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diff --git a/www/tutorial.html b/www/tutorial.html new file mode 100755 index 0000000000000..d3b7ec89a5ada --- /dev/null +++ b/www/tutorial.html @@ -0,0 +1,726 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> +<link href="style.css" rel="stylesheet" type="text/css" /> +<title>LLDB Tutorial</title> +</head> + +<body> + <div class="www_title"> + The <strong>LLDB</strong> Debugger + </div> + +<div id="container"> + <div id="content"> + <!--#include virtual="sidebar.incl"--> + <div id="middle"> + <div class="post"> + <h1 class ="postheader">Getting Started</h1> + <div class="postcontent"> + + <p>Here's a short precis of how to run lldb if you are familiar with the gdb command set. + We will start with some details on lldb command structure and syntax to help orient you.</p> + + </div> + <div class="postfooter"></div> + + <div class="post"> + <h1 class ="postheader">Command Structure</h1> + <div class="postcontent"> + + <p>Unlike gdb's command set, which is rather free-form, we tried to make + the lldb command syntax fairly structured. The commands are all of the + form:</p> + + <code color=#ff0000> + <noun> <verb> [-options [option-value]] [argument [argument...]] + </code> + + <p>The command line parsing is done before command execution, so it is + uniform across all the commands. The command syntax for basic commands is very simple, + arguments, options and option values are all white-space + separated, and double-quotes are used to protect white-spaces in an argument. + If you need to put a backslash or double-quote character + in an argument you back-slash it in the argument. That makes the + command syntax more regular, but it also means you may have to + quote some arguments in lldb that you wouldn't in gdb.</p> + + <p>Options can be placed anywhere on the command line, but if the arguments + begin with a "<code>-</code>" then you have to tell lldb that you're done with options + for the current command by adding an option termination: "<code>--</code>" + So for instance if you want to launch a process and give the "process launch" command + the "<code>--stop-at-entry</code>" option, yet you want the + process you are about to launch to be launched with the arguments + "<code>-program_arg value</code>", you would type:</p> + + <code> + (lldb) process launch --stop-at-entry -- -program_arg value + </code> + + <p>We also tried to reduce the number of special purpose argument + parsers, which sometimes forces the user to be a little more explicit + about stating their intentions. The first instance you'll note of + this is the breakpoint command. In gdb, to set a breakpoint, you + might enter</p> + + <code> + (gdb) break foo.c:12 + </code> + <p>to break at line 12 of foo.c, and:</p> + <code> + (gdb) break foo + </code> + + <p>to break at the function <code>foo</code>. As time went on, the parser that tells <code>foo.c:12</code> + from <code>foo</code> from <code>foo.c::foo</code> (which means the function foo in the file + foo.c) got more and more complex and bizarre, and especially in C++ + there are times where there's really no way to specify the function + you want to break on. The lldb commands are more verbose but also more precise + and allow for intelligent auto completion. + + <p>To set the same file and line breakpoint in LLDB you can enter either of:</p> + + <code> + (lldb) breakpoint set --file foo.c --line 12 + <br>(lldb) breakpoint set -f foo.c -l 12 + </code> + + <p>To set a breakpoint on a function named <code>foo</code> in LLDB you can enter either of:</p> + + <code> + (lldb) breakpoint set --name foo + <br>(lldb) breakpoint set -n foo + </code> + + <p>You can use the --name option multiple times to make a breakpoint on a set of functions as well. This is convenient + since it allows you to set commmon conditions or commands without having to specify them multiple times:</p> + + <code> + (lldb) breakpoint set --name foo --name bar + </code> + + <p>Setting breakpoints by name is even more specialized in LLDB as you can specify + that you want to set a breakpoint at a function by method name. To set a breakpoint + on all C++ methods named <code>foo</code> you can enter either of:</p> + + <code> + (lldb) breakpoint set --method foo + <br>(lldb) breakpoint set -M foo + </code> + + <p>To set a breakpoint Objective C selectors named <code>alignLeftEdges:</code> you can enter either of:</p> + + <code> + (lldb) breakpoint set --selector alignLeftEdges: + <br>(lldb) breakpoint set -S alignLeftEdges: + </code> + + <p>You can limit any breakpoints to a specific executable image by using + the "<code>--shlib <path></code>" ("<code>-s <path></code>" for short):</p> + + <code> + (lldb) breakpoint set --shlib foo.dylib --name foo + <br>(lldb) breakpoint set -s foo.dylib -n foo + </code> + + <p>The <code>--shlib</code> option can also be repeated to specify several shared libraries.