clang  10.0.0svn
CheckerDocumentation.cpp
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1 //===- CheckerDocumentation.cpp - Documentation checker ---------*- 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 checker lists all the checker callbacks and provides documentation for
10 // checker writers.
11 //
12 //===----------------------------------------------------------------------===//
13 
20 
21 using namespace clang;
22 using namespace ento;
23 
24 // All checkers should be placed into anonymous namespace.
25 // We place the CheckerDocumentation inside ento namespace to make the
26 // it visible in doxygen.
27 namespace clang {
28 namespace ento {
29 
30 /// This checker documents the callback functions checkers can use to implement
31 /// the custom handling of the specific events during path exploration as well
32 /// as reporting bugs. Most of the callbacks are targeted at path-sensitive
33 /// checking.
34 ///
35 /// \sa CheckerContext
36 class CheckerDocumentation : public Checker< check::PreStmt<ReturnStmt>,
37  check::PostStmt<DeclStmt>,
38  check::PreObjCMessage,
39  check::PostObjCMessage,
40  check::ObjCMessageNil,
41  check::PreCall,
42  check::PostCall,
43  check::BranchCondition,
44  check::NewAllocator,
45  check::Location,
46  check::Bind,
47  check::DeadSymbols,
48  check::BeginFunction,
49  check::EndFunction,
50  check::EndAnalysis,
51  check::EndOfTranslationUnit,
52  eval::Call,
53  eval::Assume,
54  check::LiveSymbols,
55  check::RegionChanges,
56  check::PointerEscape,
57  check::ConstPointerEscape,
58  check::Event<ImplicitNullDerefEvent>,
59  check::ASTDecl<FunctionDecl> > {
60 public:
61  /// Pre-visit the Statement.
62  ///
63  /// The method will be called before the analyzer core processes the
64  /// statement. The notification is performed for every explored CFGElement,
65  /// which does not include the control flow statements such as IfStmt. The
66  /// callback can be specialized to be called with any subclass of Stmt.
67  ///
68  /// See checkBranchCondition() callback for performing custom processing of
69  /// the branching statements.
70  ///
71  /// check::PreStmt<ReturnStmt>
72  void checkPreStmt(const ReturnStmt *DS, CheckerContext &C) const {}
73 
74  /// Post-visit the Statement.
75  ///
76  /// The method will be called after the analyzer core processes the
77  /// statement. The notification is performed for every explored CFGElement,
78  /// which does not include the control flow statements such as IfStmt. The
79  /// callback can be specialized to be called with any subclass of Stmt.
80  ///
81  /// check::PostStmt<DeclStmt>
82  void checkPostStmt(const DeclStmt *DS, CheckerContext &C) const;
83 
84  /// Pre-visit the Objective C message.
85  ///
86  /// This will be called before the analyzer core processes the method call.
87  /// This is called for any action which produces an Objective-C message send,
88  /// including explicit message syntax and property access.
89  ///
90  /// check::PreObjCMessage
92 
93  /// Post-visit the Objective C message.
94  /// \sa checkPreObjCMessage()
95  ///
96  /// check::PostObjCMessage
98 
99  /// Visit an Objective-C message whose receiver is nil.
100  ///
101  /// This will be called when the analyzer core processes a method call whose
102  /// receiver is definitely nil. In this case, check{Pre/Post}ObjCMessage and
103  /// check{Pre/Post}Call will not be called.
104  ///
105  /// check::ObjCMessageNil
107 
108  /// Pre-visit an abstract "call" event.
109  ///
110  /// This is used for checkers that want to check arguments or attributed
111  /// behavior for functions and methods no matter how they are being invoked.
112  ///
113  /// Note that this includes ALL cross-body invocations, so if you want to
114  /// limit your checks to, say, function calls, you should test for that at the
115  /// beginning of your callback function.
116  ///
117  /// check::PreCall
118  void checkPreCall(const CallEvent &Call, CheckerContext &C) const {}
119 
120  /// Post-visit an abstract "call" event.
121  /// \sa checkPreObjCMessage()
122  ///
123  /// check::PostCall
124  void checkPostCall(const CallEvent &Call, CheckerContext &C) const {}
125 
126  /// Pre-visit of the condition statement of a branch (such as IfStmt).
