golang execution process

golang is an efficient, fast and concise programming language. Its execution process is mainly divided into two stages: compilation and running. This article will introduce the execution process of golang in detail with specific examples.

1. Compilation phase

Golang uses static compilation. The source code is compiled into a binary file by the compiler and then executed through the operating system. The compilation process is mainly divided into steps such as lexical analysis, syntax analysis, semantic analysis, intermediate code generation, and target code generation.

(1) Lexical analysis

The lexical analyzer is the first component of the golang compiler. Its function is to convert the character sequence in the source code into a token sequence. The lexical analyzer classifies various symbols in the source code and converts them into tokens that the compiler can recognize.

For example, the following code:

func main() {
    fmt.Println("Hello World!")
}

In this code, the lexical analyzer will recognize the function name "main" and the package name "fmt" as identifiers, and will print the function "Println" Recognize it as an identifier and convert "Hello World!" into a string constant.

(2) Syntax analysis

The syntax analyzer performs syntax analysis on the token generated by the lexical analyzer. Its main job is to verify whether the code follows golang syntax rules and convert the code into an abstract syntax tree (AST).

For example, the following code:

a := 1
b := 2
c := a + b

In this code, the syntax analyzer will generate the following AST by analyzing the variable declaration statement and addition expression:

    :=
   /   
  a     1
   
    :=
   /   
  b     2

    +
   /   
  a     b
      / 
     /  
     c

(3) Semantic analysis

The semantic analyzer analyzes the abstract syntax tree. Its main job is to perform type checking and semantic checking on the code to ensure that the code can be executed correctly. If an error occurs during the check, it will output the appropriate error message.

For example, the following code:

a := "1"
b := 2
c := a + b  // 这里会报错，因为a是字符串类型，b是整型

The semantic analyzer will check the types of variables a and b and find that their types are incompatible, so the following error message will be output:

cannot use b (type int) as type string in argument to fmt.Sprint

(4) Intermediate code generation

The intermediate code generator converts AST into intermediate code. Intermediate code is a form of code between source code and target machine code that is usually not directly related to any computer architecture.

For example, the following code:

func add(a int, b int) int {
    return a + b
}

The intermediate code generator will convert this code into the following intermediate code:

func add {
    a := get_param(1)
    b := get_param(2)
    c := a + b
    return c
}

(5) Target code generation

The target code generator converts the intermediate code into machine code. This process is usually completed by the compiler of the operating system.

2. Running phase

After the compilation is completed, the operating system will load the generated target code into the memory and then execute the program.

In golang, the entry function of the program is the main function. When the program is running, the operating system will find the entry address of the main function and execute the code in the main function.

For example, the following code:

package main

import "fmt"

func main() {
    fmt.Println("Hello World!")
}

When the program is running, the operating system will find the entry address of the main function, execute the Println function in the fmt package, and output "Hello World!".

To sum up, the execution process of golang can be simply summarized as: writing source code → compiling source code → running executable program. Mastering the execution process of golang can better help us understand golang programming in depth and take advantage of golang's high performance and efficiency.

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