* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
* GDB/MI:: @value{GDBN}'s Machine Interface.
* Annotations:: @value{GDBN}'s annotation interface.
+* JIT Interface:: Using the JIT debugging interface.
* GDB Bugs:: Reporting bugs in @value{GDBN}
who have worked on the Xtensa port of @value{GDBN} in the past include
Steve Tjiang, John Newlin, and Scott Foehner.
+Michael Eager and staff of Xilinx, Inc., contributed support for the
+Xilinx MicroBlaze architecture.
+
@node Sample Session
@chapter A Sample @value{GDBN} Session
@item apropos @var{args}
The @code{apropos} command searches through all of the @value{GDBN}
commands, and their documentation, for the regular expression specified in
-@var{args}. It prints out all matches found. For example:
+@var{args}. It prints out all matches found. For example:
@smallexample
apropos reload
* Attach:: Debugging an already-running process
* Kill Process:: Killing the child process
-* Inferiors:: Debugging multiple inferiors
+* Inferiors and Programs:: Debugging multiple inferiors and programs
* Threads:: Debugging programs with multiple threads
-* Processes:: Debugging programs with multiple processes
+* Forks:: Debugging forks
* Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
@end menu
reads the symbol table again (while trying to preserve your current
breakpoint settings).
-@node Inferiors
-@section Debugging Multiple Inferiors
+@node Inferiors and Programs
+@section Debugging Multiple Inferiors and Programs
-Some @value{GDBN} targets are able to run multiple processes created
-from a single executable. This can happen, for instance, with an
-embedded system reporting back several processes via the remote
-protocol.
+@value{GDBN} lets you run and debug multiple programs in a single
+session. In addition, @value{GDBN} on some systems may let you run
+several programs simultaneously (otherwise you have to exit from one
+before starting another). In the most general case, you can have
+multiple threads of execution in each of multiple processes, launched
+from multiple executables.
@cindex inferior
@value{GDBN} represents the state of each program execution with an
object called an @dfn{inferior}. An inferior typically corresponds to
a process, but is more general and applies also to targets that do not
have processes. Inferiors may be created before a process runs, and
-may (in future) be retained after a process exits. Each run of an
-executable creates a new inferior, as does each attachment to an
-existing process. Inferiors have unique identifiers that are
-different from process ids, and may optionally be named as well.
-Usually each inferior will also have its own distinct address space,
-although some embedded targets may have several inferiors running in
-different parts of a single space.
+may be retained after a process exits. Inferiors have unique
+identifiers that are different from process ids. Usually each
+inferior will also have its own distinct address space, although some
+embedded targets may have several inferiors running in different parts
+of a single address space. Each inferior may in turn have multiple
+threads running in it.
-Each inferior may in turn have multiple threads running in it.
-
-To find out what inferiors exist at any moment, use @code{info inferiors}:
+To find out what inferiors exist at any moment, use @w{@code{info
+inferiors}}:
@table @code
@kindex info inferiors
@item info inferiors
Print a list of all inferiors currently being managed by @value{GDBN}.
+
+@value{GDBN} displays for each inferior (in this order):
+
+@enumerate
+@item
+the inferior number assigned by @value{GDBN}
+
+@item
+the target system's inferior identifier
+
+@item
+the name of the executable the inferior is running.
+
+@end enumerate
+
+@noindent
+An asterisk @samp{*} preceding the @value{GDBN} inferior number
+indicates the current inferior.
+
+For example,
@end table
+@c end table here to get a little more width for example
+
+@smallexample
+(@value{GDBP}) info inferiors
+ Num Description Executable
+ 2 process 2307 hello
+* 1 process 3401 goodbye
+@end smallexample
To switch focus between inferiors, use the @code{inferior} command:
@table @code
-@kindex inferior @var{inferior-id}
-@item inferior @var{inferior-id}
-Make inferior number @var{inferior-id} the current inferior. The
-argument @var{inferior-id} is the internal inferior number assigned by
-@value{GDBN}, as shown in the first field of the @samp{info inferiors}
-display.
+@kindex inferior @var{infno}
+@item inferior @var{infno}
+Make inferior number @var{infno} the current inferior. The argument
+@var{infno} is the inferior number assigned by @value{GDBN}, as shown
+in the first field of the @samp{info inferiors} display.
@end table
-To quit debugging one of the inferiors, you can either detach from it
-by using the @w{@code{detach inferior}} command (allowing it to run
-independently), or kill it using the @w{@code{kill inferior}} command:
+
+You can get multiple executables into a debugging session via the
+@code{add-inferior} and @w{@code{clone-inferior}} commands. On some
+systems @value{GDBN} can add inferiors to the debug session
+automatically by following calls to @code{fork} and @code{exec}. To
+remove inferiors from the debugging session use the
+@w{@code{remove-inferior}} command.
@table @code
-@kindex detach inferior @var{inferior-id}
-@item detach inferior @var{inferior-id}
+@kindex add-inferior
+@item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
+Adds @var{n} inferiors to be run using @var{executable} as the
+executable. @var{n} defaults to 1. If no executable is specified,
+the inferiors begins empty, with no program. You can still assign or
+change the program assigned to the inferior at any time by using the
+@code{file} command with the executable name as its argument.
+
+@kindex clone-inferior
+@item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
+Adds @var{n} inferiors ready to execute the same program as inferior
+@var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
+number of the current inferior. This is a convenient command when you
+want to run another instance of the inferior you are debugging.
+
+@smallexample
+(@value{GDBP}) info inferiors
+ Num Description Executable
+* 1 process 29964 helloworld
+(@value{GDBP}) clone-inferior
+Added inferior 2.
+1 inferiors added.
+(@value{GDBP}) info inferiors
+ Num Description Executable
+ 2 <null> helloworld
+* 1 process 29964 helloworld
+@end smallexample
+
+You can now simply switch focus to inferior 2 and run it.
+
+@kindex remove-inferior
+@item remove-inferior @var{infno}
+Removes the inferior @var{infno}. It is not possible to remove an
+inferior that is running with this command. For those, use the
+@code{kill} or @code{detach} command first.
+
+@end table
+
+To quit debugging one of the running inferiors that is not the current
+inferior, you can either detach from it by using the @w{@code{detach
+inferior}} command (allowing it to run independently), or kill it
+using the @w{@code{kill inferior}} command:
+
+@table @code
+@kindex detach inferior @var{infno}
+@item detach inferior @var{infno}
Detach from the inferior identified by @value{GDBN} inferior number
-@var{inferior-id}, and remove it from the inferior list.
+@var{infno}, and remove it from the inferior list.
