probably worth an option for this

json_object.c

@@ -562,7 +562,7 @@ static int json_object_double_to_json_string(struct json_object* jso,
   } else {
     p = strchr(buf, '.');
   }
-  if (p) {
+  if (p && (flags & JSON_C_TO_STRING_NOZERO)) {
     /* last useful digit, always keep 1 zero */
     p++;
     for (q=p ; *q ; q++) {

json_object.h

@@ -42,6 +42,10 @@ extern "C" {
  * for an example of the format.
  */
 #define JSON_C_TO_STRING_PRETTY     (1<<1)
+/**
+ * A flag to drop trailing zero for float values
+ */
+#define JSON_C_TO_STRING_NOZERO     (1<<2)
 
 #undef FALSE
 #define FALSE ((json_bool)0)

tests/test_locale.c

@@ -23,8 +23,9 @@ int main(int argc, char **argv)
 
 	MC_SET_DEBUG(1);
 
-	new_obj = json_tokener_parse("[1.2,3.4,123456.78,5.0]");
+	new_obj = json_tokener_parse("[1.2,3.4,123456.78,5.0,2.3e10]");
 	printf("new_obj.to_string()=%s\n", json_object_to_json_string(new_obj));
+	printf("new_obj.to_string()=%s\n", json_object_to_json_string_ext(new_obj,JSON_C_TO_STRING_NOZERO));
 	json_object_put(new_obj);
 }