调试另一个选择器，而使用lldb单步执行Xcode [英] Debug another selector while single stepping in Xcode using lldb

问题描述

我的代码停在（lldb）提示符处的断点处。我可以发送消息对象并将其值显示在控制台上。

 （lldb）p [self computePI] 
浮点数）$ 1 = 3.0 
  

哇！这时出错了我希望能够进入computePI作为一个捷径，以确定哪些变量被弄乱了。但是，如果我在该选择器上放置了一个断点，然后再次尝试：

 （lldb）p [self computePI] 
错误：执行中断，原因：断点5.1。 
执行之前，进程已返回到状态。 
  

在这一点上我可以以某种方式进入computePI，这将是一个实时的保护。这是可能吗？我一直在看 http://lldb.llvm.org ，并没有看到任何东西。感谢您的帮助。

更新：根据Jason Molenda的回答，我使用以下便利的别名更新了我的〜/ .lldbinit文件： p>

 命令别名nup expr -u 0  -  
命令别名nupo expr -u 0 -o  -  
这可以让我使用nup（代替p）和nupo（代替po）。 
解决方案
  p 命令真的是一个 expr  -  。  expr 的选项之一是 -u 或  - 解除错误  - 在这种情况下，断点被视为一个错误（它可能被认为是一个错误 - 本身就是有争议的，有一些使用情况，它不会直观地表现为这样的行为。 ）
 
 
 
无论如何，您应该可以执行
 （lldb ）expr -u false  -  [self computePI] 
  
，它将在断点处停止。   -  这里指向 expr ，它应该停止执行选项分析，之后的所有内容都是要评估的表达式。 
 
I am in my code stopped at a breakpoint at the (lldb) prompt.  I can message objects and get their value printed on the console.
(lldb) p [self computePI]
(float) $1 = 3.0
Whoa!  Something is wrong at this point.  I would like to be able to step into computePI as a shortcut to figuring out which variables are messed up.  However, if I put a breakpoint on that selector and try again I get:
(lldb) p [self computePI]
error: Execution was interrupted, reason: breakpoint 5.1.
The process has been returned to the state before execution.
It would be a real time saver if I could somehow step into computePI at this point.  Is this possible or not?  I have been looking at http://lldb.llvm.org and haven't seen anything.  Thanks for your help.

UPDATE:  Based on Jason Molenda's answer I updated my ~/.lldbinit file with the following handy aliases:
command alias nup expr -u 0 -- 
command alias nupo expr -u 0 -o --
That lets me use nup (in place of p) and nupo (in place of po).  
解决方案
The p command is really an alias to expr --.  One of the options to expr is -u or --unwind-on-error -- in this case a breakpoint is treated as an "error" (which might be considered a bug in and of itself - it's debatable, there are use cases where it would be nonintuitive for this to behave differently.)

Anyway, you should be able to do
(lldb) expr -u false -- [self computePI]
and it will stop at the breakpoint.  The -- here indicates to expr that it should stop doing option parsing and everything after that is an expression to evaluate.

                        
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