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Delve

Delve1 是使用Go語言實現的，專門用來調試Go程序的工具。它跟 GDB 工具類似，相比 GDB，它簡單易用，能夠更好的理解和處理Go語言的數據結構和語言特性，比如它支持打印 goroutine 以及 defer 函數等Go特有的語法特性。Delve 簡稱 dlv，後文將以 dlv 代稱 Delve.

安裝

# 安裝最新版本
go get -u github.com/go-delve/delve/cmd/dlv
# 查看版本
dlv version

使用

開始調試

dlv 使用 debug 命令進入調試界面：

dlv debug main.go

如果當前目錄是 main 包所在目錄時候，可以不用指定 main.go 文件這個參數的。假定項目結構如下：

.
├── github.com/me/foo
├── cmd
│   └── foo
│       └── main.go
├── pkg
│   └── baz
│       ├── bar.go
│       └── bar_test.go

如果當前已在 cmd/foo 目錄下，我們可以直接執行 dlv debug 命令開始調試。在任何目錄下我們可以使用 dlv debug github.com/me/foo/cmd/foo 開始調試。

如果已構建成二進制可執行文件，我們可以使用 dlv exec 命令開始調試：

dlv exec /youpath/go_binary_file

對於需要命令行參數才能啓動的程序，我們可以通過--來傳遞命令行參數，比如如下:

dlv debug github.com/me/foo/cmd/foo -- -arg1 value
dlv exec /mypath/binary -- --config=config.toml

對於已經運行的程序，可以使用 attach 命令，進行跟蹤調試指定 pid 的Go應用：

dlv attach pid

除了上面調試 main 包外，dlv 通過 test 子命令還支持調試 test 文件：

dlv test github.com/me/foo/pkg/baz

接下來我們可以使用 help 命令查看 dlv 支持的命令有哪些：

(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.
    trace (alias: t) ------- Set tracepoint.

Viewing program variables and memory:
    args ----------------- Print function arguments.
    display -------------- Print value of an expression every time the program stops.
    examinemem (alias: x)  Examine memory:
    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.
    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.
    source --------------------- Executes a file containing a list of delve commands
    sources -------------------- Print list of source files.
    types ---------------------- Print list of types

Type help followed by a command for full documentation.

接下來我們將以下面代碼作爲示例演示如何dlv進行調試。

package main

import "fmt"

func main() {
	fmt.Println("go")
}

設置斷點

當我們使用 dlv debug main.go 命令進行 dlv 調試之後，我們可以設置斷點。

(dlv) b main.main # 在main函數處設置斷點
Breakpoint 1 set at 0x4adf8f for main.main() ./main.go:5

繼續執行

設置斷點之後，我們可以通過 continue 命令，可以簡寫成 c ，繼續執行到我們設置的斷點處。

(dlv) c
> main.main() ./main.go:5 (hits goroutine(1):1 total:1) (PC: 0x4adf8f)
     1:	package main
     2:
     3:	import "fmt"
     4:
=>   5:	func main() {
     6:		fmt.Println("go")
     7:	}

注意不同於 GDB 需要執行 run 命令啓動應用之後，才能執行 continue 命令。而 dlv 在進入調試界面之後，已經指向程序的入口地址處，可以直接執行 continue 命令

執行下一條指令

我們可以通過next命令，可以簡寫成n，來執行下一行源碼。同 GDB 一樣，next 命令是 Step over 操作，遇到函數時不會進入函數內部一行行代碼執行，而是直接執行函數，然後跳過到函數下面的一行代碼。

(dlv) n
go
> main.main() ./main.go:7 (PC: 0x4adfff)
     2:
     3:	import "fmt"
     4:
     5:	func main() {
     6:		fmt.Println("go")
=>   7:	}

打印棧信息

通過 stack 命令，我們可以查看函數棧信息：

(dlv) stack
0  0x00000000004adfff in main.main
   at ./main.go:7
1  0x0000000000436be8 in runtime.main
   at /usr/lib/go/src/runtime/proc.go:203
2  0x0000000000464621 in runtime.goexit
   at /usr/lib/go/src/runtime/asm_amd64.s:1373

