Avoid unnecessary copies of objects

[Caball009]

Sometimes large / expensive copies are made when const& could be used instead.

Major culprits:

• 30+ cases of Matrix3D (regex Matrix3D\s+\w+\s*=)
• ~10 cases of Squad::getLiveObjects
• 2 cases of PartitionSolver::getSolution

There are other cases beside these throughout the code, probably many more.

[githubawn]

Maybe we could open a meta-issue for clang-tidy? I've seen these when running a report using this tool.
In our reviews const issues are caught no matter how many times they run. This could apply to the entire codebase.

[xezon]

Yes I expect there are many of these cases.

[Caball009]

Maybe we could open a meta-issue for clang-tidy? I've seen these when running a report using this tool. In our reviews const issues are caught no matter how many times they run. This could apply to the entire codebase.

There's this check https://clang.llvm.org/extra/clang-tidy/checks/performance/unnecessary-copy-initialization.html but it didn't seem to work well enough.

[CryoTheRenegade]

when i ran it, this is what i got performance-unnecessary-copy-initialization: 73

[Caball009]

Do those include the ones I mentioned in the issue description? If so, maybe that check is good enough.

[CryoTheRenegade]

Do those include the ones I mentioned in the issue description? If so, maybe that check is good enough.

This is what my scan found https://gist.github.com/CryoTheRenegade/a3d3effe4a7f473ca50e08b000455888

But we can probably assume that there are some others that may be only used once or twice that are also expensive that this tool doesn't catch