[analyzer] Add checker callback documentation.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145495 91177308-0d34-0410-b5e6-96231b3b80d8

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diff --git a/lib/StaticAnalyzer/Checkers/CheckerDocumentation.cpp b/lib/StaticAnalyzer/Checkers/CheckerDocumentation.cpp
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+//= CheckerDocumentation.cpp - Documentation checker ---------------*- C++ -*-//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This checker lists all the checker callbacks and provides documentation for
+// checker writers.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ClangSACheckers.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
+
+using namespace clang;
+using namespace ento;
+
+// All checkers should be placed into anonymous namespace.
+// We place the CheckerDocumentation inside ento namespace to make the
+// it visible in doxygen.
+namespace ento {
+
+/// This checker documents the callback functions checkers can use to implement
+/// the custom handling of the specific events during path exploration as well
+/// as reporting bugs. Most of the callbacks are targeted at path-sensitive
+/// checking.
+///
+/// \sa CheckerContext
+class CheckerDocumentation : public Checker< check::PreStmt<DeclStmt>,
+                                       check::PostStmt<CallExpr>,
+                                       check::PreObjCMessage,
+                                       check::PostObjCMessage,
+                                       check::BranchCondition,
+                                       check::Location,
+                                       check::Bind,
+                                       check::DeadSymbols,
+                                       check::EndPath,
+                                       check::EndAnalysis,
+                                       check::EndOfTranslationUnit,
+                                       eval::Call,
+                                       eval::Assume,
+                                       check::LiveSymbols,
+                                       check::RegionChanges,
+                                       check::Event<ImplicitNullDerefEvent>,
+                                       check::ASTDecl<FunctionDecl> > {
+public:
+
+  /// \brief Pre-visit the Statement.
+  ///
+  /// The method will be called before the analyzer core processes the
+  /// statement. The notification is performed for every explored CFGElement,
+  /// which does not include the control flow statements such as IfStmt. The
+  /// callback can be specialized to be called with any subclass of Stmt.
+  ///
+  /// See checkBranchCondition() callback for performing custom processing of
+  /// the branching statements.
+  ///
+  /// check::PreStmt<DeclStmt>
+  void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {}
+
+  /// \brief Post-visit the Statement.
+  ///
+  /// The method will be called after the analyzer core processes the
+  /// statement. The notification is performed for every explored CFGElement,
+  /// which does not include the control flow statements such as IfStmt. The
+  /// callback can be specialized to be called with any subclass of Stmt.
+  ///
+  /// check::PostStmt<DeclStmt>
+  void checkPostStmt(const CallExpr *DS, CheckerContext &C) const;
+
+  /// \brief Pre-visit the Objective C messages.
+  void checkPreObjCMessage(const ObjCMessage &Msg, CheckerContext &C) const {}
+
+  /// \brief Post-visit the Objective C messages.
+  void checkPostObjCMessage(const ObjCMessage &Msg, CheckerContext &C) const {}
+
+  /// \brief Pre-visit of the condition statement of a branch (such as IfStmt).
+  void checkBranchCondition(const Stmt *Condition, CheckerContext &Ctx) const {}
+
+  /// \brief Called on a load from and a store to a location.
+  ///
+  /// The method will be called each time a location (pointer) value is
+  /// accessed.
+  /// \param Loc    The value of the location (pointer).
+  /// \param IsLoad The flag specifying if the location is a store or a load.
+  /// \param S      The load is performed while processing the statement.
+  ///
+  /// check::Location
+  void checkLocation(SVal Loc, bool IsLoad, const Stmt *S,
+                     CheckerContext &C) const {}
+
+  /// \brief Called on binding of a value to a location.
+  ///
+  /// \param Loc The value of the location (pointer).
+  /// \param Val The value which will be stored at the location Loc.
+  /// \param S   The bind is performed while processing the statement S.
+  ///
+  /// check::Bind
+  void checkBind(SVal Loc, SVal Val, const Stmt *S, CheckerContext &C) const {}
+
+
+  /// \brief Called whenever a symbol becomes dead.
+  ///
+  /// This callback should be used by the checkers to aggressively clean
+  /// up/reduce the checker state, which is important for reducing the overall
+  /// memory usage. Specifically, if a checker keeps symbol specific information
+  /// in the sate, it can and should be dropped after the symbol becomes dead.
