Re: Lilypond 2.19.80-1 hangs

[David Kastrup]

Andrew Bernard <address@hidden> writes:

> Hi Massimo,
>
> Thanks for sending the file.
>
> It compiles fine under 2.19.18 on Ubuntu,
>
> However, your file is made up of hundreds of lines like this:
>
>  %Sezione M
>  << {\parentheAll f,,8 bes,->~  bes,2.} \\ {s4  bes,,-. bes,,-.} >>
>  << {bes,,8 f,~  f,2.} \\ {s4  f,,-. f,,-.} >> <f, f,,>8 <g, g,,>
>  << {g,2.} \\ {g,,4-. g,,-.} >>
>  << {g,,8_> ees,~  ees,2.} \\ {s4  ees,,-. ees,,-. r} >> ees,4-.
>
>
> I have seen this issue before, just the same, with another user.
>
> While there is no written rule saying you cant write like that, and it is
> syntactically valid, experienced users just don't write that way. There
> seems to be a bug deep in lilypond somewhere that when this construct is
> heavily overused that the program can't cope. It is unlikely that anybody
> is going to fix this because it is a type of distortion of how lilypond is
> normally used, in my view.

A crash is a crash.  Without a tiny example and/or reproducibility, the
likelihood for a fix goes down but not because of a "type of distortion
of how LilyPond is normally used".  LilyPond exposes a complete
programming language: that makes it unlikely that we'll ever get it
withstand fuzzing gracefully.  But this does not sound anywhere like it.
It does not sound easy to pin down either, unfortunately.

> The issue seems to show up at different times on different platforms.
>
> Fixing this would be a lot of work for the developers to support a
> very idiosyncratic way of writing. I am not sure you would convince
> them to work on it.

That's simply wrong.  The elements he is using are completely common.
When they fail, that warrants a fix, even if his style of using them
appears to affect the likelihood of triggering the problem.

>> I have a "big" lilypond file (20 KB). With lilypond 2.19.80-1 it's
>> impossible to compile, because lilypond stops working and the log only
>> shows bar numbers in square brackets.

-dverbose might show more

>> With lilypond 2.18.2-1 it works.
>> I know you only accept "tiny examples", so if you are interested to
>> investigate this kind of bug I'll send you my input. Note that if I compile
>> 10 bars per time with the "showLastLength = R1*10" statement, it works, so
>> I exclude mistyping or things like that. Lilypond restart working only if I
>> delete a certain number of bars.
>> Regards
>> Massimo Lovato

-- 
David Kastrup