delve：Golang的最佳调试工具

推荐使用Golang原生调试器delve，gdb不能切换goroutine。

推荐文章Golang程序调试工具介绍(gdb vs dlv)
，分析得很棒！ gdb只能切换thread，而不能切换goroutine，将dlv切换goroutine、查看变量的过程摘抄如下：

(dlv) goroutine 6
Switched from 1 to 6 (thread 9022)

在此基础上，执行bt，则可以看到当前goroutine的调用栈情况

(dlv) bt
 0  0x0000000000454730 in runtime.systemstack_switch
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/runtime/asm_amd64.s:245
 1  0x000000000040f700 in runtime.mallocgc
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/runtime/malloc.go:643
 2  0x000000000040fc43 in runtime.rawmem
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/runtime/malloc.go:809
 3  0x000000000043c2a5 in runtime.growslice
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/runtime/slice.go:95
 4  0x000000000043c015 in runtime.growslice_n
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/runtime/slice.go:44
 5  0x0000000000459545 in fmt.(*fmt).padString
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/format.go:130
 6  0x000000000045a13f in fmt.(*fmt).fmt_s
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/format.go:322
 7  0x000000000045e905 in fmt.(*pp).fmtString
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/print.go:518
 8  0x000000000046200f in fmt.(*pp).printArg
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/print.go:797
 9  0x0000000000468a8d in fmt.(*pp).doPrintf
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/print.go:1238
10  0x000000000045c654 in fmt.Fprintf
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/print.go:188

此时输出了10层调用栈，但似乎最原始的我自身程序dbgTest.go的调用栈没有输出， 可以通过bt加depth参数，设定bt的输出深度，进而找到我们自己的调用栈，例如bt 13

(dlv) bt 13
...
10  0x000000000045c654 in fmt.Fprintf
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/print.go:188
11  0x000000000045c74b in fmt.Printf
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/fmt/print.go:197
12  0x000000000045846f in GoWorks/GoDbg/mylib.RunFunc2
    at ./mylib/dbgTest.go:50
13  0x0000000000456df0 in runtime.goexit
    at /home/lday/Tools/Dev_Tools/Go_Tools/go_1_6_2/src/runtime/asm_amd64.s:1998

我们看到，我们自己dbgTest.go的调用栈在第12层。当前goroutine已经不再我们自己的调用栈上，而是进入到系统函数的调用中，在这种情况下，使用gdb进行调试时，我们发现，此时我们没有很好的方法能够输出我们需要的调用栈变量信息。dlv可以!此时只需简单的通过frame x cmd就可以输出我们想要的调用栈信息了

(dlv) frame 12 ls
    45:        time.Sleep(10 * time.Second)
    46:        waiter.Done()
    47:    }
    48:    
    49:    func RunFunc2(variable string, waiter *sync.WaitGroup) {
=>  50:        fmt.Printf("var2:%v\n", variable)
    51:        time.Sleep(10 * time.Second)
    52:        waiter.Done()
    53:    }
    54:    
    55:    func RunFunc3(pVariable *[]int, waiter *sync.WaitGroup) {
(dlv) frame 12 print variable 
"golang dbg test"
(dlv) frame 12 print waiter
*sync.WaitGroup {
    state1: [12]uint8 [0,0,0,0,2,0,0,0,0,0,0,0],
    sema: 0,}

dlv还可以attach到一个程序进行调试。

参考：
Getting started with Delve
Debugging Go Code with GDB 官方
Using the gdb debugger with Go