[analyzer] When constructing a temporary without construction context, track it for destruction anyway.

[NoQ]

Summary

This brings back code that was doing so earlier (when we had no constructed contexts at all) but was removed too early in D43104, as discussed in D43497. This allows us to call the correct destructor sequence in the end of the operator && in the test, even if not all of them are inlined, because we keep track of all temporaries we've constructed in order to resolve situations when the number or nature of temporaries is not known in compile-time.

The test case provided in D43497 was not entirely correct: the global variable would anyway be invalidated by the other destructor that we don't inline yet. Though, yeah, it needs to be fixed as well, but it isn't addressed by the fix that i've been thinking of (this patch).

Cleanup process misbehaves when the node after the cleanup is caching out: in this case we take the node that wasn't cleaned up and hit the assertion. This was fixed as well. It's a bit disappointing that our process of constructing a single exploded node is so complicated and error-prone.

[dcoughlin]

lib/StaticAnalyzer/Core/ExprEngine.cpp

2234 ↗

(On Diff #135580)

Can you add a comment explaining the criteria under which the DidCacheOutOnCleanup part can be removed?

2257 ↗

(On Diff #135580)

I realize this isn't new code in this patch, but can you use the result of Bldr.generateNode() to determine whether we cached out and also to get the new Pred? That seems cleaner than querying the ExplodedNodeSet.

2262 ↗

(On Diff #135580)

It sounds like this means if we did cache out then there are places where the initialized temporaries are not cleared (that is, we have extra gunk in the state that we don't want).

Is that true? If so, then this relaxation of the assertion doesn't seem right to me.

Do we need to introduce a new program point when calling Bldr.generateNode on the cleaned up state (for example, with a new tag or a new program point kind)? This would make it so that when we cache out when generating a node for the state with the cleaned up temporaries we know that it is safe to early return from processEndOfFunction(). It would be safe because we would know that the other node (the one we cached out because of) has already had its temporaries cleared and notified the checkers about the end of the function, etc.

[NoQ]

Fix cleanup node generation logic.

lib/StaticAnalyzer/Core/ExprEngine.cpp

2262 ↗

(On Diff #135580)

Yep, this is a bug and also it can be simplified a lot.

cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h

public:
   void VisitUnaryOperator(const UnaryOperator* B, ExplodedNode *Pred, 
                           ExplodedNodeSet &Dst);
 
   /// Handle ++ and -- (both pre- and post-increment).
   void VisitIncrementDecrementOperator(const UnaryOperator* U,
                                        ExplodedNode *Pred,
                                        ExplodedNodeSet &Dst);
 
+  void VisitCXXBindTemporaryExpr(const CXXBindTemporaryExpr *BTE,
+                                 ExplodedNodeSet &PreVisit,
+                                 ExplodedNodeSet &Dst);
+
   void VisitCXXCatchStmt(const CXXCatchStmt *CS, ExplodedNode *Pred,
                          ExplodedNodeSet &Dst);
 
   void VisitCXXThisExpr(const CXXThisExpr *TE, ExplodedNode *Pred, 
                         ExplodedNodeSet & Dst);
 
   void VisitCXXConstructExpr(const CXXConstructExpr *E, ExplodedNode *Pred,
                              ExplodedNodeSet &Dst);

cfe/trunk/lib/StaticAnalyzer/Core/ExprEngine.cpp

if (Pred->getState()->contains<InitializedTemporaries>(
     TempDtorBuilder.markInfeasible(false);
     TempDtorBuilder.generateNode(Pred->getState(), true, Pred);
   } else {
     TempDtorBuilder.markInfeasible(true);
     TempDtorBuilder.generateNode(Pred->getState(), false, Pred);
   }
 }
 
+void ExprEngine::VisitCXXBindTemporaryExpr(const CXXBindTemporaryExpr *BTE,
+                                           ExplodedNodeSet &PreVisit,
+                                           ExplodedNodeSet &Dst) {
+  // This is a fallback solution in case we didn't have a construction
+  // context when we were constructing the temporary. Otherwise the map should
+  // have been populated there.
+  if (!getAnalysisManager().options.includeTemporaryDtorsInCFG()) {
+    // In case we don't have temporary destructors in the CFG, do not mark
+    // the initialization - we would otherwise never clean it up.
+    Dst = PreVisit;
+    return;
+  }
+  StmtNodeBuilder StmtBldr(PreVisit, Dst, *currBldrCtx);
+  for (ExplodedNode *Node : PreVisit) {
+    ProgramStateRef State = Node->getState();
+    const auto &Key = std::make_pair(BTE, Node->getStackFrame());
+
+    if (!State->contains<InitializedTemporaries>(Key)) {
+      // FIXME: Currently the state might also already contain the marker due to
+      // incorrect handling of temporaries bound to default parameters; for
+      // those, we currently skip the CXXBindTemporaryExpr but rely on adding
+      // temporary destructor nodes.
+      State = State->set<InitializedTemporaries>(Key, nullptr);
+    }
+    StmtBldr.generateNode(BTE, Node, State);
+  }
+}
+
 namespace {
 class CollectReachableSymbolsCallback final : public SymbolVisitor {
   InvalidatedSymbols Symbols;
 
 public:
   explicit CollectReachableSymbolsCallback(ProgramStateRef State) {}
   const InvalidatedSymbols &getSymbols() const { return Symbols; }
 
switch (S->getStmtClass()) {
     case Stmt::ExprWithCleanupsClass:
       // Handled due to fully linearised CFG.
       break;
 
     case Stmt::CXXBindTemporaryExprClass: {
       Bldr.takeNodes(Pred);
       ExplodedNodeSet PreVisit;
       getCheckerManager().runCheckersForPreStmt(PreVisit, Pred, S, *this);
-      getCheckerManager().runCheckersForPostStmt(Dst, PreVisit, S, *this);
+      ExplodedNodeSet Next;
+      VisitCXXBindTemporaryExpr(cast<CXXBindTemporaryExpr>(S), PreVisit, Next);
+      getCheckerManager().runCheckersForPostStmt(Dst, Next, S, *this);
       Bldr.addNodes(Dst);
       break;
     }
 