+  /// In addition, reporting a bug as soon as the checker becomes dead leads to
+  /// more precise diagnostics. (For example, one should report that a malloced
+  /// variable is not freed right after it goes out of scope.)
+  ///
+  /// \param SR The SymbolReaper object can be queried to determine which
+  ///           symbols are dead.
+  ///
+  /// check::DeadSymbols
+  void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const {}
+
+  /// \brief Called when an end of path is reached in the ExplodedGraph.
+  ///
+  /// This callback should be used to check if the allocated resources are freed.
+  ///
+  /// check::EndPath
+  void checkEndPath(CheckerContext &Ctx) const {}
+
+  /// \brief Called after all the paths in the ExplodedGraph reach end of path
+  /// - the symbolic execution graph is fully explored.
+  ///
+  /// This callback should be used in cases when a checker needs to have a
+  /// global view of the information generated on all paths. For example, to
+  /// compare execution summary/result several paths.
+  /// See IdempotentOperationChecker for a usage example.
+  ///
+  /// check::EndAnalysis
+  void checkEndAnalysis(ExplodedGraph &G,
+                        BugReporter &BR,
+                        ExprEngine &Eng) const {}
+
+  /// \brief Called after analysis of a TranslationUnit is complete.
+  ///
+  /// check::EndOfTranslationUnit
+  void checkEndTranslationUnit(const TranslationUnitDecl *TU,
+                               AnalysisManager &Mgr,
+                               BugReporter &BR) {}
+
+
+  /// \brief Evaluates function call.
+  ///
+  /// The analysis core threats all function calls in the same way. However, some
+  /// functions have special meaning, which should be reflected in the program
+  /// state. This callback allows a checker to provide domain specific knowledge
+  /// about the particular functions it knows about.
+  ///
+  /// \returns true if the call has been successfully evaluated
+  /// and false otherwise. Note, that only one checker can evaluate a call. If
+  /// more then one checker claim that they can evaluate the same call the
+  /// first one wins.
+  ///
+  /// eval::Call
+  bool evalCall(const CallExpr *CE, CheckerContext &C) const { return true; }
+
+  /// \brief Handles assumptions on symbolic values.
+  ///
+  /// This method is called when a symbolic expression is assumed to be true or
+  /// false. For example, the assumptions are performed when evaluating a
+  /// condition at a branch. The callback allows checkers track the assumptions
+  /// performed on the symbols of interest and change the state accordingly.
+  ///
+  /// eval::Assume
+  const ProgramState *evalAssume(const ProgramState *State,
+                                 SVal Cond,
+                                 bool Assumption) const { return State; }
+
+  /// Allows modifying SymbolReaper object. For example, checkers can explicitly
+  /// register symbols of interest as live. These symbols will not be marked
+  /// dead and removed.
+  ///
+  /// check::LiveSymbols
+  void checkLiveSymbols(const ProgramState *State, SymbolReaper &SR) const {}
+
+  /// check::RegionChanges
+  bool wantsRegionChangeUpdate(const ProgramState *St) const { return true; }
+  const ProgramState *
+    checkRegionChanges(const ProgramState *State,
+                       const StoreManager::InvalidatedSymbols *,
+                       ArrayRef<const MemRegion *> ExplicitRegions,
+                       ArrayRef<const MemRegion *> Regions) const {
+    return State;
+  }
+
+  /// check::Event<ImplicitNullDerefEvent>
+  void checkEvent(ImplicitNullDerefEvent Event) const {}
+
+  /// \brief Check every declaration in the AST.
+  ///
+  /// An AST traversal callback, which should only be used when the checker is
+  /// not path sensitive. It will be called for every Declaration in the AST and
+  /// can be specialized to only be called on subclasses of Decl, for example,
+  /// FunctionDecl.
+  ///
+  /// check::ASTDecl<FunctionDecl>
+  void checkASTDecl(const FunctionDecl *D,
+                    AnalysisManager &Mgr,
+                    BugReporter &BR) const {}
+
+};
+
+void CheckerDocumentation::checkPostStmt(const CallExpr *DS,
+                                         CheckerContext &C) const {
+  return;
+}
+
+} // end namespace