Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1 or
+under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``Free Software'' and ``Free Software Needs
Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
@samp{Switching to} depends on your system's conventions for identifying
threads.
+@vindex $_thread@r{, convenience variable}
+The debugger convenience variable @samp{$_thread} contains the number
+of the current thread. You may find this useful in writing breakpoint
+conditional expressions, command scripts, and so forth. See
+@xref{Convenience Vars,, Convenience Variables}, for general
+information on convenience variables.
+
@kindex thread apply
@cindex apply command to several threads
@item thread apply [@var{threadno}] [@var{all}] @var{command}
@code{info break} (@pxref{Set Breaks}).
@end table
+If you watch for a change in a numerically entered address you need to
+dereference it, as the address itself is just a constant number which will
+never change. @value{GDBN} refuses to create a watchpoint that watches
+a never-changing value:
+
+@smallexample
+(@value{GDBP}) watch 0x600850
+Cannot watch constant value 0x600850.
+(@value{GDBP}) watch *(int *) 0x600850
+Watchpoint 1: *(int *) 6293584
+@end smallexample
+
@value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
watchpoints execute very quickly, and the debugger reports a change in
value at the exact instruction where the change occurs. If @value{GDBN}
* Background Execution:: Running your program asynchronously
* Thread-Specific Breakpoints:: Controlling breakpoints
* Interrupted System Calls:: GDB may interfere with system calls
+* Observer Mode:: GDB does not alter program behavior
@end menu
@node All-Stop Mode
When such an event happens, a system call in another thread may return
prematurely, even though your program does not appear to stop.
+@node Observer Mode
+@subsection Observer Mode
+
+If you want to build on non-stop mode and observe program behavior
+without any chance of disruption by @value{GDBN}, you can set
+variables to disable all of the debugger's attempts to modify state,
+whether by writing memory, inserting breakpoints, etc. These operate
+at a low level, intercepting operations from all commands.
+
+When all of these are set to @code{off}, then @value{GDBN} is said to
+be @dfn{observer mode}. As a convenience, the variable
+@code{observer} can be set to disable these, plus enable non-stop
+mode.
+
+Note that @value{GDBN} will not prevent you from making nonsensical
+combinations of these settings. For instance, if you have enabled
+@code{may-insert-breakpoints} but disabled @code{may-write-memory},
+then breakpoints that work by writing trap instructions into the code
+stream will still not be able to be placed.
+
+@table @code
+
+@kindex observer
+@item set observer on
+@itemx set observer off
+When set to @code{on}, this disables all the permission variables
+below (except for @code{insert-fast-tracepoints}), plus enables
+non-stop debugging. Setting this to @code{off} switches back to
+normal debugging, though remaining in non-stop mode.
+
+@item show observer
+Show whether observer mode is on or off.
+
+@kindex may-write-registers
+@item set may-write-registers on
+@itemx set may-write-registers off
+This controls whether @value{GDBN} will attempt to alter the values of
+registers, such as with assignment expressions in @code{print}, or the
+@code{jump} command. It defaults to @code{on}.
+
+@item show may-write-registers
+Show the current permission to write registers.
+
+@kindex may-write-memory
+@item set may-write-memory on
+@itemx set may-write-memory off
+This controls whether @value{GDBN} will attempt to alter the contents
+of memory, such as with assignment expressions in @code{print}. It
+defaults to @code{on}.
+
+@item show may-write-memory
+Show the current permission to write memory.
+
+@kindex may-insert-breakpoints
+@item set may-insert-breakpoints on
+@itemx set may-insert-breakpoints off
+This controls whether @value{GDBN} will attempt to insert breakpoints.
+This affects all breakpoints, including internal breakpoints defined
+by @value{GDBN}. It defaults to @code{on}.
+
+@item show may-insert-breakpoints
+Show the current permission to insert breakpoints.
+
+@kindex may-insert-tracepoints
+@item set may-insert-tracepoints on
+@itemx set may-insert-tracepoints off
+This controls whether @value{GDBN} will attempt to insert (regular)
+tracepoints at the beginning of a tracing experiment. It affects only
+non-fast tracepoints, fast tracepoints being under the control of
+@code{may-insert-fast-tracepoints}. It defaults to @code{on}.
+
+@item show may-insert-tracepoints
+Show the current permission to insert tracepoints.
+
+@kindex may-insert-fast-tracepoints
+@item set may-insert-fast-tracepoints on
+@itemx set may-insert-fast-tracepoints off
+This controls whether @value{GDBN} will attempt to insert fast
+tracepoints at the beginning of a tracing experiment. It affects only
+fast tracepoints, regular (non-fast) tracepoints being under the
+control of @code{may-insert-tracepoints}. It defaults to @code{on}.
+
+@item show may-insert-fast-tracepoints
+Show the current permission to insert fast tracepoints.
+
+@kindex may-interrupt
+@item set may-interrupt on
+@itemx set may-interrupt off
+This controls whether @value{GDBN} will attempt to interrupt or stop
+program execution. When this variable is @code{off}, the
+@code{interrupt} command will have no effect, nor will
+@kbd{Ctrl-c}. It defaults to @code{on}.
+
+@item show may-interrupt
+Show the current permission to interrupt or stop the program.
+
+@end table
@node Reverse Execution
@chapter Running programs backward
When the inferior process exits, or @value{GDBN} detaches from it,
process record and replay target will automatically stop itself.
+@kindex record save
+@item record save @var{filename}
+Save the execution log to a file @file{@var{filename}}.
+Default filename is @file{gdb_record.@var{process_id}}, where
+@var{process_id} is the process ID of the inferior.
+
+@kindex record restore
+@item record restore @var{filename}
+Restore the execution log from a file @file{@var{filename}}.