-@kindex kill inferior @var{inferior-id}
-@item kill inferior @var{inferior-id}
+@kindex kill inferior @var{infno}
+@item kill inferior @var{infno}
Kill the inferior identified by @value{GDBN} inferior number
-@var{inferior-id}, and remove it from the inferior list.
+@var{infno}, and remove it from the inferior list.
@end table
+After the successful completion of a command such as @code{detach},
+@code{detach inferior}, @code{kill} or @code{kill inferior}, or after
+a normal process exit, the inferior is still valid and listed with
+@code{info inferiors}, ready to be restarted.
+
+
To be notified when inferiors are started or exit under @value{GDBN}'s
control use @w{@code{set print inferior-events}}:
inferiors have started, exited or have been detached.
@end table
+Many commands will work the same with multiple programs as with a
+single program: e.g., @code{print myglobal} will simply display the
+value of @code{myglobal} in the current inferior.
+
+
+Occasionaly, when debugging @value{GDBN} itself, it may be useful to
+get more info about the relationship of inferiors, programs, address
+spaces in a debug session. You can do that with the @w{@code{maint
+info program-spaces}} command.
+
+@table @code
+@kindex maint info program-spaces
+@item maint info program-spaces
+Print a list of all program spaces currently being managed by
+@value{GDBN}.
+
+@value{GDBN} displays for each program space (in this order):
+
+@enumerate
+@item
+the program space number assigned by @value{GDBN}
+
+@item
+the name of the executable loaded into the program space, with e.g.,
+the @code{file} command.
+
+@end enumerate
+
+@noindent
+An asterisk @samp{*} preceding the @value{GDBN} program space number
+indicates the current program space.
+
+In addition, below each program space line, @value{GDBN} prints extra
+information that isn't suitable to display in tabular form. For
+example, the list of inferiors bound to the program space.
+
+@smallexample
+(@value{GDBP}) maint info program-spaces
+ Id Executable
+ 2 goodbye
+ Bound inferiors: ID 1 (process 21561)
+* 1 hello
+@end smallexample
+
+Here we can see that no inferior is running the program @code{hello},
+while @code{process 21561} is running the program @code{goodbye}. On
+some targets, it is possible that multiple inferiors are bound to the
+same program space. The most common example is that of debugging both
+the parent and child processes of a @code{vfork} call. For example,
+
+@smallexample
+(@value{GDBP}) maint info program-spaces
+ Id Executable
+* 1 vfork-test
+ Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
+@end smallexample
+
+Here, both inferior 2 and inferior 1 are running in the same program
+space as a result of inferior 1 having executed a @code{vfork} call.
+@end table
+
@node Threads
@section Debugging Programs with Multiple Threads
Display current libthread_db search path.
@end table
-@node Processes
-@section Debugging Programs with Multiple Processes
+@node Forks
+@section Debugging Forks
@cindex fork, debugging programs which call
@cindex multiple processes
will retain control of all forked processes (including nested forks).
You can list the forked processes under the control of @value{GDBN} by
using the @w{@code{info inferiors}} command, and switch from one fork
-to another by using the @code{inferior} command (@pxref{Inferiors,
-,Debugging Multiple Inferiors}).
+to another by using the @code{inferior} command (@pxref{Inferiors and
+Programs, ,Debugging Multiple Inferiors and Programs}).
To quit debugging one of the forked processes, you can either detach
from it by using the @w{@code{detach inferior}} command (allowing it
to run independently), or kill it using the @w{@code{kill inferior}}
-command. @xref{Inferiors, ,Debugging Multiple Inferiors}.
+command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
+and Programs}.
If you ask to debug a child process and a @code{vfork} is followed by an
@code{exec}, @value{GDBN} executes the new target up to the first
cannot debug the child or parent until an @code{exec} call completes.
If you issue a @code{run} command to @value{GDBN} after an @code{exec}
-call executes, the new target restarts. To restart the parent process,
-use the @code{file} command with the parent executable name as its
-argument.
+call executes, the new target restarts. To restart the parent
+process, use the @code{file} command with the parent executable name
+as its argument. By default, after an @code{exec} call executes,
+@value{GDBN} discards the symbols of the previous executable image.
+You can change this behaviour with the @w{@code{set follow-exec-mode}}
+command.
+
+@table @code
+@kindex set follow-exec-mode
+@item set follow-exec-mode @var{mode}
+
+Set debugger response to a program call of @code{exec}. An
+@code{exec} call replaces the program image of a process.
+
+@code{follow-exec-mode} can be:
+
+@table @code
+@item new
+@value{GDBN} creates a new inferior and rebinds the process to this
+new inferior. The program the process was running before the
+@code{exec} call can be restarted afterwards by restarting the
+original inferior.
+
+For example:
+
+@smallexample
+(@value{GDBP}) info inferiors
+(gdb) info inferior
+ Id Description Executable
+* 1 <null> prog1
+(@value{GDBP}) run
+process 12020 is executing new program: prog2
+Program exited normally.
+(@value{GDBP}) info inferiors
+ Id Description Executable
+* 2 <null> prog2
+ 1 <null> prog1
+@end smallexample
+
+@item same
+@value{GDBN} keeps the process bound to the same inferior. The new
+executable image replaces the previous executable loaded in the
+inferior. Restarting the inferior after the @code{exec} call, with
+e.g., the @code{run} command, restarts the executable the process was
+running after the @code{exec} call. This is the default mode.
+
+For example:
+
+@smallexample
+(@value{GDBP}) info inferiors
+ Id Description Executable
+* 1 <null> prog1
+(@value{GDBP}) run
+process 12020 is executing new program: prog2
+Program exited normally.
+(@value{GDBP}) info inferiors
+ Id Description Executable
+* 1 <null> prog2
+@end smallexample
+
+@end table
+@end table
You can use the @code{catch} command to make @value{GDBN} stop whenever
a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
A call to @code{exec}. This is currently only available for HP-UX
and @sc{gnu}/Linux.
+@item syscall
+@itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @r{...}
+@cindex break on a system call.
+A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
+syscall is a mechanism for application programs to request a service
+from the operating system (OS) or one of the OS system services.
+@value{GDBN} can catch some or all of the syscalls issued by the
+debuggee, and show the related information for each syscall. If no
+argument is specified, calls to and returns from all system calls
+will be caught.
+
+@var{name} can be any system call name that is valid for the
+underlying OS. Just what syscalls are valid depends on the OS. On
+GNU and Unix systems, you can find the full list of valid syscall
+names on @file{/usr/include/asm/unistd.h}.
+
+@c For MS-Windows, the syscall names and the corresponding numbers
+@c can be found, e.g., on this URL:
+@c http://www.metasploit.com/users/opcode/syscalls.html
+@c but we don't support Windows syscalls yet.