</p> + + <p>Suggestions on more interesting primitives of this sort are also very welcome.</p> + + <p>Just like gdb, the lldb command interpreter does a shortest unique + string match on command names, so the following two commands will + both execute the same command:</p> + + <code> + (lldb) breakpoint set -n "-[SKTGraphicView alignLeftEdges:]" + <br>(lldb) br s -n "-[SKTGraphicView alignLeftEdges:]" + </code> + + <p>lldb also supports command completion for source file names, symbol + names, file names, etc. Completion is initiated by a hitting a <b>TAB</b>. + Individual options in a command can have different completers, so for + instance the "<code>--file <path></code>" option in "breakpoint" completes to source files, the + "<code>--shlib <path></code>" option to currently loaded shared libraries, etc. We can even do + things like if you specify "<code>--shlib <path></code>", and are completing on "<code>--file <path></code>", we will only + list source files in the shared library specified by "<code>--shlib <path></code>".</p> + + <p>The individual commands are pretty extensively documented. You can + use the <code>help</code> command to get an overview of which commands are + available or to obtain details about specific commands. There is also an + <code>apropos</code> command that will search the help text for all commands + for a particular word and dump a summary help string for each matching + command.</p> + + <p>Finally, there is a mechanism to construct aliases for commonly used + commands. So for instance if you get annoyed typing:</p> + + <code> + (lldb) breakpoint set --file foo.c --line 12 + </code> + + <p>you can do:</p> + + <code> + (lldb) command alias bfl breakpoint set -f %1 -l %2 + <br>(lldb) bfl foo.c 12 + </code> + + <p>We have added a few aliases for commonly used commands (e.g. "step", + "next" and "continue") but we haven't tried to be exhaustive because + in our experience it is more convenient to make the basic commands + unique down to a letter or two, and then learn these sequences than + to fill the namespace with lots of aliases, and then have to type them + all the way out.</p> + + <p>However, users are free to customize lldb's command set however they + like, and since lldb reads the file ~/.lldbinit at startup, you can + store all your aliases there and they will be generally available to + you. Your aliases are also documented in the help command so you can + remind yourself of what you've set up.</p> + + <p> One alias of note that we do include by popular demand is a weak emulator + of gdb's "break" command. It doesn't try to do everything that gdb's + break command does (for instance, it doesn't handle <code>foo.c::bar</code>. But + it mostly works, and makes the transition easier. Also by popular demand, it + is aliased to <code>b</code>. If you actually want to learn the lldb command + set natively, that means it will get in the way of the rest of the breakpoint + commands. Fortunately, if you don't like one of our aliases, you an easily + get rid of it by running (for example):</p> + + <code> + (lldb) command unalias b + </code> + + <p>I actually also do:</p> + + <code> + (lldb) command alias b breakpoint + </code> + + <p>so I can run the native lldb breakpoint command with just <code>b</code></p> + + <p>The lldb command parser also supports "raw" commands, where, after command options + are stripped off, the rest of the command string is passed uninterpreted to the command. + This is convenient for commands whose arguments might be some complex expression that would + be painful to backslash protect. + For instance the "expression" command