Fix thread-safety for mixin recursions check

Author: mgreter

src/expand.cpp

@@ -14,21 +14,21 @@
 namespace Sass {
 
   // simple endless recursion protection
-  const unsigned int maxRecursion = 500;
-  static unsigned int recursions = 0;
+  const size_t maxRecursion = 500;
 
   Expand::Expand(Context& ctx, Env* env, Backtrace* bt, std::vector<Selector_List_Obj>* stack)
   : ctx(ctx),
     eval(Eval(*this)),
+    recursions(0),
+    in_keyframes(false),
+    at_root_without_rule(false),
+    old_at_root_without_rule(false),
     env_stack(std::vector<Env*>()),
     block_stack(std::vector<Block_Ptr>()),
     call_stack(std::vector<AST_Node_Obj>()),
     selector_stack(std::vector<Selector_List_Obj>()),
     media_block_stack(std::vector<Media_Block_Ptr>()),
-    backtrace_stack(std::vector<Backtrace*>()),
-    in_keyframes(false),
-    at_root_without_rule(false),
-    old_at_root_without_rule(false)
+    backtrace_stack(std::vector<Backtrace*>())
   {
     env_stack.push_back(0);
     env_stack.push_back(env);
@@ -685,12 +685,13 @@ namespace Sass {
 
   Statement_Ptr Expand::operator()(Mixin_Call_Ptr c)
   {
-    recursions ++;
 
     if (recursions > maxRecursion) {
       throw Exception::StackError(*c);
     }
 
+    recursions ++;
+
     Env* env = environment();
     std::string full_name(c->name() + "[m]");
     if (!env->has(full_name)) {

src/expand.hpp

@@ -26,17 +26,18 @@ namespace Sass {
 
     Context&          ctx;
     Eval              eval;
+    size_t            recursions;
+    bool              in_keyframes;
+    bool              at_root_without_rule;
+    bool              old_at_root_without_rule;
 
     // it's easier to work with vectors
-    std::vector<Env*>           env_stack;
+    std::vector<Env*>              env_stack;
     std::vector<Block_Ptr>         block_stack;
     std::vector<AST_Node_Obj>      call_stack;
     std::vector<Selector_List_Obj> selector_stack;
     std::vector<Media_Block_Ptr>   media_block_stack;
-    std::vector<Backtrace*>     backtrace_stack;
-    bool                        in_keyframes;
-    bool                        at_root_without_rule;
-    bool                        old_at_root_without_rule;
+    std::vector<Backtrace*>        backtrace_stack;
 
     Statement_Ptr fallback_impl(AST_Node_Ptr n);