clang  9.0.0
MacOSXAPIChecker.cpp
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1 // MacOSXAPIChecker.h - Checks proper use of various MacOS X APIs --*- C++ -*-//
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 defines MacOSXAPIChecker, which is an assortment of checks on calls
10 // to various, widely used Apple APIs.
11 //
12 // FIXME: What's currently in BasicObjCFoundationChecks.cpp should be migrated
13 // to here, using the new Checker interface.
14 //
15 //===----------------------------------------------------------------------===//
16 
18 #include "clang/Basic/TargetInfo.h"
24 #include "llvm/ADT/SmallString.h"
25 #include "llvm/ADT/StringSwitch.h"
26 #include "llvm/Support/raw_ostream.h"
27 
28 using namespace clang;
29 using namespace ento;
30 
31 namespace {
32 class MacOSXAPIChecker : public Checker< check::PreStmt<CallExpr> > {
33  mutable std::unique_ptr<BugType> BT_dispatchOnce;
34 
35  static const ObjCIvarRegion *getParentIvarRegion(const MemRegion *R);
36 
37 public:
38  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
39 
40  void CheckDispatchOnce(CheckerContext &C, const CallExpr *CE,
41  StringRef FName) const;
42 
43  typedef void (MacOSXAPIChecker::*SubChecker)(CheckerContext &,
44  const CallExpr *,
45  StringRef FName) const;
46 };
47 } //end anonymous namespace
48 
49 //===----------------------------------------------------------------------===//
50 // dispatch_once and dispatch_once_f
51 //===----------------------------------------------------------------------===//
52 
53 const ObjCIvarRegion *
54 MacOSXAPIChecker::getParentIvarRegion(const MemRegion *R) {
55  const SubRegion *SR = dyn_cast<SubRegion>(R);
56  while (SR) {
57  if (const ObjCIvarRegion *IR = dyn_cast<ObjCIvarRegion>(SR))
58  return IR;
59  SR = dyn_cast<SubRegion>(SR->getSuperRegion());
60  }
61  return nullptr;
62 }
63 
64 void MacOSXAPIChecker::CheckDispatchOnce(CheckerContext &C, const CallExpr *CE,
65  StringRef FName) const {
66  if (CE->getNumArgs() < 1)
67  return;
68 
69  // Check if the first argument is improperly allocated. If so, issue a
70  // warning because that's likely to be bad news.
71  const MemRegion *R = C.getSVal(CE->getArg(0)).getAsRegion();
72  if (!R)
73  return;
74 
75  // Global variables are fine.
76  const MemRegion *RB = R->getBaseRegion();
77  const MemSpaceRegion *RS = RB->getMemorySpace();
78  if (isa<GlobalsSpaceRegion>(RS))
79  return;
80 
81  // Handle _dispatch_once. In some versions of the OS X SDK we have the case
82  // that dispatch_once is a macro that wraps a call to _dispatch_once.
83  // _dispatch_once is then a function which then calls the real dispatch_once.
84  // Users do not care; they just want the warning at the top-level call.
85  if (CE->getBeginLoc().isMacroID()) {
86  StringRef TrimmedFName = FName.ltrim('_');
87  if (TrimmedFName != FName)
88  FName = TrimmedFName;
89  }
90 
92  llvm::raw_svector_ostream os(S);
93  bool SuggestStatic = false;
94  os << "Call to '" << FName << "' uses";
95  if (const VarRegion *VR = dyn_cast<VarRegion>(RB)) {
96  const VarDecl *VD = VR->getDecl();
97  // FIXME: These should have correct memory space and thus should be filtered
98  // out earlier. This branch only fires when we're looking from a block,
99  // which we analyze as a top-level declaration, onto a static local
100  // in a function that contains the block.
101  if (VD->isStaticLocal())
102  return;
103  // We filtered out globals earlier, so it must be a local variable
104  // or a block variable which is under UnknownSpaceRegion.
