1Frame and Thread Format 2======================= 3 4LLDB has a facility to allow users to define the format of the information that 5generates the descriptions for threads and stack frames. Typically when your 6program stops at a breakpoint you will get two lines that describes why your 7thread stopped and where: 8 9:: 10 11 * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1 12 frame #0: test`main at test.c:5 13 14Stack backtraces frames also have a similar information line: 15 16:: 17 18 (lldb) thread backtrace 19 * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1 20 frame #0: 0x0000000100000e85 a.out`main + 4 at test.c:19 21 frame #1: 0x0000000100000e40 a.out`start + 52 22 23The two format strings that govern the printing in these output forms can 24currently be set using the settings set command: 25 26:: 27 28 (lldb) settings set thread-stop-format STRING 29 (lldb) settings set frame-format STRING 30 31The first of these is an abbreviated thread output, that just contains data 32about the thread, and not the stop frame. It will always get used in situations 33where the frame output follows immediately, so that information would be 34redundant. The second is the frame printing. 35 36There is another thread format used for commands like thread list where the 37thread information isn't followed by frame info. In that case, it is convenient 38to have frame zero information in the thread output. That format is set by: 39 40:: 41 42 (lldb) settings set thread-format STRING 43 44 45Format Strings 46-------------- 47 48So what is the format of the format strings? Format strings can contain plain 49text, control characters and variables that have access to the current program 50state. 51 52Normal characters are any text that doesn't contain a ``{``, ``}``, ``$``, or 53``\`` character. 54 55Variable names are found in between a ``${`` prefix, and end with a ``}`` 56suffix. In other words, a variable looks like ``${frame.pc}``. 57 58Variables 59--------- 60 61A complete list of currently supported format string variables is listed below: 62 63+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 64| **Variable Name** | **Description** | 65+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 66| ``file.basename`` | The current compile unit file basename for the current frame. | 67+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 68| ``file.fullpath`` | The current compile unit file fullpath for the current frame. | 69+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 70| ``language`` | The current compile unit language for the current frame. | 71+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 72| ``frame.index`` | The frame index (0, 1, 2, 3...) | 73+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 74| ``frame.no-debug`` | Evaluates to true if the frame has no debug info. | 75+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 76| ``frame.pc`` | The generic frame register for the program counter. | 77+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 78| ``frame.sp`` | The generic frame register for the stack pointer. | 79+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 80| ``frame.fp`` | The generic frame register for the frame pointer. | 81+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 82| ``frame.flags`` | The generic frame register for the flags register. | 83+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 84| ``frame.reg.NAME`` | Access to any platform specific register by name (replace ``NAME`` with the name of the desired register). | 85+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 86| ``function.name`` | The name of the current function or symbol. | 87+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 88| ``function.name-with-args`` | The name of the current function with arguments and values or the symbol name. | 89+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 90| ``function.name-without-args`` | The name of the current function without arguments and values (used to include a function name in-line in the ``disassembly-format``) | 91+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 92| ``function.mangled-name`` | The mangled name of the current function or symbol. | 93+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 94| ``function.pc-offset`` | The program counter offset within the current function or symbol | 95+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 96| ``function.addr-offset`` | The offset in bytes of the current function, formatted as " + dddd" | 97+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 98| ``function.concrete-only-addr-offset-no-padding`` | Similar to ``function.addr-offset`` except that there are no spaces in the output (e.g. "+dddd") and the offset is computed from the nearest concrete function -- inlined functions are not included | 99+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 100| ``function.changed`` | Will evaluate to true when the line being formatted is a different symbol context from the previous line (may be used in ``disassembly-format`` to print the new function name on a line by itself at the start of a new function). Inlined functions are not considered for this variable | 