is a "raw" command for obvious reasons. The + "help" output for a command will tell you if it is "raw" or not, so you know what to expect. + The one thing you have to watch out for is that since raw commands still can have options, + if your command string has dashes in it, you'll have to indicate these are not option + markers by putting "--" after the command name, but before your command string. + + <p>lldb also has a built-in Python interpreter, which is accessible by + the "script" command. All the functionality of the debugger is + available as classes in the Python interpreter, so the more complex + commands that in gdb you would introduce with the "define" command can + be done by writing Python functions using the lldb-Python library, + then loading the scripts into your running session and accessing them + with the "script" command.</p> + + <p>Having given an overview of lldb's command syntax, we proceed to lay out the stages + of a standard debug session.</p> + + </div> + <div class="postfooter"></div> + + + <div class="post"> + <h1 class ="postheader">Loading a program into lldb</h1> + <div class="postcontent"> + + <p>First we need to set the program to debug. As with gdb, you + can start lldb and specify the file you wish to debug on the command line:</p> + + <code> + $ lldb /Projects/Sketch/build/Debug/Sketch.app + <br>Current executable set to '/Projects/Sketch/build/Debug/Sketch.app' (x86_64). + </code> + + <p>or you can specify it after the fact with the "file" command:</p> + + <code> + $ lldb + <br>(lldb) file /Projects/Sketch/build/Debug/Sketch.app + <br>Current executable set to '/Projects/Sketch/build/Debug/Sketch.app' (x86_64). + </code> + <p> + </div> + <div class="postfooter"></div> + + <div class="post"> + <h1 class ="postheader">Setting breakpoints</h1> + <div class="postcontent"> + + <p>We've discussed how to set breakpoints above. You can use <code>help breakpoint set</code> + to see all the options for breakpoint setting. For instance, we might do:</p> + + <code> + (lldb) breakpoint set --selector alignLeftEdges: + <br>Breakpoint created: 1: name = 'alignLeftEdges:', locations = 1, resolved = 1 + </code> + + <p>You can find out about the breakpoints you've set with:</p> + + <pre><tt>(lldb) breakpoint list +Current breakpoints: +1: name = 'alignLeftEdges:', locations = 1, resolved = 1 + 1.1: where = Sketch`-[SKTGraphicView alignLeftEdges:] + 33 at /Projects/Sketch/SKTGraphicView.m:1405, address = 0x0000000100010d5b, resolved, hit count = 0 +</tt></pre> + + <p>Note that setting a breakpoint creates a <i>logical</i> breakpoint, which could + resolve to one or more <i>locations</i>. For instance, break by selector would + set a breakpoint on all the methods that implement that selector in the classes in + your program. Similarly, a file and line breakpoint might result in multiple + locations if that file and line were inlined in different places in your code.</p> + + <p>The logical breakpoint has an integer id, and it's locations have an + id within their parent breakpoint (the two are joined by a ".", + e.g. 1.1 in the example above.) </p> + + <p>Also the logical breakpoints remain <i>live</i> so that if another shared library + were to be loaded that had another implementation of the + "<code>alignLeftEdges:</code>" selector, the new location would be added to + breakpoint 1 (e.g. a "1.2" breakpoint would be set on the newly loaded + selector).</p> + + <p>The other piece of information in the breakpoint listing is whether the + breakpoint location was <i>resolved</i> or not. A location gets resolved when + the file address it corresponds to gets loaded into the program you are + debugging. For instance if you set a breakpoint in a shared library that + then gets unloaded, that breakpoint location will remain, but it will no + longer be <i>resolved</i>.