Re: Circular dependencies - Deadlock

2017-06-22 Thread Johan Vromans 
On Thu, 22 Jun 2017 06:39:08 +0200, David Kastrup  wrote:

> I don't really see this as calling for changes.  If you want to create
> utility files to be included at most once, you can try working with
> guards like it is customary for C/C++ include files.

I think we're shifting topic here from recursive include to multiple
include. The latter is general practice.

The OP is unintentional infinite recursive includes, and whether LP can
help signalling this instead of just becoming non-responsive.

Maybe it is possible to track include depth, and issue a (one) warning when
the include dept exceeds a certain threshold (20? 50? 100?).

-- Johan

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Re: Circular dependencies - Deadlock

2017-06-21 Thread David Kastrup 
Simon Albrecht  writes:

> On 21.06.2017 22:32, Michael Käppler wrote:
>> Honestly I did not try it, but I am quite sure that it would be easy
>> to implement a IFDEF mechanism like in C preprocessing with a few
>> lines of Scheme, however.
>
> That won’t be Scheme involved there.  IIRC \include statements are
> resolved even before parser (and lexer?) step in.  David K. will be
> able to say more.

\include is expanded in the lexer but there are a whole lot of setups
where multiple includes are perfectly reasonable even without thinking
about recursion: for example, you can organize a typical piece by
defining variables and including a file with a score skeleton, and
include several scores in that manner while creating one book.

I don't really see this as calling for changes.  If you want to create
utility files to be included at most once, you can try working with
guards like it is customary for C/C++ include files.

-- 
David Kastrup

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Re: Circular dependencies - Deadlock

2017-06-21 Thread Michael Käppler 

Am 21.06.2017 um 23:24 schrieb msk...@ansuz.sooke.bc.ca:

On Wed, 21 Jun 2017, caag...@gmail.com wrote:

On 06/21/2017 11:10 PM, Johan Vromans wrote:

If you have a non-infinite recursive include it will continue.

I think that would require solving the Halting Problem first.

That's true if it has to determine whether the recursion is infinite, but
my understanding of the proposal was that Lilypond would continue with a
warning in any case, not trying to decide whether it's infinite, and let
the user deal with shutting it down if in fact it is infinite.


That would be a very nice way of dealing with the recursion, IMO.


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Re: Circular dependencies - Deadlock

2017-06-21 Thread Simon Albrecht 

On 21.06.2017 23:24, msk...@ansuz.sooke.bc.ca wrote:

my understanding of the proposal was that Lilypond would continue with a
warning in any case, not trying to decide whether it's infinite, and let
the user deal with shutting it down if in fact it is infinite.


I was going to write that not every user runs Lily from command line and 
knows to hit Ctrl+C in such a case. But in Frescobaldi, you’d just have 
to click the red cross appearing when you start compilation, so actually 
that’s a good proposal.


Best, Simon

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Re: Circular dependencies - Deadlock

2017-06-21 Thread mskala 
On Wed, 21 Jun 2017, caag...@gmail.com wrote:
> On 06/21/2017 11:10 PM, Johan Vromans wrote:
> > If you have a non-infinite recursive include it will continue.
>
> I think that would require solving the Halting Problem first.

That's true if it has to determine whether the recursion is infinite, but
my understanding of the proposal was that Lilypond would continue with a
warning in any case, not trying to decide whether it's infinite, and let
the user deal with shutting it down if in fact it is infinite.

-- 
Matthew Skala
msk...@ansuz.sooke.bc.ca People before principles.
http://ansuz.sooke.bc.ca/

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Re: Circular dependencies - Deadlock

2017-06-21 Thread mskala 
On Wed, 21 Jun 2017, Johan Vromans wrote:
> Instead of aborting, LP could issue a warning that it detected a circular
> include. If it then hangs, you have a clue what is going on. If you have a
> non-infinite recursive include it will continue.

If it's only a warning (we need not get back into the "fatal warnings and
non-fatal errors" discussion) then this seems harmless.  Another point
worth considering, though, is that it's not trivial to detect whether two
paths represent the same file.  Doing it correctly is more than just a
string comparison, and unlikely to be portable.

-- 
Matthew Skala
msk...@ansuz.sooke.bc.ca People before principles.
http://ansuz.sooke.bc.ca/

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Re: Circular dependencies - Deadlock

2017-06-21 Thread caagr98 

On 06/21/2017 11:10 PM, Johan Vromans wrote:

If you have a non-infinite recursive include it will continue.


I think that would require solving the Halting Problem first.

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Re: Circular dependencies - Deadlock

2017-06-21 Thread Johan Vromans 
On Wed, 21 Jun 2017 15:57:59 -0500 (CDT), msk...@ansuz.sooke.bc.ca wrote:

> This may be a problem if there's any possibility of an include being
> conditional.  Then, someone could write a non-infinite recursive include
> deliberately, and be disappointed when Lilypond breaks it.

