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Message-ID: <7e8f0497-c37c-4d22-9c55-1b8913992636@evolvis.org>
Date: Tue, 11 Nov 2025 22:07:30 +0100 (CET)
From: Thorsten Glaser <tg@...lvis.org>
To: musl@...ts.openwall.com
cc: James Y Knight <jyknight@...gle.com>, Alejandro Colomar <alx@...nel.org>,
The 8472 <the8472.rs@...inite-source.de>,
Thiago Macieira <thiago@...ieira.org>, Florian Weimer <fw@...eb.enyo.de>,
libc-alpha@...rceware.org, Arthur O'Dwyer <arthur.j.odwyer@...il.com>,
Jonathan Wakely <jwakely@...hat.com>
Subject: Re: Re: realloci(): A realloc() variant that works in-place
On Tue, 11 Nov 2025, Rich Felker wrote:
>Is it a single problem or multiple ones that keep getting raised
>because they seem vaguely related to the topic?
I think the C++ people have a problem that they think they can
solve with this. I’m not sure whether that prompted Alex’ work
on a suggestion or whether he’s just invested into changing
realloc and they jumped on. It does seem like there are also
other people chiming in, thinking they could possibly use a
part of this anywhere, but so far, we seem to be getting only
concrete info out of C++ people.
>I'm still unclear why "size-feedback-malloc" is supposed to be useful
>enough to justify all of this. It seems like at most it's saving a
>fairly small % of space at small sizes and an even smaller % (a fixed
>maximum, the page size) at larger sizes serviced by direct mmap.
It seems like, if C++ has a need that must be served by libc’s
malloc implementation, then that’s an implementation thing, and
we don’t need to change the C standard for it, but instead ask
libc implementors to add a function specifically for the use by
C++ runtimes (which they can use once they (compile-time) tested
its availability, over the existing way).
I’ve not yet seen any use of this for C code that doesn’t have
other downsides that make it improbable to impractical.
Just my impressions,
//mirabilos
--
When he found out that the m68k port was in a pretty bad shape, he did
not, like many before him, shrug and move on; instead, he took it upon
himself to start compiling things, just so he could compile his shell.
How's that for dedication. -- Wouter, about my Debian/m68k revival
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