In what situations does the compiler automatically reserve memory in the dynamic area (heap)?

The Go compiler automatically allocates memory on the heap in the following situations:

• When a variable needs to live longer than the function in which it is declared (escape analysis). For example, if the address of a local variable is returned from a function or stored in a structure that lives longer.
• If a variable is too large for the stack or its size is unknown at compile time.

Example:

func create() *int {
    x := 10
    return &x // variable x "escapes" to the heap because a pointer is returned
}

Here, the variable x will be placed on the heap so that the pointer remains valid after the function exits. The compiler analyzes the code (escape analysis) and decides where to allocate memory.