Instead of aborting, LP could issue a warning that it detected a circular
include. If it then hangs, you have a clue what is going on. If you have a
non-infinite recursive include it will continue.

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Re: Circular dependencies - Deadlock

2017-06-21 Thread mskala 
On Wed, 21 Jun 2017, Simon Albrecht wrote:
> It would be even better, I think, if Lily noticed the circular dependency and
> aborted with an informative message instead of just running on forever.

This may be a problem if there's any possibility of an include being
conditional.  Then, someone could write a non-infinite recursive include
deliberately, and be disappointed when Lilypond breaks it.

-- 
Matthew Skala
msk...@ansuz.sooke.bc.ca People before principles.
http://ansuz.sooke.bc.ca/

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Re: Circular dependencies - Deadlock

2017-06-21 Thread Simon Albrecht 

On 21.06.2017 22:32, Michael Käppler wrote:
Honestly I did not try it, but I am quite sure that it would be easy 
to implement a IFDEF mechanism like in C preprocessing with a few 
lines of Scheme, however.


That won’t be Scheme involved there.  IIRC \include statements are 
resolved even before parser (and lexer?) step in.  David K. will be able 
to say more.


Best, Simon

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Re: Circular dependencies - Deadlock

2017-06-21 Thread Michael Käppler 
What would be wrong about just outputting a warning "Trying to include 
already included file" or something like that and reject

the recursive \include statement?
I came across this when working with a include file collecting cue notes 
like that:


\include "foo1.ly"
\include "foo2.ly"
\include "foo3.ly"
\addquote "bla1" { \foo1_bla1 }
\addquote "bla2" { \foo2_bla2 }
(...)

I change my code to circumvent the recursive loop but I needed a moment 
to figure out why LilyPond was hanging.

A warning would be nice.
Honestly I did not try it, but I am quite sure that it would be easy to 
implement a IFDEF mechanism like in C preprocessing with a few lines of 
Scheme, however.


All the best,
Michael


Am 21.06.2017 um 22:03 schrieb msk...@ansuz.sooke.bc.ca:

On Wed, 21 Jun 2017, Michael Käppler wrote:

foo.ily:
\include "bar.ly"
bar.ly:
\include "foo.ily"
Am I right to consider this a bug?

I don't think so - at least not a bug in Lilypond.  It's just doing what
you told it to do, and most other language parsers that have an "include"
facility will similarly be unable to give a useful result when fed
infinitely recursive include files.  The usual advice to users is not to
write such input.




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Re: Circular dependencies - Deadlock

2017-06-21 Thread Simon Albrecht 

On 21.06.2017 22:03, msk...@ansuz.sooke.bc.ca wrote:

On Wed, 21 Jun 2017, Michael Käppler wrote:

foo.ily:
\include "bar.ly"
bar.ly:
\include "foo.ily"
Am I right to consider this a bug?

I don't think so - at least not a bug in Lilypond.  It's just doing what
you told it to do, and most other language parsers that have an "include"
facility will similarly be unable to give a useful result when fed
infinitely recursive include files.  The usual advice to users is not to
write such input.


And indeed, the different file name extensions make this example very 
unlikely to happen.
It would be even better, I think, if Lily noticed the circular 
dependency and aborted with an informative message instead of just 
running on forever. However, that may not be very relevant/necessary to 
have.  So, a feature request, but not invalid, I’d say.


Best, Simon

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Re: Circular dependencies - Deadlock

2017-06-21 Thread mskala 
On Wed, 21 Jun 2017, Michael Käppler wrote:
> foo.ily:
> \include "bar.ly"

> bar.ly:
> \include "foo.ily"

> Am I right to consider this a bug?

I don't think so - at least not a bug in Lilypond.  It's just doing what
you told it to do, and most other language parsers that have an "include"
facility will similarly be unable to give a useful result when fed
infinitely recursive include files.  The usual advice to users is not to
write such input.

-- 
Matthew Skala
msk...@ansuz.sooke.bc.ca People before principles.
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Circular dependencies - Deadlock

2017-06-21 Thread Michael Käppler 

Hi all,

I searched the bug tracker for the following issue but did not find 
anything...


Consider two files:

foo.ily:

\version "2.19.59"
\include "bar.ly"

bar.ly:

\version "2.19.59"
\include "foo.ily"

{ c4 d e f }

If you try to compile bar.ly the parsing process continues forever, 
apparently because Lily includes the two files in a circular manner 
(maybe reaching a memory limit at some point - did not try that)


Am I right to consider this a bug?

Regards,

Michael


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