Xcode的控制台调试命令

XCode4.0以后，编译器换成了LLVM 编译器 2.0

与以前相比，更加强大：
1.LLVM 编译器是下一带开源的编译技术.完全支持C, Objective-C, 和 C++.
2.LLVM 速度比 GCC快两倍,建立的程序也会运行的更快. 因为它更好的利用现代的芯片的结构.
3.LLVM和Xcode 4完全的整合在一起.包括关键字高亮,代码完整性等全都是由LLVM语法分析器来分析的. 这样可以在编辑的时候就可以很好的了解你的代码.

编译器进化之后，控制台调试命令前缀，也由原来的gdb更改成了lldb，所以当你看到控制台没有gdb而出现lldb的时候，不用惊慌，因为我们以前常用的调试命令依然可以使用：

使用前提：

1.既然是调试命令，理所当然的，程序模式应该选择Debug模式。

2.在Debug模式下，如果你的程序在运行中崩溃（Crash）掉，那么恭喜你，使用lldb调试的机会来了。

符合以上两个条件之后，控制台（即日志输出窗口All Output）会自动打出一个（lldb）命令，你在其后输入bt，回车。

恭喜你，这时Xcode会自动输出最后的一次调用堆栈。如下：

当然还有其他的命令（和gdb命令通用）：

Debugger commands:

apropos -- Find a list of debugger commands related to a particular

word/subject.

breakpoint -- A set of commands for operating on breakpoints. Also see

_regexp-break.

command -- A set of commands for managing or customizing the

debugger commands.

disassemble -- Disassemble bytes in the current function, or elsewhere

in the executable program as specified by the user.

expression -- Evaluate an expression (ObjC++ or Swift) in the current

program context, using user defined variables and

variables currently in scope.

frame -- A set of commands for operating on the current thread's

frames.

gdb-remote -- Connect to a remote GDB server. If no hostname is

provided, localhost is assumed.

gui -- Switch into the curses based GUI mode.

help -- Show a list of all debugger commands, or give details

about specific commands.

kdp-remote -- Connect to a remote KDP server. udp port 41139 is the

default port number.

log -- A set of commands for operating on logs.

memory -- A set of commands for operating on memory.

platform -- A set of commands to manage and create platforms.

plugin -- A set of commands for managing or customizing plugin

commands.

process -- A set of commands for operating on a process.

quit -- Quit out of the LLDB debugger.

register -- A set of commands to access thread registers.

script -- Pass an expression to the script interpreter for

evaluation and return the results. Drop into the

interactive interpreter if no expression is given.

settings -- A set of commands for manipulating internal settable

debugger variables.

source -- A set of commands for accessing source file information

target -- A set of commands for operating on debugger targets.

thread -- A set of commands for operating on one or more threads

within a running process.

type -- A set of commands for operating on the type system

version -- Show version of LLDB debugger.

watchpoint -- A set of commands for operating on watchpoints.

Current command abbreviations (type 'help command alias' for more info):

add-dsym -- ('target symbols add') Add a debug symbol file to one of the

target's current modules by specifying a path to a debug symbols

file, or using the options to specify a module to download

symbols for.

attach -- ('_regexp-attach') Attach to a process id if in decimal,

otherwise treat the argument as a process name to attach to.

b -- ('_regexp-break') Set a breakpoint using a regular expression

to specify the location, where <linenum> is in decimal and

<address> is in hex.

bt -- ('_regexp-bt') Show a backtrace. An optional argument is

accepted; if that argument is a number, it specifies the number

of frames to display. If that argument is 'all', full

backtraces of all threads are displayed.

c -- ('process continue') Continue execution of all threads in the

current process.

call -- ('expression --') Evaluate an expression (ObjC++ or Swift) in

the current program context, using user defined variables and

variables currently in scope.

continue -- ('process continue') Continue execution of all threads in the

current process.

detach -- ('process detach') Detach from the current process being

debugged.

di -- ('disassemble') Disassemble bytes in the current function, or

elsewhere in the executable program as specified by the user.

dis -- ('disassemble') Disassemble bytes in the current function, or

elsewhere in the executable program as specified by the user.

display -- ('_regexp-display') Add an expression evaluation stop-hook.

down -- ('_regexp-down') Go down "n" frames in the stack (1 frame by

default).

env -- ('_regexp-env') Implements a shortcut to viewing and setting

environment variables.

exit -- ('quit') Quit out of the LLDB debugger.

f -- ('frame select') Select a frame by index from within the

current thread and make it the current frame.

file -- ('target create') Create a target using the argument as the

main executable.

finish -- ('thread step-out') Finish executing the function of the

currently selected frame and return to its call site in

specified thread (current thread, if none specified).

image -- ('target modules') A set of commands for accessing information

for one or more target modules.

j -- ('_regexp-jump') Sets the program counter to a new address.

jump -- ('_regexp-jump') Sets the program counter to a new address.

kill -- ('process kill') Terminate the current process being debugged.

l -- ('_regexp-list') Implements the GDB 'list' command in all of

its forms except FILE:FUNCTION and maps them to the appropriate

'source list' commands.

list -- ('_regexp-list') Implements the GDB 'list' command in all of

its forms except FILE:FUNCTION and maps them to the appropriate

'source list' commands.

n -- ('thread step-over') Source level single step in specified

thread (current thread, if none specified), stepping over calls.

next -- ('thread step-over') Source level single step in specified

thread (current thread, if none specified), stepping over calls.

nexti -- ('thread step-inst-over') Single step one instruction in

specified thread (current thread, if none specified), stepping

over calls.

ni -- ('thread step-inst-over') Single step one instruction in

specified thread (current thread, if none specified), stepping

over calls.

p -- ('expression --') Evaluate an expression (ObjC++ or Swift) in

the current program context, using user defined variables and

variables currently in scope.

po -- ('expression -O -- ') Evaluate an expression (ObjC++ or Swift)

in the current program context, using user defined variables and

variables currently in scope.

print -- ('expression --') Evaluate an expression (ObjC++ or Swift) in

the current program context, using user defined variables and

variables currently in scope.

q -- ('quit') Quit out of the LLDB debugger.

r -- ('process launch -c /bin/sh --') Launch the executable in the

debugger.

rbreak -- ('breakpoint set -r %1') Sets a breakpoint or set of

breakpoints in the executable.

repl -- ('expression -r -- ') Evaluate an expression (ObjC++ or Swift)

in the current program context, using user defined variables and

variables currently in scope.

run -- ('process launch -c /bin/sh --') Launch the executable in the

debugger.

s -- ('thread step-in') Source level single step in specified thread

(current thread, if none specified).

si -- ('thread step-inst') Single step one instruction in specified

thread (current thread, if none specified).

step -- ('thread step-in') Source level single step in specified thread

(current thread, if none specified).

stepi -- ('thread step-inst') Single step one instruction in specified

thread (current thread, if none specified).

t -- ('thread select') Select a thread as the currently active

thread.

tbreak -- ('_regexp-tbreak') Set a one shot breakpoint using a regular

expression to specify the location, where <linenum> is in

decimal and <address> is in hex.

undisplay -- ('_regexp-undisplay') Remove an expression evaluation

stop-hook.

up -- ('_regexp-up') Go up "n" frames in the stack (1 frame by

default).

x -- ('memory read') Read from the memory of the process being

debugged.

For more information on any command, type 'help <command-name>'.

使用lldb调试工具，实在是查找crash的一大利器啊，很是方便！