+
+Normally, @value{GDBN} knows in advance which syscalls are valid for
+each OS, so you can use the @value{GDBN} command-line completion
+facilities (@pxref{Completion,, command completion}) to list the
+available choices.
+
+You may also specify the system call numerically. A syscall's
+number is the value passed to the OS's syscall dispatcher to
+identify the requested service. When you specify the syscall by its
+name, @value{GDBN} uses its database of syscalls to convert the name
+into the corresponding numeric code, but using the number directly
+may be useful if @value{GDBN}'s database does not have the complete
+list of syscalls on your system (e.g., because @value{GDBN} lags
+behind the OS upgrades).
+
+The example below illustrates how this command works if you don't provide
+arguments to it:
+
+@smallexample
+(@value{GDBP}) catch syscall
+Catchpoint 1 (syscall)
+(@value{GDBP}) r
+Starting program: /tmp/catch-syscall
+
+Catchpoint 1 (call to syscall 'close'), \
+ 0xffffe424 in __kernel_vsyscall ()
+(@value{GDBP}) c
+Continuing.
+
+Catchpoint 1 (returned from syscall 'close'), \
+ 0xffffe424 in __kernel_vsyscall ()
+(@value{GDBP})
+@end smallexample
+
+Here is an example of catching a system call by name:
+
+@smallexample
+(@value{GDBP}) catch syscall chroot
+Catchpoint 1 (syscall 'chroot' [61])
+(@value{GDBP}) r
+Starting program: /tmp/catch-syscall
+
+Catchpoint 1 (call to syscall 'chroot'), \
+ 0xffffe424 in __kernel_vsyscall ()
+(@value{GDBP}) c
+Continuing.
+
+Catchpoint 1 (returned from syscall 'chroot'), \
+ 0xffffe424 in __kernel_vsyscall ()
+(@value{GDBP})
+@end smallexample
+
+An example of specifying a system call numerically. In the case
+below, the syscall number has a corresponding entry in the XML
+file, so @value{GDBN} finds its name and prints it:
+
+@smallexample
+(@value{GDBP}) catch syscall 252
+Catchpoint 1 (syscall(s) 'exit_group')
+(@value{GDBP}) r
+Starting program: /tmp/catch-syscall
+
+Catchpoint 1 (call to syscall 'exit_group'), \
+ 0xffffe424 in __kernel_vsyscall ()
+(@value{GDBP}) c
+Continuing.
+
+Program exited normally.
+(@value{GDBP})
+@end smallexample
+
+However, there can be situations when there is no corresponding name
+in XML file for that syscall number. In this case, @value{GDBN} prints
+a warning message saying that it was not able to find the syscall name,
+but the catchpoint will be set anyway. See the example below:
+
+@smallexample
+(@value{GDBP}) catch syscall 764
+warning: The number '764' does not represent a known syscall.
+Catchpoint 2 (syscall 764)
+(@value{GDBP})
+@end smallexample
+
+If you configure @value{GDBN} using the @samp{--without-expat} option,
+it will not be able to display syscall names. Also, if your
+architecture does not have an XML file describing its system calls,
+you will not be able to see the syscall names. It is important to
+notice that these two features are used for accessing the syscall
+name database. In either case, you will see a warning like this:
+
+@smallexample
+(@value{GDBP}) catch syscall
+warning: Could not open "syscalls/i386-linux.xml"
+warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
+GDB will not be able to display syscall names.
+Catchpoint 1 (syscall)
+(@value{GDBP})
+@end smallexample
+
+Of course, the file name will change depending on your architecture and system.
+
+Still using the example above, you can also try to catch a syscall by its
+number. In this case, you would see something like:
+
+@smallexample
+(@value{GDBP}) catch syscall 252
+Catchpoint 1 (syscall(s) 252)
+@end smallexample
+
+Again, in this case @value{GDBN} would not be able to display syscall's names.
+
@item fork
A call to @code{fork}. This is currently only available for HP-UX
and @sc{gnu}/Linux.
Break conditions can have side effects, and may even call functions in
your program. This can be useful, for example, to activate functions
that log program progress, or to use your own print functions to
-format special data structures. The effects are completely predictable
+format special data structures. The effects are completely predictable
unless there is another enabled breakpoint at the same address. (In
that case, @value{GDBN} might see the other breakpoint first and stop your
program without checking the condition of this one.) Note that
@item show record stop-at-limit
Show the current setting of @code{stop-at-limit}.
-@kindex info record insn-number
-@item info record insn-number
-Show the current number of recorded instructions.
+@kindex info record
+@item info record
+Show various statistics about the state of process record and its
+in-memory execution log buffer, including:
+
+@itemize @bullet
+@item
+Whether in record mode or replay mode.
+@item
+Lowest recorded instruction number (counting from when the current execution log started recording instructions).
+@item
+Highest recorded instruction number.
+@item
+Current instruction about to be replayed (if in replay mode).
+@item
+Number of instructions contained in the execution log.
+@item
+Maximum number of instructions that may be contained in the execution log.
+@end itemize
@kindex record delete
@kindex rec del
program counter of the selected frame. A single argument to this
command is a program counter value; @value{GDBN} dumps the function
surrounding this value. Two arguments specify a range of addresses
-(first inclusive, second exclusive) to dump.
+(first inclusive, second exclusive) to dump. In that case, the name of
+the function is also printed (since there could be several functions in
+the given range).
+
+If the range of memory being disassembled contains current program counter,
+the instruction at that location is shown with a @code{=>} marker.
@end table
The following example shows the disassembly of a range of addresses of
@smallexample
(@value{GDBP}) disas 0x32c4 0x32e4
Dump of assembler code from 0x32c4 to 0x32e4:
-0x32c4 <main+204>: addil 0,dp
-0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
-0x32cc <main+212>: ldil 0x3000,r31
-0x32d0 <main+216>: ble 0x3f8(sr4,r31)
-0x32d4 <main+220>: ldo 0(r31),rp
-0x32d8 <main+224>: addil -0x800,dp
-0x32dc <main+228>: ldo 0x588(r1),r26
-0x32e0 <main+232>: ldil 0x3000,r31
+ 0x32c4 <main+204>: addil 0,dp
+ 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
+ 0x32cc <main+212>: ldil 0x3000,r31
+ 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
+ 0x32d4 <main+220>: ldo 0(r31),rp
+ 0x32d8 <main+224>: addil -0x800,dp
+ 0x32dc <main+228>: ldo 0x588(r1),r26
+ 0x32e0 <main+232>: ldil 0x3000,r31
End of assembler dump.
