Re: m4 lines handled everywhere?

[Karl Berry]

    I can't see the fundamental difference between an @-command that sets this 
    on or off and something on the \input line that do the same.  

The fundamental difference is that an @-command requires parsing the
Texinfo language, with unpredictable results for this case.

    I think that the \input line should remain something 'magical' 
    that turns TeX on and should never be used for enything else.

I'm ok with that.  Then the cmdline option will be the only way.

    @synchronizeline 1, filename

There's no decent way to change the filename/lineno information TeX
outputs in its error messages.  It is done in low-level code and Knuth
did not put in any hooks to customize/change it.  (It's been a problem
since day one, but nothing to do about that now.)

And given that, I don't see an advantage to transforming #line to
@synchronizeline -- either way, running tex directly will typeset, not
process, a #line in the input.

    This new command could even be an official new command of texinfo
    such that other external tools can use that feature too.  For
    example, this could be used in tools that generate texinfo code,

They could generate a #line just as well?

    On the texi2any side this wouldn't be that complicated to do as all the 
    information is already there.

If a user @macro is involved in an error, that would be an excellent
thing to include in error msgs.

Thanks,
Karl

P.S.  After a couple more hours here, I'll be effectively offline (not
looking at email) for a few days.  Back on Wednesday.