From: Alex <agrambot@gmail.com>
To: Alan Mackenzie <acm@muc.de>
Cc: Daniel Colascione <dancol@dancol.org>, emacs-devel@gnu.org
Subject: Comparing symbol-with-position using eq (was: Help please! To track down GC trying to free an already freed object.)
Date: Fri, 05 Apr 2019 11:05:59 -0600 [thread overview]
Message-ID: <87ftqwcrgo.fsf_-_@gmail.com> (raw)
In-Reply-To: <20190405082652.GA4208@ACM> (Alan Mackenzie's message of "Fri, 5 Apr 2019 08:26:52 +0000")
Hello, Alan.
Alan Mackenzie <acm@muc.de> writes:
> On Thu, Apr 04, 2019 at 22:49:22 -0600, Alex wrote:
>
>> I apologize if this topic already reached its conclusion, but IMO
>> having eq return true for two different object types is quite
>> surprising behaviour.
>
> We are comparing two symbols, both of which are 'foo, but one of which is
> annotated with its position in a source file. The two symbols are the
> same symbol.
Is it not comparing a symbol with a pseudovector containing that symbol
and a position?
> I understand the reaction to the idea, though. Even though the
> representation of these two objects is different, conceptually they are
> the same object.
Similar objects, but I don't believe that's enough for eq. Consider that
it's regarded non-portable in Lisp to compare integers with eq since the
same number may be represented by different objects, or (eq 3 3.0), or
(eq (list 1 2) (list 1 2)).
> But consider: on a make bootstrap I did last night, there were 332
> warning messages from the byte compiler. Of these, only 80 gave the
> correct line/column position, the other 252 being wrong. There have been
> several bug reports from users complaining about such false positions.
> This is what I'm trying to fix.
I agree that it's a problem very much worth fixing; thank you for
working on it.
>> Is it out of the question to leave eq alone and introduce, e.g.,
>> eq-excluding-position that strips possible positions before comparison?
>
> It is, rather. To implement this would involve rewriting everything
> which calls eq and is used by the byte compiler, to call
> eq-excluding-position instead. These functions would need to exist in
> two versions. There are rather a lot of functions which use eq. ;-)
Why would you need to rewrite the helper procedures that the byte
compiler uses? What about stripping the position at each relevant call
site?
next prev parent reply other threads:[~2019-04-05 17:05 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-02 11:25 Help please! To track down GC trying to free an already freed object Alan Mackenzie
2019-04-02 15:04 ` Eli Zaretskii
2019-04-02 20:42 ` Alan Mackenzie
2019-04-03 4:43 ` Eli Zaretskii
2019-04-04 18:57 ` Alan Mackenzie
2019-04-02 19:09 ` Daniel Colascione
2019-04-02 19:21 ` Eli Zaretskii
2019-04-02 20:46 ` Alan Mackenzie
2019-04-02 21:03 ` Daniel Colascione
2019-04-03 4:39 ` Eli Zaretskii
2019-04-03 10:01 ` Alan Mackenzie
2019-04-03 10:12 ` Eli Zaretskii
2019-04-03 15:23 ` Paul Eggert
2019-04-02 20:24 ` Alan Mackenzie
2019-04-02 20:33 ` Daniel Colascione
2019-04-02 21:00 ` Alan Mackenzie
2019-04-05 4:49 ` Alex
2019-04-05 8:26 ` Alan Mackenzie
2019-04-05 17:05 ` Alex [this message]
2019-04-05 18:21 ` Comparing symbol-with-position using eq Alan Mackenzie
2019-04-05 20:18 ` Daniel Colascione
2019-04-05 21:54 ` Alan Mackenzie
2019-04-05 22:50 ` Paul Eggert
2019-04-06 12:23 ` Clément Pit-Claudel
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