127  void checkBranchCondition(const Stmt *Condition, CheckerContext &Ctx) const {}
128 
129  /// Post-visit the C++ operator new's allocation call.
130  ///
131  /// Execution of C++ operator new consists of the following phases: (1) call
132  /// default or overridden operator new() to allocate memory (2) cast the
133  /// return value of operator new() from void pointer type to class pointer
134  /// type, (3) assuming that the value is non-null, call the object's
135  /// constructor over this pointer, (4) declare that the value of the
136  /// new-expression is this pointer. This callback is called between steps
137  /// (2) and (3). Post-call for the allocator is called after step (1).
138  /// Pre-statement for the new-expression is called on step (4) when the value
139  /// of the expression is evaluated.
140  /// \param NE The C++ new-expression that triggered the allocation.
141  /// \param Target The allocated region, casted to the class type.
142  void checkNewAllocator(const CXXNewExpr *NE, SVal Target,
143  CheckerContext &) const {}
144 
145  /// Called on a load from and a store to a location.
146  ///
147  /// The method will be called each time a location (pointer) value is
148  /// accessed.
149  /// \param Loc The value of the location (pointer).
150  /// \param IsLoad The flag specifying if the location is a store or a load.
151  /// \param S The load is performed while processing the statement.
152  ///
153  /// check::Location
154  void checkLocation(SVal Loc, bool IsLoad, const Stmt *S,
155  CheckerContext &) const {}
156 
157  /// Called on binding of a value to a location.
158  ///
159  /// \param Loc The value of the location (pointer).
160  /// \param Val The value which will be stored at the location Loc.
161  /// \param S The bind is performed while processing the statement S.
162  ///
163  /// check::Bind
164  void checkBind(SVal Loc, SVal Val, const Stmt *S, CheckerContext &) const {}
165 
166  /// Called whenever a symbol becomes dead.
167  ///
168  /// This callback should be used by the checkers to aggressively clean
169  /// up/reduce the checker state, which is important for reducing the overall
170  /// memory usage. Specifically, if a checker keeps symbol specific information
171  /// in the state, it can and should be dropped after the symbol becomes dead.
172  /// In addition, reporting a bug as soon as the checker becomes dead leads to
173  /// more precise diagnostics. (For example, one should report that a malloced
174  /// variable is not freed right after it goes out of scope.)
175  ///
176  /// \param SR The SymbolReaper object can be queried to determine which
177  /// symbols are dead.
178  ///
179  /// check::DeadSymbols
181 
182 
183  /// Called when the analyzer core starts analyzing a function,
184  /// regardless of whether it is analyzed at the top level or is inlined.
185  ///
186  /// check::BeginFunction
187  void checkBeginFunction(CheckerContext &Ctx) const {}
188 
189  /// Called when the analyzer core reaches the end of a
190  /// function being analyzed regardless of whether it is analyzed at the top
191  /// level or is inlined.
192  ///
193  /// check::EndFunction
194  void checkEndFunction(const ReturnStmt *RS, CheckerContext &Ctx) const {}
195 
196  /// Called after all the paths in the ExplodedGraph reach end of path
197  /// - the symbolic execution graph is fully explored.
198  ///
199  /// This callback should be used in cases when a checker needs to have a
200  /// global view of the information generated on all paths. For example, to
201  /// compare execution summary/result several paths.
202  /// See IdempotentOperationChecker for a usage example.
203  ///
204  /// check::EndAnalysis
206  BugReporter &BR,
207  ExprEngine &Eng) const {}
208 
209  /// Called after analysis of a TranslationUnit is complete.
210  ///
211  /// check::EndOfTranslationUnit
213  AnalysisManager &Mgr,
214  BugReporter &BR) const {}
215 
216  /// Evaluates function call.
217  ///
218  /// The analysis core treats all function calls in the same way. However, some
219  /// functions have special meaning, which should be reflected in the program
220  /// state. This callback allows a checker to provide domain specific knowledge
221  /// about the particular functions it knows about.
222  ///
223  /// \returns true if the call has been successfully evaluated
224  /// and false otherwise. Note, that only one checker can evaluate a call. If
225  /// more than one checker claims that they can evaluate the same call the
226  /// first one wins.
227  ///
228  /// eval::Call
229  bool evalCall(const CallExpr *CE, CheckerContext &C) const { return true; }
230 
231  /// Handles assumptions on symbolic values.
