[tex-k] unbalanced write

[Karl Berry]

Hi Hironobu,

    the problem reported in 2011
    https://groups.google.com/g/comp.text.tex/c/SEHJUKtksU8

Ah. I was not aware of BLF's report in 2011. I had seen the report from
"user202729" on tex.sx, in 2021:
https://tex.stackexchange.com/questions/609423
(the crash is mentioned in the middle of that lengthy multi-topic
question). 

I guess Bruno should get the credit when we send this to Knuth.
Too bad it did not make it into the 2014 or 2021 report.

    still exists.
    * bad: pdftex, xetex, eptex, euptex
    => Segmentation fault: 11

DRF found this fix, which is in tex as of the 2023 binary, I believe:
@x l.7717
if t>=cs_token_flag then
@y
if (t>=cs_token_flag)and(t<>end_write_token) then
@z

However, Tyge Thiessen then pointed out this fix was insufficient:
https://tug.org/pipermail/tex-k/2022-July/003851.html

Thus I have been awaiting a better fix from DRF, or anyone, before
installing it for the other engines. I hope he will be able to look at
it before TL24. --best, karl.