@end smallexample
-Here is an example showing mixed source+assembly for Intel x86:
+Here is an example showing mixed source+assembly for Intel x86, when the
+program is stopped just after function prologue:
@smallexample
(@value{GDBP}) disas /m main
Dump of assembler code for function main:
5 @{
-0x08048330 <main+0>: push %ebp
-0x08048331 <main+1>: mov %esp,%ebp
-0x08048333 <main+3>: sub $0x8,%esp
-0x08048336 <main+6>: and $0xfffffff0,%esp
-0x08048339 <main+9>: sub $0x10,%esp
+ 0x08048330 <+0>: push %ebp
+ 0x08048331 <+1>: mov %esp,%ebp
+ 0x08048333 <+3>: sub $0x8,%esp
+ 0x08048336 <+6>: and $0xfffffff0,%esp
+ 0x08048339 <+9>: sub $0x10,%esp
6 printf ("Hello.\n");
-0x0804833c <main+12>: movl $0x8048440,(%esp)
-
0x08048343 <main+19>: call 0x8048284 <puts@@plt>
+=> 0x0804833c <+12>: movl $0x8048440,(%esp)
+
0x08048343 <+19>: call 0x8048284 <puts@@plt>
7 return 0;
8 @}
-0x08048348 <main+24>: mov $0x0,%eax
-0x0804834d <main+29>: leave
-0x0804834e <main+30>: ret
+ 0x08048348 <+24>: mov $0x0,%eax
+ 0x0804834d <+29>: leave
+ 0x0804834e <+30>: ret
End of assembler dump.
@end smallexample
the repeat count @var{n} is used again; the other arguments default as
for successive uses of @code{x}.
+When examining machine instructions, the instruction at current program
+counter is shown with a @code{=>} marker. For example:
+
+@smallexample
+(@value{GDBP}) x/5i $pc-6
+ 0x804837f <main+11>: mov %esp,%ebp
+ 0x8048381 <main+13>: push %ecx
+ 0x8048382 <main+14>: sub $0x4,%esp
+=> 0x8048385 <main+17>: movl $0x8048460,(%esp)
+ 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
+@end smallexample
+
@cindex @code{$_}, @code{$__}, and value history
The addresses and contents printed by the @code{x} command are not saved
in the value history because there is often too much of them and they
@item $_siginfo
@vindex $_siginfo@r{, convenience variable}
-The variable @code{$_siginfo} is bound to extra signal information
-inspection (@pxref{extra signal information}).
+The variable @code{$_siginfo} contains extra signal information
+(@pxref{extra signal information}). Note that @code{$_siginfo}
+could be empty, if the application has not yet received any signals.
+For example, it will be empty before you execute the @code{run} command.
@end table
On HP-UX systems, if you refer to a function or variable name that
@section Caching Data of Remote Targets
@cindex caching data of remote targets
-@value{GDBN} can cache data exchanged between the debugger and a
+@value{GDBN} caches data exchanged between the debugger and a
remote target (@pxref{Remote Debugging}). Such caching generally improves
performance, because it reduces the overhead of the remote protocol by
-bundling memory reads and writes into large chunks. Unfortunately,
-@value{GDBN} does not currently know anything about volatile
-registers, and thus data caching will produce incorrect results when
-volatile registers are in use.
+bundling memory reads and writes into large chunks. Unfortunately, simply
+caching everything would lead to incorrect results, since @value{GDBN}
+does not necessarily know anything about volatile values, memory-mapped I/O
+addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
+memory can be changed @emph{while} a gdb command is executing.
+Therefore, by default, @value{GDBN} only caches data
+known to be on the stack@footnote{In non-stop mode, it is moderately
+rare for a running thread to modify the stack of a stopped thread
+in a way that would interfere with a backtrace, and caching of
+stack reads provides a significant speed up of remote backtraces.}.
+Other regions of memory can be explicitly marked as
+cacheable; see @pxref{Memory Region Attributes}.
@table @code
@kindex set remotecache
@item set remotecache on
@itemx set remotecache off
-Set caching state for remote targets. When @code{ON}, use data
-caching. By default, this option is @code{OFF}.
+This option no longer does anything; it exists for compatibility
+with old scripts.
@kindex show remotecache
@item show remotecache
-Show the current state of data caching for remote targets.
+Show the current state of the obsolete remotecache flag.
+
+@kindex set stack-cache
+@item set stack-cache on
+@itemx set stack-cache off
+Enable or disable caching of stack accesses. When @code{ON}, use
+caching. By default, this option is @code{ON}.
+
+@kindex show stack-cache
+@item show stack-cache
+Show the current state of data caching for memory accesses.
@kindex info dcache
-@item info dcache
+@item info dcache @r{[}line@r{]}
Print the information about the data cache performance. The
-information displayed includes: the dcache width and depth; and for
-each cache line, how many times it was referenced, and its data and
-state (invalid, dirty, valid). This command is useful for debugging
-the data cache operation.
+information displayed includes the dcache width and depth, and for
+each cache line, its number, address, and how many times it was
+referenced. This command is useful for debugging the data cache
+operation.
+
+If a line number is specified, the contents of that line will be
+printed in hex.
@end table
@node Searching Memory
* Create and Delete Tracepoints::
* Enable and Disable Tracepoints::
* Tracepoint Passcounts::
+* Tracepoint Conditions::
* Tracepoint Actions::
* Listing Tracepoints::
* Starting and Stopping Trace Experiments::
@noindent
You can abbreviate @code{trace} as @code{tr}.
+@item trace @var{location} if @var{cond}
+Set a tracepoint with condition @var{cond}; evaluate the expression
+@var{cond} each time the tracepoint is reached, and collect data only
+if the value is nonzero---that is, if @var{cond} evaluates as true.
+@xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
+information on tracepoint conditions.
+
@vindex $tpnum
@cindex last tracepoint number
@cindex recent tracepoint number
@end smallexample
@end table
+@node Tracepoint Conditions
+@subsection Tracepoint Conditions
+@cindex conditional tracepoints
+@cindex tracepoint conditions
+
+The simplest sort of tracepoint collects data every time your program
+reaches a specified place. You can also specify a @dfn{condition} for
+a tracepoint. A condition is just a Boolean expression in your
+programming language (@pxref{Expressions, ,Expressions}). A
+tracepoint with a condition evaluates the expression each time your
+program reaches it, and data collection happens only if the condition
+is true.
+
+Tracepoint conditions can be specified when a tracepoint is set, by
+using @samp{if} in the arguments to the @code{trace} command.
+@xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
+also be set or changed at any time with the @code{condition} command,
+just as with breakpoints.
+
+Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
+the conditional expression itself. Instead, @value{GDBN} encodes the
+expression into an agent expression (@pxref{Agent Expressions}
+suitable for execution on the target, independently of @value{GDBN}.
+Global variables become raw memory locations, locals become stack
+accesses, and so forth.
