[llvm-dev] Should I worry about test failures in a release?

[mats petersson via llvm-dev]

Going from 3.6 to 3.7 would almost certainly break binary compatibility
between .bc files. You may be able to get away with it for some particular
use-cases (but in that case, it's by luck, not by design).

I'm not enough "part of the community" to say if there are rules about what
can and can't change between certain levels of releases, but my general
understanding is that "as long as the change is good, it goes in" [aside
from changes for example between 3.7.0 and 3.7.1, where there is a
guarantee that, modulo actual bugs or undefined behaviour, the two releases
are compatible].

I try to track "trunk" by updating every two-four weeks, and once every few
of those updates, I need to make changes to my compiler project. Of course,
how many and what kind of changes will depend on what features of LLVM your
project is using. There are some parts of LLVM that are very stable, there
are others with more changes - but all appear to potentially change from my
experience.

The "not guarantee for compatibility between releases" is a good and a bad
thing, where the bad part is the obvious extra work when something changes,
and the good part is that "things can be changed". I've worked on/with
projects that have very strict rules of compatibility, where changes to ABI
and API are very difficult to make and everything has to be motivated,
debated, change-controlled and finally agreed with "customers" [in quotes
as it's often some group within the overall company, but outside your own
group]. This approach makes for slow and often complex changes to "work
around" the fact that you can't actually make the change you want. It's a
right pain to work with such systems too, even if it may seem like a good
idea at times. Most importantly, it is often harming innovation and
improvements, because of the bureaucracy involved in making changes.

--
Mats

On 13 October 2015 at 12:40, Joachim Durchholz via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Thanks, that answered all questions.
>
> One last detail: What's a major version? 3.8 or 4.0?
>
> Regards,
> Jo
>
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