[kazinator]

In C, it is only undefined behavior to access an automatic object that has not been initialized.

Static objects are always initialized, so the situation cannot arise.

That leaves dynamic ones, like uninitialized struct members in a malloced structure.

Accessing uninitialized dynamic memory means isn't undefined behavior in C. It results in whatever value is implied by the uninitialized bits. If the type in question has no trap representations, then it cannot fail.