Make parse_css_variable_value non-recursive

Fixes #2658 stack overflow

Author: glebm

src/parser.cpp

@@ -1804,71 +1804,63 @@ namespace Sass {
     return schema.detach();
   }
 
-  String_Schema_Obj Parser::parse_css_variable_value(bool top_level)
+  String_Schema_Obj Parser::parse_css_variable_value()
   {
     String_Schema_Obj schema = SASS_MEMORY_NEW(String_Schema, pstate);
-    String_Schema_Obj tok;
-    if (!(tok = parse_css_variable_value_token(top_level))) {
-      return {};
-    }
-
-    schema->concat(tok);
-    while ((tok = parse_css_variable_value_token(top_level))) {
-      schema->concat(tok);
-    }
-
-    return schema.detach();
-  }
-
-  String_Schema_Obj Parser::parse_css_variable_value_token(bool top_level)
-  {
-    String_Schema_Obj schema = SASS_MEMORY_NEW(String_Schema, pstate);
-    if (
-      (top_level && lex< css_variable_top_level_value >(false)) ||
-      (!top_level && lex< css_variable_value >(false))
-    ) {
-      Token str(lexed);
-      schema->append(SASS_MEMORY_NEW(String_Constant, pstate, str));
-    }
-    else if (Expression_Obj tok = lex_interpolation()) {
-      if (String_Schema* s = Cast<String_Schema>(tok)) {
-        schema->concat(s);
-      } else {
-        schema->append(tok);
-      }
-    }
-    else if (lex< quoted_string >()) {
-      Expression_Obj tok = parse_string();
-      if (String_Schema* s = Cast<String_Schema>(tok)) {
-        schema->concat(s);
-      } else {
-        schema->append(tok);
-      }
-    }
-    else {
-      if (peek< alternatives< exactly<'('>, exactly<'['>, exactly<'{'> > >()) {
-        if (lex< exactly<'('> >()) {
-          schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string("(")));
-          if (String_Schema_Obj tok = parse_css_variable_value(false)) schema->concat(tok);
-          if (!lex< exactly<')'> >()) css_error("Invalid CSS", " after ", ": expected \")\", was ");
-          schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string(")")));
+    std::vector<char> brackets;
+    while (true) {
+      if (
+        (brackets.empty() && lex< css_variable_top_level_value >(false)) ||
+        (!brackets.empty() && lex< css_variable_value >(false))
+      ) {
+        Token str(lexed);
+        schema->append(SASS_MEMORY_NEW(String_Constant, pstate, str));
+      } else if (Expression_Obj tok = lex_interpolation()) {
+        if (String_Schema* s = Cast<String_Schema>(tok)) {
+          if (s->empty()) break;
+          schema->concat(s);
+        } else {
+          schema->append(tok);
         }
-        else if (lex< exactly<'['> >()) {
-          schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string("[")));
-          if (String_Schema_Obj tok = parse_css_variable_value(false)) schema->concat(tok);
-          if (!lex< exactly<']'> >()) css_error("Invalid CSS", " after ", ": expected \"]\", was ");
-          schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string("]")));
+      } else if (lex< quoted_string >()) {
+        Expression_Obj tok = parse_string();
+        if (tok.isNull()) break;
+        if (String_Schema* s = Cast<String_Schema>(tok)) {
+          if (s->empty()) break;
+          schema->concat(s);
+        } else {
+          schema->append(tok);
         }
-        else if (lex< exactly<'{'> >()) {
-          schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string("{")));
-          if (String_Schema_Obj tok = parse_css_variable_value(false)) schema->concat(tok);
-          if (!lex< exactly<'}'> >()) css_error("Invalid CSS", " after ", ": expected \"}\", was ");
-          schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string("}")));
+      } else if (lex< alternatives< exactly<'('>, exactly<'['>, exactly<'{'> > >()) {
+        const char opening_bracket = *(position - 1);
+        brackets.push_back(opening_bracket);
+        schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string(1, opening_bracket)));
+      } else if (const char *match = peek< alternatives< exactly<')'>, exactly<']'>, exactly<'}'> > >()) {
+        if (brackets.empty()) break;
+        const char closing_bracket = *(match - 1);
+        if (brackets.back() != Util::opening_bracket_for(closing_bracket)) {
+          std::string message = ": expected \"";
+          message += Util::closing_bracket_for(brackets.back());
+          message += "\", was ";
+          css_error("Invalid CSS", " after ", message);
         }
+        lex< alternatives< exactly<')'>, exactly<']'>, exactly<'}'> > >();
+        schema->append(SASS_MEMORY_NEW(String_Constant, pstate, std::string(1, closing_bracket)));
+        brackets.pop_back();
+      } else {
+        break;
       }
     }
 
-    return schema->length() > 0 ? schema.detach() : NULL;
+    if (!brackets.empty()) {
+      std::string message = ": expected \"";
+      message += Util::closing_bracket_for(brackets.back());
+      message += "\", was ";
+      css_error("Invalid CSS", " after ", message);
+    }
+
+    if (schema->empty()) return {};
+    return schema.detach();
   }
 
   Value_Obj Parser::parse_static_value()

src/parser.hpp

@@ -294,8 +294,7 @@ namespace Sass {
     String_Obj parse_interpolated_chunk(Token, bool constant = false, bool css = true);
     String_Obj parse_string();
     Value_Obj parse_static_value();
-    String_Schema_Obj parse_css_variable_value(bool top_level = true);
-    String_Schema_Obj parse_css_variable_value_token(bool top_level = true);
+    String_Schema_Obj parse_css_variable_value();
     String_Obj parse_ie_property();
     String_Obj parse_ie_keyword_arg();
     String_Schema_Obj parse_value_schema(const char* stop);

src/util_string.cpp

@@ -53,5 +53,23 @@ std::string normalize_decimals(const std::string& str) {
   return normalized;
 }
 
+char opening_bracket_for(char closing_bracket) {
+  switch (closing_bracket) {
+    case ')': return '(';
+    case ']': return '[';
+    case '}': return '{';
+    default: return '\0';
+  }
+}
+
+char closing_bracket_for(char opening_bracket) {
+  switch (opening_bracket) {
+    case '(': return ')';
+    case '[': return ']';
+    case '{': return '}';
+    default: return '\0';
+  }
+}
+
 }  // namespace Sass
 }  // namespace Util

src/util_string.hpp

@@ -11,6 +11,8 @@ std::string rtrim(const std::string& str);
 std::string normalize_newlines(const std::string& str);
 std::string normalize_underscores(const std::string& str);
 std::string normalize_decimals(const std::string& str);
+char opening_bracket_for(char closing_bracket);
+char closing_bracket_for(char opening_bracket);
 
 }  // namespace Sass
 }  // namespace Util