odb: fix 3dblox declaration mismatches

[ahmed532]

Some structs in src/odb/include/odb/3dblox.h where forward declared as classes. Which errored with "-Wmismatched-tags" compiler flag. Also, found another mismatch in PartitionMgr.h
Note that C++ does not distinguish between class and struct in a forward declaration. Only MSVC can have issues with it.

[gemini-code-assist]

Code Review

This pull request correctly fixes mismatched forward declarations of structs that were declared as class, which resolves -Wmismatched-tags compiler warnings. The changes in src/odb/include/odb/3dblox.h and src/par/include/par/PartitionMgr.h are accurate and improve code correctness by ensuring consistency between declarations and definitions. The grouping of struct forward declarations in 3dblox.h also slightly improves readability. The changes look good to me.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[maliberty]

Apparently it matters on mac as well which doesn't use MSVC.

[ahmed532]

Apparently it matters on mac as well which doesn't use MSVC.

OK I'll add it to compile options for clang then.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[ahmed532]

This started with #9093 which was reported by Stefan who uses a mac. To my knowledge we have zero MSVC users (nobody has ever reported an issue). In the report it is a warning but we should clean it up. In the CI we treat warnings as errors to keep them from creeping in.
I don't think you need to make it always an error as non-devs should be able to build even if we have a mismatch
option(ALLOW_WARNINGS "Flag to allow compilation with compiler warnings: on by default" ON)

if (NOT ALLOW_WARNINGS)
  add_compile_options(
    $<$<CXX_COMPILER_ID:GNU>:-Werror>
  )
endif()

in src/CMakeLists.txt
in the CI ALLOW_WARNINGS=0

Quote by @maliberty