Is it safe for threads to share automatic storage duration (stack) objects via pointers or references?
Only if you can guarantee that the lifetime of the stack object will not end while other threads might still access the object. Thus the safest practice is to avoid sharing stack objects, particularly in designs where threads are created and destroyed dynamically. Restrict sharing of stack objects to simple designs with very clear and unchanging function and thread lifetimes. (Suggested by Darryl Green).
