Go的调试工具gdb-vs-dlv

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GoLand 编辑器虽然很强大，但是在展示内存及堆栈信息这一块还是比较的弱，有可能是我的姿势不对，所以，开始切入了 gdb 调试，但是 gdb 踩到了坑，并没有解决，也就引发了 gdb 与 dlv 的对比了

gdb

安装 

yum install ncures-devel
wget http://ftp.gnu.org/gnu/gdb/gdb-8.2.tar.gz
tar zxf gdb-8.2.tar.gz
cd gdb-8.2
make && make install

进入调试 

go build -gcflags '-N -l' main.go
gdb main

使用

  1. 启动调试程序（gdb）

    [lday@alex GoDbg]$ gdb ./GoDbg

  2. 在 main 函数上设置断点（b）

    (gdb) b main.main
Breakpoint 1 at 0x401000: file /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go, line 9.

  3. 带参数启动程序（r）

    (gdb) r arg1 arg2
Starting program: /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/GoDbg arg1 arg2
[New LWP 8412]
[New LWP 8413]
[New LWP 8414]
[New LWP 8415]

Breakpoint 1, main.main () at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:9
9    func main() {

  4. 在文件 dbgTest.go 上通过行号设置断点（b）

    (gdb) b dbgTest.go:16
Breakpoint 3 at 0x457960: file /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/mylib/dbgTest.go, line 16.

  5. 查看断点设置情况（info b）

    (gdb) info b
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x0000000000401000 in main.main 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:9
    breakpoint already hit 1 time
2       breakpoint     keep y   0x0000000000401000 in main.main 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:9
    breakpoint already hit 1 time
3       breakpoint     keep y   0x0000000000457960 in GoWorks/GoDbg/mylib.DBGTestRun 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/mylib/dbgTest.go:16

  6. 禁用断点（dis n）

    (gdb) dis 1   
(gdb) info b
Num     Type           Disp Enb Address            What
1       breakpoint     keep n   0x0000000000401000 in main.main 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:9
    breakpoint already hit 1 time
2       breakpoint     keep y   0x0000000000401000 in main.main 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:9
    breakpoint already hit 1 time
3       breakpoint     keep y   0x0000000000457960 in GoWorks/GoDbg/mylib.DBGTestRun 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/mylib/dbgTest.go:16

  7. 删除断点（del n）

    (gdb) del 1
(gdb) info b
Num     Type           Disp Enb Address            What
2       breakpoint     keep y   0x0000000000401000 in main.main 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:9
    breakpoint already hit 1 time
3       breakpoint     keep y   0x0000000000457960 in GoWorks/GoDbg/mylib.DBGTestRun 
                                                   at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/mylib/dbgTest.go:16

  8. 断点后继续执行（c）

    (gdb) c
Continuing.
Golang dbg test...
argc:3
argv:[/home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/GoDbg arg1 arg2]

Breakpoint 3, GoWorks/GoDbg/mylib.DBGTestRun (var1=1, var2="golang dbg test")
    at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/mylib/dbgTest.go:16
16    func DBGTestRun(var1 int, var2 string, var3 []int, var4 MyStruct) {(gdb)

  9. 显示代码（l）

    (gdb) l
11        B string
12        C map[int]string
13        D []string
14    }
15    
16    func DBGTestRun(var1 int, var2 string, var3 []int, var4 MyStruct) {17        fmt.Println("DBGTestRun Begin!\n")
18        waiter := &sync.WaitGroup{}
19    
20        waiter.Add(1)

  10. 单步执行（n）

    (gdb) n
DBGTestRun Begin!

18        waiter := &sync.WaitGroup{}

  11. 打印变量信息（print/p）
    在进入 DBGTestRun 的地方设置断点 (b dbgTest.go:16)，进入该函数后，通过 p 命令显示对应变量：

    (gdb) l 17
12        C map[int]string
13        D []string
14    }
15    
16    func DBGTestRun(var1 int, var2 string, var3 []int, var4 MyStruct) {17        fmt.Println("DBGTestRun Begin!\n")
18        waiter := &sync.WaitGroup{}
19    
20        waiter.Add(1)
21        go RunFunc1(var1, waiter)
(gdb) p var1 
$3 = 1
(gdb) p var2
$4 = "golang dbg test"
(gdb) p var3
No symbol "var3" in current context.

    从上面的输出我们可以看到一个很奇怪的事情，虽然 DBGTestRun 有 4 个参数传入，但是，似乎 var3 和 var4 gdb 无法识别，在后续对 dlv 的实验操作中，我们发现，dlv 能够识别 var3，var4.

  12. 查看调用栈（bt），切换调用栈（f n），显示当前栈变量信息 

    (gdb) bt
#0  GoWorks/GoDbg/mylib.DBGTestRun (var1=1, var2="golang dbg test")
    at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/mylib/dbgTest.go:17
#1  0x00000000004018c2 in main.main () at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:27
(gdb) f 1
#1  0x00000000004018c2 in main.main () at /home/lday/Works/Go_Works/GoLocalWorks/src/GoWorks/GoDbg/main.go:27
27        mylib.DBGTestRun(var1, var2, var3, var4)
(gdb) l
22        var4.A = 1
23        var4.B = "golang dbg my struct field B"
24        var4.C = map[int]string{1: "value1", 2: "value2", 3: "value3"}
25        var4.D = []string{"D1", "D2", "D3"}
26    
27        mylib.DBGTestRun(var1, var2, var3, var4)
28        fmt.Println("Golang dbg test over")
29    }
(gdb) print var1 
$5 = 1
(gdb) print var2
$6 = "golang dbg test"
(gdb) print var3
$7 =  []int = {1, 2, 3}

(gdb) print var4
$8 = {A = 1, B = "golang dbg my struct field B", C = map[int]string = {[1] = "value1", [2] = "value2", [3] = "value3"}, 
D =  []string = {"D1", "D2", "D3"}}

dlv(推荐)

安装 

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

进入调试 

dlv debug main.go

使用 

    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 $EDITOR
    exit (alias: quit | q) ------ Exit the debugger.
    frame ----------------------- Set the current frame, or execute command on a different frame.
    funcs ----------------------- Print list of functions.
    goroutine ------------------- Shows or changes current goroutine
    goroutines ------------------ List program goroutines.
    help (alias: h) ------------- Prints the help message.
    libraries ------------------- List loaded dynamic libraries
    list (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 commands
    sources --------------------- 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 --------------------- 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 types
    up -------------------------- Move the current frame up.
    vars ------------------------ Print package variables.
    whatis ---------------------- Prints type of an expression.

总结

  1. dlv 对 goroutine 的支持更好，我使用 gdb 的没有找到 goroutine 的调试方法，可能姿势不对

  2. gdb 对于局部引用变量无法调试，dlv 不会 

    func main() {
  i := 10
  j := &i
}

    如上代码，gdb 使用 p j 打印变量 j 的时候报错，dlv 却可以

  3. dlv 无法调试 interface 等 Go 内部实现的一些结构，gdb 是可以的

参考

《Golang 程序调试工具介绍 (gdb vs dlv)》

正文完
debug gdb golang
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2019-08-15
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