[luatex] \write16 (or 128) loosing tokens after null character

jfbu jfbu at free.fr
Fri Nov 20 10:45:59 CET 2015

Le 20 nov. 2015 à 10:33, Hans Hagen <pragma at wxs.nl> a écrit :

> On 11/20/2015 9:54 AM, jfbu wrote:
>> Le 19 nov. 2015 à 23:44, jfbu <jfbu at free.fr> a écrit :
>>> Hi,
>>> this might be the same issue than one with \scantokens
>>> which was discussed some time ago on this list (lost the reference)
>> this was
>> http://tug.org/pipermail/luatex/2015-March/005138.html
>> [luatex] behavior of \write in LuaTeX differs from the one of	PdfTeX/XeTeX
>> which referenced some other threads,
>> I tried also running pdftex with -8bit switch which
>> was mentioned by Hans in the previous thread and this gives
>> This is pdfTeX, Version 3.14159265-2.6-1.40.16 (TeX Live 2015) (preloaded format=pdftex 2015.10.14)  20 NOV 2015 09:50
>> entering extended mode
>>  restricted \write18 enabled.
>>  %&-line parsing enabled.
>> **testlualog.tex
>> (./testlualog.tex macro:->\romannumeral ` foo bar foo bar foo bar
>> macro:->\romannumeral ` foo bar foo bar foo bar
>>  )
>>  (contains two null characters)
>> The log with luatex is:
>> This is LuaTeX, Version beta-0.80.0 (TeX Live 2015) (rev 5238) (format=luatex 2015.10.14)  20 NOV 2015 09:53
>>  restricted \write18 enabled.
>> **\input testlualog.tex
>> (./testlualog.tex macro:->\romannumeral ` foo bar foo bar foo bar
>> macro:->\romannumeral `
>> )
>> only one null character in \message output
>> in \write output the null character is not there
>> (and the other things are gone)
>> best,
> well, because we're in a mixed tex/lua environment 0's can  always be sort of an issue .. just try to avoid them .. the times that we needed those slots for fonts are gone (in fact: avoid chars < 32)

I see, but the null slot here is not used for typesetting but
for TeX programming tricks. The specific issue I face can
be overcome by checking for Lua engine and doing extra things
(the goal is to provide some info in the log, it is peripheral
to the main package activities, but dropping it would mean
I must add an explication in the user manual as well)
but I am wondering: 

as LuaTeX enhances greatly all TeX abilities, does not that
include processing of files which may legitimately contain
ascii chars < 32 ? isn't it paradoxal if such non-typographical
programming like manipulations of data files suffers some
limitation of \write under LuaTeX ?

and why does \message behave differently than \write ?


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