+File must have been created with @code{record save}.
+
@kindex set record insn-number-max
@item set record insn-number-max @var{limit}
Set the limit of instructions to be recorded. Default value is 200000.
@item show record stop-at-limit
Show the current setting of @code{stop-at-limit}.
+@kindex set record memory-query
+@item set record memory-query
+Control the behavior when @value{GDBN} is unable to record memory
+changes caused by an instruction. If ON, @value{GDBN} will query
+whether to stop the inferior in that case.
+
+If this option is OFF (the default), @value{GDBN} will automatically
+ignore the effect of such instructions on memory. Later, when
+@value{GDBN} replays this execution log, it will mark the log of this
+instruction as not accessible, and it will not affect the replay
+results.
+
+@kindex show record memory-query
+@item show record memory-query
+Show the current setting of @code{memory-query}.
+
@kindex info record
@item info record
Show various statistics about the state of process record and its
function name to avoid ambiguity when there are identically named
functions in different source files.
+@item @var{label}
+Specifies the line at which the label named @var{label} appears.
+@value{GDBN} searches for the label in the function corresponding to
+the currently selected stack frame. If there is no current selected
+stack frame (for instance, if the inferior is not running), then
+@value{GDBN} will not search for a label.
+
@item *@var{address}
Specifies the program address @var{address}. For line-oriented
commands, such as @code{list} and @code{edit}, this specifies a source
The variable @code{$_exitcode} is automatically set to the exit code when
the program being debugged terminates.
+@item $_sdata
+@vindex $_sdata@r{, inspect, convenience variable}
+The variable @code{$_sdata} contains extra collected static tracepoint
+data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
+@code{$_sdata} could be empty, if not inspecting a trace buffer, or
+if extra static tracepoint data has not been collected.
+
@item $_siginfo
@vindex $_siginfo@r{, convenience variable}
The variable @code{$_siginfo} contains extra signal information
@samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
@table @code
+@kindex info os
+@item info os
+List the types of OS information available for the target. If the
+target does not return a list of possible types, this command will
+report an error.
+
@kindex info os processes
@item info os processes
Display the list of processes on the target. For each process,
a different way (such as with a jump instead of a trap), that is
faster but possibly restricted in where they may be installed.
+@cindex static tracepoints
+@cindex markers, static tracepoints
+@cindex probing markers, static tracepoints
+Regular and fast tracepoints are dynamic tracing facilities, meaning
+that they can be used to insert tracepoints at (almost) any location
+in the target. Some targets may also support controlling @dfn{static
+tracepoints} from @value{GDBN}. With static tracing, a set of
+instrumentation points, also known as @dfn{markers}, are embedded in
+the target program, and can be activated or deactivated by name or
+address. These are usually placed at locations which facilitate
+investigating what the target is actually doing. @value{GDBN}'s
+support for static tracing includes being able to list instrumentation
+points, and attach them with @value{GDBN} defined high level
+tracepoints that expose the whole range of convenience of
+@value{GDBN}'s tracepoints support. Namelly, support for collecting
+registers values and values of global or local (to the instrumentation
+point) variables; tracepoint conditions and trace state variables.
+The act of installing a @value{GDBN} static tracepoint on an
+instrumentation point, or marker, is referred to as @dfn{probing} a
+static tracepoint marker.
+
+@code{gdbserver} supports tracepoints on some target systems.
+@xref{Server,,Tracepoints support in @code{gdbserver}}.
+
This section describes commands to set tracepoints and associated
conditions and actions.
* Trace State Variables::
* Tracepoint Actions::
* Listing Tracepoints::
+* Listing Static Tracepoint Markers::
* Starting and Stopping Trace Experiments::
* Tracepoint Restrictions::
@end menu
@item ftrace @var{location} [ if @var{cond} ]
@cindex set fast tracepoint
+@cindex fast tracepoints, setting
@kindex ftrace
The @code{ftrace} command sets a fast tracepoint. For targets that
support them, fast tracepoints will use a more efficient but possibly
@value{GDBN} handles arguments to @code{ftrace} exactly as for
@code{trace}.
+@item strace @var{location} [ if @var{cond} ]
+@cindex set static tracepoint
+@cindex static tracepoints, setting
+@cindex probe static tracepoint marker
+@kindex strace
+The @code{strace} command sets a static tracepoint. For targets that
+support it, setting a static tracepoint probes a static
+instrumentation point, or marker, found at @var{location}. It may not
+be possible to set a static tracepoint at the desired location, in
+which case the command will exit with an explanatory message.
+
+@value{GDBN} handles arguments to @code{strace} exactly as for
+@code{trace}, with the addition that the user can also specify
+@code{-m @var{marker}} as @var{location}. This probes the marker
+identified by the @var{marker} string identifier. This identifier
+depends on the static tracepoint backend library your program is
+using. You can find all the marker identifiers in the @samp{ID} field
+of the @code{info static-tracepoint-markers} command output.
+@xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
+Markers}. For example, in the following small program using the UST
+tracing engine:
+
+@smallexample
+main ()
+@{
+ trace_mark(ust, bar33, "str %s", "FOOBAZ");
+@}
+@end smallexample
+
+@noindent
+the marker id is composed of joining the first two arguments to the
+@code{trace_mark} call with a slash, which translates to:
+
+@smallexample
+(@value{GDBP}) info static-tracepoint-markers
+Cnt Enb ID Address What
+1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
+ Data: "str %s"
+[etc...]
+@end smallexample
+
+@noindent
+so you may probe the marker above with:
+
+@smallexample
+(@value{GDBP}) strace -m ust/bar33
+@end smallexample
+
+Static tracepoints accept an extra collect action --- @code{collect
+$_sdata}. This collects arbitrary user data passed in the probe point
+call to the tracing library. In the UST example above, you'll see
+that the third argument to @code{trace_mark} is a printf-like format
+string. The user data is then the result of running that formating
+string against the following arguments. Note that @code{info
+static-tracepoint-markers} command output lists that format string in
+the @samp{Data:} field.
