GNU bug report logs - #40407
[PATCH] slow ENCODE_FILE and DECODE_FILE

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Message #101 received at 40407 <at> debbugs.gnu.org (full text, mbox):

From: Mattias Engdegård <mattiase <at> acm.org>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 40407 <at> debbugs.gnu.org
Subject: Re: bug#40407: [PATCH] slow ENCODE_FILE and DECODE_FILE
Date: Mon, 6 Apr 2020 20:13:43 +0200

[Message part 1 (text/plain, inline)]

5 apr. 2020 kl. 17.56 skrev Eli Zaretskii <eliz <at> gnu.org>:

> Once we do set up default-file-name-coding-system, these macros will
> never return their argument (unless someone forcefully sets the
> encoding to nil, in which case they deserve what they get).  Do you
> agree?

Thank you, and yes, I do agree partly: ENCODE_FILE is the identity for all unibyte strings no matter the coding system in use.

However, my point (which I didn't do a very good job explaining) was that if either ENCODE_FILE or DECODE_FILE are called with the assumption that they return a new string, that is at least a latent bug.

Thus I went through them all once again, and found a few questionable calls that I'd like to fix. They rely on Fexpand_file_name returning a new string, which may or may not be true now but we would be better without such assumptions. (I also stumbled on a potential GC-related bug.) Patch attached!

With these fixed, nothing prevents those two functions from using no-copy semantics. I agree this approach is better and safer than going straight for code_convert_string_norecord in one pass.

[0001-Don-t-rely-on-copying-in-EN-DE-CODE_FILE.patch (application/octet-stream, attachment)]

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