Bugfix: Fix the Clang compilation of MET version 11.0

[JohnHalleyGotway]

Describe the Problem

METplus discussion dtcenter/METplus#2127 from @climbfuji notes that while MET version 10.1.1 does compile with Clang on MacOS, MET version 11.0.2 does not. Doing so results in a set of compiler errors and warnings.

This tasks for this issue include:

• Fix the main_v11.0 branch to compile via Clang. And then create an 11.0.3 bugfix release.
• Fix the develop branch to compile via Clang.

The remainder of these changes have been moved to issue MET #2564.

• Update the MET documentation on the develop branch with information about Clang.
• Add a new GHA test to the develop branch to compile with Clang for each pull request to ensure that it continues working. Note that this will require adding a new tag to the dtcenter/METbaseimage repository to provide the environment in which MET should be compiled via Clang.
• Consider also enhancing compile_MET_all.sh to support Clang.

As noted in dtcenter/METplus#2127, test the compilation using Clang version 13.

Expected Behavior

MET version 11.0.2 (and all future versions) should compile with Clang.

Environment

Describe your runtime environment:
1. Machine: Mac Laptop
2. OS: MacOS Monterey (version 12.6.2)
3. Software version number(s): MET version 11.0.2 or the main_v11.0 branch

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• METplus, MET, METdataio, METviewer, METexpress, METcalcpy, METplotpy
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[JohnHalleyGotway]

Notes on compiling with Clang.

1. Install Clang via MacPorts. Start with existing GNU development environment and then run:

sudo port install clang-13
export CXX=`which clang`
export CC=`which clang`

2. Compile MET's dependent libraries using Clang.
   Get the tar files:

wget https://dtcenter.ucar.edu/dfiles/code/METplus/MET/installation/tar_files.tgz
tar -zxf tar_files.tgz

And adapt the compile_MET_all.sh script.
Success with Clang: GSL, BUFRLIB, ZLIB, LIBPNG, G2CLIB, HDF5, NETCDF-C, NETCDF-CXX
Failure with Clang: Jasper (using GNU instead)
Skipped: HDF, HDFEOS, FREETYPE, CAIRO

[srherbener]

@JohnHalleyGotway thanks for creating this issue. I am a UCAR employee working on spack-stack for part of my time. Dom (@climbfuji) is my immediate supervisor. I may have a little bit of time to help with this issue if that is desirable.

I'm trying your instructions above for compiling the library dependencies.

I'm interested, for now, in trying to find a reasonable way to get 11.0.1 to compile successfully on the Mac in our spack-stack build process. Some questions I have are:

• When do you think a bug fix will be available?
• What is the intended C++ language standard for MET?
• Do we need C++ GNU extensions?

I can set the language standard/extensions in our flow if necessary. It's not clear to me what Apple Clang is using by default, but that default may not match what is required and be part of the issue.

Thank you for your help with this!

[srherbener]

@JohnHalleyGotway I have gotten the MacOS build working using the latest 11.0.2 version. I made two minor code changes to the MET source code (in the build process) as part of this. I'm interested in getting this addressed in the MET code base, and I want to do this in a manner compatible with your methods and practices. My plan is to create a PR in the MET code base with the changes I used and we can work from there. Again, I'm perfectly fine with finding a different approach if I'm not following your methods/practices with my changes.

Does this sound good with you? Thanks!

[JohnHalleyGotway]

Yes, that sounds great! Glad to hear you were able to make progress. Please submit a PR to propose those changes to the main_v11.0 branch. We can use that to create another 11.0 bugfix release. And then I can incorporate the changes into develop for inclusion in future releases.

Thanks
John

[srherbener]

I've submitted a PR (#2556) containing the patches I used to get the spack-stack process to work properly. I tried to fill out the PR description as best I could, but please advise and I can make updates as needed. Thanks!

[climbfuji]

Thanks @JohnHalleyGotway and @srherbener for fixing the MET 11 build for macOS.

[JohnHalleyGotway]

@climbfuji my plan was to also wait for a fix for #2578 from @hsoh-u prior to cutting the 11.0.3 bugfix release.

But I wanted to check in with you about that. Is there a date/deadline on your end driving the need for us to cut the 11.0.3 bugfix release soon?

[climbfuji]

No rush. We have the bug fixes that are needed for previous versions 11.0.x in spack-stack, so we can build those.

[climbfuji]

But it would be good to know when 11.0.3 is release so that we can add it to spack-stack and not apply the bug fixes from that version onwards.

[JohnHalleyGotway]

Reopening this issue since it needs to be fixed again. This was noted by @srherbener in this release acceptance testing comment.

The needed changes were merged into develop by #2563, but those changes were partially overridden the following day by #2570!

Reopening this issue to re-do this change for the main_v11.1 branch. Note that we only need to do this in main_v11.1 since we'll merge all changes from main_v11.1 into develop after the 11.1.0 release.