[Scons-users] Creating SConscripts on the fly
Bill Deegan
bill at baddogconsulting.com
Fri Feb 23 21:57:01 EST 2018
If it's missing files, it means that your SConstruct logic is incomplete
and missing dependencies and/or outputs and you should fix that..
But yes duplicate=0 will be faster (the amount depending on the speed and
type of filesystem you're using)
On Fri, Feb 23, 2018 at 8:07 PM, Jason Kenny <dragon512 at live.com> wrote:
> >> So with VariantDir (or variant_dir), you're saying build is a super
> lightweight copy of src. And in most cases either only copy what you use,
> or copy nothing, but act as if the source files were there.
>
> Just a quick note.. this only “copies” what SCons thinks it need to build.
> If you or Scons miss something the build can fail. I have also had issues
> with it correctly updating some files when it copies files vs making a hard
> link. System like Windows SCons and certain “remote” file system on lLnux
> will always copy.
>
> You may want to use the “duplicate=False” argument in the SConscript()
> function. This has prevented a large number of issues for me. It also
> speeds up the build a little.
>
> Jason
>
>
>
>
>
> *From:* Scons-users [mailto:scons-users-bounces at scons.org] *On Behalf Of *Bill
> Deegan
> *Sent:* Friday, February 23, 2018 2:06 PM
> *To:* SCons users mailing list <scons-users at scons.org>
> *Subject:* Re: [Scons-users] Creating SConscripts on the fly
>
>
>
>
>
>
>
> On Fri, Feb 23, 2018 at 1:56 PM, Hua Yanghao <huayanghao at gmail.com> wrote:
>
> Thanks for the tip Bill.
>
> Wouldn't it be good that after VariantDir(), all subsequent calls will
> assume a current working directory of the "build/src/a" folder
> already?
>
>
>
> No.
>
> You may choose to have several VariantDir()'s grouped together in your
> file, plus that would be implicit behavior.. (not so Pythonic)
>
>
>
>
> My original confusion comes from: after VariantDir() call, I actually
> want to setup a variant_dir for the entire source tree that has many
> SConscript files (why would I need to setup a variant_dir for every
> single SConscript anyway ...).
>
>
>
> You don't have to.
>
>
>
> And however, I have to call SConscript on the variant_dir SConscript
> file instead of the original SConscript file which was driving me
> crazy back then. Any hints on why this is designed this way?
>
>
>
> Because you can have N variant_dirs for a given source dir allowing
> multiple variations of a build to run at the same time.
>
> For example {32,64}/{release/debug/profile}/{linux,win32,osx} could
> potentially all build at the same time.
>
> So with VariantDir (or variant_dir), you're saying build is a super
> lightweight copy of src. And in most cases either only copy what you use,
> or copy nothing, but act as if the source files were there.
>
>
>
> On Fri, Feb 23, 2018 at 3:56 PM, Bill Deegan <bill at baddogconsulting.com>
> wrote:
> > Yanghao,
> >
> > Yes that's correct.
> > That's what we used to do before variant_dir was added to SConscript.
> >
> > But not entirely complete.
> >
> > An initial # (hash mark) on a path name means that the rest of the file
> > name is interpreted relative to the directory containing the top-level
> > SConstruct file, even if the # is followed by a directory separator
> > character (slash or backslash).
> >
> > You can reference the "current dir" via #
> >
> > So:
> > VariantDir('build/src/a","src/a")
> > SConscript("build/src/a/SConscript",...)
> >
> > Then all local references don't need to use build/src/a, but can use #
> >
> > -Bill
> >
> > On Fri, Feb 23, 2018 at 3:43 AM, Hua Yanghao <huayanghao at gmail.com>
> wrote:
> >>
> >> @Bill, my understanding is if you use VariantDir() and when building
> >> the object list you will have to add the build path for each and every
> >> one of them? as compared if the object list is directly returned from
> >> a SConscript() call with variant_dir parameter then the object
> >> location is already in the build folder. I think you have even give an
> >> example for it:
> >>
> >> From your email last time:
> >> > Here's two ways which are similar to using variant_dir in a SConscript
> >> > call.
> >>
> >> > env.Program('some_build_dir/program', ['src/a.c','src/b.c'])
> >> > Assuming you have duplicate = 0
> >>
> >> > Or you can specify the
> >>
> >> > VariantDir('some_build_dir','src')
> >> > env.Program('some_build_dir/program', [os.path.join('some_build_dir'
> ,a)
> >> > for a in ['a.c','b.c'])
> >>
> >> Best Regards,
> >> Yanghao
> >>
> >> On Thu, Feb 22, 2018 at 2:45 PM, Bill Deegan <bill at baddogconsulting.com
> >
> >> wrote:
> >> > variant_dir is just a short cut for VariantDir and SConscript.
