At what stage and in which component of the system is the decision made about the storage location of a value type?

The decision on where to store a value of a type in iOS is made at compile time and linking, as well as at runtime, depending on the type and context.

The main component responsible for this is the Swift (or Objective-C) compiler, which determines whether the value will be stored on the stack, in the heap, or in a processor register.

For example:

• Values of simple types (Int, Float, Bool) are usually stored on the stack if they are local.
• For class types (reference types), an object is created on the heap, and the variable contains a reference to it.
• For structures (value types), storage occurs on the stack or inside the object if the structure is nested.

Thus, the compiler and runtime jointly decide on data placement, considering the type, scope, and lifetime of the object.