Re: [Lmod-users] [EXTERNAL] Re: changes to tcl 'break' statement in lmod 8 series

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Hey Robert,

Thank you for the 'module --config' command. I've used 'module --config' before; it is good to know that the TCL information is in there as well.

We went ahead and updated to 8.6.15, just to see how our tcl modulefiles behave, and they behave better than in 8.4.10. That is, we do not get the "unexpected symbol near '}' error when using a modulefile that pairs a 'puts stderr ...' command right before a break command. They also seem to properly stop loading at the point 'break' is called.

That being said, we did stumble on some strange behavior with a semi-bad modulefile (meaning, it shouldn't be used in any serious capacity) and a user-side mistaken use of 'module load'. In Lmod 7.8.16, we get errors for the aberrant behavior, but in Lmod 8.6.15, we get no errors and, in one case, an infinite loop.

It is probably easiest to just provide an example. Here is a "bad" modulefile ("bad" because it can never be unloaded):

$> cat foo3/1.0
#%Module

catch {set foo $env(FOO)}
if { [info exists foo] } {
  puts stderr "already set"
  break
}
setenv FOO "just me"

If this modulefile is loaded and then unloaded, Lmod 8.6.15 silently moves on, and the modulefile is not unloaded:

$> module load foo3/1.0
$> echo $FOO
just me
$> module rm foo3/1.0
already set
$> echo $FOO
just me
$> module list

Currently Loaded Modules:
  1) foo3/1.0

In Lmod 7.8.16, we get this:

$> module load foo3/1.0
$> echo $FOO
just me
$> module rm foo3/1.0
already set
Lmod has detected the following error:  /users/dshrader/modulefiles/common/foo3/1.0: (foo3/1.0):
While processing the following module(s):
    Module fullname  Module Filename
    ---------------  ---------------
    foo3/1.0         /users/dshrader/modulefiles/common/foo3/1.0

$> module list

Currently Loaded Modules:
  1) foo3/1.0

What's more, if one tries to load foo3/1.0 at this point (done completely by accident by myself, not through any intelligent choice 😉), Lmod 8.6.15 goes in to an infinite loop:

$> module list

Currently Loaded Modules:
  1) foo3/1.0

$> module load foo3/1.0
already set
already set
already set
already set
already set
already set
...continues until crtl+c...

In Lmod 7.8.16, we get an error:

$> module list

Currently Loaded Modules:
  1) foo3/1.0

$> module load foo3/1.0
already set
Lmod has detected the following error:  /users/dshrader/modulefiles/common/foo3/1.0: (foo3/1.0):
While processing the following module(s):
    Module fullname  Module Filename
    ---------------  ---------------
    foo3/1.0         /users/dshrader/modulefiles/common/foo3/1.0

So, it is possible to get Lmod 8.6.15 in to an interesting state. For myself, I do prefer the error messages from Lmod 7.8.16 over 8.6.15's current behavior. Since all of the above is based on a pretty poor modulefile, though, I'm not sure how much time should be spent on dealing with the above behavior. But, I wanted to at least let you know what we found as we were playing around with our tcl modulefiles under 8.6.15. For the most part, going to 8.6.15 looks like it will be fairly seamless for the existing TCL modulefiles, so we'll push for our OS vendors to update to 8.6.15 rather than stay at 8.4.10.

Thanks again!

David

________________________________
From: Robert McLay <mc...@ta...>
Sent: Monday, March 21, 2022 4:49 PM
To: Shrader, David Lee
Cc: lmod-users
Subject: Re: [EXTERNAL] Re: [Lmod-users] changes to tcl 'break' statement in lmod 8 series

It is not a bug.  There was no support for break in Lmod before 8.6+.  It is just that having the tcl interpreter as a separate program meant that you got away with it.

> Do you mean that all of the 8.x versions include their own TCL interpreter, and 7.x relies on the system's TCL interpreter?
Yes

> We typically get Lmod from the OS vendor; is there a quick way to find out if the TCL interpreter was included?

 $ module --config 2>&1 | grep -i "Use attached TCL"
Use attached TCL over system call  yes

I would be best if you upgraded to Lmod 8.6.15 or later

Best,
Robert

On Mon, Mar 21, 2022 at 4:06 PM Shrader, David Lee <dsh...@la...<mailto:dsh...@la...>> wrote:

Hey Robert,

If I understand what you are saying, there should be no difference in how break is handled between 7.x and <8.6? If that is the case, then we may have hit a bug of some sort. But, since the latest version of Lmod is quite a ways beyond what we're looking to get (8.4.10), there may be little utility in trying to track it down. It might just be easier to try to get our upstream to provide an 8.6+...

Do you mean that all of the 8.x versions include their own TCL interpreter, and 7.x relies on the system's TCL interpreter?

We typically get Lmod from the OS vedor; is there a quick way to find out if the TCL interpreter was included?

Thanks again!

David

________________________________
From: Robert McLay <mc...@ta...<mailto:mc...@ta...>>
Sent: Monday, March 21, 2022 2:40 PM
To: Shrader, David Lee
Cc: lmod-users
Subject: [EXTERNAL] Re: [Lmod-users] changes to tcl 'break' statement in lmod 8 series

Well yes and no.  There is no change in how break is or has been handled since forever. The change in supporting break is in Lmod 8.6+

The change is that by default Lmod now includes the TCL interpreter as part of the Lmod executable instead of executing a system call (/usr/bin/tclsh ....).  You can configure Lmod to not include the tcl interpreter library as part of Lmod.  That should give you the old behavior.  Use --with-fastTCLInterp=no to configure Lmod without the tcl integration.

I would be interested in seeing how Lmod 8.6+ works with your modules even if you don't deploy it to users.

Best,
Robert.

On Mon, Mar 21, 2022 at 2:20 PM Shrader, David Lee via Lmod-users <lmo...@li...<mailto:lmo...@li...>> wrote:

Hello,

We're are potentially going from Lmod 7.8.16 to 8.4.10, and we have noticed that our tcl modulefiles that call "break" after a "puts stderr ..." message now generate something like the following error:

Lmod has detected the following error:  Unable to load module because of error when evaluating modulefile: foo3
     /modulefiles/foo3/1.0: [string "LmodMsgRaw([===[already set..."]:4: unexpected symbol near '}'

We have used this method of "puts stderr...; break" to exit out of a particular modulefile when an error occurs, such as a missing directory.

In looking over the readthedocs tcl function page, it looks like the "break" function has seen some attention, but we are looking at 8.4.10, not 8.6+. Did something change for the "break" command in 8.0 to 8.5 such that it won't work as we have been using it in 7.x?

Thank you very much for any and all help!

David

--
David Shrader
HPC-ENV High Performance Computing Systems
Los Alamos National Lab
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--
Robert McLay, Ph.D.
Manager of Software Tools, HPC
mc...@ta...<mailto:mc...@ta...>

--
Robert McLay, Ph.D.
Manager of Software Tools, HPC
mc...@ta...<mailto:mc...@ta...>

Re: [Lmod-users] [EXTERNAL] Re: changes to tcl 'break' statement in lmod 8 series

A Lua based environment module system that reads TCL modulefiles.

Re: [Lmod-users] [EXTERNAL] Re: changes to tcl 'break' statement in lmod 8 series