All the way, I was forced to talk about C code debugging skills and remote debugging

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One ： background

1. Tell a story

Every time the project is pre delivered , There will always be all kinds of wonderful flowers , I think it's necessary to sort it out and how to solve it quickly , Let the latter avoid the pit , This article will talk about what I have heard and met ：

• I went to , The code of local environment runs very fast , There's something wrong with the test environment
• I went to , Provided by a third party dll Run out bug 了

Two ： The solution of two big holes

1. The local environment is OK , There's something wrong with the test

I believe that many friends have similar experience with me , Clearly program code , Configuration files are the same , Move a nest and there's a problem , You say no , Now that the problem has gone wrong, how to solve it quickly ？ Yes , It's just debugging , But the program is deployed in centos On , Send a visualstudio It's not realistic to go up there , What do you want to do with debugging under this constraint level ？ Pretty good , It can be debugged remotely , Then we quickly found that one of the environment variables in the test machine was wrong , The whole story is clear , Next, let's see how to achieve local To centos Of Remote debugging .

1) Test code

For the convenience of demonstration , I was there Action Read from strategy environment variable .

    public class HomeController : Controller
    {
        public IActionResult Index()
        {
            ViewBag.strategy = Environment.GetEnvironmentVariable("strategy");

            return View();
        }
    }

2) install SSH

To debug remotely , It needs to be installed on the remote machine SSH, Because the process debugging is attached later With the help of SSH Get through .

yum install openssh-server unzip curl

After installation , You can see 22 Port started

[root@localhost data]# netstat -tlnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      1126/sshd           
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      3037/cupsd          
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      1739/master    
tcp6       0      0 :::22                   :::*                    LISTEN      1126/sshd           
tcp6       0      0 ::1:631                 :::*                    LISTEN      3037/cupsd          
tcp6       0      0 ::1:25                  :::*                    LISTEN      1739/master  

3) Program release configuration

Release configuration , The first thing to make sure is debug edition , The second thing to make sure is Portable mode (Portable), Here's the picture ：

4) Debug with attached processes

Select... In the menu bar ：Debug -> Attach To Process, Then fill in ssh All kinds of information needed , Here's the picture ：

Click on Connect after , You can see the remote machine dotnet Program Process number , Select the process to attach , stay Select Code Type Choose from Nanaged (.NET Core for Unix) that will do , Here's the picture ：

5) Smooth debugging

stay Type ： http://192.168.142.130/Home/Index , You can see my C# Code hit , I also got the remote machine's environment variable , The problem is solved .

2. The third party dll Out bug 了

Debugging programs use F9 debug , I believe many friends know that breakpoints can be edited , for instance ： Set expression breakpoints , Filter breakpoints , Hit number breakpoint , Action breakpoint , Here is the picture ：

The first question is , These fancy breakpoints , Do you really know how to use ？ Do you really use it often ？

Let me answer , I won't use it until I have to , I'd rather add test statements that are easy to debug into my code , There are three reasons ：

• More flexible

That's obvious , Setting conditions in the panel is much more cumbersome than setting conditions with pure statements , Point to point , And conditional superposition , It's complicated , I don't like .

• Powerful

There are only simple and relationships on the edit panel , And the conditions are the same level , It is impossible to achieve the inclusion relation of each condition or relation and hierarchy or recursion , therefore ... Can't ...

• Easier to save

This is interesting , Right click on the breakpoint to pop up the edit panel , Click the left button to close the breakpoint , Here's the problem , Often because of cheap hands , I want to click the right button, but I click the left button .... The hard set conditions are gone ... It's really gone , From then on , The road turns black . Here's the picture ：

So breakpoint editing really doesn't work ？ I think it's only in debugging scenarios where you can't modify statements , For example, I met debugging factory packaged dll, ha-ha , Now that we're talking about breakpoints , I will use it. dnspy Demonstrate a few breakpoints for you to review ！

1) Test code

For the convenience of demonstration , use for The circular case is the best .

        public static void Main(string[] args)
        {
            var sum = 0;

            for (int i = 0; i < 10000; i++)
            {
                sum += i;
            }

            Console.WriteLine($"sum={sum}");
        }

2) I hope to sum = 1035 Hit the breakpoint

The conditional expression breakpoint is OK , It's simple , As shown below ：

3) Find all that can be 1800 Divisible number , And record what happened at that time i and sum value

You can use Action Logging of breakpoints , stay for In loop iteration , There is no need to break breakpoints , Just record the current... In a specific state i and sum Value , Very helpful for debugging code , Here's the picture ：

3、 ... and ： summary

Generally speaking, these two experiences are also included in my step-by-step experience , It would be better if I could help you , So much for this article , See you later ！

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