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Re: Order of expansion of recipe lines

From: Zoltan
Subject: Re: Order of expansion of recipe lines
Date: Mon, 14 Mar 2016 11:07:57 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:42.0) Gecko/20100101 SeaMonkey/2.39

On 03/14/2016 10:59 AM, Paul Smith wrote:
> On Mon, 2016-03-14 at 10:36 -0700, Zoltan wrote:
>> I don't particularly see a reason to change current behavior, but if 
>> you want to, how about implementing it like a "delayed" expansion 
>> except for recipe lines, so instead of $(...whatever....), it would 
>> be written $$(...whatever...) in order to not not break backward 
>> compatibility and still allow new uses as you describe.  Sort of like 
>> in .SECONDEXPANSION conceptually, and could maybe even be tied to 
>> .SECONDEXPANSION if needed.
> Ouch!  The escaping of "$" with "$$" is used EVERYWHERE in recipes, and
> this would break all instances of that by doing a double-expansion.
> Even if we managed to work out a way around this somehow, trying to
> explain the expansion rules would be a nightmare.  It's already the
> most difficult part of make for new users to grasp.
> Nope.  As far as I'm concerned either things stay as they are or they
> change to the new method, and that's it.  If someone can provide me
> with a compelling reason for the current behavior, which would include
> an in-use configuration which relies on it, then the discussion is over
> and we'll leave things as they are.
> If no one can come up with a good reason for the current behavior, then
> I'll leave the possibility open :).

Not exactly escaping '$' with '$$'.  From your example of $(info ...), I'm
actually suggesting to escape '$(' with '$$('.  So not quite the same thing at
all.  And this is already implemented, and already "explained," so no extra
work there.

For cases of recipe lines that do not have a '$(' construct, would there
actually be any difference at all, whether or not you change the expansion
style?  I can't think of one...or maybe its just I can't think...at any rate,
your proposed change primarily impacts recipe lines with '$(...)' on them.
The rest, not so much...

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