[bug#67822] [PATCH v3] gnu: maths: petsc: Reduce closure size.

[Ludovic Courtès]

Hi,

Efraim Flashner <efraim@flashner.co.il> skribis:

> On Fri, Jan 05, 2024 at 12:52:02PM +0100, Lars Bilke wrote:
>> Hi Ludo,
>> 
>> On 5 Jan 2024, at 12:08, Ludovic Courtès wrote:
>> 
>> > Can we instead patch the thing that creates ‘petscvariables’ in the
>> > first place?
>> >
>> > The reason I’m suggesting it is because in general we avoid hardcoding
>> > /gnu/store in substitution patterns because it’s possible to configure
>> > Guix with a different store directory.
>> 
>> Thanks for your feedback!
>> 
>> In v1 of this patch I removed the 'petscvariables'-file completely but this 
>> broke dependent packages as well as not-yet packaged projects which use the 
>> file for finding the PETSc library and configuriung their build system.
>> 
>> Is there a possibility to replace the hard-coded /gnu/store with a variable 
>> which evaluates to the current store directory?
>
> There's %store-directory in (guix build utils).  In fact, it looks like
> git might have some code that you can borrow.

Yes.  However, I think we should use literal strings for patterns in
‘substitute*’.  That is, I would avoid:

  (substitute* …
    (((string-append (%store-directory) "/bin/whatever"))
     …))

in favor of, say:

  (substitute* …
    (("([[:graph:]]+)/bin/whatever")
      …))

This is to make things easier to understand, 100% correct (in theory we
should use ‘regexp-quote’ when turning strings into regexps), and to
leave room for how ‘substitute*’ is implemented.

Thanks,
Ludo’.