打印gorountine信息

通過goroutines命令，可以簡寫成grs，我們可以查看所有 goroutine：

(dlv) goroutines
* Goroutine 1 - User: ./main.go:7 main.main (0x4adfff) (thread 14358)
  Goroutine 2 - User: /usr/lib/go/src/runtime/proc.go:305 runtime.gopark (0x436f9b)
  Goroutine 3 - User: /usr/lib/go/src/runtime/proc.go:305 runtime.gopark (0x436f9b)
  Goroutine 4 - User: /usr/lib/go/src/runtime/proc.go:305 runtime.gopark (0x436f9b)
  Goroutine 5 - User: /usr/lib/go/src/runtime/mfinal.go:161 runtime.runfinq (0x418f80)
[5 goroutines]

goroutine 命令，可以簡寫成 gr，用來顯示當前 goroutine 信息：

(dlv) goroutine
Thread 14358 at ./main.go:7
Goroutine 1:
	Runtime: ./main.go:7 main.main (0x4adfff)
	User: ./main.go:7 main.main (0x4adfff)
	Go: /usr/lib/go/src/runtime/asm_amd64.s:220 runtime.rt0_go (0x462594)
	Start: /usr/lib/go/src/runtime/proc.go:113 runtime.main (0x436a20)

查看彙編代碼

通過 disassemble 命令，可以簡寫成 disass ，我們可以查看彙編代碼：

(dlv) disass
TEXT main.main(SB) /tmp/dlv/main.go
	main.go:5		0x4adf80	64488b0c25f8ffffff	mov rcx, qword ptr fs:[0xfffffff8]
	main.go:5		0x4adf89	483b6110		cmp rsp, qword ptr [rcx+0x10]
	main.go:5		0x4adf8d	767a			jbe 0x4ae009
	main.go:5		0x4adf8f*	4883ec68		sub rsp, 0x68
	main.go:5		0x4adf93	48896c2460		mov qword ptr [rsp+0x60], rbp
	main.go:5		0x4adf98	488d6c2460		lea rbp, ptr [rsp+0x60]
	main.go:6		0x4adf9d	0f57c0			xorps xmm0, xmm0
	main.go:6		0x4adfa0	0f11442438		movups xmmword ptr [rsp+0x38], xmm0
	main.go:6		0x4adfa5	488d442438		lea rax, ptr [rsp+0x38]
	main.go:6		0x4adfaa	4889442430		mov qword ptr [rsp+0x30], rax
	main.go:6		0x4adfaf	8400			test byte ptr [rax], al
	main.go:6		0x4adfb1	488d0d28ed0000		lea rcx, ptr [rip+0xed28]
	main.go:6		0x4adfb8	48894c2438		mov qword ptr [rsp+0x38], rcx
	main.go:6		0x4adfbd	488d0dcce10300		lea rcx, ptr [rip+0x3e1cc]
	main.go:6		0x4adfc4	48894c2440		mov qword ptr [rsp+0x40], rcx
	main.go:6		0x4adfc9	8400			test byte ptr [rax], al
	main.go:6		0x4adfcb	eb00			jmp 0x4adfcd
	main.go:6		0x4adfcd	4889442448		mov qword ptr [rsp+0x48], rax
	main.go:6		0x4adfd2	48c744245001000000	mov qword ptr [rsp+0x50], 0x1
	main.go:6		0x4adfdb	48c744245801000000	mov qword ptr [rsp+0x58], 0x1
	main.go:6		0x4adfe4	48890424		mov qword ptr [rsp], rax
	main.go:6		0x4adfe8	48c744240801000000	mov qword ptr [rsp+0x8], 0x1
	main.go:6		0x4adff1	48c744241001000000	mov qword ptr [rsp+0x10], 0x1
	main.go:6		0x4adffa	e811a1ffff		call $fmt.Println
=>	main.go:7		0x4adfff	488b6c2460		mov rbp, qword ptr [rsp+0x60]
	main.go:7		0x4ae004	4883c468		add rsp, 0x68
	main.go:7		0x4ae008	c3			ret
	main.go:5		0x4ae009	e8e247fbff		call $runtime.morestack_noctxt
	<autogenerated>:1	0x4ae00e	e96dffffff		jmp $main.main

dlv 默認顯示的是 intel 風格彙編代碼，我們可以通過 config 命令設置 gnu 或者 go 風格代碼：

(dlv) config disassemble-flavor go

這種方式更改的配置只會對此次調試有效，若保證下次調試一樣有效，我們需要將其配置到配置文件中。dlv 默認配置文件是 HOME/.config/dlv/config.yml。我們只需要在配置文件加入以下內容：

disassemble-flavor: go

  1. https://github.com/go-delve/delve ↩