105  if (VR != R)
106  os << " memory within";
107  if (VD->hasAttr<BlocksAttr>())
108  os << " the block variable '";
109  else
110  os << " the local variable '";
111  os << VR->getDecl()->getName() << '\'';
112  SuggestStatic = true;
113  } else if (const ObjCIvarRegion *IVR = getParentIvarRegion(R)) {
114  if (IVR != R)
115  os << " memory within";
116  os << " the instance variable '" << IVR->getDecl()->getName() << '\'';
117  } else if (isa<HeapSpaceRegion>(RS)) {
118  os << " heap-allocated memory";
119  } else if (isa<UnknownSpaceRegion>(RS)) {
120  // Presence of an IVar superregion has priority over this branch, because
121  // ObjC objects are on the heap even if the core doesn't realize this.
122  // Presence of a block variable base region has priority over this branch,
123  // because block variables are known to be either on stack or on heap
124  // (might actually move between the two, hence UnknownSpace).
125  return;
126  } else {
127  os << " stack allocated memory";
128  }
129  os << " for the predicate value. Using such transient memory for "
130  "the predicate is potentially dangerous.";
131  if (SuggestStatic)
132  os << " Perhaps you intended to declare the variable as 'static'?";
133 
134  ExplodedNode *N = C.generateErrorNode();
135  if (!N)
136  return;
137 
138  if (!BT_dispatchOnce)
139  BT_dispatchOnce.reset(new BugType(this, "Improper use of 'dispatch_once'",
140  "API Misuse (Apple)"));
141 
142  auto report = llvm::make_unique<BugReport>(*BT_dispatchOnce, os.str(), N);
143  report->addRange(CE->getArg(0)->getSourceRange());
144  C.emitReport(std::move(report));
145 }
146 
147 //===----------------------------------------------------------------------===//
148 // Central dispatch function.
149 //===----------------------------------------------------------------------===//
150 
151 void MacOSXAPIChecker::checkPreStmt(const CallExpr *CE,
152  CheckerContext &C) const {
153  StringRef Name = C.getCalleeName(CE);
154  if (Name.empty())
155  return;
156 
157  SubChecker SC =
158  llvm::StringSwitch<SubChecker>(Name)
159  .Cases("dispatch_once",
160  "_dispatch_once",
161  "dispatch_once_f",
162  &MacOSXAPIChecker::CheckDispatchOnce)
163  .Default(nullptr);
164 
165  if (SC)
166  (this->*SC)(C, CE, Name);
167 }
168 
169 //===----------------------------------------------------------------------===//
170 // Registration.
171 //===----------------------------------------------------------------------===//
172 
173 void ento::registerMacOSXAPIChecker(CheckerManager &mgr) {
174  mgr.registerChecker<MacOSXAPIChecker>();
175 }
176 
177 bool ento::shouldRegisterMacOSXAPIChecker(const LangOptions &LO) {
178  return true;
179 }
Expr * getArg(unsigned Arg)
getArg - Return the specified argument.
Definition: Expr.h:2673
unsigned getNumArgs() const
getNumArgs - Return the number of actual arguments to this call.
Definition: Expr.h:2660
Represents a variable declaration or definition.
Definition: Decl.h:812
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:49
bool hasAttr() const
Definition: DeclBase.h:542
Dataflow Directional Tag Classes.
bool isMacroID() const
bool isStaticLocal() const
Returns true if a variable with function scope is a static local variable.
Definition: Decl.h:1059
SourceRange getSourceRange() const LLVM_READONLY
SourceLocation tokens are not useful in isolation - they are low level value objects created/interpre...
Definition: Stmt.cpp:251
Defines the clang::TargetInfo interface.
CallExpr - Represents a function call (C99 6.5.2.2, C++ [expr.call]).
Definition: Expr.h:2516
StringRef getName() const
Get the name of identifier for this declaration as a StringRef.
Definition: Decl.h:275
SourceLocation getBeginLoc() const LLVM_READONLY
Definition: Expr.cpp:1522