Mail Archives: cygwin/2011/07/31/13:35:56
I've made a new version of the gdb debugger available for installation.
This version is a refresh from the main branch of the CVS repository on
sourceware.org. The package no longer contains the "insight" graphical
debugger. Time permitting, there will be a separate package introduced
for insight.
A copy of the NEWS file from this release is included below. I've been
extremely remiss in releasing a new version of gdb (the last one was
in 2008!) so the NEWS file is long. I'll try to adopt a more regular
release cadence in the future.
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What has changed in GDB?
(Organized release by release)
*** Changes since GDB 7.3
* GDB has two new commands: "set remote hardware-watchpoint-length-limit"
and "show remote hardware-watchpoint-length-limit". These allows to
set or show the maximum length limit (in bytes) of a remote
target hardware watchpoint.
This allows e.g. to use "unlimited" hardware watchpoints with the
gdbserver integrated in Valgrind version >= 3.7.0. Such Valgrind
watchpoints are slower than real hardware watchpoints but are
significantly faster than gdb software watchpoints.
* Python scripting
** The "maint set python print-stack on|off" command has been
deprecated, and a new command: "set python print-stack on|off" has
replaced it. Additionally, the default for "print-stack" is now
"off".
** A prompt subsitution hook (prompt_hook) is now available to the
Python API.
* libthread-db-search-path now supports two special values: $sdir and $pdir.
$sdir specifies the default system locations of shared libraries.
$pdir specifies the directory where the libpthread used by the application
lives.
GDB no longer looks in $sdir and $pdir after it has searched the directories
mentioned in libthread-db-search-path. If you want to search those
directories, they must be specified in libthread-db-search-path.
The default value of libthread-db-search-path on GNU/Linux and Solaris
systems is now "$sdir:$pdir".
$pdir is not supported by gdbserver, it is currently ignored.
$sdir is supported by gdbserver.
* New configure option --with-iconv-bin.
When using the internationalization support like the one in the GNU C
library, GDB will invoke the "iconv" program to get a list of supported
character sets. If this program lives in a non-standard location, one can
use this option to specify where to find it.
* When natively debugging programs on PowerPC BookE processors running
a Linux kernel version 2.6.34 or later, GDB supports masked hardware
watchpoints, which specify a mask in addition to an address to watch.
The mask specifies that some bits of an address (the bits which are
reset in the mask) should be ignored when matching the address accessed
by the inferior against the watchpoint address. See the "PowerPC Embedded"
section in the user manual for more details.
* The new option --once causes GDBserver to stop listening for connections once
the first connection is made. The listening port used by GDBserver will
become available after that.
* New commands "info macros", and "info definitions" have been added.
* Changed commands
watch EXPRESSION mask MASK_VALUE
The watch command now supports the mask argument which allows creation
of masked watchpoints, if the current architecture supports this feature.
info auto-load-scripts [REGEXP]
This command was formerly named "maintenance print section-scripts".
It is now generally useful and is no longer a maintenance-only command.
* Tracepoints can now be enabled and disabled at any time after a trace
experiment has been started using the standard "enable" and "disable"
commands. It is now possible to start a trace experiment with no enabled
tracepoints; GDB will display a warning, but will allow the experiment to
begin, assuming that tracepoints will be enabled as needed while the trace
is running.
* New remote packets
QTEnable
Dynamically enable a tracepoint in a started trace experiment.
QTDisable
Dynamically disable a tracepoint in a started trace experiment.
* Dcache size (number of lines) and line-size are now runtime-configurable
via "set dcache line" and "set dcache line-size" commands.
*** Changes in GDB 7.3
* GDB has a new command: "thread find [REGEXP]".
It finds the thread id whose name, target id, or thread extra info
matches the given regular expression.
* The "catch syscall" command now works on mips*-linux* targets.
* The -data-disassemble MI command now supports modes 2 and 3 for
dumping the instruction opcodes.
* New command line options
-data-directory DIR Specify DIR as the "data-directory".
This is mostly for testing purposes.
* The "maint set python auto-load on|off" command has been renamed to
"set auto-load-scripts on|off".
* GDB has a new command: "set directories".
It is like the "dir" command except that it replaces the
source path list instead of augmenting it.
* GDB now understands thread names.
On GNU/Linux, "info threads" will display the thread name as set by
prctl or pthread_setname_np.
There is also a new command, "thread name", which can be used to
assign a name internally for GDB to display.
* OpenCL C
Initial support for the OpenCL C language (http://www.khronos.org/opencl)
has been integrated into GDB.
* Python scripting
** The function gdb.Write now accepts an optional keyword 'stream'.
This keyword, when provided, will direct the output to either
stdout, stderr, or GDB's logging output.
** Parameters can now be be sub-classed in Python, and in particular
you may implement the get_set_doc and get_show_doc functions.
This improves how Parameter set/show documentation is processed
and allows for more dynamic content.
** Symbols, Symbol Table, Symbol Table and Line, Object Files,
Inferior, Inferior Thread, Blocks, and Block Iterator APIs now
have an is_valid method.
** Breakpoints can now be sub-classed in Python, and in particular
you may implement a 'stop' function that is executed each time
the inferior reaches that breakpoint.
