Re: [PATCH 1/4] Makefile: don't re-define PERL_DEFINES

[Jeff King <peff@peff.net>]

On Thu, May 06, 2021 at 11:04:34AM +0200, Ævar Arnfjörð Bjarmason wrote:

> > Actually, strictly speaking there was *no* bug because assigning
> > three items with := made sure the previous recursively expanded one
> > to be ineffective.  In other words, there was a valid reason to use
> > ":=" there in the original version.
> 
> Yes, there wasn't any bug with the the eventual value being
> incorrect. I.e. both of these are equivalent in a Makefile:
> 
>     FOO = abc
>     FOO := def
>     FOO += ghi
> 
> And:
> 
>     FOO = abc
>     FOO = def
>     FOO += ghi
> 
> Both will yield "def ghi". They're just different in a case like:
>     
>     X = Y
>     FOO = abc
>     FOO := $(X)
>     X = Z
>     FOO += ghi
> 
> Where using := will echo "Y ghi", and using = will echo "Z ghi". As a
> practical matter the distinction doesn't matter in this case.

Yeah, I don't think the ":=" was impacting the bug or no bug (not to
mention that even if we duplicated those entries in the variable, it
_still_ wouldn't be a bug, since the whole point of the variable is just
to notice when the content changes).

> > Now your patch removed the recursively expanded one that was
> > immediately invalidated, there no longer is a reason to use :=
> > there.  So "unrelated to the more narrow bugfix" is a rather lame
> > excuse to do only half a task.  If we remove that extra one (which
> > is a good thing), then we should correct := into = because the
> > original used := only because there was the unwanted extra one, no?
> 
> I don't see how removing the stray line changes the reason to use ":="
> or "=" there. I agree it should be removed, it's just unrelated to
> removing the stay line. Looking at 07d90eadb50 it's clear that it's just
> some copy/pasting error.

Yeah, I'd agree it is truly orthogonal. I don't mind seeing it cleaned
up in addition (or am even actively happy to see it cleaned up :) ), but
IMHO it would not need to hold up the series.

-Peff