Go Object File Generation

This challenge focuses on understanding how Go compiles source code into machine code. You will create a Go program that simulates the creation of an object file from a Go source file. This process is fundamental to understanding the compilation pipeline and how Go programs are built.

Problem Description

Your task is to write a Go program that takes a Go source file as input and generates a simplified representation of an object file. This representation should contain essential information that would typically be found in a real object file, such as function names and their corresponding entry points.

Key Requirements:

1. Input: The program should accept the path to a Go source file (.go) as a command-line argument.
2. Parsing: You need to parse the Go source file to identify function declarations.
3. Output Format: The program should output a structured representation of the "object file". For this challenge, we'll define a simple format:
   • A header indicating the file name.
   • A list of functions, where each entry includes the function name and its approximate byte offset (simulated).
4. Simulated Offsets: Since we are not performing actual compilation, you will need to simulate byte offsets for function entry points. A simple approach is to assign increasing offsets based on the order functions are found.
5. Error Handling: Handle cases where the input file does not exist or is not a valid Go file.

Expected Behavior:

Given a Go source file, the program should output a text-based representation of its "object file" content.

Edge Cases:

• Source files with no function declarations.
• Source files with comments and empty lines.
• Source files with multiple packages (though for this exercise, focus on functions declared at the top level).
• Input file path that is invalid or inaccessible.

Examples

Example 1:

Input: A file named hello.go with the following content:

package main

import "fmt"

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

func greet(name string) {
    fmt.Printf("Hello, %s!\n", name)
}

Output:

Object File: hello.go
---
Functions:
  - Name: main, Offset: 0
  - Name: greet, Offset: 50
---

Explanation: The program identifies main and greet as functions. main is assigned an offset of 0. greet is assigned an offset of 50 (a simulated value representing where its compiled code might start).

Example 2:

Input: A file named empty.go with the following content:

package utils

// This file contains no functions.
var version = "1.0"

Output:

Object File: empty.go
---
Functions:
  (No functions found)
---

Explanation: The program correctly identifies that there are no function declarations and indicates this in the output.

Constraints

• The input Go source file will be a single file.
• The simulated offsets will be integers.
• The program should aim for reasonable performance, but complex optimization is not required for this challenge.
• The output format must strictly adhere to the specified structure.

Notes

• You will need to use Go's built-in go/parser and go/ast packages to parse the Go source code.
• Consider how to differentiate between function declarations and other code constructs.
• Think about how to iterate through the Abstract Syntax Tree (AST) to find function declarations.
• The "offset" is a conceptual value for this exercise. You can use a simple counter incremented for each function found, or a slightly more sophisticated approach based on line numbers if you wish. The goal is to demonstrate the concept of identifying and referencing functions.