Switch custom Bzip2 cmake module to standard

[zklaus]

This replaces the custom Cmake modules FindBz2.cmake and FindBzip2.cmake with the standard FindBZip2, included in Cmake. This entails a few changed variable names, but I tried to contain them in the Cmake parts of the build system, maintaining compatibility with the Autotools version.

It is noteworthy that what appears to be the current incarnation of the original source of those custom modules at https://github.com/sidch/CMake/tree/main/Modules does not contain them anymore.

It is not completely clear to me why there are two different detection methods in the current sources, so I may be missing something, but it does lead to problems with the Bzip2 plugin installation (see #2717).

I also backported this change to 4.9.2, using it in the Conda-forge build, where it successfully installs the Bzip2 plugin.

Closes #2717.

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[DennisHeimbigner]

If memory serves, I found certain platforms had bz2 and not bzip2 and other platforms vice-versa.
Have you tried this under Windows using visual studio?

[zklaus]

I have used this patch in the Conda-forge builds since conda-forge/libnetcdf-feedstock#178 and there it works on Windows, see here and here.

Allow me to highlight that the approach currently in main does not work for any platform because the top-level CMakeLists.txt file calls only FindBz2 (via FIND_PACKAGE(Bz2)), but the plugin installation uses the variables that would be set by FindBzip2.

[DennisHeimbigner]

Its coming back to me again. Under Ubuntu-22, I found that apt
has not libbzip2-dev package. It only has libbz2-dev package.
That was why I tried to test for both bz2 and bzip2.

[zklaus]

Ah, that makes sense. The problem still needs to be addressed, though. Do you know where you got the FindBzip2.cmake and FindBz2.cmake from?

Regardless, the good news is that the built-in module takes care of this by looking for both bzip2 and bz2 and setting everything up accordingly, see https://gitlab.kitware.com/cmake/cmake/-/blob/master/Modules/FindBZip2.cmake#L65.

[DennisHeimbigner]

The only clue I see is this line: # Author: Siddhartha Chaudhuri, 2009

[DennisHeimbigner]

This change fails for me under Ubuntu 22. It says:

-- Could NOT find BZip2 (missing: BZIP2_LIBRARIES BZIP2_INCLUDE_DIR)

[WardF]

I'm seeing the same behavior as Dennis, but will investigate further.

[WardF]

This is working for me on MacOS so I'll see if I can figure out what's happening on Ubuntu 22.04.

[DennisHeimbigner]

what bzip2 package is being installed under MACOS? bz2 or bzip2? My guess us bzip2.

[WardF]

Dennis, I'll have to dig to see what's installed as part of the development packages re: 'bz2 vs. bzip2', but the library itself is libbz2, so I would suspect bz2.

[zklaus]

The only clue I see is this line: # Author: Siddhartha Chaudhuri, 2009

Yeah, I did see that and it is what lead me to https://github.com/sidch/CMake, which is a repository with a relatively large collection of Cmake modules by (presumably) the same author. I thought I might find the two modules used here there as well, but they are not present. The history of that repository stretches back only to August 2012 with an initial commit that already adds a lot of modules, so what I think happened is that the author has maintained the collection for some time, in 2009 including the Bzip2 modules, and removing them sometime between 2009 and the move of the collection to git in 2012, probably in favor of the upstream one.

This change fails for me under Ubuntu 22. It says:

-- Could NOT find BZip2 (missing: BZIP2_LIBRARIES BZIP2_INCLUDE_DIR)

Is that Ubuntu 22.04 Jammy or Ubuntu 22.10 Kinetic?

With libbz2-dev installed, both should have bzlib.h and libbz.so (see filelists for Jammy and Kinetic), which should be enough to find the library.
Perhaps you could share your build/CMakeCache.txt and build/CMakeFiles/CMake*.log files?

what bzip2 package is being installed under MACOS? bz2 or bzip2? My guess us bzip2.

Just to check I am not missing something: There aren't really two separate packages, right? It's all the same library, just that some packagers choose different names for their respective packages, right? As such, the question would maybe rather be "Which package manager are you using?" with Homebrew and Macports being the two most likely candidates for Macos.

As binary on Linux, I have only seen libbz2.so. This is true on Ubuntu (package name libbz2-dev), RHEL (bzip2-devel), and Conda-forge (bzip2).

[ZedThree]

The FindBzip2 module defines an imported library, so might be better to use that, as it will take care of the header locations too:

Suggested change

	SET(TLL_LIBS ${TLL_LIBS} ${BZIP2_LIBRARIES})
	SET(TLL_LIBS ${TLL_LIBS} BZip2::BZip2)

(and below on the buildplugin line)

[WardF]

Re-checking these PR's in an attempt to get caught up on the backlog.

[WardF]

@K20shores Can you take a look at the conflict and confirm where this should go instead, keeping in line with the changes you've made?