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On 05/26/2016 21:28, Kent Fredric wrote: |
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> On 27 May 2016 at 10:28, rindeal <dev.rindeal@×××××.com> wrote: |
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>> |
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>> 1) what are they? |
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>> 2) why are they used? |
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> |
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> |
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> My best explanation is its a way to re-use very large amounts of code |
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> between 2 ebuilds, without resorting to: |
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> |
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> a) Copying the whole ebuild and hoping you find the relevant part in diffs |
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> b) Not needing reams of version-specific conditional code to make |
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> copying ebuilds between versions easier. |
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> c) Not needing confusing eclasses that exist to serve a single |
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> package, loaded with lots of weird conditional logic. |
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> |
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> My understanding is you could effectively roll the eblits back into |
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> the ebuild statically, just doing so would make keeping the changes |
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> consistent harder. |
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> |
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> Its clearly designed for a system where you have ~10 different |
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> versions of Perl available or ~10 different versions of glibc |
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> available, but you don't want to pay the price of duplicating that |
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> logic wholesale for every minor concurrent revision, and only want to |
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> update essential differences when you need to, not because you have |
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> to. |
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> |
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> That said, its a very confusing system to get your head around, |
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> because its *basically* yet another "mixin" system like "inherit", but |
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> done in bash, which itself is a rather strange language to be doing |
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> something as complicated as mixins. |
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|
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An accurate explanation, but probably better to say they're more like "local |
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eclasses". If you think of the existing eclasses in ${PORTDIR}/eclass as |
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"global", that is, they contain common code utilized by multiple unrelated |
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ebuild packages, then eblits were originally envisioned as localized versions |
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of eclasses to share package-specific code between multiple ebuilds of |
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differing versions. |
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|
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Whether the idea is useful in the present day and age, eh, who knows. For the |
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mips-sources ebuilds, eblits let me centralize the per-machine notes and |
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unpacking logic, which reduced each ebuild's size from ~18KB a few years ago |
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down to ~4.9KB today. |
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|
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-- |
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Joshua Kinard |
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Gentoo/MIPS |
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kumba@g.o |
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6144R/F5C6C943 2015-04-27 |
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177C 1972 1FB8 F254 BAD0 3E72 5C63 F4E3 F5C6 C943 |
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|
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"The past tempts us, the present confuses us, the future frightens us. And our |
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lives slip away, moment by moment, lost in that vast, terrible in-between." |
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|
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--Emperor Turhan, Centauri Republic |
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