** New function gdb.lookup_global_symbol looks up a global symbol.
** GDB values in Python are now callable if the value represents a
function. For example, if 'some_value' represents a function that
takes two integer parameters and returns a value, you can call
that function like so:
result = some_value (10,20)
** Module gdb.types has been added.
It contains a collection of utilities for working with gdb.Types objects:
get_basic_type, has_field, make_enum_dict.
** Module gdb.printing has been added.
It contains utilities for writing and registering pretty-printers.
New classes: PrettyPrinter, SubPrettyPrinter,
RegexpCollectionPrettyPrinter.
New function: register_pretty_printer.
** New commands "info pretty-printers", "enable pretty-printer" and
"disable pretty-printer" have been added.
** gdb.parameter("directories") is now available.
** New function gdb.newest_frame returns the newest frame in the
selected thread.
** The gdb.InferiorThread class has a new "name" attribute. This
holds the thread's name.
** Python Support for Inferior events.
Python scripts can add observers to be notified of events
occurring in the process being debugged.
The following events are currently supported:
- gdb.events.cont Continue event.
- gdb.events.exited Inferior exited event.
- gdb.events.stop Signal received, and Breakpoint hit events.
* C++ Improvements:
** GDB now puts template parameters in scope when debugging in an
instantiation. For example, if you have:
template<int X> int func (void) { return X; }
then if you step into func<5>, "print X" will show "5". This
feature requires proper debuginfo support from the compiler; it
was added to GCC 4.5.
** The motion commands "next", "finish", "until", and "advance" now
work better when exceptions are thrown. In particular, GDB will
no longer lose control of the inferior; instead, the GDB will
stop the inferior at the point at which the exception is caught.
This functionality requires a change in the exception handling
code that was introduced in GCC 4.5.
* GDB now follows GCC's rules on accessing volatile objects when
reading or writing target state during expression evaluation.
One notable difference to prior behavior is that "print x = 0"
no longer generates a read of x; the value of the assignment is
now always taken directly from the value being assigned.
* GDB now has some support for using labels in the program's source in
linespecs. For instance, you can use "advance label" to continue
execution to a label.
* GDB now has support for reading and writing a new .gdb_index
section. This section holds a fast index of DWARF debugging
information and can be used to greatly speed up GDB startup and
operation. See the documentation for `save gdb-index' for details.
* The "watch" command now accepts an optional "-location" argument.
When used, this causes GDB to watch the memory referred to by the
expression. Such a watchpoint is never deleted due to it going out
of scope.
* GDB now supports thread debugging of core dumps on GNU/Linux.
GDB now activates thread debugging using the libthread_db library
when debugging GNU/Linux core dumps, similarly to when debugging
live processes. As a result, when debugging a core dump file, GDB
is now able to display pthread_t ids of threads. For example, "info
threads" shows the same output as when debugging the process when it
was live. In earlier releases, you'd see something like this:
(gdb) info threads
* 1 LWP 6780 main () at main.c:10
While now you see this:
(gdb) info threads
* 1 Thread 0x7f0f5712a700 (LWP 6780) main () at main.c:10
It is also now possible to inspect TLS variables when debugging core
dumps.
When debugging a core dump generated on a machine other than the one
used to run GDB, you may need to point GDB at the correct
libthread_db library with the "set libthread-db-search-path"
command. See the user manual for more details on this command.
* When natively debugging programs on PowerPC BookE processors running
a Linux kernel version 2.6.34 or later, GDB supports ranged breakpoints,
which stop execution of the inferior whenever it executes an instruction
at any address within the specified range. See the "PowerPC Embedded"
section in the user manual for more details.
* New features in the GDB remote stub, GDBserver
** GDBserver is now supported on PowerPC LynxOS (versions 4.x and 5.x),
and i686 LynxOS (version 5.x).
** GDBserver is now supported on Blackfin Linux.
* New native configurations
ia64 HP-UX ia64-*-hpux*
* New targets:
Analog Devices, Inc. Blackfin Processor bfin-*
* Ada task switching is now supported on sparc-elf targets when
debugging a program using the Ravenscar Profile. For more information,
see the "Tasking Support when using the Ravenscar Profile" section
in the GDB user manual.
* Guile support was removed.
* New features in the GNU simulator
** The --map-info flag lists all known core mappings.
** CFI flashes may be simulated via the "cfi" device.
*** Changes in GDB 7.2
* Shared library support for remote targets by default
When GDB is configured for a generic, non-OS specific target, like
for example, --target=arm-eabi or one of the many *-*-elf targets,
GDB now queries remote stubs for loaded shared libraries using the
`qXfer:libraries:read' packet. Previously, shared library support
was always disabled for such configurations.
* C++ Improvements:
** Argument Dependent Lookup (ADL)
In C++ ADL lookup directs function search to the namespaces of its
arguments even if the namespace has not been imported.
For example:
namespace A
{
class B { };
void foo (B) { }
}
...
A::B b
foo(b)
Here the compiler will search for `foo' in the namespace of 'b'
and find A::foo. GDB now supports this. This construct is commonly
used in the Standard Template Library for operators.
** Improved User Defined Operator Support
In addition to member operators, GDB now supports lookup of operators
defined in a namespace and imported with a `using' directive, operators
defined in the global scope, operators imported implicitly from an
anonymous namespace, and the ADL operators mentioned in the previous
entry.
GDB now also supports proper overload resolution for all the previously
mentioned flavors of operators.
** static const class members
Printing of static const class members that are initialized in the
class definition has been fixed.
