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Subject: [boost] Policy for breaking changes
From: Louis Dionne (ldionne.2_at_[hidden])
Date: 2017-12-02 21:44:44

Hi all,

So far, I've been careful about not doing any breaking changes to Hana.
Hana obeys semantic versioning, and I'm accumulating desirable breaking
changes until I'm ready to publish a new major version.

I'm wondering what's the policy for major breaking changes with Boost
libraries. For example, let's say I wanted to do an update of Hana with
C++17 features; this would be a large breaking change, with all kinds
of API changes, etc..

- Are such drastic changes prohibited altogether? Or perhaps they’re not
  prohibited but there’s historical evidence showing it’s always a bad
- Do such changes require going through a mini review?
- Is it customary to leave the old version of the library there in a
  separate directory (or put the new one in a separate directory)?
  I think Spirit does that, e.g. Spirit Classic is still available IIRC.

I think I know the answer to these questions from observing other author's
behavior, but I'd like to see what the community thinks about this. It has
an impact on the Boost libraries as a whole, since a major breaking change
in one library could prevent users from updating Boost as a whole, which
has an impact on all of us.

I'm looking forward to hearing other people's thoughts on the matter.


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