+
+For instance, suppose you have a function that is usually called
+frequently, but should not be called after an error has occurred. You
+could use the following tracepoint command to collect data about calls
+of that function that happen while the error code is propagating
+through the program; an unconditional tracepoint could end up
+collecting thousands of useless trace frames that you would have to
+search through.
+
+@smallexample
+(@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
+@end smallexample
+
@node Tracepoint Actions
@subsection Tracepoint Action Lists
There are two encodings in use, depending on the architecture: BID (Binary
Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
-PowerPC. @value{GDBN} will use the appropriate encoding for the configured
+PowerPC. @value{GDBN} will use the appropriate encoding for the configured
target.
Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
underflow, overflow and divide by zero exceptions.
In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
-to inspect @code{_Decimal128} values stored in floating point registers. See
-@ref{PowerPC,,PowerPC} for more details.
+to inspect @code{_Decimal128} values stored in floating point registers.
+See @ref{PowerPC,,PowerPC} for more details.
@node Objective-C
@subsection Objective-C
@table @code
@item **
-The exponentiation operator. It raises the first operand to the power
+The exponentiation operator. It raises the first operand to the power
of the second one.
@item :
precedence as @code{*}.
@item -
-Negative. Defined on @code{INTEGER} and @code{REAL} data.
+Negative. Defined on @code{INTEGER} and @code{REAL} data.
@item ^
Pointer dereferencing. Defined on pointer types.
@item show opaque-type-resolution
Show whether opaque types are resolved or not.
-@kindex set print symbol-loading
-@cindex print messages when symbols are loaded
-@item set print symbol-loading
-@itemx set print symbol-loading on
-@itemx set print symbol-loading off
-The @code{set print symbol-loading} command allows you to enable or
-disable printing of messages when @value{GDBN} loads symbols.
-By default, these messages will be printed, and normally this is what
-you want. Disabling these messages is useful when debugging applications
-with lots of shared libraries where the quantity of output can be more
-annoying than useful.
-
-@kindex show print symbol-loading
-@item show print symbol-loading
-Show whether messages will be printed when @value{GDBN} loads symbols.
-
@kindex maint print symbols
@cindex symbol dump
@kindex maint print psymbols
@table @code
@kindex info sharedlibrary
@kindex info share
-@item info share
-@itemx info sharedlibrary
-Print the names of the shared libraries which are currently loaded.
+@item info share @var{regex}
+@itemx info sharedlibrary @var{regex}
+Print the names of the shared libraries which are currently loaded
+that match @var{regex}. If @var{regex} is omitted then print
+all shared libraries that are loaded.
@kindex sharedlibrary
@kindex share
usually @file{@var{executable}.debug}, where @var{executable} is the
name of the corresponding executable file without leading directories
(e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
-debug link specifies a CRC32 checksum for the debug file, which
-@value{GDBN} uses to validate that the executable and the debug file
-came from the same build.
+debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
+checksum for the debug file, which @value{GDBN} uses to validate that
+the executable and the debug file came from the same build.
@item
The executable contains a @dfn{build ID}, a unique bit string that is
@noindent
-Since there are many different ways to compute CRC's for the debug
-link (different polynomials, reversals, byte ordering, etc.), the
-simplest way to describe the CRC used in @code{.gnu_debuglink}
-sections is to give the complete code for a function that computes it:
+@cindex CRC algorithm definition
+The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
+IEEE 802.3 using the polynomial:
+
+@c TexInfo requires naked braces for multi-digit exponents for Tex
+@c output, but this causes HTML output to barf. HTML has to be set using
+@c raw commands. So we end up having to specify this equation in 2
+@c different ways!
+@ifhtml
+@display
+@html
+ <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
+ + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
+@end html
+@end display
+@end ifhtml
+@ifnothtml
+@display
+ @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
+ @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
+@end display
+@end ifnothtml
+
+The function is computed byte at a time, taking the least
+significant bit of each byte first. The initial pattern
+@code{0xffffffff} is used, to ensure leading zeros affect the CRC and
+the final result is inverted to ensure trailing zeros also affect the
+CRC.
+
+@emph{Note:} This is the same CRC polynomial as used in handling the
+@dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
+, @value{GDBN} Remote Serial Protocol}). However in the
+case of the Remote Serial Protocol, the CRC is computed @emph{most}
+significant bit first, and the result is not inverted, so trailing
+zeros have no effect on the CRC value.
+
+To complete the description, we show below the code of the function
+which produces the CRC used in @code{.gnu_debuglink}. Inverting the
+initially supplied @code{crc} argument means that an initial call to
+this function passing in zero will start computing the CRC using
+@code{0xffffffff}.
@kindex gnu_debuglink_crc32
@smallexample
Disable or enable specific debugging messages associated with the remote
protocol (@pxref{Remote Protocol}).
+@item monitor set libthread-db-search-path [PATH]
+@cindex gdbserver, search path for @code{libthread_db}
+When this command is issued, @var{path} is a colon-separated list of
+directories to search for @code{libthread_db} (@pxref{Threads,,set
+libthread-db-search-path}). If you omit @var{path},
+@samp{libthread-db-search-path} will be reset to an empty list.
+
@item monitor exit
Tell gdbserver to exit immediately. This command should be followed by
@code{disconnect} to close the debugging session. @code{gdbserver} will
target system. If it is not set, the target will use a default
filename (e.g.@: the last program run).
+@item set remote interrupt-sequence
+@cindex interrupt remote programs
+@cindex select Ctrl-C, BREAK or BREAK-g
+Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
+@samp{BREAK-g} as the
+sequence to the remote target in order to interrupt the execution.
+@samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
+is high level of serial line for some certain time.
+Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
+It is @code{BREAK} signal followed by character @code{g}.
+
+@item show interrupt-sequence
+Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
+is sent by @value{GDBN} to interrupt the remote program.
+@code{BREAK-g} is BREAK signal followed by @code{g} and
+also known as Magic SysRq g.
+
+@item set remote interrupt-on-connect
+@cindex send interrupt-sequence on start
+Specify whether interrupt-sequence is sent to remote target when
+@value{GDBN} connects to it. This is mostly needed when you debug
+Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
+which is known as Magic SysRq g in order to connect @value{GDBN}.
+
+@item show interrupt-on-connect
+Show whether interrupt-sequence is sent
+to remote target when @value{GDBN} connects to it.
+
@kindex set tcp
@kindex show tcp
@item set tcp auto-retry on
@cindex Cygwin-specific commands
@value{GDBN} supports native debugging of MS Windows programs, including
-DLLs with and without symbolic debugging information. There are various
-additional Cygwin-specific commands, described in this section.
-Working with DLLs that have no debugging symbols is described in
-@ref{Non-debug DLL Symbols}.
