Go compilation and execution flow - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple Go program with init and main

What is the output of this Go program when compiled and run?

Go

package main
import "fmt"

func init() {
    fmt.Println("Init function called")
}

func main() {
    fmt.Println("Main function called")
}

A Init function called\nMain function called

B Main function called\nInit function called

C Init function called

D Main function called

💡 Hint

Remember that init functions run before main in Go.

In Go, the init function runs automatically before main. So the output first prints from init, then from main.

❓ Predict Output

intermediate

Output of Go program with multiple init functions

What is the output of this Go program with two init functions in the same package?

Go

package main
import "fmt"

func init() {
    fmt.Println("First init")
}

func init() {
    fmt.Println("Second init")
}

func main() {
    fmt.Println("Main function")
}

A Main function\nFirst init\nSecond init

B First init\nMain function\nSecond init

C Second init\nFirst init\nMain function

D First init\nSecond init\nMain function

💡 Hint

Multiple init functions run in the order they appear in the source file.

Go runs multiple init functions in the order they are declared in the source file before main.

❓ Predict Output

advanced

Output of Go program with package-level variable initialization

What is the output of this Go program considering package-level variable initialization order?

Go

package main
import "fmt"

var a = initializeA()
var b = initializeB()

func initializeA() int {
    fmt.Println("Initializing A")
    return 1
}

func initializeB() int {
    fmt.Println("Initializing B")
    return 2
}

func main() {
    fmt.Println("a =", a, ", b =", b)
}

A Initializing A\nInitializing B\na = 1 , b = 2

B a = 0 , b = 0

C a = 1 , b = 2\nInitializing A\nInitializing B

D Initializing B\nInitializing A\na = 1 , b = 2

💡 Hint

Package-level variables are initialized in the order they are declared.

Variables a and b are initialized in order. So initializeA runs first, then initializeB, then main prints values.

❓ Predict Output

advanced

Output of Go program with multiple packages and init functions

Given two packages, main and util, what is the output when running the main package?

Go

package util

import "fmt"

func init() {
    fmt.Println("util init")
}

func UtilFunc() {
    fmt.Println("util function")
}

---

package main

import (
    "fmt"
    "util"
)

func init() {
    fmt.Println("main init")
}

func main() {
    fmt.Println("main function")
    util.UtilFunc()
}

A main function\nutil init\nmain init\nutil function

B util init\nmain init\nmain function\nutil function

C main init\nutil init\nmain function\nutil function

D util function\nutil init\nmain init\nmain function

💡 Hint

Package init functions run before main, and dependencies init first.

Go initializes imported packages first, so util's init runs before main's init, then main runs.

🧠 Conceptual

expert

Order of compilation and linking in Go build process

Which of the following correctly describes the order of steps in Go's compilation and execution flow when building and running a program?

A Execution → Linking → Compilation to object files → Type checking → Source code parsing

B Linking → Compilation to object files → Type checking → Source code parsing → Execution

C Source code parsing → Type checking → Compilation to object files → Linking → Execution

D Compilation to object files → Source code parsing → Type checking → Linking → Execution

💡 Hint

Think about how source code is processed step-by-step before running.

Go first parses source code, then checks types, compiles to object files, links them, then runs the program.