try

src/json.hpp.re2c

@@ -2402,7 +2402,8 @@ class basic_json
             end_object,
             name_separator,
             value_separator,
-            parse_error
+            parse_error,
+            end_of_input
         };
 
         /// the type of a lexer character
@@ -2611,15 +2612,19 @@ class basic_json
                 re2c:define:YYLIMIT  = buffer_re2c_limit;
             */
 
-            for (;;)
-            {
+lexer_start:
             // set current to the begin of the buffer
             current_re2c = buffer_re2c;
 
+            if (current_re2c == buffer_re2c_limit)
+            {
+                return last_token = token_type::end_of_input;
+            }
+
             /*!re2c
                 // whitespace
                 ws = [ \t\n\r]*;
-                    ws   { continue; }
+                ws   { goto lexer_start; }
 
                 // structural characters
                 "[" { return last_token = token_type::begin_array; }
@@ -2661,7 +2666,6 @@ class basic_json
                 * { return last_token = token_type::parse_error; }
             */
         }
-        }
 
         inline static std::string token_type_name(token_type t)
         {
@@ -2693,6 +2697,8 @@ class basic_json
                     return ",";
                 case (token_type::parse_error):
                     return "<parse error>";
+                case (token_type::end_of_input):
+                    return "<end of input>";
             }
         }