# [tex-live] [luatex] Spaces in the log: \scrollmode or not, LuaTeX or pdfTeX

Hans Hagen pragma at wxs.nl
Sun Aug 21 12:34:07 CEST 2016

On 8/20/2016 4:49 PM, Frank Mittelbach wrote:
> Am 20.08.16 um 15:43 schrieb Joseph Wright:
>
>> [..]
>
>> (and similar for other engines) whilst LuaTeX gives respectively
>>
>>     This is LuaTeX, Version 0.95.0 (TeX Live 2016)
>>      restricted system commands enabled.
>>     (./test.tex
>>     (./test.tex
>>     ))
>>     warning  (pdf backend): no pages of output.
>>     Transcript written on test.log.
>>
>> and
>>
>>     This is LuaTeX, Version 0.95.0 (TeX Live 2016)
>>      restricted system commands enabled.
>>     (./test.tex (./test.tex))
>>     warning  (pdf backend): no pages of output.
>>     Transcript written on test.log.
>>
>> Is there some logic to the variation here?
>
> I think there is not much you can do here other than accept the
> differences (and expect more in the future)
>
> and somehow program around it.
>
> In the 20 years regression testing for LaTeX I remember several
> occasions where spaces popped up in new places (or linebreaks) when a
> new release of web2c was released. This is the same thing and as Hans
> said, lua code will interrupt things and so start new lines in places.
>
> It is a bit surprising that there is a lot of space differences between
> batch and scroll mode but ...
>
> would be nice if there are less, but it is fairly clear that the
> different engines will behave differently here as this is not something
> that matters except when trying to parse the .log file
>
> Guess you need to normalize by hunting for ) as the first char in a line
> combine it with the previous line and then see how far that gets you

maybe it helps to know that there are

- tex messages and errors: these go through the more or less traditional
machinery, but spaces and newlines can creep in as a side effect of
linebreaks (max length, utf etc); some extended mechanisms can output a
bit more in tracing

- backend (or subsystem) warnings and errors: in pdftex/xetex some might
come from kpse, some from third party libraries, some from within but in
luatex most of them are normalized (which took a bit of time / effort),
so where the pdftex backend can report "bla bla" luatex will often
report "category: bla bla"; some harmless errors became warnings and
some warnings became errors, so that also can be different); for too
isolated libraries one can expect anything in terms of messages but
normally it's then a fatal error anyway

Hans

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