+
+You can inspect this data when analyzing the trace buffer, by printing
+the $_sdata variable like any other variable available to
+@value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
+
@vindex $tpnum
@cindex last tracepoint number
@cindex recent tracepoint number
@table @code
@item $regs
-collect all registers
+Collect all registers.
@item $args
-collect all function arguments
+Collect all function arguments.
@item $locals
-collect all local variables.
+Collect all local variables.
+
+@item $_sdata
+@vindex $_sdata@r{, collect}
+Collect static tracepoint marker specific data. Only available for
+static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
+Lists}. On the UST static tracepoints library backend, an
+instrumentation point resembles a @code{printf} function call. The
+tracing library is able to collect user specified data formatted to a
+character string using the format provided by the programmer that
+instrumented the program. Other backends have similar mechanisms.
+Here's an example of a UST marker call:
+
+@smallexample
+ const char master_name[] = "$your_name";
+ trace_mark(channel1, marker1, "hello %s", master_name)
+@end smallexample
+
+In this case, collecting @code{$_sdata} collects the string
+@samp{hello $yourname}. When analyzing the trace buffer, you can
+inspect @samp{$_sdata} like any other variable available to
+@value{GDBN}.
@end table
You can give several consecutive @code{collect} commands, each one
This command can be abbreviated @code{info tp}.
@end table
+@node Listing Static Tracepoint Markers
+@subsection Listing Static Tracepoint Markers
+
+@table @code
+@kindex info static-tracepoint-markers
+@cindex information about static tracepoint markers
+@item info static-tracepoint-markers
+Display information about all static tracepoint markers defined in the
+program.
+
+For each marker, the following columns are printed:
+
+@table @emph
+@item Count
+An incrementing counter, output to help readability. This is not a
+stable identifier.
+@item ID
+The marker ID, as reported by the target.
+@item Enabled or Disabled
+Probed markers are tagged with @samp{y}. @samp{n} identifies marks
+that are not enabled.
+@item Address
+Where the marker is in your program, as a memory address.
+@item What
+Where the marker is in the source for your program, as a file and line
+number. If the debug information included in the program does not
+allow @value{GDBN} to locate the source of the marker, this column
+will be left blank.
+@end table
+
+@noindent
+In addition, the following information may be printed for each marker:
+
+@table @emph
+@item Data
+User data passed to the tracing library by the marker call. In the
+UST backend, this is the format string passed as argument to the
+marker call.
+@item Static tracepoints probing the marker
+The list of static tracepoints attached to the marker.
+@end table
+
+@smallexample
+(@value{GDBP}) info static-tracepoint-markers
+Cnt ID Enb Address What
+1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
+ Data: number1 %d number2 %d
+ Probed by static tracepoints: #2
+2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
+ Data: str %s
+(@value{GDBP})
+@end smallexample
+@end table
+
@node Starting and Stopping Trace Experiments
@subsection Starting and Stopping Trace Experiments
@menu
* Files:: Commands to specify files
* Separate Debug Files:: Debugging information in separate files
+* Index Files:: Index files speed up GDB
* Symbol Errors:: Errors reading symbol files
* Data Files:: GDB data files
@end menu
This computation does not apply to the ``build ID'' method.
+@node Index Files
+@section Index Files Speed Up @value{GDBN}
+@cindex index files
+@cindex @samp{.gdb_index} section
+
+When @value{GDBN} finds a symbol file, it scans the symbols in the
+file in order to construct an internal symbol table. This lets most
+@value{GDBN} operations work quickly---at the cost of a delay early
+on. For large programs, this delay can be quite lengthy, so
+@value{GDBN} provides a way to build an index, which speeds up
+startup.
+
+The index is stored as a section in the symbol file. @value{GDBN} can
+write the index to a file, then you can put it into the symbol file
+using @command{objcopy}.
+
+To create an index file, use the @code{save gdb-index} command:
+
+@table @code
+@item save gdb-index @var{directory}
+@kindex save gdb-index
+Create an index file for each symbol file currently known by
+@value{GDBN}. Each file is named after its corresponding symbol file,
+with @samp{.gdb-index} appended, and is written into the given
+@var{directory}.
+@end table
+
+Once you have created an index file you can merge it into your symbol
+file, here named @file{symfile}, using @command{objcopy}:
+
+@smallexample
+$ objcopy --add-section .gdb_index=symfile.gdb-index \
+ --set-section-flags .gdb_index=readonly symfile symfile
+@end smallexample
+
+There are currently some limitation on indices. They only work when
+for DWARF debugging information, not stabs. And, they do not
+currently work for programs using Ada.
+
+
@node Symbol Errors
@section Errors Reading Symbol Files
@cindex active targets
@cindex multiple targets
-There are three classes of targets: processes, core files, and
-executable files. @value{GDBN} can work concurrently on up to three
-active targets, one in each class. This allows you to (for example)
-start a process and inspect its activity without abandoning your work on
-a core file.
-
-For example, if you execute @samp{gdb a.out}, then the executable file
-@code{a.out} is the only active target. If you designate a core file as
-well---presumably from a prior run that crashed and coredumped---then
-@value{GDBN} has two active targets and uses them in tandem, looking
-first in the corefile target, then in the executable file, to satisfy
-requests for memory addresses. (Typically, these two classes of target
-are complementary, since core files contain only a program's
-read-write memory---variables and so on---plus machine status, while
-executable files contain only the program text and initialized data.)