</p> + + <p>One other thing to note for gdb users is that lldb acts like gdb with:</p> + + <code> + (gdb) set breakpoint pending on + </code> + + <p>That is, lldb will always make a breakpoint from your specification, even + if it couldn't find any locations that match the specification. You can tell + whether the expression was resolved or not by checking the locations field + in "breakpoint list", and we report the breakpoint as "pending" when you + set it so you can tell you've made a typo more easily, if that was indeed + the reason no locations were found:</p> + + <code> + (lldb) breakpoint set --file foo.c --line 12 + <br>Breakpoint created: 2: file ='foo.c', line = 12, locations = 0 (pending) + <br>WARNING: Unable to resolve breakpoint to any actual locations. + </code> + + <p>You can delete, disable, set conditions and ignore counts either on all the + locations generated by your logical breakpoint, or on any one of the particular locations + your specification resolved to. For instance if we wanted to add a command + to print a backtrace when we hit this breakpoint we could do:</p> + + <code> + (lldb) breakpoint command add 1.1 + <br>Enter your debugger command(s). Type 'DONE' to end. + <br>> bt + <br>> DONE + </code> + + <p>By default, the <code> breakpoint command add</code> command takes lldb command line commands. + You can also specify this explicitly by passing the "<code>--command</code>" option. + Use "<code>--script</code>" if you want to implement your breakpoint command using the Python script instead.</p> + + <p>This is an convenient point to bring up another feature of the lldb command help. Do:</p> + + <code> + (lldb) help break command add + <br>Add a set of commands to a breakpoint, to be executed whenever the breakpoint is hit. + <br> + <br>Syntax: breakpoint command add <cmd-options> <breakpt-id> + <br> etc... + </code> + + <p>When you see arguments to commands specified in the Syntax in angle + brackets like <code><breakpt-id></code>, that indicates that + that is some common argument type that you can get further help on from the command system. + So in this case you could do:</p> + + <code> + (lldb) help <breakpt-id> + <br><breakpt-id> -- Breakpoint ID's consist major and minor numbers; the major + <br> etc... + </code> + + </div> + <div class="postfooter"></div> + + <div class="post"> + <h1 class ="postheader">Setting watchpoints</h1> + <div class="postcontent"> + + <p>In addition to breakpoints, you can use <code>help watchpoint</code> + to see all the commands for watchpoint manipulations. For instance, we might do the following to watch + a variable called 'global' for write operation, but only stop if the condition '(global==5)' is true:</p> + + <pre><tt>(lldb) watch set var global +Watchpoint created: Watchpoint 1: addr = 0x100001018 size = 4 state = enabled type = w + declare @ '/Volumes/data/lldb/svn/ToT/test/functionalities/watchpoint/watchpoint_commands/condition/main.cpp:12' +(lldb) watch modify -c '(global==5)' +(lldb) watch list +Current watchpoints: +Watchpoint 1: addr = 0x100001018 size = 4 state = enabled type = w + declare @ '/Volumes/data/lldb/svn/ToT/test/functionalities/watchpoint/watchpoint_commands/condition/main.cpp:12' + condition = '(global==5)' +(lldb) c +Process 15562 resuming +(lldb) about to write to 'global'... +Process 15562 stopped and was programmatically restarted. +Process 15562 stopped and was programmatically restarted. +Process 15562 stopped and was programmatically restarted. +Process 15562 stopped and was programmatically restarted. +Process 15562 stopped +* thread #1: tid = 0x1c03, 0x0000000100000ef5 a.out`modify + 21 at main.cpp:16, stop reason = watchpoint 1 + frame #0: 0x0000000100000ef5 a.out`modify + 21 at main.cpp:16 + 13 + 14 static void modify(int32_t &var) { + 15 ++var; +-> 16 } + 17 + 18 int main(int argc, char** argv) { + 19 int local = 0; +(lldb) bt +* thread #1: tid = 0x1c03, 0x0000000100000ef5 a.out`modify + 21 at main.cpp:16, stop reason = watchpoint 1 + frame #0: 0x0000000100000ef5 a.out`modify + 21 at main.cpp:16 + frame #1: 0x0000000100000eac a.out`main + 108 at main.cpp:25 + frame #2: 0x00007fff8ac9c7e1 libdyld.dylib`start + 1 +(lldb) frame var global +(int32_t) global = 5 +(lldb) watch list -v +Current watchpoints: +Watchpoint 1: addr = 0x100001018 size = 4 state = enabled type = w + declare @ '/Volumes/data/lldb/svn/ToT/test/functionalities/watchpoint/watchpoint_commands/condition/main.cpp:12' + condition = '(global==5)' + hw_index = 0 hit_count = 5 ignore_count = 0 +(lldb) </tt></pre> + </div> + <div class="postfooter"></div> + + <div class="post"> + <h1 class ="postheader">Starting or attaching to your Program</h1> + <div class="postcontent"> + + <p>To