bug#55727: 29.0.50; Incorrect zero symbol transcoding between applications

[Po Lu]

Петров Андрей <an.petrov@pay-lab.ru> writes:

> Hello, team!
>
> Please check the following behavior:
>
> 1. Start two instances of emacs -Q.
> 2. Switch to the "*scratch*" buffer of the first one and type the following:
>    M-: (insert (format "%S"  "000\000000")) [RET]
>    You should see "000^@000" string.
> 3. Copy the string into clipboard and paste into the other instance of
>    Emacs (which you have started before).
>    I get "000\0000" instead of "000\000000"
> 4. Try evaluating inserted text ("000\0000")
>    C-c C-e
>    I get "000^@0" instead of "000^@000".
>
> It seems that "^@" is transcoded between applications into "\0"
>  instead of "\000". If I do the same test inside single instance
>  of Emacs I get the correct result.

That's not a bug.  Most programs cannot tolerate NUL bytes inside
selection strings, so the Emacs selection converter deliberately
replaces those inside a string with "\0" before sending the string to a
requestor.

When one Emacs instance owns the selection, the contents of the kill
ring are used directly when yanking text, so that conversion doesn't
take place.