101+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 102| ``function.initial-function`` | Will evaluate to true if this is the start of the first function, as opposed to a change of functions (may be used in ``disassembly-format`` to print the function name for the first function being disassembled) | 103+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 104| ``line.file.basename`` | The line table entry basename to the file for the current line entry in the current frame. | 105+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 106| ``line.file.fullpath`` | The line table entry fullpath to the file for the current line entry in the current frame. | 107+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 108| ``line.number`` | The line table entry line number for the current line entry in the current frame. | 109+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 110| ``line.start-addr`` | The line table entry start address for the current line entry in the current frame. | 111+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 112| ``line.end-addr`` | The line table entry end address for the current line entry in the current frame. | 113+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 114| ``module.file.basename`` | The basename of the current module (shared library or executable) | 115+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 116| ``module.file.fullpath`` | The path of the current module (shared library or executable) | 117+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 118| ``process.file.basename`` | The basename of the file for the process | 119+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 120| ``process.file.fullpath`` | The path of the file for the process | 121+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 122| ``process.id`` | The process ID native to the system on which the inferior runs. | 123+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 124| ``process.name`` | The name of the process at runtime | 125+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 126| ``thread.id`` | The thread identifier for the current thread | 127+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 128| ``thread.index`` | The unique one based thread index ID which is guaranteed to be unique as threads come and go. | 129+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 130| ``thread.name`` | The name of the thread if the target OS supports naming threads | 131+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 132| ``thread.queue`` | The queue name of the thread if the target OS supports dispatch queues | 133+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 134| ``thread.stop-reason`` | A textual reason why the thread stopped. If the thread have a recognized frame, this displays its recognized stop reason. Otherwise, gets the stop info description. | 135+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 136| ``thread.stop-reason-raw`` | A textual reason why the thread stopped. Always returns stop info description. | 137+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 138| ``thread.return-value`` | The return value of the latest step operation (currently only for step-out.) | 139+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 140| ``thread.completed-expression`` | The expression result for a thread that just finished an interrupted expression evaluation. | 141+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 142| ``target.arch`` | The architecture of the current target | 143+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 144| ``target.file.basename`` | The basename of the current target | 145+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 146| ``target.file.fullpath`` | The path of the current target | 147+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 148| ``script.target:python_func`` | Use a Python function to generate a piece of textual output | 149+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 150| ``script.process:python_func`` | Use a Python function to generate a piece of textual output | 151+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 152| ``script.thread:python_func`` | Use a Python function to generate a piece of textual output | 153+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 154| ``script.frame:python_func`` | Use a Python function to generate a piece of textual output | 155+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 156| ``current-pc-arrow`` | Prints either ``->`` or `` `` if the current pc value is matched (used in ``disassembly-format``) | 157+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 158| ``addr-file-or-load`` | Formats an address either as a load address, or if process has not yet been launched, as a load address (used in ``disassembly-format``) | 159+---------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 160 161Control Characters 162------------------ 163 164Control characters include ``{``, ``}``, and ``\``. 165 166The ``{`` and ``}`` are used for scoping blocks, and the ``\`` character allows 167you to desensitize control characters and also emit non-printable characters. 