launch a program in lldb we use the "<code>process launch</code>" command or + one of its built in aliases:</p> + + <code> + (lldb) process launch + <br>(lldb) run + <br>(lldb) r + </code> + + <p>You can also attach to a process by process ID or process name. + When attaching to a process by name, lldb also supports the "<code>--waitfor</code>" option which waits for the + next process that has that name to show up, and attaches to it</p> + + <code> + (lldb) process attach --pid 123 + <br>(lldb) process attach --name Sketch + <br>(lldb) process attach --name Sketch --waitfor + </code> + + <p>After you launch or attach to a process, your process might stop + somewhere:</p> + <code> + (lldb) process attach -p 12345 + <br>Process 46915 Attaching + <br>Process 46915 Stopped + <br>1 of 3 threads stopped with reasons: + <br>* thread #1: tid = 0x2c03, 0x00007fff85cac76a, where = libSystem.B.dylib`__getdirentries64 + 10, stop reason = signal = SIGSTOP, queue = com.apple.main-thread + </code> + + + <p>Note the line that says "<code>1 of 3 threads stopped with reasons:</code>" and the + lines that follow it. In a multi-threaded environment it is very + common for more than one thread to hit your breakpoint(s) before the + kernel actually returns control to the debugger. In that case, you + will see all the threads that stopped for some interesting reason + listed in the stop message.</p> + + </div> + <div class="postfooter"></div> + + <div class="post"> + <h1 class ="postheader">Controlling your Program</h1> + <div class="postcontent"> + + + <p>After launching, we can continue until we hit our breakpoint. The primitive + commands for process control all exist under the "thread" command:</p> + + <code> + (lldb) thread continue + <br>Resuming thread 0x2c03 in process 46915 + <br>Resuming process 46915 + <br>(lldb) + </code> + + <p>At present you can only operate on one thread at a time, but the + design will ultimately support saying "step over the function in + Thread 1, and step into the function in Thread 2, and continue Thread + 3" etc. When we eventually support keeping some threads running while + others are stopped this will be particularly important. For + convenience, however, all the stepping commands have easy aliases. + So "thread continue" is just "c", etc.</p> + + <p>The other program stepping commands are pretty much the same as in gdb. + You've got:</p> + + <pre><tt>(lldb) thread step-in // The same as gdb's "step" or "s" +(lldb) thread step-over // The same as gdb's "next" or "n" +(lldb) thread step-out // The same as gdb's "finish" or "f" +</tt></pre> + + <p>By default, lldb does defined aliases to all common gdb process control + commands ("<code>s</code>", "<code>step</code>", "<code>n</code>", "<code>next</code>", "<code>finish</code>"). + If we have missed any, please add them to your <code>~/.lldbinit</code> file + using the "<code>command alias</code>" command. + + <p>lldb also supported the <i>step by instruction</i> versions:</p> + <pre><tt>(lldb) thread step-inst // The same as gdb's "stepi" / "si" +(lldb) thread step-over-inst // The same as gdb's "nexti" / "ni" +</tt></pre> + + <p>Finally, lldb has a <i>run until line or frame exit</i> stepping mode:</p> + + <code> + (lldb) thread until 100 + </code> + + <p>This command will run the thread in the current frame till it reaches line 100 in + this frame or stops if it leaves the current frame. This is a pretty + close equivalent to gdb's "<code>until</code>" command.</p> + + <p>A process, by default, will share the lldb terminal with the inferior + process. When in this mode, much like when debugging with gdb, when + the process is running anything you type will go to the STDIN of the + inferior process. To interrupt your inferior program, type CTRL+C.</p> + + <p>If you attach to a process, or launch a process with the "<code>--no-stdin</code>" + option, the command interpreter is always available to enter commands. This + might be a little disconcerting to gdb users when always have an <code>(lldb)</code> + prompt. This allows you to set a breakpoint, etc without having to explicitly interrupt + the program you are debugging:</p> + + <code> + (lldb) process continue + <br>(lldb) breakpoint set --name stop_here + </code> + + <p>There are many commands that won't work while running, and the command + interpreter should do a good job of letting you know when this is the + case. If you find any instances where the command interpreter isn't + doing its job, please file a bug. This way of operation will set us + up for a future debugging mode called <i>thread centric debugging</i>. + This mode will allow us to run all threads and only stop the threads + that are at breakpoints or have exceptions or signals.