From 76ffe5adf4f6497945684e700dec15c809897d77 Mon Sep 17 00:00:00 2001
From: David Kerkeslager <kerkeslager@gmail.com>
Date: Tue, 12 Dec 2017 18:55:15 -0500
Subject: [PATCH] Use snapshots of the stack to restore stack to its previous
 state

---
 templates/function_definition.c |  7 ++-----
 templates/program.c             | 16 ++++++++++++++++
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/templates/function_definition.c b/templates/function_definition.c
index d20eba6..9af7632 100644
--- a/templates/function_definition.c
+++ b/templates/function_definition.c
@@ -4,17 +4,14 @@ Object user${{name}}$implementation(EnvironmentPool* environmentPool, Environmen
   environment = Environment_construct(environmentPool, environment);
 
   Stack* stack = Stack_construct();
+  StackSnapshot stackSnapshot = Stack_takeSnapshot(stack);
 
   jmp_buf jump;
   if(setjmp(jump) != 0)
   {
     fprintf(stderr, "\tin {{name}}\n");
 
-    while(Stack_any(stack))
-    {
-      Object item = Stack_pop(stack);
-      Object_deinitialize(&item);
-    }
+    Stack_rewind(stack, stackSnapshot);
     Environment_setLive(environment, false);
 
     Stack_destruct(stack);
diff --git a/templates/program.c b/templates/program.c
index b25f7dc..25f9acb 100644
--- a/templates/program.c
+++ b/templates/program.c
@@ -333,6 +333,22 @@ void Object_deinitialize(Object* self)
   }
 }
 
+typedef uint32_t StackSnapshot;
+
+StackSnapshot Stack_takeSnapshot(Stack* self)
+{
+  return (StackSnapshot) self->length;
+}
+
+void Stack_rewind(Stack* self, StackSnapshot snapshot)
+{
+  while(self->length > snapshot)
+  {
+    Object item = Stack_pop(self);
+    Object_deinitialize(&item);
+  }
+}
+
 void Environment_deinitialize(Environment* self)
 {
   EnvironmentNode* next;
-- 
2.20.1