-
-When you type @code{run}, your executable file becomes an active process
-target as well. When a process target is active, all @value{GDBN}
-commands requesting memory addresses refer to that target; addresses in
-an active core file or executable file target are obscured while the
-process target is active.
-
-Use the @code{core-file} and @code{exec-file} commands to select a new
-core file or executable target (@pxref{Files, ,Commands to Specify
-Files}). To specify as a target a process that is already running, use
-the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
-Process}).
+There are multiple classes of targets such as: processes, executable files or
+recording sessions. Core files belong to the process class, making core file
+and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
+on multiple active targets, one in each class. This allows you to (for
+example) start a process and inspect its activity, while still having access to
+the executable file after the process finishes. Or if you start process
+recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
+presented a virtual layer of the recording target, while the process target
+remains stopped at the chronologically last point of the process execution.
+
+Use the @code{core-file} and @code{exec-file} commands to select a new core
+file or executable target (@pxref{Files, ,Commands to Specify Files}). To
+specify as a target a process that is already running, use the @code{attach}
+command (@pxref{Attach, ,Debugging an Already-running Process}).
@node Target Commands
@section Commands for Managing Targets
@end table
+@subsection Tracepoints support in @code{gdbserver}
+@cindex tracepoints support in @code{gdbserver}
+
+On some targets, @code{gdbserver} supports tracepoints, fast
+tracepoints and static tracepoints.
+
+For fast or static tracepoints to work, a special library called the
+@dfn{in-process agent} (IPA), must be loaded in the inferior process.
+This library is built and distributed as an integral part of
+@code{gdbserver}. In addition, support for static tracepoints
+requires building the in-process agent library with static tracepoints
+support. At present, the UST (LTTng Userspace Tracer,
+@url{http://lttng.org/ust}) tracing engine is supported. This support
+is automatically available if UST development headers are found in the
+standard include path when @code{gdbserver} is built, or if
+@code{gdbserver} was explicitly configured using @option{--with-ust}
+to point at such headers. You can explicitly disable the support
+using @option{--with-ust=no}.
+
+There are several ways to load the in-process agent in your program:
+
+@table @code
+@item Specifying it as dependency at link time
+
+You can link your program dynamically with the in-process agent
+library. On most systems, this is accomplished by adding
+@code{-linproctrace} to the link command.
+
+@item Using the system's preloading mechanisms
+
+You can force loading the in-process agent at startup time by using
+your system's support for preloading shared libraries. Many Unixes
+support the concept of preloading user defined libraries. In most
+cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
+in the environment. See also the description of @code{gdbserver}'s
+@option{--wrapper} command line option.
+
+@item Using @value{GDBN} to force loading the agent at run time
+
+On some systems, you can force the inferior to load a shared library,
+by calling a dynamic loader function in the inferior that takes care
+of dynamically looking up and loading a shared library. On most Unix
+systems, the function is @code{dlopen}. You'll use the @code{call}
+command for that. For example:
+
+@smallexample
+(@value{GDBP}) call dlopen ("libinproctrace.so", ...)
+@end smallexample
+
+Note that on most Unix systems, for the @code{dlopen} function to be
+available, the program needs to be linked with @code{-ldl}.
+@end table
+
+On systems that have a userspace dynamic loader, like most Unix
+systems, when you connect to @code{gdbserver} using @code{target
+remote}, you'll find that the program is stopped at the dynamic
+loader's entry point, and no shared library has been loaded in the
+program's address space yet, including the in-process agent. In that
+case, before being able to use any of the fast or static tracepoints
+features, you need to let the loader run and load the shared
+libraries. The simplest way to do that is to run the program to the
+main procedure. E.g., if debugging a C or C@t{++} program, start
+@code{gdbserver} like so:
+
+@smallexample
+$ gdbserver :9999 myprogram
+@end smallexample
+
+Start GDB and connect to @code{gdbserver} like so, and run to main:
+
+@smallexample
+$ gdb myprogram
+(@value{GDBP}) target remote myhost:9999
+0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
+(@value{GDBP}) b main
+(@value{GDBP}) continue
+@end smallexample
+
+The in-process tracing agent library should now be loaded into the
+process; you can confirm it with the @code{info sharedlibrary}
+command, which will list @file{libinproctrace.so} as loaded in the
+process. You are now ready to install fast tracepoints, list static
+tracepoint markers, probe static tracepoints markers, and start
+tracing.
+
@node Remote Configuration
@section Remote Configuration
@tab @code{qXfer:memory-map:read}
@tab @code{info mem}
+@item @code{read-sdata-object}
+@tab @code{qXfer:sdata:read}
+@tab @code{print $_sdata}
+
@item @code{read-spu-object}
@tab @code{qXfer:spu:read}
@tab @code{info spu}
printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
@end smallexample
+@kindex eval
+@item eval @var{template}, @var{expressions}@dots{}
+Convert the values of one or more @var{expressions} under the control of
+the string @var{template} to a command line, and call it.
+
@end table
@node Python
Python programming language}. This feature is available only if
@value{GDBN} was configured using @option{--with-python}.
+@cindex python directory
+Python scripts used by @value{GDBN} should be installed in
+@file{@var{data-directory}/python}, where @var{data-directory} is
+the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
+is automatically added to the Python Search Path in order to allow
+the Python interpreter to locate all scripts installed at this location.
+
@menu
* Python Commands:: Accessing Python from @value{GDBN}.
* Python API:: Accessing @value{GDBN} from Python.
* Types In Python:: Python representation of types.
* Pretty Printing API:: Pretty-printing values.
* Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
+* Disabling Pretty-Printers:: Disabling broken printers.
+* Inferiors In Python:: Python representation of inferiors (processes)
+* Threads In Python:: Accessing inferior threads from Python.