* Windows Thread Information Block access.
On Windows targets, GDB now supports displaying the Windows Thread
Information Block (TIB) structure. This structure is visible either
by using the new command `info w32 thread-information-block' or, by
dereferencing the new convenience variable named `$_tlb', a
thread-specific pointer to the TIB. This feature is also supported
when remote debugging using GDBserver.
* Static tracepoints
Static tracepoints are calls in the user program into a tracing
library. One such library is a port of the LTTng kernel tracer to
userspace --- UST (LTTng Userspace Tracer, http://lttng.org/ust).
When debugging with GDBserver, GDB now supports combining the GDB
tracepoint machinery with such libraries. For example: the user can
use GDB to probe a static tracepoint marker (a call from the user
program into the tracing library) with the new "strace" command (see
"New commands" below). This creates a "static tracepoint" in the
breakpoint list, that can be manipulated with the same feature set
as fast and regular tracepoints. E.g., collect registers, local and
global variables, collect trace state variables, and define
tracepoint conditions. In addition, the user can collect extra
static tracepoint marker specific data, by collecting the new
$_sdata internal variable. When analyzing the trace buffer, you can
inspect $_sdata like any other variable available to GDB. For more
information, see the "Tracepoints" chapter in GDB user manual. New
remote packets have been defined to support static tracepoints, see
the "New remote packets" section below.
* Better reconstruction of tracepoints after disconnected tracing
GDB will attempt to download the original source form of tracepoint
definitions when starting a trace run, and then will upload these
upon reconnection to the target, resulting in a more accurate
reconstruction of the tracepoints that are in use on the target.
* Observer mode
You can now exercise direct control over the ways that GDB can
affect your program. For instance, you can disallow the setting of
breakpoints, so that the program can run continuously (assuming
non-stop mode). In addition, the "observer" variable is available
to switch all of the different controls; in observer mode, GDB
cannot affect the target's behavior at all, which is useful for
tasks like diagnosing live systems in the field.
* The new convenience variable $_thread holds the number of the
current thread.
* New remote packets
qGetTIBAddr
Return the address of the Windows Thread Information Block of a given thread.
qRelocInsn
In response to several of the tracepoint packets, the target may now
also respond with a number of intermediate `qRelocInsn' request
packets before the final result packet, to have GDB handle
relocating an instruction to execute at a different address. This
is particularly useful for stubs that support fast tracepoints. GDB
reports support for this feature in the qSupported packet.
qTfSTM, qTsSTM
List static tracepoint markers in the target program.
qTSTMat
List static tracepoint markers at a given address in the target
program.
qXfer:statictrace:read
Read the static trace data collected (by a `collect $_sdata'
tracepoint action). The remote stub reports support for this packet
to gdb's qSupported query.
QAllow
Send the current settings of GDB's permission flags.
QTDPsrc
Send part of the source (textual) form of a tracepoint definition,
which includes location, conditional, and action list.
* The source command now accepts a -s option to force searching for the
script in the source search path even if the script name specifies
a directory.
* New features in the GDB remote stub, GDBserver
- GDBserver now support tracepoints (including fast tracepoints, and
static tracepoints). The feature is currently supported by the
i386-linux and amd64-linux builds. See the "Tracepoints support
in gdbserver" section in the manual for more information.
GDBserver JIT compiles the tracepoint's conditional agent
expression bytecode into native code whenever possible for low
overhead dynamic tracepoints conditionals. For such tracepoints,
an expression that examines program state is evaluated when the
tracepoint is reached, in order to determine whether to capture
trace data. If the condition is simple and false, processing the
tracepoint finishes very quickly and no data is gathered.
GDBserver interfaces with the UST (LTTng Userspace Tracer) library
for static tracepoints support.
- GDBserver now supports x86_64 Windows 64-bit debugging.
* GDB now sends xmlRegisters= in qSupported packet to indicate that
it understands register description.
* The --batch flag now disables pagination and queries.
* X86 general purpose registers
GDB now supports reading/writing byte, word and double-word x86
general purpose registers directly. This means you can use, say,
$ah or $ax to refer, respectively, to the byte register AH and
16-bit word register AX that are actually portions of the 32-bit
register EAX or 64-bit register RAX.
* The `commands' command now accepts a range of breakpoints to modify.
A plain `commands' following a command that creates multiple
breakpoints affects all the breakpoints set by that command. This
applies to breakpoints set by `rbreak', and also applies when a
single `break' command creates multiple breakpoints (e.g.,
breakpoints on overloaded c++ functions).
* The `rbreak' command now accepts a filename specification as part of
its argument, limiting the functions selected by the regex to those
in the specified file.
* Support for remote debugging Windows and SymbianOS shared libraries
from Unix hosts has been improved. Non Windows GDB builds now can
understand target reported file names that follow MS-DOS based file
system semantics, such as file names that include drive letters and
use the backslash character as directory separator. This makes it
possible to transparently use the "set sysroot" and "set
solib-search-path" on Unix hosts to point as host copies of the
target's shared libraries. See the new command "set
target-file-system-kind" described below, and the "Commands to
specify files" section in the user manual for more information.
* New commands
eval template, expressions...
