Re: [Automake-NG] [PATCH 00/11] Several changes to parallel-tests support

[Stefano Lattarini]

On 05/10/2012 10:01 PM, Bob Friesenhahn wrote:
> On Thu, 10 May 2012, Stefano Lattarini wrote:
>>>
>> I don't follow here.  Automake will simply re-order the ":=" definitions it
>> finds *its internal* '.am' fragments to ensure that they appear after all
>> the other variable definitions (both those coming from the user and those
>> coming from Automake).  This shouldn't be anymore difficult than the
>> reordering that is already being done by Automake (i.e., the variable
>> definitions from Automake get placed before variable definitions from
>> the user, which in turn get placed before the rules and recipes, either
>> Automake-provided or user-provided).
>>
>> What is not clear exactly?
> 
> Perhaps I wrongly assumed that Automake includes were included "in place".
> I was not aware that Automake is already re-writing the order.
>
Oh it is rewriting and reshuffling things all over the place :-)
Too much sometimes...

> Using := syntax is much less flexible and more fragile than traditional
> syntax.
>
True, and thus is should only be used sparsely and for the situation where
a speed-up would be important -- e.g., almost-null rebuilds (as you've
pointed out) and almost-null testsuite re-runs (I add).

Also, if used unwisely, ":=" could actually cause slow-dons (think a
situation where the RHS is quite costly to calculate, and is only
expanded in a seldom-used recipe).

> It is valuable to use, but is much more sensitive to ordering.
> 
Yep, another downside to consider.

Regards,
  Stefano