> (for instance when the global state is writable from unexpected places in the code base or from other threads)
...or from a function that calls itself, directly or indirectly. This automatically becomes possible basically whenever the function accesses a user-supplied callback. So you'll run into issues unless you have full control over your callees, or only access the global array in logically-atomic patterns.
(To give an ancient example: to enable function calls, PDP-8 programs allocated a word of static memory before the top of each subroutine to store the return address. However, if a subroutine tried to recurse into itself, then the old return address would be overwritten, and it would never be able to return properly. Supposedly this could result in very gnarly errors to debug.)
...or from a function that calls itself, directly or indirectly. This automatically becomes possible basically whenever the function accesses a user-supplied callback. So you'll run into issues unless you have full control over your callees, or only access the global array in logically-atomic patterns.
(To give an ancient example: to enable function calls, PDP-8 programs allocated a word of static memory before the top of each subroutine to store the return address. However, if a subroutine tried to recurse into itself, then the old return address would be overwritten, and it would never be able to return properly. Supposedly this could result in very gnarly errors to debug.)