Re: Suggestion for a change in the out of date algorithm

[Ramón García]

Sure, the patch should be as isolated as posible. I think that with an
interface of comparison between target and each source would help,
because it could be placed in the same place where timestamps are
compared.

> Hm.  I think the idea is useful, but the details suggested above seem
> too specific to me.  In other words, I can imagine there might be a
> number of different situations where you might want to be able to
> evaluate a variable in the context of a file (a "different scope" as it
> were) that don't have anything to do with out of date determination.

Perhaps I didn't express myself well. The intention was that the new
functions could be used for anything, not neccessary for out of date
evaluation. In fact, it was a feature of this proposed design to split
the functionality in small parts as general as posible so that they
could be used for anything else.

>         $(<target>::<variable>)

I also prefer your syntax. It fits better existing usage.


> The thing that concerns me about this method is that it seems to me like
> you're evaluating the changed variable again every time a file is used
> as a prerequisite.

Correct me if I am wrong. Wouldn't this issue be corrected by changing:

%: changed = ${changed-value md5 ${md5sum  address@hidden

into

%: changed := ${changed-value md5 ${md5sum  address@hidden

My intention was that changed-value was a special function evaluted
exactly once for each  <name> parameter, and the next times it would
remember the cached value. (Well, not just name, but name and current
target).

> For example, maybe we can say that for any given file, it will have only
> one value that determines its up-to-date-ness.  Then, instead of
> evaluating that value again every time the file appears as a
> prerequisite, make would automatically evaluate that value once, after
> the file was treated as a target and its commands were successfully
> invoked.

This is a slightly less general way of doing it. The only difference
is that I propose that one can define whatever function for that
determination, provided that it is invoked from .OUT_OF_DATE