diff --git a/Makefile b/Makefile
index 81961ce1bb..d6efed7069 100644
--- a/Makefile
+++ b/Makefile
@@ -24,7 +24,7 @@ libsass: libsass_objs
 			prelexer.o
 
 libsass_objs: sass_interface.cpp $(CPP_FILES)
-	g++ -O2 -c -combine sass_interface.cpp $(CPP_FILES)
+	g++ -O2 -Wall -c -combine sass_interface.cpp $(CPP_FILES)
 
 clean:
 	rm -rf *.o *.a
\ No newline at end of file
diff --git a/document.cpp b/document.cpp
index 9faec2aa07..e0138df8bc 100644
--- a/document.cpp
+++ b/document.cpp
@@ -139,9 +139,11 @@ namespace Sass {
     case expanded:
       root.emit_expanded_css(output, "");
       break;
+    default:
+      break;
     }
     string retval(output.str());
     if (!retval.empty()) retval.resize(retval.size()-1);
     return retval;
   }
-}
\ No newline at end of file
+}
diff --git a/document_parser.cpp b/document_parser.cpp
index 2d987dd703..13de0553af 100644
--- a/document_parser.cpp
+++ b/document_parser.cpp
@@ -85,6 +85,8 @@ namespace Sass {
     catch (string& path) {
       read_error("error reading file \"" + path + "\"");
     }
+    // unreached statement
+    return Node(Node::none); 
   }
 
   Node Document::parse_mixin_definition()
@@ -370,10 +372,9 @@ namespace Sass {
     else if (peek< exactly<'['> >(position)) {
       return parse_attribute_selector();
     }
-    else {
-      syntax_error("invalid selector after " + lexed.to_string());
-    }
-  }
+    syntax_error("invalid selector after " + lexed.to_string());
+    // unreached statement
+    return Node(Node::none);}
   
   Node Document::parse_pseudo() {
     if (lex< pseudo_not >()) {
@@ -420,9 +421,9 @@ namespace Sass {
     else if (lex < sequence< pseudo_prefix, identifier > >()) {
       return Node(Node::pseudo, line_number, lexed);
     }
-    else {
-      syntax_error("unrecognized pseudo-class or pseudo-element");
-    }
+    syntax_error("unrecognized pseudo-class or pseudo-element");
+    // unreached statement
+    return Node(Node::none);
   }
   
   Node Document::parse_attribute_selector()
@@ -477,7 +478,7 @@ namespace Sass {
           block.has_statements = true;
         }
         else {
-          for (int i = 0; i < imported_tree.size(); ++i) {
+          for (size_t i = 0; i < imported_tree.size(); ++i) {
             if (imported_tree[i].type == Node::comment ||
                 imported_tree[i].type == Node::rule) {
               block[0].has_statements = true;
@@ -512,7 +513,7 @@ namespace Sass {
       //   block << parse_ruleset();
       //   block.has_blocks = true;
       // }
-      else if (const char* p = lookahead_for_selector(position)) {
+      else if (lookahead_for_selector(position)) {
         block << parse_ruleset(definition);
         block[0].has_blocks = true;
       }
@@ -834,6 +835,8 @@ namespace Sass {
     }
     
     syntax_error("error reading values after " + lexed.to_string());
+    // unreached statement
+    return Node(Node::none);
   }
   
   extern const char hash_lbrace[] = "#{";
@@ -852,7 +855,8 @@ namespace Sass {
     
     Node schema(Node::string_schema, context.registry, line_number, 1);
     while (i < str.end) {
-      if (p = find_first_in_interval< sequence< negate< exactly<'\\'> >, exactly<hash_lbrace> > >(i, str.end)) {
+      p = find_first_in_interval< sequence< negate< exactly<'\\'> >, exactly<hash_lbrace> > >(i, str.end);
+      if (p) {
         if (i < p) schema << Node(Node::identifier, line_number, Token::make(i, p)); // accumulate the preceding segment if it's nonempty
         const char* j = find_first_in_interval< exactly<rbrace> >(p, str.end); // find the closing brace
         if (j) {
@@ -1122,4 +1126,4 @@ namespace Sass {
 //     
 //     return p;
 //   }
-// }
\ No newline at end of file
+// }
diff --git a/eval_apply.cpp b/eval_apply.cpp
index 6b531e0634..8a09e3bc43 100644
--- a/eval_apply.cpp
+++ b/eval_apply.cpp
@@ -142,6 +142,9 @@ namespace Sass {
           case Node::gte: return (lhs >= rhs) ? T : F;
           case Node::lt:  return (lhs < rhs)  ? T : F;
           case Node::lte: return (lhs <= rhs) ? T : F;
+          default:
+            eval_error("unknown comparison operator " + expr.content.token.to_string(), expr.line_number, expr.file_name);
+            return Node(Node::none);
         }
       } break;
 