> >> > You don't loose anything.
> >> >
> >> > -Bill
> >> >
> >> > On Thu, Feb 22, 2018 at 4:28 AM, Hua Yanghao <huayanghao at gmail.com>
> >> > wrote:
> >> >>
> >> >> One slight drawback of this approach I see is: you lost the out of
> box
> >> >> variant_dir parameter support.
> >> >>
> >> >> Bill did show a way in another threads how this can be done also
> >> >> directly using VariantDir(), so I think this slight drawback is
> >> >> solvable.
> >> >>
> >> >> I am thinking this is really a way to solve my SConscript
> >> >> "default_import" issue, however this means also SConscript will be
> >> >> hiding from module developers. But I think this is not a problem for
> >> >> me.
> >> >>
> >> >> On Thu, Feb 22, 2018 at 7:08 AM, Gary Granger <granger at ucar.edu>
> wrote:
> >> >> > Hi Spencer,
> >> >> >
> >> >> > If you already have the information to generate the SConscript file
> >> >> > from
> >> >> > within a scons builder, then why not just call the builders
> directly
> >> >> > and
> >> >> > let
> >> >> > scons build the software normally, without requiring an
> intermediate
> >> >> > SConscript file? What purpose does generating the SConscript file
> >> >> > serve?
> >> >> >
> >> >> > In normal operation, SCons first reads all the SConscript files to
> >> >> > build
> >> >> > up
> >> >> > the graph of nodes and dependencies, and then it builds whatever
> >> >> > nodes
> >> >> > are
> >> >> > outdated or missing. So I don't think you can specify that a
> >> >> > SConscript
> >> >> > file is a node that needs to be built, then read that SConscript
> file
> >> >> > to
> >> >> > modify the graph of nodes and build again, not without running
> SCons
> >> >> > twice.
> >> >> >
> >> >> > So in your code which determines whether a module needs to be
> built,
> >> >> > rather
> >> >> > than generating a SConscript file, just call the builders that the
> >> >> > SConscript file would have called. If a module does not need to be
> >> >> > built,
> >> >> > then it is ok to skip calling those builders. Once all the
> builders
> >> >> > for
> >> >> > all
> >> >> > the modules have been called, SCons will build all the modules in
> one
> >> >> > run.
> >> >> >
> >> >> > I hope I understood your situation and this makes sense...
> >> >> > Gary
> >> >> >
> >> >> >
> >> >> > On 02/21/2018 10:35 PM, Spencer Yost wrote:
> >> >> >
> >> >> > I know this has been covered before, and I apologize for plowing
> old
> >> >> > ground.
> >> >> > I did search around but came up empty handed. I have a question:
> >> >> >
> >> >> > I create my SConscript files on the fly. I have my own system for
> >> >> > determining whether or not it needs to be built for a particular
> >> >> > module
> >> >> > in
> >> >> > the tree, then I build it if needed and then make the SConscript()
> >> >> > call.
> >> >> > this works great. So I decided I want to create a builder for this
> >> >> > SConscript creation - just because that seemed to be the "right"
> way
> >> >> > to
> >> >> > do
> >> >> > it. But if I use a custom builder it will not build the software
> if
> >> >> > it
> >> >> > determines the SConscript file needs to be built. It just creates
> >> >> > the
> >> >> > SConscript file. If it doesn't have to create/recreate, it will
> build
> >> >> > the
> >> >> > software.
> >> >> >
> >> >> > I have become experienced enough with Scons now to realize why it
> is
> >> >> > doing
> >> >> > this. But there has to be a way to get it to build the SConscript
> >> >> > file
> >> >> > using
> >> >> > a builder and build the software without running a second time.
> Does
> >> >> > anyone
> >> >> > have a slick way of combining the creation of the SConscript while
> >> >> > also
> >> >> > building? I do not have a "root"(at the SConstruct level)
> SConscript
> >> >> > file -
> >> >> > which may the be the answer - but thought I would ask smarter
> people
> >> >> > than
> >> >> > me before I spent the time.
> >> >> >
> >> >> > Thanks in advance!
> >> >> >
> >> >> > Spencer Yost
> >> >> >
> >> >> > _______________________________________________
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> >> >> >
> >> >> >
> >> >> >
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> >> >
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