Merge pull request #2437 from mgreter/bugfix/segfaults

Fix a few segfaults

Author: mgreter

src/ast.cpp

@@ -1225,7 +1225,7 @@ namespace Sass {
         } else {
           last()->head_->concat(h);
         }
-      } else {
+      } else if (last()->head_) {
         last()->head_->concat(h);
       }
     } else {

src/bind.cpp

@@ -218,7 +218,9 @@ namespace Sass {
         Map_Obj argmap = Cast<Map>(a->value());
 
         for (auto key : argmap->keys()) {
-          std::string param = "$" + unquote(Cast<String_Constant>(key)->value());
+          String_Constant_Ptr val = Cast<String_Constant>(key);
+          if (val == NULL) throw Exception::InvalidVarKwdType(key->pstate(), key->inspect(), a);
+          std::string param = "$" + unquote(val->value());
 
           if (!param_map.count(param)) {
             std::stringstream msg;

src/extend.cpp

@@ -718,7 +718,7 @@ namespace Sass {
     }
 
     Node chunk2 = Node::createCollection();
-    while (!chunker(seq2)) {
+    while (!seq2.collection()->empty() && !chunker(seq2)) {
       chunk2.collection()->push_back(seq2.collection()->front());
       seq2.collection()->pop_front();
     }
@@ -1953,12 +1953,14 @@ namespace Sass {
                         Wrapped_Selector_Ptr ext_ws = Cast<Wrapped_Selector>(ext_head->first());
                         if (ext_ws/* && ext_cs->length() == 1*/) {
                           Selector_List_Obj ws_cs = Cast<Selector_List>(ext_ws->selector());
-                          Compound_Selector_Obj ws_ss = ws_cs->first()->head();
-                          if (!(
-                            Cast<Pseudo_Selector>(ws_ss->first()) ||
-                            Cast<Element_Selector>(ws_ss->first()) ||
-                            Cast<Placeholder_Selector>(ws_ss->first())
-                          )) continue;
+                          if (ws_cs && !ws_cs->empty() && ws_cs->first()) {
+                            Compound_Selector_Obj ws_ss = ws_cs->first()->head();
+                            if (ws_ss && !ws_ss->empty() && !(
+                              Cast<Pseudo_Selector>(ws_ss->first()) ||
+                              Cast<Element_Selector>(ws_ss->first()) ||
+                              Cast<Placeholder_Selector>(ws_ss->first())
+                            )) continue;
+                          }
                         }
                         cpy_ws_sl->append(ext_cs->first());
                       }

src/functions.cpp

@@ -1829,10 +1829,10 @@ namespace Sass {
       Expand expand(ctx, &d_env, backtrace, &selector_stack);
       Expression_Obj cond = ARG("$condition", Expression)->perform(&expand.eval);
       bool is_true = !cond->is_false();
-      Expression_Ptr res = ARG(is_true ? "$if-true" : "$if-false", Expression);
+      Expression_Obj res = ARG(is_true ? "$if-true" : "$if-false", Expression);
       res = res->perform(&expand.eval);
       res->set_delayed(false); // clone?
-      return res;
+      return res.detach();
     }
 
     //////////////////////////