Scope: pop_scope() returns IntrusivePtr<>

Make sure unused scopes are freed to fix memory leaks.

The comment inside pop_scope() is now obsolete and I deleted it,
because this commit implements the real solution.

Note that this requires us to add a reference to the
push_existing_scope() call in dbg_eval_expr(), because it never owned
the reference.

src/Debug.cc

@@ -20,6 +20,7 @@ using namespace std;
 #include "Stmt.h"
 #include "Frame.h"
 #include "Func.h"
+#include "IntrusivePtr.h"
 #include "Scope.h"
 #include "PolicyFile.h"
 #include "Desc.h"
@@ -968,7 +969,10 @@ Val* dbg_eval_expr(const char* expr)
 
 	const BroFunc* func = frame->GetFunction();
 	if ( func )
+		{
+		Ref(func->GetScope());
 		push_existing_scope(func->GetScope());
+		}
 
 	// ### Possibly push a debugger-local scope?
 

src/Scope.cc

@@ -5,6 +5,7 @@
 #include "Scope.h"
 #include "Desc.h"
 #include "ID.h"
+#include "IntrusivePtr.h"
 #include "Val.h"
 #include "Reporter.h"
 #include "module_util.h"
@@ -204,21 +205,17 @@ void push_scope(ID* id, attr_list* attrs)
 	scopes.push_back(top_scope);
 	}
 
-Scope* pop_scope()
+IntrusivePtr<Scope> pop_scope()
 	{
 	if ( scopes.empty() )
 		reporter->InternalError("scope underflow");
 	scopes.pop_back();
 
 	Scope* old_top = top_scope;
-	// Don't delete the scope; keep it around for later name resolution
-	// in the debugger.
-	// ### SERIOUS MEMORY LEAK!?
-	// delete top_scope;
 
 	top_scope = scopes.empty() ? nullptr : scopes.back();
 
-	return old_top;
+	return {AdoptRef{}, old_top};
 	}
 
 Scope* current_scope()

src/Scope.h

@@ -10,6 +10,7 @@
 #include "BroList.h"
 #include "TraverseTypes.h"
 
+template <class T> class IntrusivePtr;
 class ID;
 class BroType;
 class ListVal;
@@ -89,7 +90,7 @@ extern void push_scope(ID* id, attr_list* attrs);
 extern void push_existing_scope(Scope* scope);
 
 // Returns the one popped off; it's not deleted.
-extern Scope* pop_scope();
+extern IntrusivePtr<Scope> pop_scope();
 extern Scope* current_scope();
 extern Scope* global_scope();
 

src/Var.cc

@@ -8,6 +8,7 @@
 #include "Val.h"
 #include "Expr.h"
 #include "Func.h"
+#include "IntrusivePtr.h"
 #include "Stmt.h"
 #include "Scope.h"
 #include "Reporter.h"
@@ -468,7 +469,7 @@ TraversalCode OuterIDBindingFinder::PostExpr(const Expr* expr)
 
 void end_func(IntrusivePtr<Stmt> body)
 	{
-	auto ingredients = std::make_unique<function_ingredients>(pop_scope(), body.release());
+	auto ingredients = std::make_unique<function_ingredients>(pop_scope().release(), body.release());
 
 	if ( streq(ingredients->id->Name(), "anonymous-function") )
 		{

src/parse.y

@@ -82,6 +82,7 @@
 #include "Desc.h"
 #include "Expr.h"
 #include "Func.h"
+#include "IntrusivePtr.h"
 #include "Stmt.h"
 #include "Val.h"
 #include "Var.h"
@@ -1250,7 +1251,7 @@ anonymous_function:
 
 			// Gather the ingredients for a BroFunc from the current scope
 			auto ingredients = std::make_unique<function_ingredients>(current_scope(), $5);
-			id_list outer_ids = gather_outer_ids(pop_scope(), $5);
+			id_list outer_ids = gather_outer_ids(pop_scope().get(), $5);
 
 			$$ = new LambdaExpr(std::move(ingredients), std::move(outer_ids));
 			}