[Scons-users] clarification on Depends()

Tue Jun 5 17:08:34 EDT 2018

Matthew,

What's target for you?
The output of some other builder?

-Bill

On Tue, Jun 5, 2018 at 1:20 PM, Matthew Marinets <
Matthew.Marinets at kardium.com> wrote:

> When *should* Depends() be used?
>
>
>
> I’m using SCons to compile a lot of Java (*gasp* it’s not well supported,
> I know), and I need to make sure jars in the classpath are built before the
> javac command is run.
>
>
>
> My understanding is that there are three kinds of dependencies:
>
>    - Sources
>    - Implicit dependencies (from running scanners)
>    - Explicit dependencies (specified with Depends())
>
>
>
> A Jar is not a source, at least not in the same sense as a .java file, so
> jar files shouldn’t go there. It’s more of an implicit dependency, but you
> can’t determine the name of the jar file by scanning either the .java or
> .class files.
>
>
>
> So I have to use Depends(), right? Currently, I’ve added a line to the
> Java emitter that creates an explicit dependency using env.Depends() in my
> project, but should that be the solution? And is there a better way of
> invoking it than env.Depends; say:
>
>
>
>                 for t in target
>
>                                 t.add_dependency(env.get(‘JAVACLASSPATH’,
> []))
>
>
>
> -Matthew
>
>
>
>
>
> *From:* Scons-users <scons-users-bounces at scons.org> *On Behalf Of *Bill
> Deegan
> *Sent:* June 5, 2018 12:29
> *To:* Jason Kenny <dragon512 at live.com>
> *Cc:* SCons users mailing list <scons-users at scons.org>
>
> *Subject:* Re: [Scons-users] clarification on Depends()
>
>
>
> The caution I'd have about Depends as a the goto solution for this is that
> proper scanner/emitter/builder's may not be created.
>
>
>
> Do you have a specific example you can share?
>
>
>
> Also the users can do something like.
>
> Depends('filename.$SHOBSUFFIX','fake.txt')
>
>
>
>
>
> On Tue, Jun 5, 2018 at 12:09 PM, Jason Kenny <dragon512 at live.com> wrote:
>
> In my example fake.txt is nothing more than something to show a behavior
> independent of the scanner. The point of Depends is to make a mapping that
> we did not scan for some reason. The question I get a lot is why Depends
> did nothing. It seems to be because one has to make a depends mapping on
> the target node not the source node. However for certain complex builders
> chains this "middle" targets are not known to the user.
>
>
>
> Jason
>
>
> ------------------------------
>
> *From:* Scons-users <scons-users-bounces at scons.org> on behalf of Bill
> Deegan <bill at baddogconsulting.com>
> *Sent:* Tuesday, June 5, 2018 1:16 PM
> *To:* SCons users mailing list
>
> *Subject:* Re: [Scons-users] clarification on Depends()
>
>
>
> Jason,
>
>
>
> In your example how does fake.txt invalidate the C file?
>
> Is the C file being generated?
>
>
>
> -Bill
>
>
>
> On Tue, Jun 5, 2018 at 10:10 AM, Jason Kenny <dragon512 at live.com> wrote:
>
> I wanted to clarify this.. as I think it sort of broken. builders like
> SharedLibrary() that chain different builder sets make it hard to know what
> the internal target is to map the Depends() to.
>
>
>
> Jason
>
>
> ------------------------------
>
> *From:* Jason Kenny
> *Sent:* Tuesday, June 5, 2018 9:44 AM
> *To:* SCons users mailing list
> *Subject:* RE: [Scons-users] clarification on Depends()
>
>
>
> Opps.. Yes that is correct,
>
>
>
> The second example should be
>
>
>
> Depends(["hello.o")],["fake.txt"])
>
> Program("hello","hello.c")
>
>
>
> Jason
>
>
>
>
>
> *From:* Scons-users <scons-users-bounces at scons.org> *On Behalf Of *Bill
> Deegan
> *Sent:* Monday, June 4, 2018 11:28 PM
> *To:* SCons users mailing list <scons-users at scons.org>
> *Subject:* Re: [Scons-users] clarification on Depends()
>
>
>
> I think you mistyped your second Depend example?
>
> Shouldn't it be this?
>
> Depends('hello.o',['fake.txt'])
>
>
>
> On Mon, Jun 4, 2018 at 9:05 PM, Jason Kenny <dragon512 at live.com> wrote:
>
> HI,
>
>
>
> I just want to clarify behavior of Depends() in SCons.
>
>
>
> I have a small sample:
>
>
>
> Depends(["hello.c")],["fake.txt"])
>
> Program("hello","hello.c")
>
>
>
>
>
> If I run this sample “hello” will build. If I change fake.txt, nothing
> will rebuild.
>
>
>
> I have a tree like this:
>
>
>
> +-hello
>
>   | +-hello.o
>
>   | | +-hello.c
>
>   | | +-fake.txt
>
>   | | +-/usr/bin/gcc
>
>   | +-/usr/bin/gcc
>
>
>
> If I change the sample to this ( depends() is not hello.o vs hello.c)
>
>
>
> Depends(["hello.c")],["fake.txt"])
>
> Program("hello","hello.c")
>
>
>
> Now when I change fake.txt hello.o will rebuild. The tree here looks like:
>
>
>
> +-hello
>
>   | +-hello.o
>
>   | | +-hello.c
>
>   | | +-fake.txt
>
>   | | +-/usr/bin/gcc
>
>   | +-/usr/bin/gcc
>
>
>
> Is this right… I have to know the target of a builder to use? I cannot use
> the source of a builder?
>
>
>
> Jason
>
>
>
>
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