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This is just a minor rant:

In C++, const references are useful for parameters, because they avoid copying the arguments to a method. Non-const references, on the other hand, are pure evil, because there’s no way (at the call site) to immediately see that a method might change a variable:

int expectedVersion = 1;

ValidateVersion(expectedVersion);

By looking at this, you can’t tell that ValidateVersion is declared as void ValidateVersion(int &version) and might actually change the value.

Use a pointer instead:

ValidateVersion(&expectedVersion);

Then, when I’m looking at the call site, I have an expectation that the value might change.