+DLLs with and without symbolic debugging information.
+
+@cindex Ctrl-BREAK, MS-Windows
+@cindex interrupt debuggee on MS-Windows
+MS-Windows programs that call @code{SetConsoleMode} to switch off the
+special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
+by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
+supports @kbd{C-@key{BREAK}} as an alternative interrupt key
+sequence, which can be used to interrupt the debuggee even if it
+ignores @kbd{C-c}.
+
+There are various additional Cygwin-specific commands, described in
+this section. Working with DLLs that have no debugging symbols is
+described in @ref{Non-debug DLL Symbols}.
@table @code
@kindex info w32
tools, DLL export symbols are made available with a prefix based on the
DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
also entered into the symbol table, so @code{CreateFileA} is often
-sufficient. In some cases there will be name clashes within a program
+sufficient. In some cases there will be name clashes within a program
(particularly if the executable itself includes full debugging symbols)
necessitating the use of the fully qualified name when referring to the
-contents of the DLL. Use single-quotes around the name to avoid the
+contents of the DLL. Use single-quotes around the name to avoid the
exclamation mark (``!'') being interpreted as a language operator.
Note that the internal name of the DLL may be all upper-case, even
-though the file name of the DLL is lower-case, or vice-versa. Since
+though the file name of the DLL is lower-case, or vice-versa. Since
symbols within @value{GDBN} are @emph{case-sensitive} this may cause
some confusion. If in doubt, try the @code{info functions} and
@code{info variables} commands or even @code{maint print msymbols}
* ARM:: ARM RDI
* M32R/D:: Renesas M32R/D
* M68K:: Motorola M68K
+* MicroBlaze:: Xilinx MicroBlaze
* MIPS Embedded:: MIPS Embedded
* OpenRISC 1000:: OpenRisc 1000
* PA:: HP PA Embedded
@end table
+@node MicroBlaze
+@subsection MicroBlaze
+@cindex Xilinx MicroBlaze
+@cindex XMD, Xilinx Microprocessor Debugger
+
+The MicroBlaze is a soft-core processor supported on various Xilinx
+FPGAs, such as Spartan or Virtex series. Boards with these processors
+usually have JTAG ports which connect to a host system running the Xilinx
+Embedded Development Kit (EDK) or Software Development Kit (SDK).
+This host system is used to download the configuration bitstream to
+the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
+communicates with the target board using the JTAG interface and
+presents a @code{gdbserver} interface to the board. By default
+@code{xmd} uses port @code{1234}. (While it is possible to change
+this default port, it requires the use of undocumented @code{xmd}
+commands. Contact Xilinx support if you need to do this.)
+
+Use these GDB commands to connect to the MicroBlaze target processor.
+
+@table @code
+@item target remote :1234
+Use this command to connect to the target if you are running @value{GDBN}
+on the same system as @code{xmd}.
+
+@item target remote @var{xmd-host}:1234
+Use this command to connect to the target if it is connected to @code{xmd}
+running on a different system named @var{xmd-host}.
+
+@item load
+Use this command to download a program to the MicroBlaze target.
+
+@item set debug microblaze @var{n}
+Enable MicroBlaze-specific debugging messages if non-zero.
+
+@item show debug microblaze @var{n}
+Show MicroBlaze-specific debugging level.
+@end table
+
@node MIPS Embedded
@subsection MIPS Embedded
@end table
+When @value{GDBN} is debugging a combined PowerPC/SPU application
+on the Cell Broadband Engine, it provides in addition the following
+special commands:
+
+@table @code
+@item set spu stop-on-load @var{arg}
+@kindex set spu
+Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
+will give control to the user when a new SPE thread enters its @code{main}
+function. The default is @code{off}.
+
+@item show spu stop-on-load
+@kindex show spu
+Show whether to stop for new SPE threads.
+
+@item set spu auto-flush-cache @var{arg}
+Set whether to automatically flush the software-managed cache. When set to
+@code{on}, @value{GDBN} will automatically cause the SPE software-managed
+cache to be flushed whenever SPE execution stops. This provides a consistent
+view of PowerPC memory that is accessed via the cache. If an application
+does not use the software-managed cache, this option has no effect.
+
+@item show spu auto-flush-cache
+Show whether to automatically flush the software-managed cache.
+
+@end table
+
@node PowerPC
@subsection PowerPC
@cindex PowerPC architecture
* ABI:: Configuring the current ABI
* Messages/Warnings:: Optional warnings and messages
* Debugging Output:: Optional messages about internal happenings
+* Other Misc Settings:: Other Miscellaneous Settings
@end menu
@node Prompt
@end table
+@anchor{confirmation requests}
By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
lot of stupid questions to confirm certain commands. For example, if
you try to run a program which is already running:
Displays the current state of XML debugging messages.
@end table
+@node Other Misc Settings
+@section Other Miscellaneous Settings
+@cindex miscellaneous settings
+
+@table @code
+@kindex set interactive-mode
+@item set interactive-mode
+If @code{on}, forces @value{GDBN} to operate interactively.
+If @code{off}, forces @value{GDBN} to operate non-interactively,
+If @code{auto} (the default), @value{GDBN} guesses which mode to use,
+based on whether the debugger was started in a terminal or not.
+
+In the vast majority of cases, the debugger should be able to guess
+correctly which mode should be used. But this setting can be useful
+in certain specific cases, such as running a MinGW @value{GDBN}
+inside a cygwin window.
+
+@kindex show interactive-mode
+@item show interactive-mode
+Displays whether the debugger is operating in interactive mode or not.
+@end table
+
@node Extending GDB
@chapter Extending @value{GDBN}
@cindex extending GDB
The following methods are provided:
@table @code
+@defmethod Value cast type
+Return a new instance of @code{gdb.Value} that is the result of
+casting this instance to the type described by @var{type}, which must
+be a @code{gdb.Type} object. If the cast cannot be performed for some
+reason, this method throws an exception.
+@end defmethod
+
@defmethod Value dereference
For pointer data types, this method returns a new @code{gdb.Value} object
whose contents is the object pointed to by the pointer. For example, if
@ignore
@subheading The @code{-break-catch} Command
@findex -break-catch
+@end ignore
@subheading The @code{-break-commands} Command
@findex -break-commands
-@end ignore
+@subsubheading Synopsis
+
+@smallexample
+ -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
+@end smallexample
+
+Specifies the CLI commands that should be executed when breakpoint
+@var{number} is hit. The parameters @var{command1} to @var{commandN}
+are the commands. If no command is specified, any previously-set
+commands are cleared. @xref{Break Commands}. Typical use of this
+functionality is tracing a program, that is, printing of values of
+some variables whenever breakpoint is hit and then continuing.
