除了 GDB，还可以使用 LLDB debug go code
熟练调试工具是程序员的必备技能，lldb 的发展势头，大有取缔 gdb 的趋势，因此需要把 lldb 加入到自己的工具箱里。
LLDB 命令
LLDB 的所有命令都遵从以下格式：
<noun> <verb> [-options [option-value]] [argument [argument...]]
对于常用命令，可设置别名，降低输入负担。(可通过别名设置和 GDB 相同的语法，降低记忆负担)。
常用命令集
go build -gcflags "-N -l" -o test test.go 关闭编译优化
b test.go:10 设置断点，如果项目中存在同名文件，会根据行号对应的内容选择一个，或者两个都选
run 运行到断点处
n 运行到下一行
ni 回到当前运行的代码片段
p varname 打印变量值
frame variable 打印当然 frame 中的所有变量
r 重新运行程序
LLDB 练习
以下通过一个例子程序的调试，了解 LLDB 的基本用法。待调试程序如下：
package main
import (
"fmt"
"time"
)
func counting(c chan<- int) {
for i := 0; i < 10; i++ {
time.Sleep(1 * time.Second)
c <- i
}
close(c)
}
func main() {
msg := "Starting main"
fmt.Println(msg)
bus := make(chan int)
msg = "starting a gorountie"
go counting(bus)
for count := range bus {
fmt.Println("count:", count)
}
}
编译源码，使用 -gcflags "-N -l" 参数关闭编译器代码优化。
$ go build -gcflags "-N -l" -o test test.go
通过 lldb 命令启动调试:
可通过 run (r) 运行整个程序，如下所示，和我们在终端运行命令结果一致。
(lldb) run
Process 3242 launched: '/Users/zdd/Projects/Go/src/github.com/zddhub/test/test' (x86_64)
Starting main
count: 0
count: 1
count: 2
count: 3
count: 4
count: 5
count: 6
count: 7
count: 8
count: 9
Process 3242 exited with status = 0 (0x00000000)
(lldb)
断点命令
(lldb) breakpoint set --file test.go --line 17
(lldb) b test.go:17 #简写
为程序设置断点并查看断点，
(lldb) b test.go:10
Breakpoint 1: where = test`main.counting + 43 at test.go:10, address = 0x000000000000206b
(lldb) b test.go:23
Breakpoint 2: where = test`main.main + 514 at test.go:23, address = 0x00000000000022f2
(lldb) br list
Current breakpoints:
1: file = 'test.go', line = 10, locations = 1
1.1: where = test`main.counting + 43 at test.go:10, address = test[0x000000000000206b], unresolved, hit count = 0
2: file = 'test.go', line = 23, locations = 1
2.1: where = test`main.main + 514 at test.go:23, address = test[0x00000000000022f2], unresolved, hit count = 0
运行一次到第一个断点
(lldb) run
Process 3302 launched: '/Users/zdd/Projects/Go/src/github.com/zddhub/test/test' (x86_64)
Starting main
Process 3302 stopped
* thread #1: tid = 0x11ca78, 0x000000000000206b test`main.counting(c=0x000000c820070000) + 43 at test.go:10, stop reason = breakpoint 1.1
frame #0: 0x000000000000206b test`main.counting(c=0x000000c820070000) + 43 at test.go:10
7
8 func counting(c chan<- int) {
9 for i := 0; i < 10; i++ {
-> 10 time.Sleep(1 * time.Second)
11 c <- i
12 }
13 close(c)
(lldb)
之后，通过 c 或 n 继续运行程序。
查看变量的值:
* thread #10, stop reason = breakpoint 3.1
frame #0: 0x0000000001093939 xx`main.counting(c=0x000000c420076060) at xx.go:10
7
8 func counting(c chan<- int) {
9 for i := 0; i < 10; i++ {
-> 10 time.Sleep(1 * time.Second)
11 c <- i
12 }
13 close(c)
(lldb) p i
(int) i = 0
(lldb) p c
(chan<- int) c = 0x000000c420076060
查看当前 frame 中的所有变量
(lldb) frame variable
(chan<- int) c = 0x000000c420076060
(int) i = 0
([]*runtime.g) runtime.allgs = (len 5, cap 8) {
[0] = 0x000000c420000180
[1] = 0x000000c420000600
[2] = 0x000000c420000a80
[3] = 0x000000c420000f00
[4] = 0x000000c420001080
}
命令 ni 回到当前断点所在的代码片段
(lldb) ni
Process 35396 stopped
* thread #10, stop reason = instruction step over
frame #0: 0x0000000001093941 xx`main.counting(c=0x000000c420076060) at xx.go:10
7
8 func counting(c chan<- int) {
9 for i := 0; i < 10; i++ {
-> 10 time.Sleep(1 * time.Second)
11 c <- i
12 }
13 close(c)
watch 变量的值：
(lldb) watch set var i
Watchpoint created: Watchpoint 1: addr = 0xc820026798 size = 8 state = enabled type = w
watchpoint spec = 'i'
new value: 0
(lldb) c
Process 3302 resuming
Watchpoint 1 hit:
old value: 0
new value: 1
Process 3302 stopped
* thread #1: tid = 0x11ca78, 0x00000000000020be test`main.counting(c=0x000000c820070000) + 126 at test.go:9, stop reason = watchpoint 1
frame #0: 0x00000000000020be test`main.counting(c=0x000000c820070000) + 126 at test.go:9
6 )
7
8 func counting(c chan<- int) {
-> 9 for i := 0; i < 10; i++ {
10 time.Sleep(1 * time.Second)
11 c <- i
12 }
(lldb)
列举所有观测变量：
(lldb) watch list -v
Number of supported hardware watchpoints: 4
Current watchpoints:
Watchpoint 1: addr = 0xc820026798 size = 8 state = enabled type = w
watchpoint spec = 'i'
old value: 0
new value: 1
hw_index = 0 hit_count = 1 ignore_count = 0
Watchpoint 2: addr = 0xc8200267b8 size = 8 state = enabled type = w
watchpoint spec = 'c'
new value: 0x000000c820070000
hw_index = -1 hit_count = 0 ignore_count = 0
(lldb)
(lldb) fr v
(long) i = 2
(chan<- int) c = 0x000000c820070000
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