</p> + + <p>The commands that currently work while running include + interrupting the process to halt execution ("<code>process interrupt</code>"), + getting the process status ("<code>process status</code>"), + breakpoint setting and clearing ("<code> breakpoint [set|clear|enable|disable|list] ...</code>"), + and memory reading and writing ("<code> memory [read|write] ...</code>"). + </p> + + <p>The question of disabling stdio when running brings up a good opportunity to + show how to set debugger properties in general. + If you always want to run in the <code>--no-stdin</code> mode, you can set this + as a generic process property using the lldb "<code>settings</code>" command, + which is equivalent to gdb's "<code>set</code>" command. For instance, + in this case you would say:</p> + + <code> + (lldb) settings set target.process.disable-stdio true + </code> + + <p>Over time, gdb's "<code>set</code> command became a wilderness of disordered options, + so that there were useful options that even experienced gdb users didn't know about + because they were too hard to find. We tried to organize the settings hierarchically + using the structure of the basic entities in the debugger. For the most part anywhere + you can specify a setting on a generic entity (threads, for example) you can also apply + the option to a particular instance, which can also be convenient at times. + You can view the available settings with "<code>settings list</code>" and + there is help on the settings command explaining how it works more generally.</p> + + </div> + <div class="postfooter"></div> + + <div class="post"> + <h1 class ="postheader">Examining Thread State</h1> + <div class="postcontent"> + + <p>Once you've stopped, lldb will choose a current thread, usually the + one that stopped "for a reason", and a current frame in that thread (on stop this is always the bottom-most frame). + Many the commands for inspecting state work on this current + thread/frame.</p> + + <p>To inspect the current state of your process, you can start with the + threads:</p> + + <pre><tt>(lldb) thread list +Process 46915 state is Stopped +* thread #1: tid = 0x2c03, 0x00007fff85cac76a, where = libSystem.B.dylib`__getdirentries64 + 10, stop reason = signal = SIGSTOP, queue = com.apple.main-thread + thread #2: tid = 0x2e03, 0x00007fff85cbb08a, where = libSystem.B.dylib`kevent + 10, queue = com.apple.libdispatch-manager + thread #3: tid = 0x2f03, 0x00007fff85cbbeaa, where = libSystem.B.dylib`__workq_kernreturn + 10 +</tt></pre> + + <p>The * indicates that Thread 1 is the current thread. To get a + backtrace for that thread, do:</p> + + <pre><tt>(lldb) thread backtrace +thread #1: tid = 0x2c03, stop reason = breakpoint 1.1, queue = com.apple.main-thread + frame #0: 0x0000000100010d5b, where = Sketch`-[SKTGraphicView alignLeftEdges:] + 33 at /Projects/Sketch/SKTGraphicView.m:1405 + frame #1: 0x00007fff8602d152, where = AppKit`-[NSApplication sendAction:to:from:] + 95 + frame #2: 0x00007fff860516be, where = AppKit`-[NSMenuItem _corePerformAction] + 365 + frame #3: 0x00007fff86051428, where = AppKit`-[NSCarbonMenuImpl performActionWithHighlightingForItemAtIndex:] + 121 + frame #4: 0x00007fff860370c1, where = AppKit`-[NSMenu performKeyEquivalent:] + 272 + frame #5: 0x00007fff86035e69, where = AppKit`-[NSApplication _handleKeyEquivalent:] + 559 + frame #6: 0x00007fff85f06aa1, where = AppKit`-[NSApplication sendEvent:] + 3630 + frame #7: 0x00007fff85e9d922, where = AppKit`-[NSApplication run] + 474 + frame #8: 0x00007fff85e965f8, where = AppKit`NSApplicationMain + 364 + frame #9: 0x0000000100015ae3, where = Sketch`main + 33 at /Projects/Sketch/SKTMain.m:11 + frame #10: 0x0000000100000f20, where = Sketch`start + 52 +</tt></pre> + + <p>You can also provide a list of threads to backtrace, or the keyword + "all" to