Upgrade to CXX20

[mitchute]

Pull request overview

This can be a throw away PR if needed. Spending a bit of time exploring what is needed to upgrade beyond CXX17.

Description of the purpose of this PR

Pull Request Author

• Title of PR should be user-synopsis style (clearly understandable in a standalone changelog context)
• Label the PR with at least one of: Defect, Refactoring, NewFeature, Performance, and/or DoNoPublish
• Pull requests that impact EnergyPlus code must also include unit tests to cover enhancement or defect repair
• Author should provide a "walkthrough" of relevant code changes using a GitHub code review comment process
• If any diffs are expected, author must demonstrate they are justified using plots and descriptions
• If changes fix a defect, the fix should be demonstrated in plots and descriptions
• If any defect files are updated to a more recent version, upload new versions here or on DevSupport
• If IDD requires transition, transition source, rules, ExpandObjects, and IDFs must be updated, and add IDDChange label
• If structural output changes, add to output rules file and add OutputChange label
• If adding/removing any LaTeX docs or figures, update that document's CMakeLists file dependencies
• If adding/removing any output files (e.g., eplustbl.*)
  • Update ..\scripts\Epl-run.bat
  • Update ..\scripts\RunEPlus.bat
  • Update ..\src\EPLaunch\ MainModule.bas, epl-ui.frm, and epl.vbp (VersionComments)
  • Update ...github\workflows\energyplus.py

Reviewer

• Perform a Code Review on GitHub
• If branch is behind develop, merge develop and build locally to check for side effects of the merge
• If defect, verify by running develop branch and reproducing defect, then running PR and reproducing fix
• If feature, test running new feature, try creative ways to break it
• CI status: all green or justified
• Check that performance is not impacted (CI Linux results include performance check)
• Run Unit Test(s) locally
• Check any new function arguments for performance impacts
• Verify IDF naming conventions and styles, memos and notes and defaults
• If new idf included, locally check the err file and other outputs

[mitchute]

Anything worth reviewing up to this point is contained in bd870fd and 9d1519f

[mitchute]

OK, I think we're building with CXX20 now.

17e6c17 can probably be ignored. This is just fully qualifying most of the format statements with EnergyPlus:: so they don't conflict with std::format that is now available. Similar changes in the remaining commits can also likely be ignored.

Assuming there is agreement to move forward here, I would propose this gets merged soon. We can then slowly begin to migrate EnergyPlus::format and fmt::format over to usestd::format which will require us to move away from the Fortran string format syntax. Diffs resulting from these transitions can then be dealt with in a piecemeal fashion.

[mitchute]

Other things to note: fmt-8.0.1 and Eigen were patched. The first doesn't matter really since I think want to get rid of it anyway, and Eigen will probably be updated when kiva eventually gets upgraded.

[jasondegraw]

@mitchute It looks like most of the changes in "E+ proper" are to formatting operations. Is that correct? I guess the only question I have is if this would complicate anything on less-standard platforms.

[mitchute]

That’s correct.

By “less standard” are you referring to Red Hat or some other HPC environment?

[jasondegraw]

@mitchute Yes, but also I recall that there was some cut-down environment that was getting used to build the code for Python packaging purposes. Not sure what all happened with that.

[mitchute]

@jasondegraw it looks like manylinux_2_28 uses GCC 14, which has full C++ 20 support. manylinux_2_28 is in ELTS, and given that there are a number of newer versions available, I'm not expecting any issues related to this.