Pass-by-value vs pass-by-reference

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From a multithreaded and multi-processor/core perspective, what would be safer, pass-by-value or pass-by-reference?

I know there's no hard and fast rules, but what would you consider as a general guideline?

To me it feels that pass-by-reference is more risky in a multithreaded environment. Another thread can modify an object while a function is busy operating on it. Using pass-by-value decreases the chance of a mess happening. The downside of course is the overhead associated with passing large objects by value.