Fix memory leak and internal leak detector

Media_Blocks are prone to have circular references.
Copy could leak memory if it does not get picked up.
Looks like we are able to reset block reference for copy
Good as it will ensure a low memory overhead for this fix
So this is a cheap solution with a minimal price

Author: mgreter

src/context.cpp

@@ -67,6 +67,7 @@ namespace Sass {
     plugins(),
     emitter(c_options),
 
+    ast_gc(),
     strings(),
     resources(),
     sheets(),

src/context.hpp

@@ -43,6 +43,9 @@ namespace Sass {
     Plugins plugins;
     Output emitter;
 
+    // generic ast node garbage container
+    // used to avoid possible circular refs
+    std::vector<AST_Node_Obj> ast_gc;
     // resources add under our control
     // these are guaranteed to be freed
     std::vector<char*> strings;

src/expand.cpp

@@ -176,7 +176,13 @@ namespace Sass {
 
   Statement_Ptr Expand::operator()(Media_Block_Ptr m)
   {
-    Media_Block_Ptr cpy = m->copy();
+    Media_Block_Obj cpy = SASS_MEMORY_COPY(m);
+    // Media_Blocks are prone to have circular references
+    // Copy could leak memory if it does not get picked up
+    // Looks like we are able to reset block reference for copy
+    // Good as it will ensure a low memory overhead for this fix
+    // So this is a cheap solution with a minimal price
+    ctx.ast_gc.push_back(cpy); cpy->block(0);
     Expression_Obj mq = eval(m->media_queries());
     std::string str_mq(mq->to_string(ctx.c_options));
     char* str = sass_copy_c_string(str_mq.c_str());

src/memory/SharedPtr.cpp

@@ -17,8 +17,8 @@ namespace Sass {
       std::cerr << "###################################\n";
       std::cerr << "# REPORTING MISSING DEALLOCATIONS #\n";
       std::cerr << "###################################\n";
-      for (auto var : all) {
-        if (AST_Node_Ptr ast = Cast<AST_Node>(var)) {
+      for (SharedObj* var : all) {
+        if (AST_Node_Ptr ast = dynamic_cast<AST_Node*>(var)) {
           debug_ast(ast);
         } else {
           std::cerr << "LEAKED " << var << "\n";
@@ -60,7 +60,7 @@ namespace Sass {
       #endif
       if (node->refcounter == 0) {
         #ifdef DEBUG_SHARED_PTR
-          AST_Node_Ptr ptr = Cast<AST_Node>(node);
+          // AST_Node_Ptr ast = dynamic_cast<AST_Node*>(node);
           if (node->dbg) std::cerr << "DELETE NODE " << node << "\n";
         #endif
         if (!node->detached) {

src/memory/SharedPtr.hpp

@@ -17,7 +17,7 @@ namespace Sass {
   #ifdef DEBUG_SHARED_PTR
 
     #define SASS_MEMORY_NEW(Class, ...) \
-      ((new Class(__VA_ARGS__))->trace(__FILE__, __LINE__)) \
+      ((Class*)(new Class(__VA_ARGS__))->trace(__FILE__, __LINE__)) \
 
     #define SASS_MEMORY_COPY(obj) \
       ((obj)->copy(__FILE__, __LINE__)) \

src/parser.cpp

@@ -541,7 +541,7 @@ namespace Sass {
     // selector schema re-uses string schema implementation
     String_Schema_Ptr schema = SASS_MEMORY_NEW(String_Schema, pstate);
     // the selector schema is pretty much just a wrapper for the string schema
-    Selector_Schema_Ptr selector_schema = SASS_MEMORY_NEW(Selector_Schema, pstate, schema);
+    Selector_Schema_Obj selector_schema = SASS_MEMORY_NEW(Selector_Schema, pstate, schema);
     selector_schema->connect_parent(chroot == false);
     selector_schema->media_block(last_media_block);
 
@@ -605,7 +605,7 @@ namespace Sass {
     after_token = before_token = pstate;
 
     // return parsed result
-    return selector_schema;
+    return selector_schema.detach();
   }
   // EO parse_selector_schema
 
@@ -1668,7 +1668,7 @@ namespace Sass {
       return str_quoted;
     }
 
-    String_Schema_Ptr schema = SASS_MEMORY_NEW(String_Schema, pstate);
+    String_Schema_Obj schema = SASS_MEMORY_NEW(String_Schema, pstate);
     schema->is_interpolant(true);
     while (i < chunk.end) {
       p = constant ? find_first_in_interval< exactly<hash_lbrace> >(i, chunk.end) :
@@ -1704,7 +1704,7 @@ namespace Sass {
       ++ i;
     }
 
-    return schema;
+    return schema.detach();
   }
 
   String_Constant_Obj Parser::parse_static_value()