Go language source level debugger delve

Hello everyone , I am a frank.

01

Introduce

Delve It's a simple 、 Powerful and easy to use Go Language source level debugger , It's also Go Officially recommended debugger .

02

install

Delve Very simple installation , If readers use Go 1.16 Or later , You can use it directly go install install ：

go install github.com/go-delve/delve/cmd/[email protected]

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If readers use less than Go 1.16 Version of , But download it first Delve Source code , And then use go install install ：

git clone https://github.com/go-delve/delve
cd delve
go install github.com/go-delve/delve/cmd/dlv

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After installation , have access to go help install see dlv Detailed location of executable . I suggest readers to dlv Executable file , Configuration to PATH environment variable .

It should be noted that , If readers use macOS, You also need to install command line development tools ：

xcode-select --install

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To avoid every use of dlv All need authorization to use debugger, Readers are advised to open the developer mode ：

sudo /usr/sbin/DevToolsSecurity -enable

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03

practice

At the completion of Part 02 After all operations in , We use dlv version Check dlv Whether the executable program can be used .

We can use dlv Start a modal session with any available command of , The commonly used command is dlv debug, dlv exec and dlv test. Limited to space , In this paper we introduce dlv debug How to use .

Sample code ：

package main

import (
    "fmt"
)

func main() {
    a := 1
    b := 2
    c := sum(a, b)
    fmt.Println(c)
}

func sum(a, b int) int {
    res :=  a + b
    return res
}

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Read the above code example we will use to debug the session , It contains a main Function and a sum function ,main Function to define variables a And variables b, call sub function , And assign the returned result to the variable c, Finally, print the variable c Value .

Start a debugging session ：

[[email protected] work]# dlv debug
Type 'help' for list of commands.
(dlv)

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Read the code above , We use dlv debug Start a debugging session , Without any parameters ,Delve Compile and start debugging main package .

We can also specify a file name ,Delve Will compile the specified file main package , And start a debugging session .

[[email protected] work]# dlv debug main.go
Type 'help' for list of commands.
(dlv)

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After the debugging session starts , We can use the debug command to debug the program .

list command ：

dlv debug
Type 'help' for list of commands.
(dlv) list main.main
Showing /work/main.go:7 (PC: 0x49670a)
     2:
     3: import (
     4:  "fmt"
     5: )
     6:
     7: func main() {
     8:  a := 1
     9:  b := 2
    10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
(dlv) list ./main.go:7
Showing /work/main.go:7 (PC: 0x49670a)
     2:
     3: import (
     4:  "fmt"
     5: )
     6:
     7: func main() {
     8:  a := 1
     9:  b := 2
    10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
(dlv)

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After the debugging session starts , We can use list The command lists the source code of the specified location , There are two ways , The first way is <package name>.<func name>, The second way is <file name>:<line number>.

break command ：

dlv debug
Type 'help' for list of commands.
(dlv) break main.main
Breakpoint 1 set at 0x49670a for main.main() ./main.go:7
(dlv)

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We can use break Command add breakpoint , and list command , Add the location of the breakpoint , You can also use the above two methods .

We can use breakpoints command , List all breakpoints , have access to clear Command deletes the specified breakpoint , have access to clearall Delete all assertions .

continue、next、step、stepout and print command ：

 dlv debug
Type 'help' for list of commands.
(dlv) break main.main
Breakpoint 1 set at 0x49670a for main.main() ./main.go:7
(dlv) continue
> main.main() ./main.go:7 (hits goroutine(1):1 total:1) (PC: 0x49670a)
     2:
     3: import (
     4:  "fmt"
     5: )
     6:
=>   7: func main() {
     8:  a := 1
     9:  b := 2
    10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
(dlv) next
> main.main() ./main.go:8 (PC: 0x496718)
     3: import (
     4:  "fmt"
     5: )
     6:
     7: func main() {
=>   8:  a := 1
     9:  b := 2
    10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
    13:
(dlv) next
> main.main() ./main.go:9 (PC: 0x496721)
     4:  "fmt"
     5: )
     6:
     7: func main() {
     8:  a := 1
=>   9:  b := 2
    10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
    13:
    14: func sum(a, b int) int {
(dlv) next
> main.main() ./main.go:10 (PC: 0x49672a)
     5: )
     6:
     7: func main() {
     8:  a := 1
     9:  b := 2
=>  10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
    13:
    14: func sum(a, b int) int {
    15:  res :=  a + b
(dlv) print a
1
(dlv) print b
2
(dlv) step
> main.sum() ./main.go:14 (PC: 0x4967e0)
     9:  b := 2
    10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
    13:
=>  14: func sum(a, b int) int {
    15:  res :=  a + b
    16:  return res
    17: }
(dlv) next
> main.sum() ./main.go:15 (PC: 0x496800)
    10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
    13:
    14: func sum(a, b int) int {
=>  15:  res :=  a + b
    16:  return res
    17: }
(dlv) next
> main.sum() ./main.go:16 (PC: 0x49680f)
    11:  fmt.Println(c)
    12: }
    13:
    14: func sum(a, b int) int {
    15:  res :=  a + b
=>  16:  return res
    17: }
(dlv) next
> main.main() ./main.go:10 (PC: 0x496739)
Values returned:
 ~r0: 3

     5: )
     6:
     7: func main() {
     8:  a := 1
     9:  b := 2
=>  10:  c := sum(a, b)
    11:  fmt.Println(c)
    12: }
    13:
    14: func sum(a, b int) int {
    15:  res :=  a + b
(dlv) next
> main.main() ./main.go:11 (PC: 0x49673e)
     6:
     7: func main() {
     8:  a := 1
     9:  b := 2
    10:  c := sum(a, b)
=>  11:  fmt.Println(c)
    12: }
    13:
    14: func sum(a, b int) int {
    15:  res :=  a + b
    16:  return res
(dlv) print c
3
(dlv)

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Read the code above , We use Delve After adding breakpoints , perform continue command , The program will execute to the breakpoint ; perform next command , The program continues to execute the next line of code ; perform step command , The program steps into the calling function ; perform stepout command , The program steps out to the calling position of the calling function ; perform print command , Print the value of the specified parameter .

Readers use the above commands , It can meet most debugging scenarios . For ease of understanding , The commands used in the above examples do not use the abbreviated form , In actual use , It will be more convenient to use abbreviated forms .

Abbreviation form ：

• break(b)
• continue(c)
• next(n)
• step(s)
• stepout(so)
• print(p)

04

summary

In this article, we briefly introduce Go Language debugger Delve The basic way of use , Readers can put Delve Use up , Replace with print Debug the code in the form of printing .

About Delve Advanced features of , For example, debugging goroutines、 Attach the debugger to an existing process 、 Remote debugging and from VSCode Editor or Goland IDE Use Delve. Interested readers can refer to Delve Help document for .

Reference material ：

1. https://go.dev/doc/gdb
2. https://github.com/go-delve/delve/tree/master/Documentation