* Commands In Python:: Implementing new commands in Python.
+* Parameters In Python:: Adding new @value{GDBN} parameters.
* Functions In Python:: Writing new convenience functions.
* Progspaces In Python:: Program spaces.
* Objfiles In Python:: Object files.
@value{GDBN} automatically @code{import}s the @code{gdb} module for
use in all scripts evaluated by the @code{python} command.
+@findex gdb.PYTHONDIR
+@defvar PYTHONDIR
+A string containing the python directory (@pxref{Python}).
+@end defvar
+
@findex gdb.execute
-@defun execute command [from_tty]
+@defun execute command [from_tty] [to_string]
Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
If a GDB exception happens while @var{command} runs, it is
translated as described in @ref{Exception Handling,,Exception Handling}.
-If no exceptions occur, this function returns @code{None}.
@var{from_tty} specifies whether @value{GDBN} ought to consider this
command as having originated from the user invoking it interactively.
It must be a boolean value. If omitted, it defaults to @code{False}.
+
+By default, any output produced by @var{command} is sent to
+@value{GDBN}'s standard output. If the @var{to_string} parameter is
+@code{True}, then output will be collected by @code{gdb.execute} and
+returned as a string. The default is @code{False}, in which case the
+return value is @code{None}.
@end defun
@findex gdb.breakpoints
Python statement closest to where the @value{GDBN} error occured as the
traceback.
+@findex gdb.GdbError
+When implementing @value{GDBN} commands in Python via @code{gdb.Command},
+it is useful to be able to throw an exception that doesn't cause a
+traceback to be printed. For example, the user may have invoked the
+command incorrectly. Use the @code{gdb.GdbError} exception
+to handle this case. Example:
+
+@smallexample
+(gdb) python
+>class HelloWorld (gdb.Command):
+> """Greet the whole world."""
+> def __init__ (self):
+> super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
+> def invoke (self, args, from_tty):
+> argv = gdb.string_to_argv (args)
+> if len (argv) != 0:
+> raise gdb.GdbError ("hello-world takes no arguments")
+> print "Hello, World!"
+>HelloWorld ()
+>end
+(gdb) hello-world 42
+hello-world takes no arguments
+@end smallexample
+
@node Values From Inferior
@subsubsection Values From Inferior
@cindex values from inferior, with Python
@subsubsection Selecting Pretty-Printers
The Python list @code{gdb.pretty_printers} contains an array of
-functions that have been registered via addition as a pretty-printer.
+functions or callable objects that have been registered via addition
+as a pretty-printer.
Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
Each @code{gdb.Objfile} also contains a @code{pretty_printers}
attribute.
@value{GDBN} first checks the @code{pretty_printers} attribute of each
@code{gdb.Objfile} in the current program space and iteratively calls
-each function in the list for that @code{gdb.Objfile} until it receives
+each enabled function (@pxref{Disabling Pretty-Printers})
+in the list for that @code{gdb.Objfile} until it receives
a pretty-printer object.
If no pretty-printer is found in the objfile lists, @value{GDBN} then
searches the pretty-printer list of the current program space,
-calling each function until an object is returned.
+calling each enabled function until an object is returned.
After these lists have been exhausted, it tries the global
-@code{gdb.pretty-printers} list, again calling each function until an
+@code{gdb.pretty_printers} list, again calling each enabled function until an
object is returned.
The order in which the objfiles are searched is not specified. For a
gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
@end smallexample
+@node Disabling Pretty-Printers
+@subsubsection Disabling Pretty-Printers
+@cindex disabling pretty-printers
+
+For various reasons a pretty-printer may not work.
+For example, the underlying data structure may have changed and
+the pretty-printer is out of date.
+
+The consequences of a broken pretty-printer are severe enough that
+@value{GDBN} provides support for enabling and disabling individual
+printers. For example, if @code{print frame-arguments} is on,
+a backtrace can become highly illegible if any argument is printed
+with a broken printer.
+
+Pretty-printers are enabled and disabled by attaching an @code{enabled}
+attribute to the registered function or callable object. If this attribute
+is present and its value is @code{False}, the printer is disabled, otherwise
+the printer is enabled.
+
+@node Inferiors In Python
+@subsubsection Inferiors In Python
+@cindex inferiors in python
+
+@findex gdb.Inferior
+Programs which are being run under @value{GDBN} are called inferiors
+(@pxref{Inferiors and Programs}). Python scripts can access
+information about and manipulate inferiors controlled by @value{GDBN}
+via objects of the @code{gdb.Inferior} class.
+
+The following inferior-related functions are available in the @code{gdb}
+module:
+
+@defun inferiors
+Return a tuple containing all inferior objects.
+@end defun
+
+A @code{gdb.Inferior} object has the following attributes:
+
+@table @code
+@defivar Inferior num
+ID of inferior, as assigned by GDB.
+@end defivar
+
+@defivar Inferior pid
+Process ID of the inferior, as assigned by the underlying operating
+system.
+@end defivar
+
+@defivar Inferior was_attached
+Boolean signaling whether the inferior was created using `attach', or
+started by @value{GDBN} itself.
+@end defivar
+@end table
+
+A @code{gdb.Inferior} object has the following methods:
+
+@table @code
+@defmethod Inferior threads
+This method returns a tuple holding all the threads which are valid
+when it is called. If there are no valid threads, the method will
+return an empty tuple.
+@end defmethod
+
+@findex gdb.read_memory
+@defmethod Inferior read_memory address length
+Read @var{length} bytes of memory from the inferior, starting at
+@var{address}. Returns a buffer object, which behaves much like an array
+or a string. It can be modified and given to the @code{gdb.write_memory}
+function.