Convert the values of one or more expressions under the control
of the string template to a command line, and call it.
set target-file-system-kind unix|dos-based|auto
show target-file-system-kind
Set or show the assumed file system kind for target reported file
names.
save breakpoints <filename>
Save all current breakpoint definitions to a file suitable for use
in a later debugging session. To read the saved breakpoint
definitions, use the `source' command.
`save tracepoints' is a new alias for `save-tracepoints'. The latter
is now deprecated.
info static-tracepoint-markers
Display information about static tracepoint markers in the target.
strace FN | FILE:LINE | *ADDR | -m MARKER_ID
Define a static tracepoint by probing a marker at the given
function, line, address, or marker ID.
set observer on|off
show observer
Enable and disable observer mode.
set may-write-registers on|off
set may-write-memory on|off
set may-insert-breakpoints on|off
set may-insert-tracepoints on|off
set may-insert-fast-tracepoints on|off
set may-interrupt on|off
Set individual permissions for GDB effects on the target. Note that
some of these settings can have undesirable or surprising
consequences, particularly when changed in the middle of a session.
For instance, disabling the writing of memory can prevent
breakpoints from being inserted, cause single-stepping to fail, or
even crash your program, if you disable after breakpoints have been
inserted. However, GDB should not crash.
set record memory-query on|off
show record memory-query
Control whether to stop the inferior if memory changes caused
by an instruction cannot be recorded.
* Changed commands
disassemble
The disassemble command now supports "start,+length" form of two arguments.
* Python scripting
** GDB now provides a new directory location, called the python directory,
where Python scripts written for GDB can be installed. The location
of that directory is <data-directory>/python, where <data-directory>
is the GDB data directory. For more details, see section `Scripting
GDB using Python' in the manual.
** The GDB Python API now has access to breakpoints, symbols, symbol
tables, program spaces, inferiors, threads and frame's code blocks.
Additionally, GDB Parameters can now be created from the API, and
manipulated via set/show in the CLI.
** New functions gdb.target_charset, gdb.target_wide_charset,
gdb.progspaces, gdb.current_progspace, and gdb.string_to_argv.
** New exception gdb.GdbError.
** Pretty-printers are now also looked up in the current program space.
** Pretty-printers can now be individually enabled and disabled.
** GDB now looks for names of Python scripts to auto-load in a
special section named `.debug_gdb_scripts', in addition to looking
for a OBJFILE-gdb.py script when OBJFILE is read by the debugger.
* Tracepoint actions were unified with breakpoint commands. In particular,
there are no longer differences in "info break" output for breakpoints and
tracepoints and the "commands" command can be used for both tracepoints and
regular breakpoints.
* New targets
ARM Symbian arm*-*-symbianelf*
* D language support.
GDB now supports debugging programs written in the D programming
language.
* GDB now supports the extended ptrace interface for PowerPC which is
available since Linux kernel version 2.6.34. This automatically enables
any hardware breakpoints and additional hardware watchpoints available in
the processor. The old ptrace interface exposes just one hardware
watchpoint and no hardware breakpoints.
* GDB is now able to use the Data Value Compare (DVC) register available on
embedded PowerPC processors to implement in hardware simple watchpoint
conditions of the form:
watch ADDRESS|VARIABLE if ADDRESS|VARIABLE == CONSTANT EXPRESSION
This works in native GDB running on Linux kernels with the extended ptrace
interface mentioned above.
*** Changes in GDB 7.1
* C++ Improvements
** Namespace Support
GDB now supports importing of namespaces in C++. This enables the
user to inspect variables from imported namespaces. Support for
namepace aliasing has also been added. So, if a namespace is
aliased in the current scope (e.g. namepace C=A; ) the user can
print variables using the alias (e.g. (gdb) print C::x).
** Bug Fixes
All known bugs relating to the printing of virtual base class were
fixed. It is now possible to call overloaded static methods using a
qualified name.
** Cast Operators
The C++ cast operators static_cast<>, dynamic_cast<>, const_cast<>,
and reinterpret_cast<> are now handled by the C++ expression parser.
* New targets
Xilinx MicroBlaze microblaze-*-*
Renesas RX rx-*-elf
* New Simulators
Xilinx MicroBlaze microblaze
Renesas RX rx
* Multi-program debugging.
GDB now has support for multi-program (a.k.a. multi-executable or
multi-exec) debugging. This allows for debugging multiple inferiors
simultaneously each running a different program under the same GDB
session. See "Debugging Multiple Inferiors and Programs" in the
manual for more information. This implied some user visible changes
in the multi-inferior support. For example, "info inferiors" now
lists inferiors that are not running yet or that have exited
already. See also "New commands" and "New options" below.
* New tracing features
GDB's tracepoint facility now includes several new features:
** Trace state variables
GDB tracepoints now include support for trace state variables, which
are variables managed by the target agent during a tracing
experiment. They are useful for tracepoints that trigger each
other, so for instance one tracepoint can count hits in a variable,
and then a second tracepoint has a condition that is true when the
count reaches a particular value. Trace state variables share the
$-syntax of GDB convenience variables, and can appear in both
tracepoint actions and condition expressions. Use the "tvariable"
command to create, and "info tvariables" to view; see "Trace State
Variables" in the manual for more detail.
** Fast tracepoints
GDB now includes an option for defining fast tracepoints, which
targets may implement more efficiently, such as by installing a jump
into the target agent rather than a trap instruction. The resulting
speedup can be by two orders of magnitude or more, although the
tradeoff is that some program locations on some target architectures
might not allow fast tracepoint installation, for instance if the
instruction to be replaced is shorter than the jump. To request a
fast tracepoint, use the "ftrace" command, with syntax identical to
the regular trace command.
