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Re: 31395511: "Don’t attempt to modify constant strings"

From: João Távora
Subject: Re: 31395511: "Don’t attempt to modify constant strings"
Date: Sat, 6 Jun 2020 12:47:45 +0100

On Sat, Jun 6, 2020 at 12:41 PM João Távora <joaotavora@gmail.com> wrote:
On Sat, Jun 6, 2020 at 2:43 AM Paul Eggert <eggert@cs.ucla.edu> wrote:
On 6/5/20 4:19 PM, João Távora wrote:
> I totally agree it is
> undefined behaviour to change structure of literals (quoted or
> self-evaluating objects), also in Common Lisp, because compilers are
> probably allowed to reuse parts of the internal structure of such
> objects.  But that's a far cry from having two different manifestations
> of `equal` such objects _be_ the same object, but only for compiled
> code.

I don't understand this remark, as the idea that "compilers are allowed to reuse
parts" necessarily implies that (eq "a" "a") can be t if the compiler decides to
reuse the string.

Depending on the implementation of sequences, it could reuse only the
later parts of the sequences to maintain uniqueness and still have

I forgot to finish the sentence: "and still have some some reuse".


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