+@end defmethod
+
+@findex gdb.write_memory
+@defmethod Inferior write_memory address buffer @r{[}length@r{]}
+Write the contents of @var{buffer} to the inferior, starting at
+@var{address}. The @var{buffer} parameter must be a Python object
+which supports the buffer protocol, i.e., a string, an array or the
+object returned from @code{gdb.read_memory}. If given, @var{length}
+determines the number of bytes from @var{buffer} to be written.
+@end defmethod
+
+@findex gdb.search_memory
+@defmethod Inferior search_memory address length pattern
+Search a region of the inferior memory starting at @var{address} with
+the given @var{length} using the search pattern supplied in
+@var{pattern}. The @var{pattern} parameter must be a Python object
+which supports the buffer protocol, i.e., a string, an array or the
+object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
+containing the address where the pattern was found, or @code{None} if
+the pattern could not be found.
+@end defmethod
+@end table
+
+@node Threads In Python
+@subsubsection Threads In Python
+@cindex threads in python
+
+@findex gdb.InferiorThread
+Python scripts can access information about, and manipulate inferior threads
+controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
+
+The following thread-related functions are available in the @code{gdb}
+module:
+
+@findex gdb.selected_thread
+@defun selected_thread
+This function returns the thread object for the selected thread. If there
+is no selected thread, this will return @code{None}.
+@end defun
+
+A @code{gdb.InferiorThread} object has the following attributes:
+
+@table @code
+@defivar InferiorThread num
+ID of the thread, as assigned by GDB.
+@end defivar
+
+@defivar InferiorThread ptid
+ID of the thread, as assigned by the operating system. This attribute is a
+tuple containing three integers. The first is the Process ID (PID); the second
+is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
+Either the LWPID or TID may be 0, which indicates that the operating system
+does not use that identifier.
+@end defivar
+@end table
+
+A @code{gdb.InferiorThread} object has the following methods:
+
+@table @code
+@defmethod InferiorThread switch
+This changes @value{GDBN}'s currently selected thread to the one represented
+by this object.
+@end defmethod
+
+@defmethod InferiorThread is_stopped
+Return a Boolean indicating whether the thread is stopped.
+@end defmethod
+
+@defmethod InferiorThread is_running
+Return a Boolean indicating whether the thread is running.
+@end defmethod
+
+@defmethod InferiorThread is_exited
+Return a Boolean indicating whether the thread is exited.
+@end defmethod
+@end table
+
@node Commands In Python
@subsubsection Commands In Python
If this method throws an exception, it is turned into a @value{GDBN}
@code{error} call. Otherwise, the return value is ignored.
+
+@findex gdb.string_to_argv
+To break @var{argument} up into an argv-like string use
+@code{gdb.string_to_argv}. This function behaves identically to
+@value{GDBN}'s internal argument lexer @code{buildargv}.
+It is recommended to use this for consistency.
+Arguments are separated by spaces and may be quoted.
+Example:
+
+@smallexample
+print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
+['1', '2 "3', '4 "5', "6 '7"]
+@end smallexample
+
@end defmethod
@cindex completion of Python commands
Python code is read into @value{GDBN}, you may need to import the
@code{gdb} module explicitly.
+@node Parameters In Python
+@subsubsection Parameters In Python
+
+@cindex parameters in python
+@cindex python parameters
+@tindex gdb.Parameter
+@tindex Parameter
+You can implement new @value{GDBN} parameters using Python. A new
+parameter is implemented as an instance of the @code{gdb.Parameter}
+class.
+
+Parameters are exposed to the user via the @code{set} and
+@code{show} commands. @xref{Help}.
+
+There are many parameters that already exist and can be set in
+@value{GDBN}. Two examples are: @code{set follow fork} and
+@code{set charset}. Setting these parameters influences certain
+behavior in @value{GDBN}. Similarly, you can define parameters that
+can be used to influence behavior in custom Python scripts and commands.
+
+@defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
+The object initializer for @code{Parameter} registers the new
+parameter with @value{GDBN}. This initializer is normally invoked
+from the subclass' own @code{__init__} method.
+
+@var{name} is the name of the new parameter. If @var{name} consists
+of multiple words, then the initial words are looked for as prefix
+parameters. An example of this can be illustrated with the
+@code{set print} set of parameters. If @var{name} is
+@code{print foo}, then @code{print} will be searched as the prefix
+parameter. In this case the parameter can subsequently be accessed in
+@value{GDBN} as @code{set print foo}.
+
+If @var{name} consists of multiple words, and no prefix parameter group
+can be found, an exception is raised.
+
+@var{command-class} should be one of the @samp{COMMAND_} constants
+(@pxref{Commands In Python}). This argument tells @value{GDBN} how to
+categorize the new parameter in the help system.
+
+@var{parameter-class} should be one of the @samp{PARAM_} constants
+defined below. This argument tells @value{GDBN} the type of the new
+parameter; this information is used for input validation and
+completion.
+
+If @var{parameter-class} is @code{PARAM_ENUM}, then
+@var{enum-sequence} must be a sequence of strings. These strings
+represent the possible values for the parameter.
+
+If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
+of a fourth argument will cause an exception to be thrown.
+
+The help text for the new parameter is taken from the Python
+documentation string for the parameter's class, if there is one. If
+there is no documentation string, a default value is used.
+@end defmethod
+
+@defivar Parameter set_doc
+If this attribute exists, and is a string, then its value is used as
+the help text for this parameter's @code{set} command. The value is
+examined when @code{Parameter.__init__} is invoked; subsequent changes
+have no effect.
+@end defivar
+
+@defivar Parameter show_doc
+If this attribute exists, and is a string, then its value is used as
+the help text for this parameter's @code{show} command. The value is
+examined when @code{Parameter.__init__} is invoked; subsequent changes
+have no effect.
