如何在Xcode 6中的异常断点上打印异常？

Question

我的应用程序正在崩溃,似乎它被异常断点捕获(这是有道理的),但我无法找到崩溃的原因.

这是我尝试过的:

• po $eax
• po $rax
• po $r0
• po *(id *)($esp + 4)

对于上述所有尝试,我收到以下错误:

error: use of undeclared identifier '$<register name>' error: 1 errors parsing expression

我也找到了这个LLDB命令指南,但没有找到任何有用的东西(有点令人困惑,你不知道你在寻找什么).

如何打印坠机原因？

我正在运行iOS 8,lldb和Xcode 6.

编辑

现在我明白为什么找不到这些寄存器.这是我跑步时得到的register read:

General Purpose Registers:
x0 = 0x0000000000000001
x1 = 0x0000000000000000
x2 = 0x0000000000000000
x3 = 0x0000000195531a74  libsystem_malloc.dylib`nano_free_definite_size
x4 = 0x0000000000000000
x5 = 0x0000000000000000
x6 = 0x676e697274534643
x7 = 0x0000000000000f80
x8 = 0x00000001569d5a10
x9 = 0x0000000000000000
x10 = 0x000001a574056051
x11 = 0x0000000000000001
x12 = 0x000000000000003d
x13 = 0x0000000000000000
x14 = 0x0000000000000001
x15 = 0x0000000000000052
x16 = 0x0000000194d6e510  libobjc.A.dylib`object_setClass
x17 = 0x0000000000000000
x18 = 0x0000000000000000
x19 = 0x00000001702823f0
x20 = 0x0000000174038eaa
x21 = 0x000000019130a778  "release"
x22 = 0x0000000000000000
x23 = 0x0000000174246d20
x24 = 0x0000000174038ea0
x25 = 0x00000001895d22fa  "forwardingTargetForSelector:"
x26 = 0x00000001745186a0
x27 = 0x0000000000000000
x28 = 0x00000000a40008ff
fp = 0x0000000105757720
lr = 0x000000018462a440  CoreFoundation`___forwarding___ + 968
sp = 0x00000001057576c0
pc = 0x000000018462a440  CoreFoundation`___forwarding___ + 968
cpsr = 0x20000000

正如您所看到的那样,使用的寄存器不包含我之前尝试过的任何寄存器.但是,我仍然无法找到例外.

Answer 1

你应该只输入：

po $arg1

有关更多信息，请查看：如何用断点导航器中的定义替换 NSUncaughtExceptionHandler？