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 
14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
16 #include "clang/StaticAnalyzer/Core/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
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>
checkPreStmt(const ReturnStmt * DS,CheckerContext & C) const72   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
checkPreObjCMessage(const ObjCMethodCall & M,CheckerContext & C) const91   void checkPreObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const {}
92 
93   /// Post-visit the Objective C message.
94   /// \sa checkPreObjCMessage()
95   ///
96   /// check::PostObjCMessage
checkPostObjCMessage(const ObjCMethodCall & M,CheckerContext & C) const97   void checkPostObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const {}
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
checkObjCMessageNil(const ObjCMethodCall & M,CheckerContext & C) const106   void checkObjCMessageNil(const ObjCMethodCall &M, CheckerContext &C) const {}
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
checkPreCall(const CallEvent & Call,CheckerContext & C) const118   void checkPreCall(const CallEvent &Call, CheckerContext &C) const {}
119 
120   /// Post-visit an abstract "call" event.
121   /// \sa checkPreObjCMessage()
122   ///
123   /// check::PostCall
checkPostCall(const CallEvent & Call,CheckerContext & C) const124   void checkPostCall(const CallEvent &Call, CheckerContext &C) const {}
125 
126   /// Pre-visit of the condition statement of a branch (such as IfStmt).
checkBranchCondition(const Stmt * Condition,CheckerContext & Ctx) const127   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.
checkNewAllocator(const CXXNewExpr * NE,SVal Target,CheckerContext &) const142   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
checkLocation(SVal Loc,bool IsLoad,const Stmt * S,CheckerContext &) const154   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
checkBind(SVal Loc,SVal Val,const Stmt * S,CheckerContext &) const164   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
checkDeadSymbols(SymbolReaper & SR,CheckerContext & C) const180   void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const {}
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
checkBeginFunction(CheckerContext & Ctx) const187   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
checkEndFunction(const ReturnStmt * RS,CheckerContext & Ctx) const194   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
checkEndAnalysis(ExplodedGraph & G,BugReporter & BR,ExprEngine & Eng) const205   void checkEndAnalysis(ExplodedGraph &G,
206                         BugReporter &BR,
207                         ExprEngine &Eng) const {}
208 
209   /// Called after analysis of a TranslationUnit is complete.
210   ///
211   /// check::EndOfTranslationUnit
checkEndOfTranslationUnit(const TranslationUnitDecl * TU,AnalysisManager & Mgr,BugReporter & BR) const212   void checkEndOfTranslationUnit(const TranslationUnitDecl *TU,
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
evalCall(const CallExpr * CE,CheckerContext & C) const229   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
evalAssume(ProgramStateRef State,SVal Cond,bool Assumption) const239   ProgramStateRef evalAssume(ProgramStateRef State,
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
checkLiveSymbols(ProgramStateRef State,SymbolReaper & SR) const248   void checkLiveSymbols(ProgramStateRef State, SymbolReaper &SR) const {}
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
272   ProgramStateRef
checkRegionChanges(ProgramStateRef State,const InvalidatedSymbols * Invalidated,ArrayRef<const MemRegion * > ExplicitRegions,ArrayRef<const MemRegion * > Regions,const LocationContext * LCtx,const CallEvent * Call) const273     checkRegionChanges(ProgramStateRef State,
274                        const InvalidatedSymbols *Invalidated,
275                        ArrayRef<const MemRegion *> ExplicitRegions,
276                        ArrayRef<const MemRegion *> Regions,
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.
checkPointerEscape(ProgramStateRef State,const InvalidatedSymbols & Escaped,const CallEvent * Call,PointerEscapeKind Kind) const295   ProgramStateRef checkPointerEscape(ProgramStateRef 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
checkConstPointerEscape(ProgramStateRef State,const InvalidatedSymbols & Escaped,const CallEvent * Call,PointerEscapeKind Kind) const306   ProgramStateRef checkConstPointerEscape(ProgramStateRef State,
307                                      const InvalidatedSymbols &Escaped,
308                                      const CallEvent *Call,
309                                      PointerEscapeKind Kind) const {
310     return State;
311   }
312 
313   /// check::Event<ImplicitNullDerefEvent>
checkEvent(ImplicitNullDerefEvent Event) const314   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>
checkASTDecl(const FunctionDecl * D,AnalysisManager & Mgr,BugReporter & BR) const324   void checkASTDecl(const FunctionDecl *D,
325                     AnalysisManager &Mgr,
326                     BugReporter &BR) const {}
327 };
328 
checkPostStmt(const DeclStmt * DS,CheckerContext & C) const329 void CheckerDocumentation::checkPostStmt(const DeclStmt *DS,
330                                          CheckerContext &C) const {
331 }
332 
333 } // end namespace ento
334 } // end namespace clang
335