+
+@subsubheading @value{GDBN} Command
+
+The corresponding @value{GDBN} command is @samp{commands}.
+
+@subsubheading Example
+
+@smallexample
+(gdb)
+-break-insert main
+^done,bkpt=@{number="1",type="breakpoint",disp="keep",
+enabled="y",addr="0x000100d0",func="main",file="hello.c",
+fullname="/home/foo/hello.c",line="5",times="0"@}
+(gdb)
+-break-commands 1 "print v" "continue"
+^done
+(gdb)
+@end smallexample
@subheading The @code{-break-condition} Command
@findex -break-condition
@subsubheading Synopsis
@smallexample
- -stack-list-arguments @var{show-values}
+ -stack-list-arguments @var{print-values}
[ @var{low-frame} @var{high-frame} ]
@end smallexample
@var{high-frame} may be larger than the actual number of frames, in
which case only existing frames will be returned.
-The @var{show-values} argument must have a value of 0 or 1. A value of
-0 means that only the names of the arguments are listed, a value of 1
-means that both names and values of the arguments are printed.
+If @var{print-values} is 0 or @code{--no-values}, print only the names of
+the variables; if it is 1 or @code{--all-values}, print also their
+values; and if it is 2 or @code{--simple-values}, print the name,
+type and value for simple data types, and the name and type for arrays,
+structures and unions.
+
+Use of this command to obtain arguments in a single frame is
+deprecated in favor of the @samp{-stack-list-variables} command.
@subsubheading @value{GDBN} Command
@var{print-values} is 0 or @code{--no-values}, print only the names of
the variables; if it is 1 or @code{--all-values}, print also their
values; and if it is 2 or @code{--simple-values}, print the name,
-type and value for simple data types and the name and type for arrays,
+type and value for simple data types, and the name and type for arrays,
structures and unions. In this last case, a frontend can immediately
display the value of simple data types and create variable objects for
other data types when the user wishes to explore their values in
more detail.
+This command is deprecated in favor of the
+@samp{-stack-list-variables} command.
+
@subsubheading @value{GDBN} Command
@samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
(gdb)
@end smallexample
+@subheading The @code{-stack-list-variables} Command
+@findex -stack-list-variables
+
+@subsubheading Synopsis
+
+@smallexample
+ -stack-list-variables @var{print-values}
+@end smallexample
+
+Display the names of local variables and function arguments for the selected frame. If
+@var{print-values} is 0 or @code{--no-values}, print only the names of
+the variables; if it is 1 or @code{--all-values}, print also their
+values; and if it is 2 or @code{--simple-values}, print the name,
+type and value for simple data types, and the name and type for arrays,
+structures and unions.
+
+@subsubheading Example
+
+@smallexample
+(gdb)
+-stack-list-variables --thread 1 --frame 0 --all-values
+^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
+(gdb)
+@end smallexample
+
@subheading The @code{-stack-select-frame} Command
@findex -stack-select-frame
@item @strong{Operation}
@tab @strong{Description}
+@item @code{-enable-pretty-printing}
+@tab enable Python-based pretty-printing
@item @code{-var-create}
@tab create a variable object
@item @code{-var-delete}
@tab update the variable and its children
@item @code{-var-set-frozen}
@tab set frozeness attribute
+@item @code{-var-set-update-range}
+@tab set range of children to display on update
@end multitable
In the next subsection we describe each operation in detail and suggest
@subheading Description And Use of Operations on Variable Objects
+@subheading The @code{-enable-pretty-printing} Command
+@findex -enable-pretty-printing
+
+@smallexample
+-enable-pretty-printing
+@end smallexample
+
+@value{GDBN} allows Python-based visualizers to affect the output of the
+MI variable object commands. However, because there was no way to
+implement this in a fully backward-compatible way, a front end must
+request that this functionality be enabled.
+
+Once enabled, this feature cannot be disabled.
+
+Note that if Python support has not been compiled into @value{GDBN},
+this command will still succeed (and do nothing).
+
+This feature is currently (as of @value{GDBN} 7.0) experimental, and
+may work differently in future versions of @value{GDBN}.
+
@subheading The @code{-var-create} Command
@findex -var-create
@samp{$@var{regname}} --- a CPU register name
@end itemize
+@cindex dynamic varobj
+A varobj's contents may be provided by a Python-based pretty-printer. In this
+case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
+have slightly different semantics in some cases. If the
+@code{-enable-pretty-printing} command is not sent, then @value{GDBN}
+will never create a dynamic varobj. This ensures backward
+compatibility for existing clients.
+
@subsubheading Result
-This operation returns the name, number of children and the type of the
-object created. Type is returned as a string as the ones generated by
-the @value{GDBN} CLI. If a fixed variable object is bound to a
-specific thread, the thread is is also printed:
+This operation returns attributes of the newly-created varobj. These
+are:
+
+@table @samp
+@item name
+The name of the varobj.
+
+@item numchild
+The number of children of the varobj. This number is not necessarily
+reliable for a dynamic varobj. Instead, you must examine the
+@samp{has_more} attribute.
+
+@item value
+The varobj's scalar value. For a varobj whose type is some sort of
+aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
+will not be interesting.
+
+@item type
+The varobj's type. This is a string representation of the type, as
+would be printed by the @value{GDBN} CLI.
+
+@item thread-id
+If a variable object is bound to a specific thread, then this is the
+thread's identifier.
+
+@item has_more
+For a dynamic varobj, this indicates whether there appear to be any
+children available. For a non-dynamic varobj, this will be 0.
+
+@item dynamic
+This attribute will be present and have the value @samp{1} if the
+varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
+then this attribute will not be present.
+
+@item displayhint
+A dynamic varobj can supply a display hint to the front end. The
+value comes directly from the Python pretty-printer object's
+@code{display_hint} method. @xref{Pretty Printing}.
+@end table
+
+Typical output will look like this:
@smallexample
- name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
+ name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
+ has_more="@var{has_more}"
@end smallexample
numchild=@var{n}
@end smallexample
+Note that this number is not completely reliable for a dynamic varobj.
+It will return the current number of children, but more children may
+be available.
+
@subheading The @code{-var-list-children} Command
@findex -var-list-children
@subsubheading Synopsis
@smallexample
- -var-list-children [@var{print-values}] @var{name}
+ -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
@end smallexample
@anchor{-var-list-children}
value for simple data types and just the name for arrays, structures
and unions.
+@var{from} and @var{to}, if specified, indicate the range of children
+to report. If @var{from} or @var{to} is less than zero, the range is
+reset and all children will be reported. Otherwise, children starting
+at @var{from} (zero-based) and up to and excluding @var{to} will be
+reported.
