clang/lib/StaticAnalyzer/Checkers/CheckerDocumentation.cpp

   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>
  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
  91   void checkPreObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const {}
  92
  93   /// Post-visit the Objective C message.
  94   /// \sa checkPreObjCMessage()
  95   ///
  96   /// check::PostObjCMessage
  97   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
 106   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
 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
 180   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
 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
 205   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
 212   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
 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
 239   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
 248   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
 273     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.
 295   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
 306   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>
 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
 329 void CheckerDocumentation::checkPostStmt(const DeclStmt *DS,
 330                                          CheckerContext &C) const {
 331 }
 332
 333 } // end namespace ento
 334 } // end namespace clang