+@end defivar
+
+@defivar Parameter value
+The @code{value} attribute holds the underlying value of the
+parameter. It can be read and assigned to just as any other
+attribute. @value{GDBN} does validation when assignments are made.
+@end defivar
+
+
+When a new parameter is defined, its type must be specified. The
+available types are represented by constants defined in the @code{gdb}
+module:
+
+@table @code
+@findex PARAM_BOOLEAN
+@findex gdb.PARAM_BOOLEAN
+@item PARAM_BOOLEAN
+The value is a plain boolean. The Python boolean values, @code{True}
+and @code{False} are the only valid values.
+
+@findex PARAM_AUTO_BOOLEAN
+@findex gdb.PARAM_AUTO_BOOLEAN
+@item PARAM_AUTO_BOOLEAN
+The value has three possible states: true, false, and @samp{auto}. In
+Python, true and false are represented using boolean constants, and
+@samp{auto} is represented using @code{None}.
+
+@findex PARAM_UINTEGER
+@findex gdb.PARAM_UINTEGER
+@item PARAM_UINTEGER
+The value is an unsigned integer. The value of 0 should be
+interpreted to mean ``unlimited''.
+
+@findex PARAM_INTEGER
+@findex gdb.PARAM_INTEGER
+@item PARAM_INTEGER
+The value is a signed integer. The value of 0 should be interpreted
+to mean ``unlimited''.
+
+@findex PARAM_STRING
+@findex gdb.PARAM_STRING
+@item PARAM_STRING
+The value is a string. When the user modifies the string, any escape
+sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
+translated into corresponding characters and encoded into the current
+host charset.
+
+@findex PARAM_STRING_NOESCAPE
+@findex gdb.PARAM_STRING_NOESCAPE
+@item PARAM_STRING_NOESCAPE
+The value is a string. When the user modifies the string, escapes are
+passed through untranslated.
+
+@findex PARAM_OPTIONAL_FILENAME
+@findex gdb.PARAM_OPTIONAL_FILENAME
+@item PARAM_OPTIONAL_FILENAME
+The value is a either a filename (a string), or @code{None}.
+
+@findex PARAM_FILENAME
+@findex gdb.PARAM_FILENAME
+@item PARAM_FILENAME
+The value is a filename. This is just like
+@code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
+
+@findex PARAM_ZINTEGER
+@findex gdb.PARAM_ZINTEGER
+@item PARAM_ZINTEGER
+The value is an integer. This is like @code{PARAM_INTEGER}, except 0
+is interpreted as itself.
+
+@findex PARAM_ENUM
+@findex gdb.PARAM_ENUM
+@item PARAM_ENUM
+The value is a string, which must be one of a collection string
+constants provided when the parameter is created.
+@end table
+
@node Functions In Python
@subsubsection Writing new convenience functions
Return a list of the children of the specified variable object and
create variable objects for them, if they do not already exist. With
-a single argument or if @var{print-values} has a value for of 0 or
+a single argument or if @var{print-values} has a value of 0 or
@code{--no-values}, print only the names of the variables; if
@var{print-values} is 1 or @code{--all-values}, also print their
values; and if it is 2 or @code{--simple-values} print the name and
a recursive definition of the data type as stored in @value{GDBN}'s
data structures, including its flags and contained types.
+@kindex maint set dwarf2 always-disassemble
+@kindex maint show dwarf2 always-disassemble
+@item maint set dwarf2 always-disassemble
+@item maint show dwarf2 always-disassemble
+Control the behavior of @code{info address} when using DWARF debugging
+information.
+
+The default is @code{off}, which means that @value{GDBN} should try to
+describe a variable's location in an easily readable format. When
+@code{on}, @value{GDBN} will instead display the DWARF location
+expression in an assembly-like format. Note that some locations are
+too complex for @value{GDBN} to describe simply; in this case you will
+always see the disassembly form.
+
+Here is an example of the resulting disassembly:
+
+@smallexample
+(gdb) info addr argc
+Symbol "argc" is a complex DWARF expression:
+ 1: DW_OP_fbreg 0
+@end smallexample
+
+For more information on these expressions, see
+@uref{http://www.dwarfstd.org/, the DWARF standard}.
+
@kindex maint set dwarf2 max-cache-age
@kindex maint show dwarf2 max-cache-age
@item maint set dwarf2 max-cache-age
@table @samp
+@item QAllow:@var{op}:@var{val}@dots{}
+@cindex @samp{QAllow} packet
+Specify which operations @value{GDBN} expects to request of the
+target, as a semicolon-separated list of operation name and value
+pairs. Possible values for @var{op} include @samp{WriteReg},
+@samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
+@samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
+indicating that @value{GDBN} will not request the operation, or 1,
+indicating that it may. (The target can then use this to set up its
+own internals optimally, for instance if the debugger never expects to
+insert breakpoints, it may not need to install its own trap handler.)
+
@item qC
@cindex current thread, remote request
@cindex @samp{qC} packet
more thread IDs, separated by commas.
@value{GDBN} will respond to each reply with a request for more thread
ids (using the @samp{qs} form of the query), until the target responds
-with @samp{l} (lower-case el, for @dfn{last}).
+with @samp{l} (lower-case ell, for @dfn{last}).
Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
fields.
description. If the stub sees @samp{xmlRegisters=} with target
specific strings separated by a comma, it will report register
description.
+
+@item qRelocInsn
+This feature indicates whether @value{GDBN} supports the
+@samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
+instruction reply packet}).