** Disconnected tracing
It is now possible to detach GDB from the target while it is running
a trace experiment, then reconnect later to see how the experiment
is going. In addition, a new variable disconnected-tracing lets you
tell the target agent whether to continue running a trace if the
connection is lost unexpectedly.
** Trace files
GDB now has the ability to save the trace buffer into a file, and
then use that file as a target, similarly to you can do with
corefiles. You can select trace frames, print data that was
collected in them, and use tstatus to display the state of the
tracing run at the moment that it was saved. To create a trace
file, use "tsave <filename>", and to use it, do "target tfile
<name>".
** Circular trace buffer
You can ask the target agent to handle the trace buffer as a
circular buffer, discarding the oldest trace frames to make room for
newer ones, by setting circular-trace-buffer to on. This feature may
not be available for all target agents.
* Changed commands
disassemble
The disassemble command, when invoked with two arguments, now requires
the arguments to be comma-separated.
info variables
The info variables command now displays variable definitions. Files
which only declare a variable are not shown.
source
The source command is now capable of sourcing Python scripts.
This feature is dependent on the debugger being build with Python
support.
Related to this enhancement is also the introduction of a new command
"set script-extension" (see below).
* New commands (for set/show, see "New options" below)
record save [<FILENAME>]
Save a file (in core file format) containing the process record
execution log for replay debugging at a later time.
record restore <FILENAME>
Restore the process record execution log that was saved at an
earlier time, for replay debugging.
add-inferior [-copies <N>] [-exec <FILENAME>]
Add a new inferior.
clone-inferior [-copies <N>] [ID]
Make a new inferior ready to execute the same program another
inferior has loaded.
remove-inferior ID
Remove an inferior.
maint info program-spaces
List the program spaces loaded into GDB.
set remote interrupt-sequence [Ctrl-C | BREAK | BREAK-g]
show remote interrupt-sequence
Allow the user to select one of ^C, a BREAK signal or BREAK-g
as the sequence to the remote target in order to interrupt the execution.
Ctrl-C is a default. Some system prefers BREAK which is high level of
serial line for some certain time. Linux kernel prefers BREAK-g, a.k.a
Magic SysRq g. It is BREAK signal and character 'g'.
set remote interrupt-on-connect [on | off]
show remote interrupt-on-connect
When interrupt-on-connect is ON, gdb sends interrupt-sequence to
remote target when gdb connects to it. This is needed when you debug
Linux kernel.
set remotebreak [on | off]
show remotebreak
Deprecated. Use "set/show remote interrupt-sequence" instead.
tvariable $NAME [ = EXP ]
Create or modify a trace state variable.
info tvariables
List trace state variables and their values.
delete tvariable $NAME ...
Delete one or more trace state variables.
teval EXPR, ...
Evaluate the given expressions without collecting anything into the
trace buffer. (Valid in tracepoint actions only.)
ftrace FN / FILE:LINE / *ADDR
Define a fast tracepoint at the given function, line, or address.
* New expression syntax
GDB now parses the 0b prefix of binary numbers the same way as GCC does.
GDB now parses 0b101010 identically with 42.
* New options
set follow-exec-mode new|same
show follow-exec-mode
Control whether GDB reuses the same inferior across an exec call or
creates a new one. This is useful to be able to restart the old
executable after the inferior having done an exec call.
set default-collect EXPR, ...
show default-collect
Define a list of expressions to be collected at each tracepoint.
This is a useful way to ensure essential items are not overlooked,
such as registers or a critical global variable.
set disconnected-tracing
show disconnected-tracing
If set to 1, the target is instructed to continue tracing if it
loses its connection to GDB. If 0, the target is to stop tracing
upon disconnection.
set circular-trace-buffer
show circular-trace-buffer
If set to on, the target is instructed to use a circular trace buffer
and discard the oldest trace frames instead of stopping the trace due
to a full trace buffer. If set to off, the trace stops when the buffer
fills up. Some targets may not support this.
set script-extension off|soft|strict
show script-extension
If set to "off", the debugger does not perform any script language
recognition, and all sourced files are assumed to be GDB scripts.
If set to "soft" (the default), files are sourced according to
filename extension, falling back to GDB scripts if the first
evaluation failed.
If set to "strict", files are sourced according to filename extension.
set ada trust-PAD-over-XVS on|off
show ada trust-PAD-over-XVS
If off, activate a workaround against a bug in the debugging information
generated by the compiler for PAD types (see gcc/exp_dbug.ads in
the GCC sources for more information about the GNAT encoding and
PAD types in particular). It is always safe to set this option to
off, but this introduces a slight performance penalty. The default
is on.
* Python API Improvements
** GDB provides the new class gdb.LazyString. This is useful in
some pretty-printing cases. The new method gdb.Value.lazy_string
provides a simple way to create objects of this type.
** The fields returned by gdb.Type.fields now have an
`is_base_class' attribute.
** The new method gdb.Type.range returns the range of an array type.
** The new method gdb.parse_and_eval can be used to parse and
evaluate an expression.
* New remote packets
QTDV
Define a trace state variable.
qTV
Get the current value of a trace state variable.
