bug#42296: 27.0.91; Correct manual entry for 'concat' w.r.t. allocation [PATCH]

["Mattias Engdegård" <mattiase@acm.org>]

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9 juli 2020 kl. 19.31 skrev Eli Zaretskii <eliz@gnu.org>:

> This loses too much useful information, IMO.  Let's please say that
> the result is sometimes ("frequently"?), but not always, a new string,
> and that programs should not rely on that aspect.

Here is a new version that adds this information, and recommends copy-sequence for mutability.


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From 4fcd3b13509ab94ddd552d3478c7c3cd9fe95279 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mattias=20Engdeg=C3=A5rd?= <mattiase@acm.org>
Date: Thu, 9 Jul 2020 17:32:13 +0200
Subject: [PATCH] Correct 'concat' manual entry

* doc/lispref/strings.texi (Creating Strings): 'concat' does not
necessarily return a newly allocated string.  This has been the case
at least since 1997 (Emacs 20.3).
---
 doc/lispref/strings.texi | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/doc/lispref/strings.texi b/doc/lispref/strings.texi
index 2ef88b9025..455f3efc27 100644
--- a/doc/lispref/strings.texi
+++ b/doc/lispref/strings.texi
@@ -248,7 +248,7 @@ Creating Strings
 @defun concat &rest sequences
 @cindex copying strings
 @cindex concatenating strings
-This function returns a new string consisting of the characters in the
+This function returns a string consisting of the characters in the
 arguments passed to it (along with their text properties, if any).  The
 arguments may be strings, lists of numbers, or vectors of numbers; they
 are not themselves changed.  If @code{concat} receives no arguments, it
@@ -269,9 +269,9 @@ Creating Strings
 @end example
 
 @noindent
-This function always constructs a new string that is not @code{eq} to
-any existing string, except when the result is the empty string (to
-save space, Emacs makes only one empty multibyte string).
+The returned string cannot be relied upon to be unique or newly
+allocated; it should be considered immutable.  Use
+@code{copy-sequence} on the result if a mutable string is needed.
 
 For information about other concatenation functions, see the
 description of @code{mapconcat} in @ref{Mapping Functions},
-- 
2.21.1 (Apple Git-122.3)