bug#62009: 29.0.60; Emacs crashes on setf symbol-name

[Dmitry Gutov <dgutov@yandex.ru>]

On 10/03/2023 14:24, Daniel Mendler wrote:
> On 3/10/23 13:13, Eli Zaretskii wrote:
>>> Date: Fri, 10 Mar 2023 12:36:17 +0100
>>> Cc: Gregory Heytings<gregory@heytings.org>,
>>>   Philip Kaludercic<philipk@posteo.net>,michael_heerdegen@web.de,
>>>   monnier@iro.umontreal.ca,62009@debbugs.gnu.org, Eli Zaretskii
>>>   <eliz@gnu.org>, Augusto Stoffel<arstoffel@gmail.com>
>>> From: Daniel Mendler<mail@daniel-mendler.de>
>>>
>>>>        /* Number of characters in string; MSB is used as the mark bit.  */
>>>>        ptrdiff_t size;
>>>>        /* If nonnegative, number of bytes in the string (which is multibyte).
>>>> 	 If negative, the string is unibyte:
>>>> 	 -1 for data normally allocated
>>>> 	 -2 for data in rodata (C string constants)
>>>> 	 -3 for data that must be immovable (used for bytecode)  */
>>>>        ptrdiff_t size_byte;
>>> Thanks! That's good. Given that a read only flag already exists, it is
>>> easy to fix the issue. We just have to make sure that the size is
>>> negative for the symbol names and add a check in `aset`.
>> Let's not do that!
> Why not? There won't be a performance cost.

Perhaps we could use some exact benchmark results.