QTDisconnected
Set desired tracing behavior upon disconnection.
QTBuffer:circular
Set the trace buffer to be linear or circular.
qTfP, qTsP
Get data about the tracepoints currently in use.
* Bug fixes
Process record now works correctly with hardware watchpoints.
Multiple bug fixes have been made to the mips-irix port, making it
much more reliable. In particular:
- Debugging threaded applications is now possible again. Previously,
GDB would hang while starting the program, or while waiting for
the program to stop at a breakpoint.
- Attaching to a running process no longer hangs.
- An error occurring while loading a core file has been fixed.
- Changing the value of the PC register now works again. This fixes
problems observed when using the "jump" command, or when calling
a function from GDB, or even when assigning a new value to $pc.
- With the "finish" and "return" commands, the return value for functions
returning a small array is now correctly printed.
- It is now possible to break on shared library code which gets executed
during a shared library init phase (code executed while executing
their .init section). Previously, the breakpoint would have no effect.
- GDB is now able to backtrace through the signal handler for
non-threaded programs.
PIE (Position Independent Executable) programs debugging is now supported.
This includes debugging execution of PIC (Position Independent Code) shared
libraries although for that, it should be possible to run such libraries as an
executable program.
*** Changes in GDB 7.0
* GDB now has an interface for JIT compilation. Applications that
dynamically generate code can create symbol files in memory and register
them with GDB. For users, the feature should work transparently, and
for JIT developers, the interface is documented in the GDB manual in the
"JIT Compilation Interface" chapter.
* Tracepoints may now be conditional. The syntax is as for
breakpoints; either an "if" clause appended to the "trace" command,
or the "condition" command is available. GDB sends the condition to
the target for evaluation using the same bytecode format as is used
for tracepoint actions.
* The disassemble command now supports: an optional /r modifier, print the
raw instructions in hex as well as in symbolic form, and an optional /m
modifier to print mixed source+assembly.
* Process record and replay
In a architecture environment that supports ``process record and
replay'', ``process record and replay'' target can record a log of
the process execution, and replay it with both forward and reverse
execute commands.
* Reverse debugging: GDB now has new commands reverse-continue, reverse-
step, reverse-next, reverse-finish, reverse-stepi, reverse-nexti, and
set execution-direction {forward|reverse}, for targets that support
reverse execution.
* GDB now supports hardware watchpoints on MIPS/Linux systems. This
feature is available with a native GDB running on kernel version
2.6.28 or later.
* GDB now has support for multi-byte and wide character sets on the
target. Strings whose character type is wchar_t, char16_t, or
char32_t are now correctly printed. GDB supports wide- and unicode-
literals in C, that is, L'x', L"string", u'x', u"string", U'x', and
U"string" syntax. And, GDB allows the "%ls" and "%lc" formats in
`printf'. This feature requires iconv to work properly; if your
system does not have a working iconv, GDB can use GNU libiconv. See
the installation instructions for more information.
* GDB now supports automatic retrieval of shared library files from
remote targets. To use this feature, specify a system root that begins
with the `remote:' prefix, either via the `set sysroot' command or via
the `--with-sysroot' configure-time option.
* "info sharedlibrary" now takes an optional regex of libraries to show,
and it now reports if a shared library has no debugging information.
* Commands `set debug-file-directory', `set solib-search-path' and `set args'
now complete on file names.
* When completing in expressions, gdb will attempt to limit
completions to allowable structure or union fields, where appropriate.
For instance, consider:
# struct example { int f1; double f2; };
# struct example variable;
(gdb) p variable.
If the user types TAB at the end of this command line, the available
completions will be "f1" and "f2".
* Inlined functions are now supported. They show up in backtraces, and
the "step", "next", and "finish" commands handle them automatically.
* GDB now supports the token-splicing (##) and stringification (#)
operators when expanding macros. It also supports variable-arity
macros.
* GDB now supports inspecting extra signal information, exported by
the new $_siginfo convenience variable. The feature is currently
implemented on linux ARM, i386 and amd64.
* GDB can now display the VFP floating point registers and NEON vector
registers on ARM targets. Both ARM GNU/Linux native GDB and gdbserver
can provide these registers (requires Linux 2.6.30 or later). Remote
and simulator targets may also provide them.
* New remote packets
qSearch:memory:
Search memory for a sequence of bytes.
QStartNoAckMode
Turn off `+'/`-' protocol acknowledgments to permit more efficient
operation over reliable transport links. Use of this packet is
controlled by the `set remote noack-packet' command.
vKill
Kill the process with the specified process ID. Use this in preference
to `k' when multiprocess protocol extensions are supported.
qXfer:osdata:read
Obtains additional operating system information
qXfer:siginfo:read
qXfer:siginfo:write
Read or write additional signal information.
* Removed remote protocol undocumented extension
An undocumented extension to the remote protocol's `S' stop reply
packet that permited the stub to pass a process id was removed.
Remote servers should use the `T' stop reply packet instead.
* GDB now supports multiple function calling conventions according to the
DWARF-2 DW_AT_calling_convention function attribute.
* The SH target utilizes the aforementioned change to distinguish between gcc
and Renesas calling convention. It also adds the new CLI commands
`set/show sh calling-convention'.
* GDB can now read compressed debug sections, as produced by GNU gold
with the --compress-debug-sections=zlib flag.
* 64-bit core files are now supported on AIX.
