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Re: Make: Unexpected Behavior with Dependencies and include Statement

From: Paul Smith
Subject: Re: Make: Unexpected Behavior with Dependencies and include Statement
Date: Wed, 23 Sep 2015 16:52:23 -0400

On Wed, 2015-09-23 at 15:00 -0500, John Westing wrote:
> > You are doing exactly Basic Auto-dependencies.  But that works because
> > of the re-exec if include files are rebuilt
> I don't think that's true, as the author explains in regards to the
> basic method:
> "Let’s address the first problem above: the re-invocation of make. If
> you think about it, this re-invocation is really not necessary. Since
> we know some prerequisite of the target changed, we must rebuild the
> target; having a more up-to-date list won’t affect that decision. What
> we really need is to ensure that the prerequisite list is up-to-date
> for the next invocation of make, when we need to decide whether to
> update it again."

Well, it's possible I've lost the thread of this part of the discussion
and am misunderstanding what you mean.

However, that paragraph is describing a _problem_ with the Basic method,
not a _feature_ of that method.  Or put another way, it's pointing out
that the Basic method always re-invokes make, but that the re-invocation
could be avoided if we rearranged the behavior of the makefile.

This paragraph introduces the key insight that allows us to move away
from the Basic method (which always re-execs make) and towards the
Advanced method (which never re-execs make--at least not because of
dependency tracking).  That's why this paragraph appears in the section
on Advanced Auto-Dependencies, not in the section on Basic

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