F39 proposal: Boost 1.81 upgrade (System-Wide Change proposal)

[Ben Cotton]

https://fedoraproject.org/wiki/Changes/F39Boost181

This document represents a proposed Change. As part of the Changes
process, proposals are publicly announced in order to receive
community feedback. This proposal will only be implemented if approved
by the Fedora Engineering Steering Committee.


== Summary ==
This change brings Boost 1.81 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/F37Boost178]], [[Changes/F35Boost176]],
[[Changes/F34Boost175]], [[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 39 includes Boost 1.81.

Fedora will stay relevant, as far as Boost clients are concerned.

Boost 1.81 does not bring any new components, but includes one new
header-only library -
* URL: Boost.URL is a portable C++ library which provides containers
and algorithms which model a URL.

Boost 1.81 also includes many fixes and enhancements to existing
components, including major and potentially
breaking changes to -
* Container Hash: removal of specializations to boost::hash, removal
of support for BOOST_HASH_NO_EXTENSION, improved performance and
quality of generated hashes.
* Locale: Removal of C++03 support, C++11 or later is now required
(BREAKING CHANGE)

Boost 1.81 includes additional enhancements and breaking changes from
Boost 1.80 and Boost 1.79 -
* Filesystem: boost/filesystem/string_file.hpp header is deprecated
and no longer included by boost/filesystem.hpp
* GIL: Deprecates C++11 support, C++14 will be the new minimum
language standard.
* Math: Deprecates C++11 support, C++14 will be the new minimum
language standard.
* Multiprecision: Deprecates C++11 support, C++14 will be the new
minimum language standard.


== Scope ==
* Proposal owners:
** Build will be done with Boost.Build v2 (which is the
upstream-sanctioned way of building Boost)
** Request a "f39-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.


* Release engineering: TODO
* 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.

== 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 F39 with Boost 1.78, which is already in rawhide.
* Blocks release? No
* Blocks product? None

== Documentation ==
* https://www.boost.org/users/history/version_1_81_0.html (expected
release mid December 2022)
* https://www.boost.org/users/history/version_1_79_0.html (released on
10th August 2022)
* https://www.boost.org/users/history/version_1_79_0.html (released on
13th April 2022)
* https://www.boost.org/development/index.html

== Release Notes ==


-- 
Ben Cotton
He / Him / His
Fedora Program Manager
Red Hat
TZ=America/Indiana/Indianapolis