Golang调试工具Delve使用简介

Delve 是一款很不错的 Golang 调试工具，可以实现类似 Visual Studio 的断点调试功能，也可以用来在程序 Crash 的时候生成 Coredump 文件，此外 Delve 也适合用于调试 Web Server。

Delve 项目

Github链接

安装 Delve

go get -u github.com/go-delve/delve/cmd/dlv

Delve 常用命令

命令	功能
dlv attach	后面跟 pid，用来 Debug 编译好的 Golang 程序
dlv core	用于 coredump
dlv debug	后面跟要调试的 go 文件，进入 Debug
dlv test	Debug test 函数

编写用于 Debug 的 Golang Web Server

main.go，写一个 Hello World 的 Web Server

package mainimport ("net/http"
)const endpoint = ":8000"type helloHandler struct{}func (h *helloHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {w.Write([]byte("Hello, world!"))
}func main() {http.Handle("/", &helloHandler{})http.ListenAndServe(endpoint, nil)
}

进行断点调试

➜  test dlv debug ./main.go
Type 'help' for list of commands.
(dlv) help
The following commands are available:args ------------------------ Print function arguments.break (alias: b) ------------ Sets a breakpoint.breakpoints (alias: bp) ----- Print out info for active breakpoints.call ------------------------ Resumes process, injecting a function call (EXPERIMENTAL!!!)clear ----------------------- Deletes breakpoint.clearall -------------------- Deletes multiple breakpoints.condition (alias: cond) ----- Set breakpoint condition.config ---------------------- Changes configuration parameters.continue (alias: c) --------- Run until breakpoint or program termination.deferred -------------------- Executes command in the context of a deferred call.disassemble (alias: disass) - Disassembler.down ------------------------ Move the current frame down.edit (alias: ed) ------------ Open where you are in $DELVE_EDITOR or $EDITORexit (alias: quit | q) ------ Exit the debugger.frame ----------------------- Set the current frame, or execute command on a different frame.funcs ----------------------- Print list of functions.goroutine (alias: gr) ------- Shows or changes current goroutinegoroutines (alias: grs) ----- List program goroutines.help (alias: h) ------------- Prints the help message.libraries ------------------- List loaded dynamic librarieslist (alias: ls | l) -------- Show source code.locals ---------------------- Print local variables.next (alias: n) ------------- Step over to next source line.on -------------------------- Executes a command when a breakpoint is hit.print (alias: p) ------------ Evaluate an expression.regs ------------------------ Print contents of CPU registers.restart (alias: r) ---------- Restart process.set ------------------------- Changes the value of a variable.source ---------------------- Executes a file containing a list of delve commandssources --------------------- Print list of source files.stack (alias: bt) ----------- Print stack trace.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.thread (alias: tr) ---------- Switch to the specified thread.threads --------------------- Print out info for every traced thread.trace (alias: t) ------------ Set tracepoint.types ----------------------- Print list of typesup -------------------------- Move the current frame up.vars ------------------------ Print package variables.whatis ---------------------- Prints type of an expression.
Type help followed by a command for full documentation.

在这个交换环境下可以进行断点调试，支持的命令主要有：

命令	alias	功能
break	b	设置断点
continue	c	运行至断点
print	p	打印变量
funcs		显示支持的函数

查看包名/函数名包含 main 的函数

funcs main

(dlv) funcs main
crypto/x509.domainToReverseLabels
crypto/x509.matchDomainConstraint
internal/x/net/http/httpproxy.(*domainMatch).match
internal/x/net/http/httpproxy.domainMatch.match
main.(*helloHandler).ServeHTTP
main.init
main.main
net.absDomainName
net.isDomainName
net/http.(*body).bodyRemains
net/http.requestBodyRemains
runtime.main
runtime.main.func1
runtime.main.func2
type..eq.internal/x/net/http/httpproxy.domainMatch
type..hash.internal/x/net/http/httpproxy.domainMatch

funcs [param] 默认是返回包含 param 的func，可以看到 main package 包含3个 func

main.(*helloHandler).ServeHTTP
main.init
main.main

设置断点

break [name] <linespec>

在 main 处设置一个断点，break 的参数可以是 funcs 查看等到的 func name

break main.main

(dlv) break main.main
Breakpoint 1 set at 0x1331513 for main.main() ./main.go:15

设置断点的另外一种方式

<filename>:<line>

(dlv) break ./main.go:15
Breakpoint 1 set at 0x1331513 for main.main() ./main.go:15

linespec 支持的完整形式
linespec说明

*<address> Specifies the location of memory address address. address can be specified as a decimal, hexadecimal or octal number<filename>:<line> Specifies the line line in filename. filename can be the partial path to a file or even just the base name as long as the expression remains unambiguous.<line> Specifies the line line in the current file+<offset> Specifies the line offset lines after the current one-<offset> Specifies the line offset lines before the current one<function>[:<line>] Specifies the line line inside function. The full syntax for function is <package>.(*<receiver type>).<function name> however the only required element is the function name, everything else can be omitted as long as the expression remains unambiguous. For setting a breakpoint on an init function (ex: main.init), the <filename>:<line> syntax should be used to break in the correct init function at the correct location./<regex>/ Specifies the location of all the functions matching regex

运行至断点

continue 命令运行至断点

continue

(dlv) continue
> main.main() ./main.go:15 (hits goroutine(1):1 total:1) (PC: 0x1331513)10:11:   func (h *helloHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {12:       w.Write([]byte("Hello, world!"))13:   }14:
=>  15: func main() {16:        http.Handle("/", &helloHandler{})17:      http.ListenAndServe(endpoint, nil)18:   }

打印变量

可以继续设置断点至 ServeHTTP 函数，并执行 continue 开启 Web Server 服务

(dlv) break main.(*helloHandler).ServeHTTP
Breakpoint 2 set at 0x1331443 for main.(*helloHandler).ServeHTTP() ./main.go:11
(dlv) c

访问 Web Server
这时候 Web Server 的 Delve 需要输入
```
➜  curl http://localhost:8000
Hello, world!%
```

在执行至断点 ServeHTTP 时，可输入 print 查询变量

输入 n 回车，单步执行，
输入 args 打印出所有的方法参数信息
输入 locals 打印所有的本地变量

(dlv) c
> main.(*helloHandler).ServeHTTP() ./main.go:11 (hits goroutine(26):1 total:13) (PC: 0x1331443)6:7:  const endpoint = ":8000"8:9: type helloHandler struct{}10:
=>  11: func (h *helloHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {12:       w.Write([]byte("Hello, world!"))13:   }14:15: func main() {16:        http.Handle("/", &helloHandler{})
(dlv) n
> main.(*helloHandler).ServeHTTP() ./main.go:12 (PC: 0x1331451)7:    const endpoint = ":8000"8:9: type helloHandler struct{}10:11:    func (h *helloHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {=>  12:     w.Write([]byte("Hello, world!"))13:   }14:15: func main() {16:        http.Handle("/", &helloHandler{})17:      http.ListenAndServe(endpoint, nil)
(dlv) args
h = (*main.helloHandler)(0x16485d0)
w = net/http.ResponseWriter(*net/http.response) 0xc00010b998
r = ("*net/http.Request")(0xc0001c0200)
(dlv) locals
(no locals)
(dlv) print r.Method
"GET"
(dlv)

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