Re: 31395511: "Don’t attempt to modify constant strings"

[Paul Eggert <eggert@cs.ucla.edu>]

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On 6/3/20 5:43 PM, Paul Eggert wrote:
> On 6/3/20 4:48 PM, João Távora wrote:
>> I think I'd rather this previous behavior were retained, or at least
>> achievable by request.
> 
> It's tricky, as make-text-button in emacs-27 (and earlier) modifies its string
> argument, which is buggy because string constants are not always unique.

On second thought, I'll work on coming up with a better workaround for the
problem along the lines I suggested in my previous message: make-text-button can
copy the button label string only if the string's not mutable. I hope this helps
with SLY (as I hope SLY is not trying to modify string literals...). In the
meantime I've reverted the change by installing the attached patch; this means
the bug I mentioned in my previous message remains unfixed.

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From dd3484bedb7f0207c64ed391d1d7e699741e9917 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 3 Jun 2020 18:15:54 -0700
Subject: [PATCH] Revert make-text-button string copy
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* lisp/button.el (make-text-button): Don’t make a copy of
a button’s string label.  This reverts the change made in
2020-05-17T05:23:28Z!eggert@cs.ucla.edu, which broke SLY.
Problem reported by João Távora in:
https://lists.gnu.org/r/emacs-devel/2020-06/msg00117.html
However, we’ll need a better fix for this once string
literals become contents, if SLY uses string constants
for text button labels.
---
 lisp/button.el | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lisp/button.el b/lisp/button.el
index a91b0482ac..3a6a6de774 100644
--- a/lisp/button.el
+++ b/lisp/button.el
@@ -349,7 +349,6 @@ make-text-button
 	 (or (plist-member properties 'type)
 	     (plist-member properties :type))))
     (when (stringp beg)
-      (setq beg (copy-sequence beg)) ;; In case BEG is not mutable.
       (setq object beg beg 0 end (length object)))
     ;; Disallow setting the `category' property directly.
     (when (plist-get properties 'category)
-- 
2.25.4