@@ -150,7 +153,7 @@ namespace Sass {
         acc << eval(expr[0], env, f_env, registry);
         Node rhs(eval(expr[2], env, f_env, registry));
         accumulate(expr[1].type, acc, rhs, registry);
-        for (int i = 3; i < expr.size(); i += 2) {
+        for (size_t i = 3; i < expr.size(); i += 2) {
           Node rhs(eval(expr[i+1], env, f_env, registry));
           accumulate(expr[i].type, acc, rhs, registry);
         }
@@ -163,7 +166,7 @@ namespace Sass {
           acc << eval(expr[0], env, f_env, registry);
           Node rhs(eval(expr[2], env, f_env, registry));
           accumulate(expr[1].type, acc, rhs, registry);
-          for (int i = 3; i < expr.size(); i += 2) {
+          for (size_t i = 3; i < expr.size(); i += 2) {
             Node rhs(eval(expr[i+1], env, f_env, registry));
             accumulate(expr[i].type, acc, rhs, registry);
           }
@@ -248,7 +251,7 @@ namespace Sass {
       case Node::string_schema:
       case Node::value_schema: {
         // cerr << "evaluating schema of size " << expr.size() << endl;
-        for (int i = 0; i < expr.size(); ++i) {
+        for (size_t i = 0; i < expr.size(); ++i) {
           expr[i] = eval(expr[i], env, f_env, registry);
         }
         return expr;
@@ -258,6 +261,8 @@ namespace Sass {
         return expr;
       }
     }
+
+    return expr;
   }
 
   Node accumulate(Node::Type op, Node& acc, Node& rhs, vector<vector<Node>*>& registry)
@@ -400,7 +405,7 @@ namespace Sass {
       }
     }
     // plug the holes with default arguments if any
-    for (int i = 0; i < params.size(); ++i) {
+    for (size_t i = 0; i < params.size(); ++i) {
       if (params[i].type == Node::assignment) {
         Node param(params[i]);
         Token name(param[0].content.token);
@@ -411,7 +416,7 @@ namespace Sass {
     }
     // lexically link the new environment and eval the mixin's body
     bindings.link(env.global ? *env.global : env);
-    for (int i = 0; i < body.size(); ++i) {
+    for (size_t i = 0; i < body.size(); ++i) {
       body[i] = eval(body[i], bindings, f_env, registry);
     }
     return body;
diff --git a/functions.cpp b/functions.cpp
index 23059be0e8..f4b6b241b6 100644
--- a/functions.cpp
+++ b/functions.cpp
@@ -568,12 +568,11 @@ namespace Sass {
       else if (!n1.is_numeric() && !n2.is_numeric()) {
         eval_error("arguments to comparable must be numeric", n1.line_number, n1.file_name);
       }
-      else {
-        Node F(Node::boolean);
-        F.line_number = n1.line_number;
-        F.content.boolean_value = false;
-        return F;
-      }
+      
+      Node F(Node::boolean);
+      F.line_number = n1.line_number;
+      F.content.boolean_value = false;
+      return F;
     }
     
     // Boolean Functions ///////////////////////////////////////////////////
@@ -597,4 +596,4 @@ namespace Sass {
     
     
   }
-}
\ No newline at end of file
+}
diff --git a/node.cpp b/node.cpp
index 3d635e452d..381710a165 100644
--- a/node.cpp
+++ b/node.cpp
@@ -60,11 +60,9 @@ namespace Sass {
         //   result += at(0).to_string(t == backref ? prefix : "");
         // }
         
-        Node::Type t = at(0).type;
         result += at(0).to_string(at(0).has_backref ? prefix : "");
 
         for (size_t i = 1; i < size(); ++i) {
-          Node::Type t = at(i).type;
           result += " ";
           result += at(i).to_string(at(i).has_backref ? prefix : "");
         }
@@ -395,6 +393,8 @@ namespace Sass {
     case value:
       buf << ' ' << string(content.token);
       break;
+    default:
+      break;
     }
   }
 
diff --git a/prelexer.hpp b/prelexer.hpp
index 73b878f84a..c2f78dc6a0 100644
--- a/prelexer.hpp
+++ b/prelexer.hpp
@@ -388,8 +388,8 @@ namespace Sass {
     template<prelexer mx>
     const char* find_first_in_interval(const char* beg, const char* end) {
       while ((beg < end) && *beg) {
-        const char* p;
-        if (p = mx(beg)) return p;
+        const char* p = mx(beg);
+        if (p) return p;
         ++beg;
       }
       return 0;
diff --git a/sass_interface.cpp b/sass_interface.cpp
index 890a1866ba..8ad6166593 100644
--- a/sass_interface.cpp
+++ b/sass_interface.cpp
@@ -13,26 +13,28 @@ extern "C" {
 
   using namespace std;
   sass_context* sass_new_context()
-    { return (sass_context*) malloc(sizeof(sass_context)); }
+    { return (sass_context*) calloc(1, sizeof(sass_context)); }
   
   void sass_free_context(sass_context* ctx)
   { 
-    free(ctx->output_string);
+    if (ctx->output_string)
+      free(ctx->output_string);
     free(ctx);
   }
 
   sass_file_context* sass_new_file_context()
-    { return (sass_file_context*) malloc(sizeof(sass_file_context)); }
+    { return (sass_file_context*) calloc(1, sizeof(sass_file_context)); }
   
   void sass_free_file_context(sass_file_context* ctx)
   { 
-    free(ctx->output_string);
+    if (ctx->output_string)
+      free(ctx->output_string);
     free(ctx);
   }
   
   sass_folder_context* sass_new_folder_context()
-    { return (sass_folder_context*) malloc(sizeof(sass_folder_context)); }
-  
+    { return (sass_folder_context*) calloc(1, sizeof(sass_folder_context)); }
+
   static char* process_document(Sass::Document& doc, int style)
   {
     using namespace Sass;