CFG: Add CFGElement for automatic variables that leave the scope

Summary:
This mimics the implementation for the implicit destructors. The
generation of this scope leaving elements is hidden behind
a flag to the CFGBuilder, thus it should not affect existing code.

Currently, I'm missing a test (it's implicitly tested by the clang-tidy
lifetime checker that I'm proposing).
I though about a test using debug.DumpCFG, but then I would
have to add an option to StaticAnalyzer/Core/AnalyzerOptions
to enable the scope leaving CFGElement,
which would only be useful to that particular test.

Any other ideas how I could make a test for this feature?

Reviewers: krememek, jordan_rose

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D15031

llvm-svn: 307759

clang/include/clang/Analysis/AnalysisContext.h

@@ -426,6 +426,7 @@ class AnalysisDeclContextManager {
                              bool addImplicitDtors = false,
                              bool addInitializers = false,
                              bool addTemporaryDtors = false,
+                             bool addLifetime = false,
                              bool synthesizeBodies = false,
                              bool addStaticInitBranches = false,
                              bool addCXXNewAllocator = true,

clang/include/clang/Analysis/CFG.h

@@ -58,6 +58,7 @@ class CFGElement {
     Statement,
     Initializer,
     NewAllocator,
+    LifetimeEnds,
     // dtor kind
     AutomaticObjectDtor,
     DeleteDtor,
@@ -167,6 +168,28 @@ class CFGNewAllocator : public CFGElement {
   }
 };
 
+/// Represents the point where the lifetime of an automatic object ends
+class CFGLifetimeEnds : public CFGElement {
+public:
+  explicit CFGLifetimeEnds(const VarDecl *var, const Stmt *stmt)
+      : CFGElement(LifetimeEnds, var, stmt) {}
+
+  const VarDecl *getVarDecl() const {
+    return static_cast<VarDecl *>(Data1.getPointer());
+  }
+
+  const Stmt *getTriggerStmt() const {
+    return static_cast<Stmt *>(Data2.getPointer());
+  }
+
+private:
+  friend class CFGElement;
+  CFGLifetimeEnds() {}
+  static bool isKind(const CFGElement &elem) {
+    return elem.getKind() == LifetimeEnds;
+  }
+};
+
 /// CFGImplicitDtor - Represents C++ object destructor implicitly generated
 /// by compiler on various occasions.
 class CFGImplicitDtor : public CFGElement {
@@ -701,6 +724,10 @@ class CFGBlock {
     Elements.push_back(CFGAutomaticObjDtor(VD, S), C);
   }
 
+  void appendLifetimeEnds(VarDecl *VD, Stmt *S, BumpVectorContext &C) {
+    Elements.push_back(CFGLifetimeEnds(VD, S), C);
+  }
+
   void appendDeleteDtor(CXXRecordDecl *RD, CXXDeleteExpr *DE, BumpVectorContext &C) {
     Elements.push_back(CFGDeleteDtor(RD, DE), C);
   }
@@ -717,6 +744,19 @@ class CFGBlock {
     *I = CFGAutomaticObjDtor(VD, S);
     return ++I;
   }
+
+  // Scope leaving must be performed in reversed order. So insertion is in two
+  // steps. First we prepare space for some number of elements, then we insert
+  // the elements beginning at the last position in prepared space.
+  iterator beginLifetimeEndsInsert(iterator I, size_t Cnt,
+                                   BumpVectorContext &C) {
+    return iterator(
+        Elements.insert(I.base(), Cnt, CFGLifetimeEnds(nullptr, nullptr), C));
+  }
+  iterator insertLifetimeEnds(iterator I, VarDecl *VD, Stmt *S) {
+    *I = CFGLifetimeEnds(VD, S);
+    return ++I;
+  }
 };
 
 /// \brief CFGCallback defines methods that should be called when a logical
@@ -753,6 +793,7 @@ class CFG {
     bool AddEHEdges;
     bool AddInitializers;
     bool AddImplicitDtors;
+    bool AddLifetime;
     bool AddTemporaryDtors;
     bool AddStaticInitBranches;
     bool AddCXXNewAllocator;
@@ -774,8 +815,10 @@ class CFG {
 
     BuildOptions()
       : forcedBlkExprs(nullptr), Observer(nullptr),
-        PruneTriviallyFalseEdges(true), AddEHEdges(false),
+        PruneTriviallyFalseEdges(true),
+        AddEHEdges(false),
         AddInitializers(false), AddImplicitDtors(false),
+        AddLifetime(false),
         AddTemporaryDtors(false), AddStaticInitBranches(false),
         AddCXXNewAllocator(false), AddCXXDefaultInitExprInCtors(false) {}
   };

clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.h

@@ -205,9 +205,15 @@ class AnalyzerOptions : public RefCountedBase<AnalyzerOptions> {
   /// Controls which C++ member functions will be considered for inlining.
   CXXInlineableMemberKind CXXMemberInliningMode;
 
+  /// \sa includeImplicitDtorsInCFG
+  Optional<bool> IncludeImplicitDtorsInCFG;
+
   /// \sa includeTemporaryDtorsInCFG
   Optional<bool> IncludeTemporaryDtorsInCFG;
-
+
+  /// \sa IncludeLifetimeInCFG
+  Optional<bool> IncludeLifetimeInCFG;
+
   /// \sa mayInlineCXXStandardLibrary
   Optional<bool> InlineCXXStandardLibrary;
 
@@ -395,6 +401,20 @@ class AnalyzerOptions : public RefCountedBase<AnalyzerOptions> {
   /// accepts the values "true" and "false".
   bool includeTemporaryDtorsInCFG();
 
+  /// Returns whether or not implicit destructors for C++ objects should
+  /// be included in the CFG.
+  ///
+  /// This is controlled by the 'cfg-implicit-dtors' config option, which
+  /// accepts the values "true" and "false".
+  bool includeImplicitDtorsInCFG();
+
+  /// Returns whether or not end-of-lifetime information should be included in
+  /// the CFG.
+  ///
+  /// This is controlled by the 'cfg-lifetime' config option, which accepts
+  /// the values "true" and "false".
+  bool includeLifetimeInCFG();
+
   /// Returns whether or not C++ standard library functions may be considered
   /// for inlining.
   ///

clang/lib/Analysis/AnalysisDeclContext.cpp

@@ -67,6 +67,7 @@ AnalysisDeclContextManager::AnalysisDeclContextManager(bool useUnoptimizedCFG,
                                                        bool addImplicitDtors,
                                                        bool addInitializers,
                                                        bool addTemporaryDtors,
+                                                       bool addLifetime,
                                                        bool synthesizeBodies,
                                                        bool addStaticInitBranch,
                                                        bool addCXXNewAllocator,
@@ -77,6 +78,7 @@ AnalysisDeclContextManager::AnalysisDeclContextManager(bool useUnoptimizedCFG,
   cfgBuildOptions.AddImplicitDtors = addImplicitDtors;
   cfgBuildOptions.AddInitializers = addInitializers;
   cfgBuildOptions.AddTemporaryDtors = addTemporaryDtors;
+  cfgBuildOptions.AddLifetime = addLifetime;
   cfgBuildOptions.AddStaticInitBranches = addStaticInitBranch;
   cfgBuildOptions.AddCXXNewAllocator = addCXXNewAllocator;
 }