Ensure that switchover vars are initialized before use:

[seelabs]

Global variables in different TUs are initialized in an undefined order. At least one global variable was accessing a global switchover variable. This caused the switchover variable to be initialized in an incorrect state.

Since the switchover is always explicitly set before transaction processing, this bug can not effect transaction processing, but could effect unit tests (and potentially the value of some global variables). Note: at the time of this patch the offending bug is not yet in production.

Type of Change

• [x ] Bug fix (non-breaking change which fixes an issue)

[HowardHinnant]

Nice job!

[gregtatcam]

👍 LGTM

[a-noni-mousse]

Why not use the thread_local compiler support for the code?

[HowardHinnant]

I think using thread_local is something we should strongly consider, but definitely not in this PR.

We use LocalValue in a few places and we should consider a PR which moves all of them to thread_local (and does nothing else). This would be a good move to reduce our technical debt.

But #4527 should remain just about fixing the bug without introducing further complications which would risk introducing a bug.

[seelabs]

@a-noni-mousse @HowardHinnant LocalValue is meant to work with coroutines and thread_local isn't going to play well with co-routines. Having said that, I'm not sure any co-routines are actually using LocalValue. If we audit the code and it's not used we may be able to replace it, but even then we'd have to make sure it was never mistakenly used with a co-routine.