232  ///
233  /// This method is called when a symbolic expression is assumed to be true or
234  /// false. For example, the assumptions are performed when evaluating a
235  /// condition at a branch. The callback allows checkers track the assumptions
236  /// performed on the symbols of interest and change the state accordingly.
237  ///
238  /// eval::Assume
240  SVal Cond,
241  bool Assumption) const { return State; }
242 
243  /// Allows modifying SymbolReaper object. For example, checkers can explicitly
244  /// register symbols of interest as live. These symbols will not be marked
245  /// dead and removed.
246  ///
247  /// check::LiveSymbols
249 
250  /// Called when the contents of one or more regions change.
251  ///
252  /// This can occur in many different ways: an explicit bind, a blanket
253  /// invalidation of the region contents, or by passing a region to a function
254  /// call whose behavior the analyzer cannot model perfectly.
255  ///
256  /// \param State The current program state.
257  /// \param Invalidated A set of all symbols potentially touched by the change.
258  /// \param ExplicitRegions The regions explicitly requested for invalidation.
259  /// For a function call, this would be the arguments. For a bind, this
260  /// would be the region being bound to.
261  /// \param Regions The transitive closure of regions accessible from,
262  /// \p ExplicitRegions, i.e. all regions that may have been touched
263  /// by this change. For a simple bind, this list will be the same as
264  /// \p ExplicitRegions, since a bind does not affect the contents of
265  /// anything accessible through the base region.
266  /// \param LCtx LocationContext that is useful for getting various contextual
267  /// info, like callstack, CFG etc.
268  /// \param Call The opaque call triggering this invalidation. Will be 0 if the
269  /// change was not triggered by a call.
270  ///
271  /// check::RegionChanges
274  const InvalidatedSymbols *Invalidated,
275  ArrayRef<const MemRegion *> ExplicitRegions,
277  const LocationContext *LCtx,
278  const CallEvent *Call) const {
279  return State;
280  }
281 
282  /// Called when pointers escape.
283  ///
284  /// This notifies the checkers about pointer escape, which occurs whenever
285  /// the analyzer cannot track the symbol any more. For example, as a
286  /// result of assigning a pointer into a global or when it's passed to a
287  /// function call the analyzer cannot model.
288  ///
289  /// \param State The state at the point of escape.
290  /// \param Escaped The list of escaped symbols.
291  /// \param Call The corresponding CallEvent, if the symbols escape as
292  /// parameters to the given call.
293  /// \param Kind How the symbols have escaped.
294  /// \returns Checkers can modify the state by returning a new state.
296  const InvalidatedSymbols &Escaped,
297  const CallEvent *Call,
298  PointerEscapeKind Kind) const {
299  return State;
300  }
301 
302  /// Called when const pointers escape.
303  ///
304  /// Note: in most cases checkPointerEscape callback is sufficient.
305  /// \sa checkPointerEscape
307  const InvalidatedSymbols &Escaped,
308  const CallEvent *Call,
309  PointerEscapeKind Kind) const {
310  return State;
311  }
312 
313  /// check::Event<ImplicitNullDerefEvent>
314  void checkEvent(ImplicitNullDerefEvent Event) const {}
315 
316  /// Check every declaration in the AST.
317  ///
318  /// An AST traversal callback, which should only be used when the checker is
319  /// not path sensitive. It will be called for every Declaration in the AST and
320  /// can be specialized to only be called on subclasses of Decl, for example,
321  /// FunctionDecl.
322  ///
323  /// check::ASTDecl<FunctionDecl>
324  void checkASTDecl(const FunctionDecl *D,
325  AnalysisManager &Mgr,
326  BugReporter &BR) const {}
327 };
328 
330  CheckerContext &C) const {
331 }
332 
333 } // end namespace ento
334 } // end namespace clang
Represents a function declaration or definition.
Definition: Decl.h:1748
void checkASTDecl(const FunctionDecl *D, AnalysisManager &Mgr, BugReporter &BR) const
Check every declaration in the AST.
void checkObjCMessageNil(const ObjCMethodCall &M, CheckerContext &C) const
Visit an Objective-C message whose receiver is nil.
Stmt - This represents one statement.