* Thread switching is now supported on Tru64.
* Watchpoints can now be set on unreadable memory locations, e.g. addresses
which will be allocated using malloc later in program execution.
* The qXfer:libraries:read remote procotol packet now allows passing a
list of section offsets.
* On GNU/Linux, GDB can now attach to stopped processes. Several race
conditions handling signals delivered during attach or thread creation
have also been fixed.
* GDB now supports the use of DWARF boolean types for Ada's type Boolean.
From the user's standpoint, all unqualified instances of True and False
are treated as the standard definitions, regardless of context.
* GDB now parses C++ symbol and type names more flexibly. For
example, given:
template<typename T> class C { };
C<char const *> c;
GDB will now correctly handle all of:
ptype C<char const *>
ptype C<char const*>
ptype C<const char *>
ptype C<const char*>
* New features in the GDB remote stub, gdbserver
- The "--wrapper" command-line argument tells gdbserver to use a
wrapper program to launch programs for debugging.
- On PowerPC and S/390 targets, it is now possible to use a single
gdbserver executable to debug both 32-bit and 64-bit programs.
(This requires gdbserver itself to be built as a 64-bit executable.)
- gdbserver uses the new noack protocol mode for TCP connections to
reduce communications latency, if also supported and enabled in GDB.
- Support for the sparc64-linux-gnu target is now included in
gdbserver.
- The amd64-linux build of gdbserver now supports debugging both
32-bit and 64-bit programs.
- The i386-linux, amd64-linux, and i386-win32 builds of gdbserver
now support hardware watchpoints, and will use them automatically
as appropriate.
* Python scripting
GDB now has support for scripting using Python. Whether this is
available is determined at configure time.
New GDB commands can now be written in Python.
* Ada tasking support
Ada tasks can now be inspected in GDB. The following commands have
been introduced:
info tasks
Print the list of Ada tasks.
info task N
Print detailed information about task number N.
task
Print the task number of the current task.
task N
Switch the context of debugging to task number N.
* Support for user-defined prefixed commands. The "define" command can
add new commands to existing prefixes, e.g. "target".
* Multi-inferior, multi-process debugging.
GDB now has generalized support for multi-inferior debugging. See
"Debugging Multiple Inferiors" in the manual for more information.
Although availability still depends on target support, the command
set is more uniform now. The GNU/Linux specific multi-forks support
has been migrated to this new framework. This implied some user
visible changes; see "New commands" and also "Removed commands"
below.
* Target descriptions can now describe the target OS ABI. See the
"Target Description Format" section in the user manual for more
information.
* Target descriptions can now describe "compatible" architectures
to indicate that the target can execute applications for a different
architecture in addition to those for the main target architecture.
See the "Target Description Format" section in the user manual for
more information.
* Multi-architecture debugging.
GDB now includes general supports for debugging applications on
hybrid systems that use more than one single processor architecture
at the same time. Each such hybrid architecture still requires
specific support to be added. The only hybrid architecture supported
in this version of GDB is the Cell Broadband Engine.
* GDB now supports integrated debugging of Cell/B.E. applications that
use both the PPU and SPU architectures. To enable support for hybrid
Cell/B.E. debugging, you need to configure GDB to support both the
powerpc-linux or powerpc64-linux and the spu-elf targets, using the
--enable-targets configure option.
* Non-stop mode debugging.
For some targets, GDB now supports an optional mode of operation in
which you can examine stopped threads while other threads continue
to execute freely. This is referred to as non-stop mode, with the
old mode referred to as all-stop mode. See the "Non-Stop Mode"
section in the user manual for more information.
To be able to support remote non-stop debugging, a remote stub needs
to implement the non-stop mode remote protocol extensions, as
described in the "Remote Non-Stop" section of the user manual. The
GDB remote stub, gdbserver, has been adjusted to support these
extensions on linux targets.
* New commands (for set/show, see "New options" below)
catch syscall [NAME(S) | NUMBER(S)]
Catch system calls. Arguments, which should be names of system
calls or their numbers, mean catch only those syscalls. Without
arguments, every syscall will be caught. When the inferior issues
any of the specified syscalls, GDB will stop and announce the system
call, both when it is called and when its call returns. This
feature is currently available with a native GDB running on the
Linux Kernel, under the following architectures: x86, x86_64,
PowerPC and PowerPC64.
find [/size-char] [/max-count] start-address, end-address|+search-space-size,
val1 [, val2, ...]
Search memory for a sequence of bytes.
maint set python print-stack
maint show python print-stack
Show a stack trace when an error is encountered in a Python script.
python [CODE]
Invoke CODE by passing it to the Python interpreter.
macro define
macro list
macro undef
These allow macros to be defined, undefined, and listed
interactively.
info os processes
Show operating system information about processes.
info inferiors
List the inferiors currently under GDB's control.
inferior NUM
Switch focus to inferior number NUM.
detach inferior NUM
Detach from inferior number NUM.
kill inferior NUM
Kill inferior number NUM.
