SVal wraps.
182  if (SymbolRef sym = val.getAsSymbol())
183    C.addTransition(state->set<T>(sym, true));
184}
185
186static QualType parameterTypeFromSVal(SVal val, CheckerContext &C) {
187  const StackFrameContext *
188    SFC = C.getLocationContext()->getCurrentStackFrame();
189  if (Optional<loc::MemRegionVal> X = val.getAs<loc::MemRegionVal>()) {
190    const MemRegion* R = X->getRegion();
191    if (const VarRegion *VR = R->getAs<VarRegion>())
192      if (const StackArgumentsSpaceRegion *
193          stackReg = dyn_cast<StackArgumentsSpaceRegion>(VR->getMemorySpace()))
194        if (stackReg->getStackFrame() == SFC)
195          return VR->getValueType();
196  }
197
198  return QualType();
199}
200
201void NSOrCFErrorDerefChecker::checkLocation(SVal loc, bool isLoad,
202                                            const Stmt *S,
203                                            CheckerContext &C) const {
204  if (!isLoad)
205    return;
206  if (loc.isUndef() || !loc.getAs<Loc>())
207    return;
208
209  ASTContext &Ctx = C.getASTContext();
210  ProgramStateRef state = C.getState();
211
212  // If we are loading from NSError**/CFErrorRef* parameter, mark the resulting
213  // SVal so that we can later check it when handling the
214  // ImplicitNullDerefEvent event.
215  // FIXME: Cumbersome! Maybe add hook at construction of SVals at start of
216  // function ?
217
218  QualType parmT = parameterTypeFromSVal(loc, C);
219  if (parmT.isNull())
220    return;
221
222  if (!NSErrorII)
223    NSErrorII = &Ctx.Idents.get("NSError");
224  if (!CFErrorII)
225    CFErrorII = &Ctx.Idents.get("CFErrorRef");
226
227  if (ShouldCheckNSError && IsNSError(parmT, NSErrorII)) {
228    setFlag<NSErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C);
229    return;
230  }
231
232  if (ShouldCheckCFError && IsCFError(parmT, CFErrorII)) {
233    setFlag<CFErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C);
234    return;
235  }
236}
237
238void NSOrCFErrorDerefChecker::checkEvent(ImplicitNullDerefEvent event) const {
239  if (event.IsLoad)
240    return;
241
242  SVal loc = event.Location;
243  ProgramStateRef state = event.SinkNode->getState();
244  BugReporter &BR = *event.BR;
245
246  bool isNSError = hasFlag<NSErrorOut>(loc, state);
247  bool isCFError = false;
248  if (!isNSError)
249    isCFError = hasFlag<CFErrorOut>(loc, state);
250
251  if (!(isNSError || isCFError))
252    return;
253
254  // Storing to possible null NSError/CFErrorRef out parameter.
255  SmallString<128> Buf;
256  llvm::raw_svector_ostream os(Buf);
257
258  os << "Potential null dereference.  According to coding standards ";
259  os << (isNSError
260         ? "in 'Creating and Returning NSError Objects' the parameter"
261         : "documented in CoreFoundation/CFError.h the parameter");
262
263  os  << " may be null";
264
265  BugType *bug = 0;
266  if (isNSError)
267    bug = new NSErrorDerefBug();
268  else
269    bug = new CFErrorDerefBug();
270  BugReport *report = new BugReport(*bug, os.str(),
271                                                    event.SinkNode);
272  BR.emitReport(report);
273}
274
275static bool IsNSError(QualType T, IdentifierInfo *II) {
276
277  const PointerType* PPT = T->getAs<PointerType>();
278  if (!PPT)
279    return false;
280
281  const ObjCObjectPointerType* PT =
282    PPT->getPointeeType()->getAs<ObjCObjectPointerType>();
283
284  if (!PT)
285    return false;
286
287  const ObjCInterfaceDecl *ID = PT->getInterfaceDecl();
288
289  // FIXME: Can ID ever be NULL?
290  if (ID)
291    return II == ID->getIdentifier();
292
293  return false;
294}
295
296static bool IsCFError(QualType T, IdentifierInfo *II) {
297  const PointerType* PPT = T->getAs<PointerType>();
298  if (!PPT) return false;
299
300  const TypedefType* TT = PPT->getPointeeType()->getAs<TypedefType>();
301  if (!TT) return false;
302
303  return TT->getDecl()->getIdentifier() == II;
304}
305
306void ento::registerNSErrorChecker(CheckerManager &mgr) {
307  mgr.registerChecker<NSErrorMethodChecker>();
308  NSOrCFErrorDerefChecker *
309    checker = mgr.registerChecker<NSOrCFErrorDerefChecker>();
310  checker->ShouldCheckNSError = true;
311}
312
313void ento::registerCFErrorChecker(CheckerManager &mgr) {
314  mgr.registerChecker<CFErrorFunctionChecker>();
315  NSOrCFErrorDerefChecker *
316    checker = mgr.registerChecker<NSOrCFErrorDerefChecker>();
317  checker->ShouldCheckCFError = true;
318}
319