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Lua之sethook学习

2015-06-17 00:27 302 查看

debug.sethook ([thread,] hook, mask [, count])

Sets the given function as a hook.The string

mask

and the number

count

describewhen the hook will be called.The string mask may have the following characters,with the given meaning:

"c"
: The hook is called every time Lua calls a function; 当函数被调用的时候触发，且在函数获得参数之前调用;

"r"
: The hook is called every time Lua returns from a function; 当函数返回之前触发hook,且不能在此时获得函数的返回值;

"l"
: The hook is called every time Lua enters a new line of code. 当执行到某一行代码之前触发hook

With a

count

different from zero,the hook is called after every

count

instructions.

When called without arguments,debug.sethook turns off the hook.

When the hook is called, its first parameter is a stringdescribing the event that has triggered its call:

"call"

"return"

(or

"tail return"

"line"

, and

"count"

.For line events,the hook also gets the new line number as its second parameter.Inside a hook,you can call

getinfo

with level 2 to get more information aboutthe running function(level 0 is the

getinfo

function,and
level 1 is the hook function),unless the event is

"tail return"

.In this case, Lua is only simulating the return,and a call to

getinfo

will return invalid data.

debug.getinfo(n)

n = 0 : 表示getinfo本身;

n = 1: 表示hook函数;

n = 2: 表示当前正在运行的函数;

debug.sethook(

optional thread,

hook function,

hook mask , -- string with "c" and/or "r" and/or "l"

optional instruction count) --[b]instruction指令行统计[/b]

下面举个例子，如何使用sethook来定位出错的代码在哪一行:

function test1()
c = nil
a = 1
b = a + 3
print(b)
print(c.x)
end

function test2()
c = {}
table.insert(c,1)
print("table size is : ".. #c)
end

function hook()
print(debug.traceback())
end
debug.sethook(hook,"l")

test1()

输出堆信息如下:

>lua -e "io.stdout:setvbuf 'no'" "test.lua"
stack traceback:
test.lua:17: in function <test.lua:16>
test.lua:21: in main chunk
[C]: ?
stack traceback:
test.lua:17: in function <test.lua:16>
test.lua:3: in function 'test1'
test.lua:21: in main chunk
[C]: ?
stack traceback:
test.lua:17: in function <test.lua:16>
test.lua:4: in function 'test1'
test.lua:21: in main chunk
[C]: ?
stack traceback:
test.lua:17: in function <test.lua:16>
test.lua:5: in function 'test1'
test.lua:21: in main chunk
[C]: ?
stack traceback:
test.lua:17: in function <test.lua:16>
test.lua:6: in function 'test1'
test.lua:21: in main chunk
[C]: ?
4
stack traceback:
test.lua:17: in function <test.lua:16>
test.lua:7: in function 'test1'
test.lua:21: in main chunk
[C]: ?
lua: test.lua:7: attempt to index global 'c' (a nil value)
stack traceback:
test.lua:7: in function 'test1'
test.lua:21: in main chunk
[C]: ?
>Exit code: 1

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