[Scons-users] when to use depends and when to use requires

[Bill Deegan]

If you need either.. you're probably doing something wrong.. (TM - Me...;)

The fact that you're using either means that the relevant files weren't
listed as a source or a target to the correct builders and/or the extra
sources/dependencies weren't found by a scanner.

Can you be a little more specific about the builder's in question?

-Bill

On Thu, Nov 10, 2022 at 11:50 AM daggs <daggs at gmx.com> wrote:

> > On 11/10/22 05:35, daggs wrote:
> > > Greetings,
> > >
> > > I still don't know what are the proper guidelines to use Depends or
> Requires.
> > > I had an example of a target a and target b, target a depends on b, b
> creates a few files, one of them is needed for target a. I used Depends
> here.
> > > depending target a on target b didn't enforced the proper order,
> adding the relevant file to the dep list didn't worked, however, when I
> changed it into Requires,
> > > the order was enforced.
> > > from that I deduce that for code files which I need to use as part of
> another target I should use Requires while for the rest, I should use
> Depends.
> > >
> > > am I right?
> >
> > I don't know if we explain it well enough - not sure I fully understand
> > either.
> >
> > At the surface level (someone please jump in and correct me here):
> >
> > Requires() is for specifying order. It does not establish dependencies.
> > If something else already decides A and B will be built, then having A
> > Require B means SCons will decide to build B before A.  Since it's not a
> > dependency, rebuilding B doesn't automatically trigger rebuilding A.
> >
> > Depends() is for declaring a dependency to SCons that it won't otherwise
> > decect by itself. It says nothing about order, because that's something
> > SCons gets to decide, based on its evaluation of the dependency graph.
> > In many cases, of course, a dependency *does* end up acting as a kind of
> > ordering - but it's not certain.
> >
> > Looking at the manpage I don't think I'm actually saying anything
> > different that it does.
>
> so I need both Depends and both Require?
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