[Scons-users] Unexpected messge with configure

[Jason Kenny]

Bill,

I think so. I am not sure what the better message would be.
Maybe something like:

No cache data for configure test/directory <test> found
Cannot run action during a dry-run


Jason

From: Scons-users <scons-users-bounces at scons.org> On Behalf Of Bill Deegan
Sent: Friday, September 7, 2018 1:16 PM
To: SCons users mailing list <scons-users at scons.org>
Subject: Re: [Scons-users] Unexpected messge with configure

Should we change the messaging?
-Bill

On Fri, Sep 7, 2018 at 2:15 PM Bill Deegan <bill at baddogconsulting.com<mailto:bill at baddogconsulting.com>> wrote:
Jason,

That seems reasonable, but maybe not simple..

_Bill

On Fri, Sep 7, 2018 at 2:10 PM Jason Kenny <dragon512 at live.com<mailto:dragon512 at live.com>> wrote:
My first thoughts are that if we can tell if the result is cached to return that value. If there are no cached values do the current behavior. I am not sure how hard this would be however at the moment.
ideally the best behavior I think might be

  *   configure item has no cached value. Error as we currently do

  *   configure item is cached, return the cached value

     *   if we can detect that it has changed and would normally re-execute print a warning message that this is the case and note that the result of the build may change when it really runs

  *   Not sure what to do with the cases of configuring items that don't cache ( such as custom functions that the user might have defined in a certain way ).
Jason
________________________________
From: Scons-users <scons-users-bounces at scons.org<mailto:scons-users-bounces at scons.org>> on behalf of Bill Deegan <bill at baddogconsulting.com<mailto:bill at baddogconsulting.com>>
Sent: Friday, September 7, 2018 12:28 PM
To: SCons users mailing list
Subject: Re: [Scons-users] Unexpected messge with configure

Jason,

I'd say it's not a known issue, it's expected behavior.
See the docstring for the exception in question.

What do you think SCons should do in this case?
The dry run would likely be affected by the results of any configure checks which might write a file or run a process (both things which scons is not supposed to do with --dry-run), so it's likely not possible to do a dry-run with configure checks which write to the filesystem?

-Bill

class ConfigureDryRunError(SConfError):
"""Raised when a file or directory needs to be updated during a Configure
process, but the user requested a dry-run"""
def __init__(self,target):
if not isinstance(target, SCons.Node.FS.File):
msg = 'Cannot create configure directory "%s" within a dry-run.' % str(target)
else:
msg = 'Cannot update configure test "%s" within a dry-run.' % str(target)
SConfError.__init__(self,msg)


On Fri, Sep 7, 2018 at 1:20 PM Bill Deegan <bill at baddogconsulting.com<mailto:bill at baddogconsulting.com>> wrote:
Mats,

How long does:
scons --help non-existant-target
Take?

-Bill

On Fri, Sep 7, 2018 at 12:26 PM Mats Wichmann <mats at wichmann.us<mailto:mats at wichmann.us>> wrote:
On 09/07/2018 09:55 AM, Jason Kenny wrote:
> I was adding some configure logic to a build I am working on. When doing a dry run i now get this error:
>
> scons: *** Cannot update configure test ".sconf_temp/conftest_0" within a dry-run.
> File "./../scons-3.0.1/SCons/Script/SConscript.py", line 614, in __call__
>
> Is this a known issue with using configure in scons?

I've run into it (you'll find my name on such questions in the mailing
list archive, afair).

When you stop and think about it, running a configure test which means
compiling code sort of doesn't fit the definition of "dry run", though.

this is a gray area to my way of thinking.  steps like cleaning, getting
help, and doing a dry-run are places where you don't want external work
to happen, just have scons go through the rules.  but sometimes you
don't know what all the dependencies actually are before you've run some
of those steps.

we'll wait for the actual experts to pipe up :)

======
Aside:
on the project I'm trying to gradually bend into shape (it had lived for
a couple of years before I came around), which uses a variant directory
build, starting with the variant directory completely absent, "scons
--help" takes seven seconds, and leaves a variant directory with 12
object files and four libraries built. I *KNOW* that's wrong, but I
haven't yet figured out how to fix it without either breaking
everything, or special-casing stuff all over the place like

if not env.GetOption('help') and not env.GetOption('clean'):

guess we could put GetOption('dry-run') in that list too (would we have
to include all of the variants of that name? -n, --no-exec,
--just-print, --dry-run, --recon)

with 200+ sconscripts, adding those cases is not appealing.

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