Fix gcc build

src/util/string.hpp

@@ -222,7 +222,8 @@ String make_non_capturing(const String& re);
 
 // ----------------------------------------------------------------------------- : Iterator utilities
 
-struct end_sentinel_t {} end_sentinel;
+struct end_sentinel_t {};
+const end_sentinel_t end_sentinel;
 
 // Iterate over a string, removing all matching substrings.
 // match.operator(it,end) should return false or return true and advance it past the substring

src/util/tagged_string.hpp

@@ -220,9 +220,9 @@ String tagged_substr_replace(const String& input, size_t start, size_t end, cons
  */
 bool check_tagged(const String& str, bool check_balance = true);
 #ifdef _DEBUG
-  #define assert_tagged(x) assert(check_tagged(x))
+  #define assert_tagged(...) assert(check_tagged(__VA_ARGS__))
 #else
-  #define assert_tagged(x) do{}while(0)
+  #define assert_tagged(...) do{}while(0)
 #endif
 
 /// Simplify a tagged string