Go delve调试工具的简单应用

Delve是个啥

Delve is a debugger for the Go programming language. The goal of the project is to provide a simple, full featured debugging tool for Go. Delve should be easy to invoke and easy to use. Chances are if you’re using a debugger, things aren’t going your way. With that in mind, Delve should stay out of your way as much as possible.

• Go语言的调试器
• 目标：提供简单、功能齐全的Go调试工具
• 容易调用、使用
• 谁家好的代码天天需要调试呀，尽量少用

如何安装

安装latest，最新版
go install github.com/go-delve/delve/cmd/dlv@latest
如果它报这个错误，证明dlv不支持该平台

go install github.com/go-delve/delve/cmd/dlv@latest
D:\goworkspace\pkg\mod\github.com\go-delve\delve@v1.21.2\service\debugger\debugger.go:32:2: found packages native (dump_other.go) and your_windows_architecture_is_not_supported_by_delve (support_sentinel_windows.go) in D:\goworkspace\pkg\mod\github.com\go-delve\delve@v1.21.2\pkg\proc\native

如何使用

go version
go version go1.20 linux/arm64

dlv version
Delve Debugger
Version: 1.21.2
Build: $Id: 98f8ab2662d926245917ade2f2bb38277315c7fc $

你说啥？不会用？我也不会

不会用就看看help吧。dlv --help

Delve is a source level debugger for Go programs.

Delve enables you to interact with your program by controlling the execution of the process,
evaluating variables, and providing information of thread / goroutine state, CPU register state and more.

The goal of this tool is to provide a simple yet powerful interface for debugging Go programs.

Pass flags to the program you are debugging using `--`, for example:

`dlv exec ./hello -- server --config conf/config.toml`

Usage:
  dlv [command]

Available Commands:
  attach      Attach to running process and begin debugging.
  connect     Connect to a headless debug server with a terminal client.
  core        Examine a core dump.
  dap         Starts a headless TCP server communicating via Debug Adaptor Protocol (DAP).
  debug       Compile and begin debugging main package in current directory, or the package specified.
  exec        Execute a precompiled binary, and begin a debug session.
  help        Help about any command
  test        Compile test binary and begin debugging program.
  trace       Compile and begin tracing program.
  version     Prints version.

Additional help topics:
  dlv backend  Help about the --backend flag.
  dlv log      Help about logging flags.
  dlv redirect Help about file redirection.

Use "dlv [command] --help" for more information about a command.

汇总一下

总结一下，上述命令中，如下5个用的多一点儿：

• attach
• debug
• exec
• core
• help

其他的看看帮助命令就好
使用dlv help 子命令可查看子命令的帮助文档哈

另外还有如下不常用的命令，暂不做介绍

Additional help topics:
  dlv backend  Help about the --backend flag.
  dlv log      Help about logging flags.
  dlv redirect Help about file redirection.

子命令的具体用法

搞一个先决条件，创建一个main.go文件，写一段简单的代码进去。
就以如下代码为例，main函数中写了一个简易版的httpServer，80端口开放，访问 “http://localhost:80/” 路径，则执行一次斐波那契数列的函数。

package main

import "net/http"

func main() {
   
        http.HandleFunc("/", func(writer http.ResponseWriter, request *http.Request) {
   
            fib(3)
        })
        if err := http.ListenAndServe(":80", nil); err != nil {
   
                panic(err)
        }
}

func fib(n int) int {
   
    if n < 2 {
   
        return 1
    }
    return fib(n-1) + fib(n-2)
}

下面对调试命令进行梳理

1. attach

dlv help attach

Attach to an already running process and begin debugging it.

This command will cause Delve to take control of an already running process, and
begin a new debug session.  When exiting the debug session you will have the
option to let the process continue or kill it.

Usage:
  dlv attach pid [executable] [flags]

Flags:
      --continue                 Continue the debugged process on start.
  -h, --help                     help for attach
      --waitfor string           Wait for a process with a name beginning with this prefix
      --waitfor-duration float   Total time to wait for a process
      --waitfor-interval float   Interval between checks of the process list, in millisecond (default 1)

Global Flags:
      --accept-multiclient               Allows a headless server to accept multiple client connections via JSON-RPC or DAP.
      --allow-non-terminal-interactive   Allows interactive sessions of Delve that don't have a terminal as stdin, stdout and stderr
      --api-version int                  Selects JSON-RPC API version when headless. New clients should use v2. Can be reset via RPCServer.SetApiVersion. See Documentation/api/json-rpc/README.md. (default 1)
      --backend string                   Backend selection (see 'dlv help backend'). (default "default")
      --check-go-version                 Exits if the version of Go in use is not compatible (too old or too new) with the version of Delve. (default true)
      --headless                         Run debug server only, in headless mode. Server will accept both JSON-RPC or DAP client connections.
      --init string                      Init file, executed by the terminal client.
  -l, --listen string                    Debugging server listen address. (default "127.0.0.1:0")
      --log                              Enable debugging server logging.
      --log-dest string                  Writes logs to the specified file or file descriptor (see 'dlv help log').
      --log-output string                Comma separated list of components that should produce debug output (see 'dlv help log')
      --only-same-user                   Only connections from the same user that started this instance of Delve are allowed to connect. (default true)

