[RecursiveASTVisitor] Introduce dataTraverseStmtPre()/dataTraverseStmtPost() to allow clients to do before/after actions during data recursive visitation.

This should fix the asan bot that hits stack overflow in a couple of test/Index tests.

llvm-svn: 260785

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -163,6 +163,18 @@ public:
   /// otherwise (including when the argument is nullptr).
   bool TraverseStmt(Stmt *S, DataRecursionQueue *Queue = nullptr);
 
+  /// Invoked before visiting a statement or expression via data recursion.
+  ///
+  /// \returns false to skip visiting the node, true otherwise.
+  bool dataTraverseStmtPre(Stmt *S) { return true; }
+
+  /// Invoked after visiting a statement or expression via data recursion.
+  /// This is not invoked if the previously invoked \c dataTraverseStmtPre
+  /// returned false.
+  ///
+  /// \returns false if the visitation was terminated early, true otherwise.
+  bool dataTraverseStmtPost(Stmt *S) { return true; }
+
   /// \brief Recursively visit a type, by dispatching to
   /// Traverse*Type() based on the argument's getTypeClass() property.
   ///
@@ -557,7 +569,10 @@ bool RecursiveASTVisitor<Derived>::TraverseStmt(Stmt *S,
     Stmt *CurrS = LocalQueue.pop_back_val();
 
     size_t N = LocalQueue.size();
-    TRY_TO(dataTraverseNode(CurrS, &LocalQueue));
+    if (getDerived().dataTraverseStmtPre(CurrS)) {
+      TRY_TO(dataTraverseNode(CurrS, &LocalQueue));
+      TRY_TO(dataTraverseStmtPost(CurrS));
+    }
     // Process new children in the order they were added.
     std::reverse(LocalQueue.begin() + N, LocalQueue.end());
   }

clang/lib/Index/IndexBody.cpp

@@ -29,11 +29,15 @@ public:
   
   bool shouldWalkTypesOfTypeLocs() const { return false; }
 
-  bool TraverseStmt(Stmt *S) {
+  bool dataTraverseStmtPre(Stmt *S) {
     StmtStack.push_back(S);
-    bool ret = base::TraverseStmt(S);
+    return true;
+  }
+
+  bool dataTraverseStmtPost(Stmt *S) {
+    assert(StmtStack.back() == S);
     StmtStack.pop_back();
-    return ret;
+    return true;
   }
 
   bool TraverseTypeLoc(TypeLoc TL) {