How does the stack differ from the heap? How does the compiler decide where to allocate an object?

The stack and heap are two different memory management methods.

Stack is a memory area where local variables of functions and parameters are stored. It is organized on a LIFO (last in, first out) principle. Allocation and deallocation of memory on the stack are very fast because it simply involves moving the stack pointer.

Heap is a memory area for dynamic allocation of objects, whose lifetime may extend beyond the function call. Memory in the heap is allocated and freed manually or by a garbage collector, which is slower than the stack.

In Go, the compiler decides where to allocate an object using escape analysis. If a variable "escapes" from a function (for example, it is returned or stored in a global variable), it is allocated on the heap. If the variable is used only within the function and does not escape its scope, it is placed on the stack.

Example:

func foo() *int {
    x := 10 // if x is returned, it is allocated on the heap
    return &x
}

func bar() {
    y := 20 // y lives only inside bar, allocated on the stack
    fmt.Println(y)
}

Thus, the compiler analyzes the variable's lifecycle and decides where to place it.