| 1 |
On 08/16/2011 12:01 AM, Michał Górny wrote: |
| 2 |
> On Mon, 15 Aug 2011 19:42:01 -0700 |
| 3 |
> Zac Medico <zmedico@g.o> wrote: |
| 4 |
> |
| 5 |
>> On 08/15/2011 11:41 AM, Michał Górny wrote: |
| 6 |
>>> Hello, |
| 7 |
>>> |
| 8 |
>>> Now that we don't have any old-style virtuals in gx86 anymore, |
| 9 |
>>> I think the 'virtual' category is basically one another plain |
| 10 |
>>> category nowadays. |
| 11 |
>> |
| 12 |
>> In sys-apps/portage, the "virtual" category is used as a hint to the |
| 13 |
>> dependency resolver it needs to look ahead in order to make the best |
| 14 |
>> possible choices. For example, in order to solve bug #141118 [1], it |
| 15 |
>> recursively expands virtual/jre and virtual/jdk in order to |
| 16 |
>> efficiently satisfy a jre dependency with whatever jdk happens to be |
| 17 |
>> installed, instead of pulling in a redundant jre. |
| 18 |
> |
| 19 |
> Isn't that another, ugly, non-PMS hack which makes people think they |
| 20 |
> are creating correct packages? |
| 21 |
|
| 22 |
Are you saying that you'd prefer to have package managers pull in |
| 23 |
redundant packages for not good reason? |
| 24 |
|
| 25 |
Anyway, the thing that's really special about virtuals is that they can |
| 26 |
be considered to contribute zero-cost when the package manager is trying |
| 27 |
minimize the overall cost of satisfying a particular dependency. To |
| 28 |
minimize cost means to eliminate redundant packages. |
| 29 |
|
| 30 |
The relevance of virtuals in terms of cost calculations is why Ciaran |
| 31 |
suggested to call it PROPERTIES="zero-install-cost" [1] instead of |
| 32 |
"virtual". |
| 33 |
|
| 34 |
>>> Considering the number of different virtuals in this category, |
| 35 |
>>> maybe it would be a good idea to split it a little? What I'm |
| 36 |
>>> proposing is maybe creating some kind of '*-virtual' categories. |
| 37 |
>>> |
| 38 |
>>> For example, half of the current virtuals are prefixed with 'perl-'. |
| 39 |
>>> Maybe they could be transformed into 'perl-virtual/*'? |
| 40 |
>> |
| 41 |
>> If you're going to do that, then I'd suggest giving them some sort of |
| 42 |
>> tag that the package manager can rely upon in order to identify them |
| 43 |
>> as virtuals. For example, we could have the ebuilds set |
| 44 |
>> PROPERTIES=virtual [2], or we could simply specify (in PMS) that any |
| 45 |
>> category whose name matches the '*-virtual' pattern will contain |
| 46 |
>> virtuals. |
| 47 |
> |
| 48 |
> Doesn't DEFINED_PHASES==- serve that purpose nowadays? |
| 49 |
|
| 50 |
That's an interesting idea. It seems like that should suffice for this |
| 51 |
purpose. |
| 52 |
|
| 53 |
[1] |
| 54 |
http://archives.gentoo.org/gentoo-dev/msg_47dc8f61c43d835c3feee77244188b02.xml |
| 55 |
-- |
| 56 |
Thanks, |
| 57 |
Zac |
Archives