see all threads:</p> + + <code> + (lldb) thread backtrace all + </code> + + <p>You can select the current thread, which will be used by default in all the commands in + the next section, with the "thread select" command:</p> + + <code> + (lldb) thread select 2 + </code> + + <p>where the thread index is just the one shown in the "<code>thread list</code>" listing. + + </div> + <div class="postfooter"></div> + + <div class="post"> + <h1 class ="postheader">Examining Stack Frame State</h1> + <div class="postcontent"> + + + <p>The most convenient way to inspect a frame's arguments and local variables is to use the "<code>frame variable</code>" command:</p> + + <code> + (lldb) frame variable + <br>self = (SKTGraphicView *) 0x0000000100208b40 + <br>_cmd = (struct objc_selector *) 0x000000010001bae1 + <br>sender = (id) 0x00000001001264e0 + <br>selection = (NSArray *) 0x00000001001264e0 + <br>i = (NSUInteger) 0x00000001001264e0 + <br>c = (NSUInteger) 0x00000001001253b0 + </code> + + <p>As you see above, if you don't specify any variable names, all arguments + and locals will be shown. If you call "<code>frame variable</code>" + passing in the names of a particular local(s), only those variables + will be printed. For instance: + </p> + + <code> + (lldb) frame variable self + <br>(SKTGraphicView *) self = 0x0000000100208b40 + </code> + + <p>You can also pass in a path to some subelement of one of the available locals, + and that sub-element will be printed. For instance: + </p> + + <code> + <br>(lldb) frame variable self.isa + <br>(struct objc_class *) self.isa = 0x0000000100023730 + </code> + + <p>The "<code>frame variable</code>" command is not a full expression + parser but it does support a few simple operations like &, *, ->, [] (no overloaded + operators). The array brackets can be used on pointers to treat pointers + as arrays:</p> + + <code> + (lldb) frame variable *self + <br>(SKTGraphicView *) self = 0x0000000100208b40 + <br>(NSView) NSView = { + <br>(NSResponder) NSResponder = { + <br>... + <br> + <br>(lldb) frame variable &self + <br>(SKTGraphicView **) &self = 0x0000000100304ab + <br> + <br>(lldb) frame variable argv[0] + <br>(char const *) argv[0] = 0x00007fff5fbffaf8 "/Projects/Sketch/build/Debug/Sketch.app/Contents/MacOS/Sketch" + </code> + + <p>The frame variable command will also perform "object printing" operations on + variables (currently we only support ObjC printing, using the object's "description" method. + Turn this on by passing the -o flag to frame variable:</p> + + <code> + (lldb) frame variable -o self + (SKTGraphicView *) self = 0x0000000100208b40 <SKTGraphicView: 0x100208b40> + </code> + + <p>You can select another frame to view with the "<code>frame select</code>" command</p> + + <code> + (lldb) frame select 9 + <br>frame #9: 0x0000000100015ae3, where = Sketch`function1 + 33 at /Projects/Sketch/SKTFunctions.m:11 + </code> + + <p>You can also move up and down the stack by passing the "<code>--relative</code>" ("<code>-r</code>") + option. And we have built-in aliases "<code>u</code>" and "<code>d</code>" which + behave like their gdb equivalents. + + <p>If you need to view more complex data or change program data, you can + use the general "expression" command. It takes an expression and + evaluates it in the scope of the currently selected frame. For instance:</p> + + <code> + (lldb) expr self + <br>$0 = (SKTGraphicView *) 0x0000000100135430 + <br>(lldb) expr self = 0x00 + <br>$1 = (SKTGraphicView *) 0x0000000000000000 + <br>(lldb) frame var self + <br>(SKTGraphicView *) self = 0x0000000000000000 + </code> + + <p>You can also call functions:</p> + + <code> + (lldb) expr (int) printf ("I have a pointer 0x%llx.\n", self) + <br>$2 = (int) 22 + <br>I have a pointer 0x0. + </code> + + <p>As I said above, "expression" is one of the "raw" commands. So + you don't have to quote your whole expression, nor backslash protect quotes, + etc...</p> + + <p>Finally, the results of the expressions are stored in persistent variables + (of the form $[0-9]+) that you can use in further expressions, like:</p> + + <code> + (lldb) expr self = $0 + <br>$4 = (SKTGraphicView *) 0x0000000100135430 + </code> + <p> + </div> + <div class="postfooter"></div> + + </div> + </div> + </div> +</div> +</body> +</html> |