Definition: Stmt.h:66
This checker documents the callback functions checkers can use to implement the custom handling of th...
void checkEndAnalysis(ExplodedGraph &G, BugReporter &BR, ExprEngine &Eng) const
Called after all the paths in the ExplodedGraph reach end of path.
void checkPreStmt(const ReturnStmt *DS, CheckerContext &C) const
Pre-visit the Statement.
void checkLocation(SVal Loc, bool IsLoad, const Stmt *S, CheckerContext &) const
Called on a load from and a store to a location.
ProgramStateRef checkPointerEscape(ProgramStateRef State, const InvalidatedSymbols &Escaped, const CallEvent *Call, PointerEscapeKind Kind) const
Called when pointers escape.
LineState State
void checkEndOfTranslationUnit(const TranslationUnitDecl *TU, AnalysisManager &Mgr, BugReporter &BR) const
Called after analysis of a TranslationUnit is complete.
Represents any expression that calls an Objective-C method.
Definition: CallEvent.h:937
void checkEndFunction(const ReturnStmt *RS, CheckerContext &Ctx) const
Called when the analyzer core reaches the end of a function being analyzed regardless of whether it i...
void checkBind(SVal Loc, SVal Val, const Stmt *S, CheckerContext &) const
Called on binding of a value to a location.
void checkBranchCondition(const Stmt *Condition, CheckerContext &Ctx) const
Pre-visit of the condition statement of a branch (such as IfStmt).
We dereferenced a location that may be null.
Definition: Checker.h:553
void checkBeginFunction(CheckerContext &Ctx) const
Called when the analyzer core starts analyzing a function, regardless of whether it is analyzed at th...
void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const
Called whenever a symbol becomes dead.
bool evalCall(const CallExpr *CE, CheckerContext &C) const
Evaluates function call.
ReturnStmt - This represents a return, optionally of an expression: return; return 4;...
Definition: Stmt.h:2610
BugReporter is a utility class for generating PathDiagnostics for analysis.
Definition: BugReporter.h:421
Kind
Represents a new-expression for memory allocation and constructor calls, e.g: "new CXXNewExpr(foo)"...
Definition: ExprCXX.h:2000
DeclStmt - Adaptor class for mixing declarations with statements and expressions. ...
Definition: Stmt.h:1203
void checkLiveSymbols(ProgramStateRef State, SymbolReaper &SR) const
Allows modifying SymbolReaper object.
SVal - This represents a symbolic expression, which can be either an L-value or an R-value...
Definition: SVals.h:75
void checkPreCall(const CallEvent &Call, CheckerContext &C) const
Pre-visit an abstract "call" event.
A class responsible for cleaning up unused symbols.
ProgramStateRef checkConstPointerEscape(ProgramStateRef State, const InvalidatedSymbols &Escaped, const CallEvent *Call, PointerEscapeKind Kind) const
Called when const pointers escape.
void checkPreObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const
Pre-visit the Objective C message.
Dataflow Directional Tag Classes.
void checkPostCall(const CallEvent &Call, CheckerContext &C) const
Post-visit an abstract "call" event.
void checkPostStmt(const DeclStmt *DS, CheckerContext &C) const
Post-visit the Statement.
ProgramStateRef evalAssume(ProgramStateRef State, SVal Cond, bool Assumption) const
Handles assumptions on symbolic values.
Represents an abstract call to a function or method along a particular path.
Definition: CallEvent.h:138
PointerEscapeKind
Describes the different reasons a pointer escapes during analysis.
void checkPostObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const
Post-visit the Objective C message.
CallExpr - Represents a function call (C99 6.5.2.2, C++ [expr.call]).
Definition: Expr.h:2516
ProgramStateRef checkRegionChanges(ProgramStateRef State, const InvalidatedSymbols *Invalidated, ArrayRef< const MemRegion *> ExplicitRegions, ArrayRef< const MemRegion *> Regions, const LocationContext *LCtx, const CallEvent *Call) const
Called when the contents of one or more regions change.
The top declaration context.
Definition: Decl.h:107
void checkEvent(ImplicitNullDerefEvent Event) const
check::Event<ImplicitNullDerefEvent>
void checkNewAllocator(const CXXNewExpr *NE, SVal Target, CheckerContext &) const
Post-visit the C++ operator new&#39;s allocation call.