Re: ‘core-updates’ is back!

[iyzsong@member.fsf.org (宋文武)]

Andy Wingo <wingo@igalia.com> writes:

> On Tue 29 Aug 2017 00:01, ludo@gnu.org (Ludovic Courtès) writes:
>
>> Yup, I just created a new ‘core-updates’ branch by pushing
>> <https://bugs.gnu.org/27849>.  Enjoy!
>>
>> Let’s freeze in one month, say Oct. 1st?
>
> It would be pretty cool if we could fix our O(n^2) problems in search
> paths in this core-updates -- basically whenever you go to create an
> environment, instead of making e.g. VAR=A:B:C:..., for all VARs
> (LIBRARY_PATH, PKG_CONFIG_PATH, etc), instead we make a union directory
> Z containing the union of A, B, C, etc and set VAR=Z.  The goal would be
> to fix quadratic run-time lookup costs by replacing it with a
> compile-time computation.  This applies to many lookups: PATH, -rpath,
> etc.

The runtime references scanner of daemon will be inefficient if the
union gets recorded with all the inputs contained, and we likely won't
apply this to packages with multiple outputs (eg: fcitx) which will make
every output including the union into its runtime reference.