     // Cases not handled yet; but will handle some day.
     case Stmt::DesignatedInitExprClass:
     case Stmt::DesignatedInitUpdateExprClass:
     case Stmt::ArrayInitLoopExprClass:

 void ExprEngine::processEndOfFunction(NodeBuilderContext& BC,
                                       ExplodedNode *Pred,
                                       const ReturnStmt *RS) {
   // See if we have any stale C++ allocator values.
   assert(areCXXNewAllocatorValuesClear(Pred->getState(),
                                        Pred->getLocationContext(),
                                        Pred->getStackFrame()->getParent()));
 
-  // FIXME: We currently assert that temporaries are clear, as lifetime extended
-  // temporaries are not always modelled correctly. In some cases when we
-  // materialize the temporary, we do createTemporaryRegionIfNeeded(), and
-  // the region changes, and also the respective destructor becomes automatic
-  // from temporary. So for now clean up the state manually before asserting.
-  // Ideally, the code above the assertion should go away, but the assertion
-  // should remain.
+  // FIXME: We currently cannot assert that temporaries are clear, because
+  // lifetime extended temporaries are not always modelled correctly. In some
+  // cases when we materialize the temporary, we do
+  // createTemporaryRegionIfNeeded(), and the region changes, and also the
+  // respective destructor becomes automatic from temporary. So for now clean up
+  // the state manually before asserting. Ideally, the code above the assertion
+  // should go away, but the assertion should remain.
   {
     ExplodedNodeSet CleanUpTemporaries;
     NodeBuilder Bldr(Pred, CleanUpTemporaries, BC);
     ProgramStateRef State = Pred->getState();
     const LocationContext *FromLC = Pred->getLocationContext();
     const LocationContext *ToLC = FromLC->getCurrentStackFrame()->getParent();
     const LocationContext *LC = FromLC;
     while (LC != ToLC) {
       assert(LC && "ToLC must be a parent of FromLC!");
       for (auto I : State->get<InitializedTemporaries>())
         if (I.first.second == LC)
           State = State->remove<InitializedTemporaries>(I.first);
 
       LC = LC->getParent();
     }
     if (State != Pred->getState()) {
-      Bldr.generateNode(Pred->getLocation(), State, Pred);
-      assert(CleanUpTemporaries.size() <= 1);
-      Pred = CleanUpTemporaries.empty() ? Pred : *CleanUpTemporaries.begin();
+      Pred = Bldr.generateNode(Pred->getLocation(), State, Pred);
+      if (!Pred) {
+        // The node with clean temporaries already exists. We might have reached
+        // it on a path on which we initialize different temporaries.
+        return;
+      }
     }
   }
   assert(areInitializedTemporariesClear(Pred->getState(),
                                         Pred->getLocationContext(),
                                         Pred->getStackFrame()->getParent()));
   assert(areTemporaryMaterializationsClear(Pred->getState(),
                                            Pred->getLocationContext(),
                                            Pred->getStackFrame()->getParent()));

cfe/trunk/test/Analysis/temporaries.cpp

 }
 } // namespace test_match_constructors_and_destructors
 
 namespace dont_forget_destructor_around_logical_op {
 int glob;
 
 class C {
 public:
-  ~C() { glob = 1; }
+  ~C() {
+    glob = 1;
+    clang_analyzer_checkInlined(true);
+#ifdef TEMPORARY_DTORS
+    // expected-warning@-2{{TRUE}}
+#endif
+  }
 };
 
 C get();
 
 bool is(C);
 
 
 void test(int coin) {
   // Here temporaries are being cleaned up after && is evaluated. There are two
   // temporaries: the return value of get() and the elidable copy constructor
   // of that return value into is(). According to the CFG, we need to cleanup
   // both of them depending on whether the temporary corresponding to the
-  // return value of get() was initialized. However, for now we don't track
-  // temporaries returned from functions, so we take the wrong branch.
+  // return value of get() was initialized. However, we didn't track
+  // temporaries returned from functions, so we took the wrong branch.
   coin && is(get()); // no-crash
-  // FIXME: We should have called the destructor, i.e. should be TRUE,
-  // at least when we inline temporary destructors.
-  clang_analyzer_eval(glob == 1); // expected-warning{{UNKNOWN}}
+  // FIXME: Should be true once we inline all destructors.
+  clang_analyzer_eval(glob); // expected-warning{{UNKNOWN}}
 }
 } // namespace dont_forget_destructor_around_logical_op
 
 #if __cplusplus >= 201103L
 namespace temporary_list_crash {
 class C {
 public:
   C() {}
   ~C() {}
 };
 
 void test() {
   std::initializer_list<C>{C(), C()}; // no-crash
 }
 } // namespace temporary_list_crash
 #endif // C++11