From: Eli Zaretskii <eliz@gnu.org>
To: vibhavp@gmail.com
Cc: rms@gnu.org, akrl@sdf.org, luangruo@yahoo.com, emacs-devel@gnu.org
Subject: Re: scratch/comp-static-data 5aa3db2f11: comp: Add support for compiling elisp constants into static data.
Date: Sun, 20 Nov 2022 18:54:48 +0200 [thread overview]
Message-ID: <8335ad5zxj.fsf@gnu.org> (raw)
In-Reply-To: <18b7286a9bd88d8c30822d195d9893f1267fd665.camel@gmail.com> (vibhavp@gmail.com)
> From: vibhavp@gmail.com
> Cc: akrl@sdf.org, luangruo@yahoo.com, emacs-devel@gnu.org
> Date: Sun, 20 Nov 2022 22:07:12 +0530
>
> The follow elisp snipper is an example of code that when compiled under
> this branch, crashes Emacs:
> ;; -*- lexical-binding: t; -*-
> (defun fault-function ()
> (let ((a [1 2 3]))
> (aset a 0 5)
> a))
>
> (fault-function)
Then I think Richard is right, and we shouldn't do this. It is OK to signal
an error in this case, but not crash the entire Emacs session.
> Therefore, `lisp_data_3' gets stored in .rodata (or .data.rel.ro),
> which causes the call to `aset' to trigger a SIGSEGV. This behaviour is
> documented by the Elisp reference manual, which states that self-
> evaluating forms are immutable, and changing then can read to
> crashes/undefined behaviour
> (https://www.gnu.org/software/emacs/manual/html_node/elisp/Self_002dEvaluating-Forms.html
> ).
The documentation says "don't do that!", but it's a far cry from an actual
crash.
Sorry, I'm against doing this in Emacs.
> The idea behind this patch is to replace the runtime initialization of
> lisp objects in the original bytecode constant vector with static
> variables, compiled into the eln itself. For now, it is able to do so
> for strings (without text properties), bare symbols in `lispsym',
> floats, vectors (and other psuedovectors in the future), and conses.
> Objects that require runtime initialization (for instance, interned
> symbols) are still created by calling their respective initialization
> functions, and are not able to be stored as consts.
I understand, but if the price is such crashes, it's a price I don't think
we want to pay.
next prev parent reply other threads:[~2022-11-20 16:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <166844679660.19180.3470364122428955894@vcs2.savannah.gnu.org>
[not found] ` <20221114172637.78215C0E4C7@vcs2.savannah.gnu.org>
2022-11-15 0:30 ` scratch/comp-static-data 5aa3db2f11: comp: Add support for compiling elisp constants into static data Po Lu
2022-11-15 9:06 ` Andrea Corallo
2022-11-16 19:36 ` Vibhav Pant
2022-11-17 19:59 ` Andrea Corallo
2022-11-17 4:32 ` Richard Stallman
2022-11-17 8:46 ` Vibhav Pant
2022-11-18 5:07 ` Richard Stallman
2022-11-18 8:28 ` Eli Zaretskii
2022-11-20 1:15 ` Richard Stallman
2022-11-20 7:37 ` Eli Zaretskii
2022-11-20 16:37 ` vibhavp
2022-11-20 16:54 ` Eli Zaretskii [this message]
2022-11-20 18:47 ` Stefan Monnier
2022-11-21 15:59 ` vibhavp
2022-11-21 0:37 ` Po Lu
2022-11-16 19:26 ` Vibhav Pant
2022-11-17 4:51 ` Po Lu
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