该命令主要部分: dlv attach pid，该pid是一个Go程序的pid

1. go build ./main.go

2. 生成了 main 可执行文件

3. 使用nohub ./main 或者 setsid ./main 启动 main 文件，此时该文件加载进内存后对应一个进程ID。

4. 这里使用ps -ef | grep main 找到程序的pid

5. 使用dlv attach PID 进行调试
   

6. 输入help 看一下帮助命令

root@Ophelia:~/test# dlv attach 1680
Type 'help' for list of commands.
(dlv) help
The following commands are available:

Running the program:
    call ------------------------ Resumes process, injecting a function call (EXPERIMENTAL!!!)
    continue (alias: c) --------- Run until breakpoint or program termination.
    next (alias: n) ------------- Step over to next source line.
    rebuild --------------------- Rebuild the target executable and restarts it. It does not work if the executable was not built by delve.
    restart (alias: r) ---------- Restart process.
    step (alias: s) ------------- Single step through program.
    step-instruction (alias: si)  Single step a single cpu instruction.
    stepout (alias: so) --------- Step out of the current function.

Manipulating breakpoints:
    break (alias: b) ------- Sets a breakpoint.
    breakpoints (alias: bp)  Print out info for active breakpoints.
    clear ------------------ Deletes breakpoint.
    clearall --------------- Deletes multiple breakpoints.
    condition (alias: cond)  Set breakpoint condition.
    on --------------------- Executes a command when a breakpoint is hit.
    toggle ----------------- Toggles on or off a breakpoint.
    trace (alias: t) ------- Set tracepoint.
    watch ------------------ Set watchpoint.

Viewing program variables and memory:
    args ----------------- Print function arguments.
    display -------------- Print value of an expression every time the program stops.
    examinemem (alias: x)  Examine raw memory at the given address.
    locals --------------- Print local variables.
    print (alias: p) ----- Evaluate an expression.
    regs ----------------- Print contents of CPU registers.
    set ------------------ Changes the value of a variable.
    vars ----------------- Print package variables.
    whatis --------------- Prints type of an expression.

Listing and switching between threads and goroutines:
    goroutine (alias: gr) -- Shows or changes current goroutine
    goroutines (alias: grs)  List program goroutines.
    thread (alias: tr) ----- Switch to the specified thread.
    threads ---------------- Print out info for every traced thread.

Viewing the call stack and selecting frames:
    deferred --------- Executes command in the context of a deferred call.
    down ------------- Move the current frame down.
    frame ------------ Set the current frame, or execute command on a different frame.
    stack (alias: bt)  Print stack trace.
    up --------------- Move the current frame up.

Other commands:
    config --------------------- Changes configuration parameters.
    disassemble (alias: disass)  Disassembler.
    dump ----------------------- Creates a core dump from the current process state
    edit (alias: ed) ----------- Open where you are in $DELVE_EDITOR or $EDITOR
    exit (alias: quit | q) ----- Exit the debugger.
    funcs ---------------------- Print list of functions.
    help (alias: h) ------------ Prints the help message.
    libraries ------------------ List loaded dynamic libraries
    list (alias: ls | l) ------- Show source code.
    packages ------------------- Print list of packages.
    source --------------------- Executes a file containing a list of delve commands
    sources -------------------- Print list of source files.
    target --------------------- Manages child process debugging.
    transcript ----------------- Appends command output to a file.
    types ---------------------- Print list of types

Type help followed by a command for full documentation.
(dlv)

可以看见子命令非常之多

如下汇总一下子命令

执行程序

操纵断点

查看程序变量和内存

进程、协程

调用栈、栈帧

其他命令

以上高亮的子命令用的多一些
打一套组合拳（啊打！）
设置断点的方式

break 包名.函数名
b 包名.函数名
break 文件名:行号
b 文件名行号

b main.main
b main.fib
c
n

其他终端: curl http://localhost:80

描述过于诡异

bp，查看一下断点
clear 1，删除一个断点，并再次查看断点
c，此时断住不动了，怎么办，怎么办?
curl http://localhost:80 当然是在其他终端输入这个啦
此时你会发现，其他终端中卡住了
此时你需要在当前终端一直

c
c
...

c下去，直到把fib函数执行完,再次断住
此时另一个终端中有结果了哦

curl http://localhost:80
StatusCode        : 200
StatusDescription : OK
Content           : {
   }
RawContent        : HTTP/1.1 200 OK
                    Content-Length: 0
                    Date: Fri, 15 Dec 2023 15:44:06 GMT
Headers           : {
   [Content-Length, 0], [Date, Fri, 15 Dec 2023 15:44:06 GMT]}
RawContentLength  : 0

其他命令自行探索

2. debug

dlv debug ./main.go
命令参考 attach

3. exec

dlv exec ./main
命令参考 attach

Reference
https://github.com/go-delve/delve