Parsing unaddressable values ​​in Go language

Pointers in the Go language are a very powerful feature that allow programmers to directly access and manipulate addresses in memory. However, there are also some unaddressable values ​​in the Go language, that is, variables whose memory address cannot be obtained. This article takes a closer look at these unaddressable values ​​and provides specific code examples to resolve the issue.

1. What is an unaddressable value

In the Go language, there are some variables whose memory addresses cannot be obtained. These variables usually include the following situations:

1. Constants: Constants are unaddressable values ​​because they have been determined and fixed at a location in memory at compile time and cannot be modified.
2. Literal: Literal refers to a numerical value or string that appears directly in the code, and is also an unaddressable value.
3. Expressions: In the Go language, many expressions cannot be addressed. For example, addition expressions such as x y cannot obtain their memory addresses.
4. Temporary variables: Some temporary variables, such as function return values ​​or variables in closures, cannot obtain their memory addresses.

2. Code sample analysis

package main

import "fmt"

func getPointer(x int) *int {
    return &x
}

func main() {
    var a int = 10
    var b *int

    b = getPointer(a)

    fmt.Printf("a的值为：%d
", a)
    fmt.Printf("b的值为：%d
", *b)
}

In the above code, we define a getPointer function to get the memory address of the parameter, and # Call this function in the ##main function to obtain the address of the variable a. Here we successfully obtained the address of variable a, because a is an ordinary variable and can be addressed.

package main

import "fmt"

func main() {
    fmt.Printf("10的内存地址为：%p
", &10) // 编译报错：cannot take the address of 10
}

10, but the compiler The processor will report an error saying that the memory address of the constant cannot be obtained. This is an example of an unaddressable value.

Try to avoid using unaddressable values: Try to choose addressable variables for operations and avoid directly operating constants or literals.
1. Use to assign a value to a variable: assign an unaddressable value to a variable, and then operate on the address of the variable.
2. Use pointer parameters: If you need to modify a value in a function, you can pass it as a pointer parameter, so that you can get its address for modification.

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