[Scons-users] Creating SConscripts on the fly

[Bill Deegan]

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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