Re: this is embarrasing... prerequisiste gets updated, but make still says it is older than target

[Lane Schwartz]

Paul,

What about this?

"Users should assume that all computation of prerequisite timestamps are
performed prior to the execution of any make rule. For performance reasons,
make may in fact check timestamps at other points, but users should not
rely on this fact."

Thanks,
Lane


On Mon, Apr 2, 2012 at 10:20 AM, Paul Smith <address@hidden> wrote:

> On Mon, 2012-04-02 at 09:57 -0400, Lane Schwartz wrote:
> > 1) "A target is out of date if it does not exist or if it is older than
> any
> > of the prerequisites (by comparison of last-modification times)."
> >
> > NEW 2) "All computation of prerequisite timestamps are performed prior to
> > the execution of any make rule."
>
> Except, that's not really true.
>
> The timestamp caching facility of GNU make causes the real behavior to
> be difficult to define in situations where the makefile doesn't
> accurately describe what the recipes really do.  The actual behavior
> depends on which files are added to the cache, and when: they are not
> all added up-front.  It's just helpful to think about it as if they were
> because if you do, then your makefile will definitely be correct.  If
> the makefile does completely describe the results of the recipes then it
> all works fine.  If not, the behavior is hard to quantify.
>
> That's why I've considered removing the cache.  However, the cache can
> be a performance win, particularly in the common "do nothing" (or at
> least "do very little") cases.
>
> Maybe it should be made optional, so you can get slower but more
> understandable (in the case of incomplete makefile definitions)
> behavior, or else faster behavior but your makefile must be well-formed
> (as today).
>
> --
>
> -------------------------------------------------------------------------------
>  Paul D. Smith <address@hidden>          Find some GNU make tips at:
>  http://www.gnu.org                      http://make.mad-scientist.net
>  "Please remain calm...I may be mad, but I am a professional." --Mad
> Scientist
>
>


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