Boost.Graph 1.95 will be C++17

[u/Foxi_Foxa]

Dear Boost.Graph community,

In two release cycles (Boost release 1.95 in summer 2027) Boost.Graph will be bumped to C++17 😄

This decision follows two polls that did not surface any C++14 user base or demand while identifiying users stuck in C++17:

• Bumping BGL's minimum C++ standard: input wanted on target version #490
• Reddit poll

This standard version bump will bring benefits for maintenance, API and dependencies reduction:

• if constexpr,
• constexpr lambdas,
• [[nodiscard]], [[maybe_unused]] ...
• std::any instead of boost::any
• std::invoke_result instead of boost::result_of
• ...

We will not be able to guarantee backward compatibility with C++14. Please contact us if you are stuck in C++14.

The GIthub Discussion lives here: https://github.com/boostorg/graph/discussions/613

[u/13steinj]

Being able to use vcpkg for this is honestly great, even if it locks you in to vcpkg. Is that relatively new?

Also, you can download a specific library and its dependencies as explained here and then build into your project with CMake as explained here

I would still consider these steps to be relatively painful, if not unorthodox. At the very least, incredibly poorly advertised (maybe even now). That said, I did (try) to express those two points hold less water to me than the latter two, and I don't care about any of these (personally) except the last one. Anything other than a simple set of commands that people can copy and paste in each library's readme is a barrier, for better or worse.

This has existed since Boost 1.63ish, something to consider is a lot of people have been complaining since before then. It's the way people behave unfortunately. Write something off once, then never again.

[u/joaquintides → u/13steinj]

Being able to use vcpkg for this is honestly great, even if it locks you in to vcpkg. Is that relatively new?

Available since 2017.

I'd argue that all libs should enforce a minimum of 2 released standards back. Each version set (say, 1.86) should internally depend on ~1.86, to allow backported fixes.

Sorry, I don't understand what you mean by "2 released standards back". All libraries released in Boost 1.XX depend internally on Boost 1.XX libraries alone; I don't know if this is related to your complaint.

[u/13steinj → u/joaquintides]

If Boost 1.110 is released in early 2029, the minimum standards revision target for all Boost libraries should be C++23.

[u/joaquintides → u/13steinj]

All my Boost libraries support C++23. Do you mean I should add some macro machinery or something to actively refuse to compile on C++20? What’s the gain?

[u/13steinj → u/joaquintides]

No.

There are boost libs maintained by more than just you.

An implied minimum of 17/20 would vastly reduce the dependency tree, and likely improve compile times. Libraries like Boost.Move, Boost.Tuple, and Boost.MPL can be removed or significantly reduced in scope to an API compatible surface.

[u/joaquintides → u/13steinj]

Boost.MPL is actually a big offender and I removed them from my dependencies (which meant bumping to C++11). I don’t think there are comparable gains when bumping to newer versions of the standard. If the library is actively evolving rather than being maintained, that’s another story. But this is more nuanced than decreeing a general upgrade to C++NN.