Fedora 34 Change proposal: Boost 1.75 upgrade (System-Wide Change)

[Ben Cotton]

https://fedoraproject.org/wiki/Changes/F34Boost175

== Summary ==
This change brings Boost 1.75 to Fedora. This will mean Fedora ships
with a recent upstream Boost release.

== Owner ==

* Name: [[User:trodgers| Thomas Rodgers]]
* Email: trodgers(a)redhat.com


== Detailed Description ==

The aim is to synchronize Fedora with the most recent Boost release.
Because ABI stability is absent from Boost, this entails rebuilding of
all dependent packages. This also entails the change owner assisting
maintainers of client packages in decoding cryptic boost-ese seen in
output from g++.

The equivalent changes for previous releases were
[[Changes/F33Boost173]], [[Changes/F30Boost169|Fedora 30 Change]],
[[Changes/F29Boost167|Fedora 29 Change]], [[Changes/F28Boost166|Fedora
28 Change]], [[Changes/F27Boost164|Fedora 27 Change]],
[[Changes/F26Boost163|Fedora 26 Change]], [[Changes/F25Boost161|Fedora
25 Change]], [[Changes/F24Boost160|Fedora 24 Change]],
[[Changes/F23Boost159|Fedora 23 Change]] and
[[Changes/F22Boost158|Fedora 22 Change]].

== Benefit to Fedora ==

Fedora 33 includes Boost 1.73 (released April 28th 2020).

Fedora will stay relevant, as far as Boost clients are concerned. In
addition to serveral bug fixes and enhancements to existing components
(including many as part of Boost 1.74's release) Boost 1.75  brings
three new components:
* [https://www.boost.org/doc/libs/1_74_0/libs/stl_interfaces
Boost.STL_Interfaces], A library to assist in writing STL conforming
iterators, views, and containers, from T. Zachary Laine (introduced in
Boost 1.74).
* [https://www.boost.org/doc/libs/1_75_0_beta1/libs/json/ Boost.JSON],
A portable C++ library which provides containers and algorithms that
implement JavaScript Object Notation, from Vinnie Falco, Krystian
Stasiowski.
* [https://www.boost.org/doc/libs/1_75_0_beta1/libs/leaf Boost.LEAF],
A lightweight error handling library for C++11, from Krystian
Stasiowski.
* [https://www.boost.org/doc/libs/1_75_0_beta1/libs/pfr Boost.PFR], A
C++14 library for very basic reflection, from Antony Polukhin.

== Scope ==
* Proposal owners:
** Build will be done with Boost.Build v2 (which is the
upstream-sanctioned way of building Boost)
** Request a "f34-boost"
[https://docs.pagure.org/releng/sop_adding_side_build_targets.html
build system tag]
([http://lists.fedoraproject.org/pipermail/devel/2011-November/159908.html
discussion]):
** Build boost into that tag (take a look at the
[http://koji.fedoraproject.org/koji/buildinfo?buildID=606493 build
#606493] for inspiration)
** Post a request for rebuilds to fedora-devel
** Work on rebuilding dependent packages in the tag.
** When most is done, re-tag all the packages to rawhide
** Watch fedora-devel and assist in rebuilding broken Boost clients
(by fixing the client, or Boost).

* Other developers:
** Those who depend on Boost DSOs will have to rebuild their packages.
Feature owners will alleviate some of this work as indicated above,
and will assist those whose packages fail to build in debugging them.
* Policies and guidelines:
** Apart from scope, this is business as usual, so no new policies, no
new guidelines.

* Trademark approval: N/A (not needed for this Change)


== Upgrade/compatibility impact ==
* No manual configuration or data migration needed.
* Some impact on other packages needing code changes to rebuild.
Historically this hasn't been too much of a problem and could always
be resolved before deadline.

== How To Test ==
* No special hardware is needed.
* Integration testing simply consists of installing Boost packages
(`dnf install boost`) on Fedora and checking that it does not break
other packages (see below for a way to obtain a list of boost
clients).


== User Experience ==
* Expected to remain largely the same.
* Developers building third-party software on Fedora may need to
rebuild against the new Boost packages, and may need to adjust their
code if the new Boost release is not source-compatible.
* Developers using `bjam` to build their own software will need to
switch to using the new name for the tool, `b2`

== Dependencies ==
Packages that must be rebuilt:
<code>$ dnf repoquery -s --releasever=rawhide --whatrequires
libboost\* --disablerepo=* --enablerepo=fedora | sort -u</code>

All clients:
<code>$ dnf repoquery --releasever=rawhide --archlist=src
--whatrequires boost-devel --disablerepo='*'
--enablerepo=fedora-source</code>

== Contingency Plan ==

* Contingency mechanism: Worst case scenario is to abandon the update
and simply ship F34 with Boost 1.73, which is already in rawhide. It
would also be possible to ship the 1.74.0 which would still be newer
than in current Fedora releases and contains numerous fixes and
improvements to existing Boost components.

* Contingency deadline: We will know whether the change can be made
once the rebuilds in the side tag are done

* Blocks release? No
* Blocks product? None


== Documentation ==
* https://www.boost.org/users/history/version_1_75_0.html (expected
release mid December 2020)
* https://www.boost.org/users/history/version_1_74_0.html (released on
14 August 2020)
* https://www.boost.org/users/history/version_1_73_0.html (released on
28 April 2020)
* https://www.boost.org/users/history/version_1_72_0.html (released on
11 December 2019)
* https://www.boost.org/users/history/version_1_71_0.html (released on
19 August 2019)
* https://www.boost.org/users/history/version_1_70_0.html (released on
12 April 2019)
* https://www.boost.org/development/index.html


-- 
Ben Cotton
He / Him / His
Senior Program Manager, Fedora & CentOS Stream
Red Hat
TZ=America/Indiana/Indianapolis