1. I'm sure this error comes from json.el.


2. I restart emacs with the 'emacs -Q' option, and emacs shows this buffer: 



3. I find this error comes from commit 6aa04a5(https://github.com/emacs-mirror/emacs/blob/6aa04a5570b50a68665e69231f3e36b2a4625f40/lisp/json.el). Please check it. 

在 2015-10-14 01:49:31，"Simen Heggestøyl" <simenheg@gmail.com> 写道：
On Fri, Oct 9, 2015 at 11:38 AM, 蔡君琦 <caijq4ever@163.com> wrote:
Hi,
I copy json.el from github(https://github.com/emacs-mirror/emacs/tree/master/lisp/json.el), override local json.el and compile it.
After I restart emacs, and emacs shows this error in startup:
---
Warning (initialization): An error occurred while loading `c:/Users/caijunqi/AppData/Roaming/.emacs.d/init.el':

error: Attempt to modify read-only object, (error)

Hi again,


I'm not sure what that error comes from. Can you produce a backtrace?


It looks like the crash happens in your init file. Can you reproduce it
starting from 'emacs -Q'?


Also, I'm unsure whether it has to do with with the commit that fixed
this bug. Could you test with a version of json.el pre commit 6b663751?


-- Simen