* New options
set spu stop-on-load
show spu stop-on-load
Control whether to stop for new SPE threads during Cell/B.E. debugging.
set spu auto-flush-cache
show spu auto-flush-cache
Control whether to automatically flush the software-managed cache
during Cell/B.E. debugging.
set sh calling-convention
show sh calling-convention
Control the calling convention used when calling SH target functions.
set debug timestamp
show debug timestamp
Control display of timestamps with GDB debugging output.
set disassemble-next-line
show disassemble-next-line
Control display of disassembled source lines or instructions when
the debuggee stops.
set remote noack-packet
show remote noack-packet
Set/show the use of remote protocol QStartNoAckMode packet. See above
under "New remote packets."
set remote query-attached-packet
show remote query-attached-packet
Control use of remote protocol `qAttached' (query-attached) packet.
set remote read-siginfo-object
show remote read-siginfo-object
Control use of remote protocol `qXfer:siginfo:read' (read-siginfo-object)
packet.
set remote write-siginfo-object
show remote write-siginfo-object
Control use of remote protocol `qXfer:siginfo:write' (write-siginfo-object)
packet.
set remote reverse-continue
show remote reverse-continue
Control use of remote protocol 'bc' (reverse-continue) packet.
set remote reverse-step
show remote reverse-step
Control use of remote protocol 'bs' (reverse-step) packet.
set displaced-stepping
show displaced-stepping
Control displaced stepping mode. Displaced stepping is a way to
single-step over breakpoints without removing them from the debuggee.
Also known as "out-of-line single-stepping".
set debug displaced
show debug displaced
Control display of debugging info for displaced stepping.
maint set internal-error
maint show internal-error
Control what GDB does when an internal error is detected.
maint set internal-warning
maint show internal-warning
Control what GDB does when an internal warning is detected.
set exec-wrapper
show exec-wrapper
unset exec-wrapper
Use a wrapper program to launch programs for debugging.
set multiple-symbols (all|ask|cancel)
show multiple-symbols
The value of this variable can be changed to adjust the debugger behavior
when an expression or a breakpoint location contains an ambiguous symbol
name (an overloaded function name, for instance).
set breakpoint always-inserted
show breakpoint always-inserted
Keep breakpoints always inserted in the target, as opposed to inserting
them when resuming the target, and removing them when the target stops.
This option can improve debugger performance on slow remote targets.
set arm fallback-mode (arm|thumb|auto)
show arm fallback-mode
set arm force-mode (arm|thumb|auto)
show arm force-mode
These commands control how ARM GDB determines whether instructions
are ARM or Thumb. The default for both settings is auto, which uses
the current CPSR value for instructions without symbols; previous
versions of GDB behaved as if "set arm fallback-mode arm".
set disable-randomization
show disable-randomization
Standalone programs run with the virtual address space randomization enabled
by default on some platforms. This option keeps the addresses stable across
multiple debugging sessions.
set non-stop
show non-stop
Control whether other threads are stopped or not when some thread hits
a breakpoint.
set target-async
show target-async
Requests that asynchronous execution is enabled in the target, if available.
In this case, it's possible to resume target in the background, and interact
with GDB while the target is running. "show target-async" displays the
current state of asynchronous execution of the target.
set target-wide-charset
show target-wide-charset
The target-wide-charset is the name of the character set that GDB
uses when printing characters whose type is wchar_t.
set tcp auto-retry (on|off)
show tcp auto-retry
set tcp connect-timeout
show tcp connect-timeout
These commands allow GDB to retry failed TCP connections to a remote stub
with a specified timeout period; this is useful if the stub is launched
in parallel with GDB but may not be ready to accept connections immediately.
set libthread-db-search-path
show libthread-db-search-path
Control list of directories which GDB will search for appropriate
libthread_db.
set schedule-multiple (on|off)
show schedule-multiple
Allow GDB to resume all threads of all processes or only threads of
the current process.
set stack-cache
show stack-cache
Use more aggressive caching for accesses to the stack. This improves
performance of remote debugging (particularly backtraces) without
affecting correctness.
set interactive-mode (on|off|auto)
show interactive-mode
Control whether GDB runs in interactive mode (on) or not (off).
When in interactive mode, GDB waits for the user to answer all
queries. Otherwise, GDB does not wait and assumes the default
answer. When set to auto (the default), GDB determines which
mode to use based on the stdin settings.
* Removed commands
info forks
For program forks, this is replaced by the new more generic `info
inferiors' command. To list checkpoints, you can still use the
`info checkpoints' command, which was an alias for the `info forks'
command.
fork NUM
Replaced by the new `inferior' command. To switch between
checkpoints, you can still use the `restart' command, which was an
alias for the `fork' command.
process PID
This is removed, since some targets don't have a notion of
processes. To switch between processes, you can still use the
`inferior' command using GDB's own inferior number.
delete fork NUM
For program forks, this is replaced by the new more generic `kill
inferior' command. To delete a checkpoint, you can still use the
`delete checkpoint' command, which was an alias for the `delete
fork' command.
detach fork NUM
For program forks, this is replaced by the new more generic `detach
inferior' command. To detach a checkpoint, you can still use the
`detach checkpoint' command, which was an alias for the `detach
fork' command.
* New native configurations
x86/x86_64 Darwin i[34567]86-*-darwin*
x86_64 MinGW x86_64-*-mingw*
* New targets
Lattice Mico32 lm32-*
x86 DICOS i[34567]86-*-dicos*
x86_64 DICOS x86_64-*-dicos*
S+core 3 score-*-*
* The GDB remote stub, gdbserver, now supports x86 Windows CE
(mingw32ce) debugging.
* Removed commands
catch load
catch unload
These commands were actually not implemented on any target.
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