168 169Desensitizing Characters in the Format String 170--------------------------------------------- 171 172The backslash control character allows your to enter the typical ``\a``, 173``\b``, ``\f``, ``\n``, ``\r``, ``\t``, ``\v``, ``\\``, characters and along 174with the standard octal representation ``\0123`` and hex ``\xAB`` characters. 175This allows you to enter escape characters into your format strings and will 176allow colorized output for terminals that support color. 177 178Scoping 179------- 180 181Many times the information that you might have in your prompt might not be 182available and you won``t want it to print out if it isn``t valid. To take care 183of this you can enclose everything that must resolve into a scope. A scope is 184starts with ``{`` and ends with ``}``. For example in order to only display the 185current frame line table entry basename and line number when the information is 186available for the current frame: 187 188:: 189 190 "{ at {$line.file.basename}:${line.number}}" 191 192 193Broken down this is: 194 195- The start the scope: ``{`` , 196- format whose content will only be displayed if all information is available: ``at {$line.file.basename}:${line.number}`` 197- end the scope: ``}`` 198 199Making the Frame Format 200----------------------- 201 202The information that we see when stopped in a frame: 203 204:: 205 206 frame #0: 0x0000000100000e85 a.out`main + 4 at test.c:19 207 208can be displayed with the following format: 209 210:: 211 212 "frame #${frame.index}: ${frame.pc}{ ${module.file.basename}`${function.name}{${function.pc-offset}}}{ at ${line.file.basename}:${line.number}}\n" 213 214This breaks down to: 215 216- Always print the frame index and frame PC: ``frame #${frame.index}: ${frame.pc}``, 217- only print the module followed by a tick if there is a valid module for the current frame: ``{ ${module.file.basename}`}``, 218- print the function name with optional offset: ``{${function.name}{${function.pc-offset}}}``, 219- print the line info if it is available: ``{ at ${line.file.basename}:${line.number}}``, 220- then finish off with a newline: ``\n``. 221 222Making Your own Formats 223----------------------- 224 225When modifying your own format strings, it is useful to start with the default 226values for the frame and thread format strings. These can be accessed with the 227``settings show`` command: 228 229:: 230 231 (lldb) settings show thread-format 232 thread-format (format-string) = "thread #${thread.index}: tid = ${thread.id%tid}{, ${frame.pc}}{ ${module.file.basename}{`${function.name-with-args}{${frame.no-debug}${function.pc-offset}}}}{ at ${line.file.basename}:${line.number}}{, name = '${thread.name}'}{, queue = '${thread.queue}'}{, activity = '${thread.info.activity.name}'}{, ${thread.info.trace_messages} messages}{, stop reason = ${thread.stop-reason}}{\nReturn value: ${thread.return-value}}{\nCompleted expression: ${thread.completed-expression}}\n" 233 (lldb) settings show frame-format 234 frame-format (format-string) = "frame #${frame.index}:{ ${frame.no-debug}${frame.pc}}{ ${module.file.basename}{`${function.name-with-args}{${frame.no-debug}${function.pc-offset}}}}{ at ${line.file.basename}:${line.number}}{${function.is-optimized} [opt]}\n" 235 236When making thread formats, you will need surround any of the information that 237comes from a stack frame with scopes ({ frame-content }) as the thread format 238doesn't always want to show frame information. When displaying the backtrace 239for a thread, we don't need to duplicate the information for frame zero in the 240thread information: 241 242:: 243 244 (lldb) thread backtrace 245 thread #1: tid = 0x2e03, stop reason = breakpoint 1.1 2.1 246 frame #0: 0x0000000100000e85 a.out`main + 4 at test.c:19 247 frame #1: 0x0000000100000e40 a.out`start + 52 248 249The frame related variables are: 250 251- ``${file.*}`` 252- ``${frame.*}`` 253- ``${function.*}`` 254- ``${line.*}`` 255- ``${module.*}`` 256 257 258Looking at the default format for the thread, and underlining the frame 259information: 260 261:: 262 263 thread #${thread.index}: tid = ${thread.id}{, ${frame.pc}}{ ${module.file.basename}`${function.name}{${function.pc-offset}}}{, stop reason = ${thread.stop-reason}}{, name = ${thread.name}}{, queue = ${thread.queue}}\n 264 265 266We can see that all frame information is contained in scopes so that when the 267thread information is displayed in a context where we only want to show thread 268information, we can do so. 269 270For both thread and frame formats, you can use ${script.target:python_func}, 271${script.process:python_func} and ${script.thread:python_func} (and of course 272${script.frame:python_func} for frame formats) In all cases, the signature of 273python_func is expected to be: 274 275:: 276 277 def python_func(object,unused): 278 ... 279 return string 280 281Where object is an instance of the SB class associated to the keyword you are 282using. 283 284e.g. Assuming your function looks like: 285 286:: 287 288 def thread_printer_func (thread,unused): 289 return "Thread %s has %d frames\n" % (thread.name, thread.num_frames) 290 291And you set it up with: 292 293:: 294 295 (lldb) settings set thread-format "${script.thread:thread_printer_func}" 296 297you would see output like: 298 299:: 300 301 * Thread main has 21 frames 302 303