@end table
Stubs should ignore any unknown values for
@tab @samp{-}
@tab Yes
+@item @samp{qXfer:sdata:read}
+@tab No
+@tab @samp{-}
+@tab Yes
+
@item @samp{qXfer:spu:read}
@tab No
@tab @samp{-}
@tab @samp{-}
@tab No
+@item @samp{QAllow}
+@tab No
+@tab @samp{-}
+@tab No
+
@end multitable
These are the currently defined stub features, in more detail:
The remote stub understands the @samp{qXfer:memory-map:read} packet
(@pxref{qXfer memory map read}).
+@item qXfer:sdata:read
+The remote stub understands the @samp{qXfer:sdata:read} packet
+(@pxref{qXfer sdata read}).
+
@item qXfer:spu:read
The remote stub understands the @samp{qXfer:spu:read} packet
(@pxref{qXfer spu read}).
The remote stub understands the @samp{QTDPsrc} packet that supplies
the source form of tracepoint definitions.
+@item QAllow
+The remote stub understands the @samp{QAllow} packet.
+
+@item StaticTracepoint
+@cindex static tracepoints, in remote protocol
+The remote stub supports static tracepoints.
+
@end table
@item qSymbol::
@itemx QTro
@itemx qTStatus
@itemx qTV
+@itemx qTfSTM
+@itemx qTsSTM
+@itemx qTSTMat
@xref{Tracepoint Packets}.
@item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
This packet is not probed by default; the remote stub must request it,
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
+@item qXfer:sdata:read::@var{offset},@var{length}
+@anchor{qXfer sdata read}
+
+Read contents of the extra collected static tracepoint marker
+information. The annex part of the generic @samp{qXfer} packet must
+be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
+Action Lists}.
+
+This packet is not probed by default; the remote stub must request it,
+by supplying an appropriate @samp{qSupported} response
+(@pxref{qSupported}).
+
@item qXfer:siginfo:read::@var{offset},@var{length}
@anchor{qXfer siginfo read}
Read contents of the extra signal information on the target
@table @samp
@item OK
The packet was understood and carried out.
+@item qRelocInsn
+@xref{Tracepoint Packets,,Relocate instruction reply packet}.
@item
The packet was not recognized.
@end table
@table @samp
@item OK
The packet was understood and carried out.
+@item qRelocInsn
+@xref{Tracepoint Packets,,Relocate instruction reply packet}.
@item
The packet was not recognized.
@end table
frame @emph{outside} the given range of addresses (exclusive).
@item QTStart
-Begin the tracepoint experiment. Begin collecting data from tracepoint
-hits in the trace frame buffer.
+Begin the tracepoint experiment. Begin collecting data from
+tracepoint hits in the trace frame buffer. This packet supports the
+@samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
+instruction reply packet}).
@item QTStop
End the tracepoint experiment. Stop collecting trace frames.
these packets follow the syntax of the @code{QTDV} packets that define
trace state variables.
+@item qTfSTM
+@itemx qTsSTM
+These packets request data about static tracepoint markers that exist
+in the target program. @value{GDBN} sends @code{qTfSTM} to get the
+first piece of data, and multiple @code{qTsSTM} to get additional
+pieces. Replies to these packets take the following form:
+
+Reply:
+@table @samp
+@item m @var{address}:@var{id}:@var{extra}
+A single marker
+@item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
+a comma-separated list of markers
+@item l
+(lower case letter @samp{L}) denotes end of list.
+@item E @var{nn}
+An error occurred. @var{nn} are hex digits.
+@item
+An empty reply indicates that the request is not supported by the
+stub.
+@end table
+
+@var{address} is encoded in hex.
+@var{id} and @var{extra} are strings encoded in hex.
+
+In response to each query, the target will reply with a list of one or
+more markers, separated by commas. @value{GDBN} will respond to each
+reply with a request for more markers (using the @samp{qs} form of the
+query), until the target responds with @samp{l} (lower-case ell, for
+@dfn{last}).
+
+@item qTSTMat:@var{address}
+This packets requests data about static tracepoint markers in the
+target program at @var{address}. Replies to this packet follow the
+syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
+tracepoint markers.
+
@item QTSave:@var{filename}
This packet directs the target to save trace data to the file name
@var{filename} in the target's filesystem. @var{filename} is encoded
@end table
+@subsection Relocate instruction reply packet
+When installing fast tracepoints in memory, the target may need to
+relocate the instruction currently at the tracepoint address to a
+different address in memory. For most instructions, a simple copy is
+enough, but, for example, call instructions that implicitly push the
+return address on the stack, and relative branches or other
+PC-relative instructions require offset adjustment, so that the effect
+of executing the instruction at a different address is the same as if
+it had executed in the original location.
+
+In response to several of the tracepoint packets, the target may also
+respond with a number of intermediate @samp{qRelocInsn} request
+packets before the final result packet, to have @value{GDBN} handle
+this relocation operation. If a packet supports this mechanism, its
+documentation will explicitly say so. See for example the above
+descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
+format of the request is:
+
+@table @samp
+@item qRelocInsn:@var{from};@var{to}
+
+This requests @value{GDBN} to copy instruction at address @var{from}
+to address @var{to}, possibly adjusted so that executing the
+instruction at @var{to} has the same effect as executing it at
+@var{from}. @value{GDBN} writes the adjusted instruction to target
+memory starting at @var{to}.
+@end table
+
+Replies:
+@table @samp
+@item qRelocInsn:@var{adjusted_size}
+Informs the stub the relocation is complete. @var{adjusted_size} is
+the length in bytes of resulting relocated instruction sequence.
+@item E @var{NN}
+A badly formed request was detected, or an error was encountered while
+relocating the instruction.
+@end table
+
@node Host I/O Packets
@section Host I/O Packets
@cindex Host I/O, remote protocol
@include gpl.texi
-@raisesections
+@node GNU Free Documentation License
+@appendix GNU Free Documentation License
@include fdl.texi
-@lowersections
@node Index
@unnumbered Index