Summarize the differences between golang and other languages ​​on pointers

Go language is a programming language that can be statically compiled into binary files. Its underlying pointers are somewhat different from other languages. This article will discuss the differences between Go language pointers and pointers in other languages.

1. Pointer type

In the Go language, the type of each pointer variable is determined by the type of the variable it points to. For example, if a pointer variable points to a variable of type int, the type of the pointer variable is *int.

Pointers in Go language can also point to structures, arrays or other custom types. This allows a function's parameters and return value to be of any type, even pointers to custom types.

2. Using pointers

In the Go language, pointers do not need to perform any explicit pointer operations, such as the address operator & or the dereference operator *. This is because in the Go language, when assigning a value to a pointer variable, the memory address pointed to by the pointer variable is actually changed to a new address.

The advantage of this method is that it can avoid common pointer errors, such as null pointers, wild pointers, etc.

The following is an example of using Go language pointers:

func main() {
    var a int = 42
    var b *int = &a

    fmt.Println(a) // 输出 42
    fmt.Println(*b) // 输出 42

    a = 27
    fmt.Println(*b) // 输出 27
}

In this example, variable a is an int type variable, and variable b is a pointer variable pointing to the a variable. By adding an * sign in front of the b variable, you can get the value of the a variable.

3. Pointer value copy

In the Go language, when a pointer variable is passed as a parameter to a function, what is actually passed is the memory address pointed to by the pointer variable. If the value pointed to by a pointer variable is modified within a function, that value will also change outside the function. This is different from other languages, where when a pointer is passed to a function, only the value of the pointer is passed.

The following is a more specific example:

func change(num *int) {
    *num = 10
}

func main() {
    var num int = 20

    fmt.Println(num) // 输出 20
    change(&num)
    fmt.Println(num) // 输出 10
}

In this example, the change function passes a pointer to the num variable as a parameter and modifies the value of the num variable to 10. Therefore, the result is correct.

4. Null pointer

In the Go language, the null pointer is represented as nil, and the nil pointer points to an uncertain memory address. Unlike other languages, Go's nil pointers can be dereferenced without causing a runtime error.

The following is an example of dereferencing a null pointer:

func main() {
    var ptr *int

    fmt.Println(ptr) // 输出 <nil>

    sum := *ptr // 报错：panic: runtime error: invalid memory address or nil pointer dereference
}

In the above example, we created a pointer variable ptr pointing to an int type variable, but no memory was allocated for it. So the pointer is nil. When we try to dereference a nil pointer, a runtime error will result.

In short, Go language pointers are slightly different from pointers in other languages. You need to pay attention to their characteristics and use them correctly.

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