Don't forget to BEGIN(INITIAL) when terminating a string

src/parser/parser.l

@@ -109,7 +109,10 @@ sizeof              return TOK_SIZEOF;
     BEGIN(str);
 }
 <str>{
-\"                  return TOK_STR_CONST;
+\" {
+    BEGIN(INITIAL);
+    return TOK_STR_CONST;
+}
 \\x[0-9A-Fa-f]{2} {
                     /* hexadecimal escape code */
                     unsigned int val;