+
+If a child range is requested, it will only affect the current call to
+@code{-var-list-children}, but not future calls to @code{-var-update}.
+For this, you must instead use @code{-var-set-update-range}. The
+intent of this approach is to enable a front end to implement any
+update approach it likes; for example, scrolling a view may cause the
+front end to request more children with @code{-var-list-children}, and
+then the front end could call @code{-var-set-update-range} with a
+different range to ensure that future updates are restricted to just
+the visible items.
+
For each child the following results are returned:
@table @var
The expression to be shown to the user by the front end to designate this child.
For example this may be the name of a structure member.
+For a dynamic varobj, this value cannot be used to form an
+expression. There is no way to do this at all with a dynamic varobj.
+
For C/C@t{++} structures there are several pseudo children returned to
designate access qualifiers. For these pseudo children @var{exp} is
@samp{public}, @samp{private}, or @samp{protected}. In this case the
type and value are not present.
+A dynamic varobj will not report the access qualifying
+pseudo-children, regardless of the language. This information is not
+available at all with a dynamic varobj.
+
@item numchild
-Number of children this child has.
+Number of children this child has. For a dynamic varobj, this will be
+0.
@item type
The type of the child.
If the variable object is frozen, this variable will be present with a value of 1.
@end table
+The result may have its own attributes:
+
+@table @samp
+@item displayhint
+A dynamic varobj can supply a display hint to the front end. The
+value comes directly from the Python pretty-printer object's
+@code{display_hint} method. @xref{Pretty Printing}.
+
+@item has_more
+This is an integer attribute which is nonzero if there are children
+remaining after the end of the selected range.
+@end table
+
@subsubheading Example
@smallexample
the @code{-var-info-path-expression} command is creating a
watchpoint from a variable object.
+This command is currently not valid for children of a dynamic varobj,
+and will give an error when invoked on one.
+
For example, suppose @code{C} is a C@t{++} class, derived from class
@code{Base}, and that the @code{Base} class has a member called
@code{m_size}. Assume a variable @code{c} is has the type of
currently running thread, it will not be updated, without any
diagnostic.
-@subsubheading Example
+If @code{-var-set-update-range} was previously used on a varobj, then
+only the selected range of children will be reported.
-@smallexample
-(gdb)
--var-assign var1 3
-^done,value="3"
-(gdb)
--var-update --all-values var1
-^done,changelist=[@{name="var1",value="3",in_scope="true",
-type_changed="false"@}]
-(gdb)
-@end smallexample
+@code{-var-update} reports all the changed varobjs in a tuple named
+@samp{changelist}.
+
+Each item in the change list is itself a tuple holding:
+
+@table @samp
+@item name
+The name of the varobj.
+@item value
+If values were requested for this update, then this field will be
+present and will hold the value of the varobj.
+
+@item in_scope
@anchor{-var-update}
-The field in_scope may take three values:
+This field is a string which may take one of three values:
@table @code
@item "true"
In the future new values may be added to this list so the front should
be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
+@item type_changed
+This is only present if the varobj is still valid. If the type
+changed, then this will be the string @samp{true}; otherwise it will
+be @samp{false}.
+
+@item new_type
+If the varobj's type changed, then this field will be present and will
+hold the new type.
+
+@item new_num_children
+For a dynamic varobj, if the number of children changed, or if the
+type changed, this will be the new number of children.
+
+The @samp{numchild} field in other varobj responses is generally not
+valid for a dynamic varobj -- it will show the number of children that
+@value{GDBN} knows about, but because dynamic varobjs lazily
+instantiate their children, this will not reflect the number of
+children which may be available.
+
+The @samp{new_num_children} attribute only reports changes to the
+number of children known by @value{GDBN}. This is the only way to
+detect whether an update has removed children (which necessarily can
+only happen at the end of the update range).
+
+@item displayhint
+The display hint, if any.
+
+@item has_more
+This is an integer value, which will be 1 if there are more children
+available outside the varobj's update range.
+
+@item dynamic
+This attribute will be present and have the value @samp{1} if the
+varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
+then this attribute will not be present.
+
+@item new_children
+If new children were added to a dynamic varobj within the selected
+update range (as set by @code{-var-set-update-range}), then they will
+be listed in this attribute.
+@end table
+
+@subsubheading Example
+
+@smallexample
+(gdb)
+-var-assign var1 3
+^done,value="3"
+(gdb)
+-var-update --all-values var1
+^done,changelist=[@{name="var1",value="3",in_scope="true",
+type_changed="false"@}]
+(gdb)
+@end smallexample
+
@subheading The @code{-var-set-frozen} Command
@findex -var-set-frozen
@anchor{-var-set-frozen}
(gdb)
@end smallexample
+@subheading The @code{-var-set-update-range} command
+@findex -var-set-update-range
+@anchor{-var-set-update-range}
+
+@subsubheading Synopsis
+
+@smallexample
+ -var-set-update-range @var{name} @var{from} @var{to}
+@end smallexample
+
+Set the range of children to be returned by future invocations of
+@code{-var-update}.
+
+@var{from} and @var{to} indicate the range of children to report. If
+@var{from} or @var{to} is less than zero, the range is reset and all
+children will be reported. Otherwise, children starting at @var{from}
+(zero-based) and up to and excluding @var{to} will be reported.
+
+@subsubheading Example
+
+@smallexample
+(gdb)
+-var-set-update-range V 1 2
+^done
+@end smallexample
+
@subheading The @code{-var-set-visualizer} command
@findex -var-set-visualizer
@anchor{-var-set-visualizer}
means that commands can be run behind a user's back by a front-end in
a transparent manner.
-The server prefix does not affect the recording of values into the value
-history; to print a value without recording it into the value history,
-use the @code{output} command instead of the @code{print} command.
+The @code{server } prefix does not affect the recording of values into
+the value history; to print a value without recording it into the
+value history, use the @code{output} command instead of the
+@code{print} command.
+
+Using this prefix also disables confirmation requests
+(@pxref{confirmation requests}).
@node Prompting
@section Annotation for @value{GDBN} Input
followed by one or more lowercase hex digits (note that this does not
depend on the language).
+@node JIT Interface
+@chapter JIT Compilation Interface
+@cindex just-in-time compilation
+@cindex JIT compilation interface
+
+This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
+interface. A JIT compiler is a program or library that generates native
+executable code at runtime and executes it, usually in order to achieve good
+performance while maintaining platform independence.
+
+Programs that use JIT compilation are normally difficult to debug because
+portions of their code are generated at runtime, instead of being loaded from
+object files, which is where @value{GDBN} normally finds the program's symbols
+and debug information. In order to debug programs that use JIT compilation,
+@value{GDBN} has an interface that allows the program to register in-memory
+symbol files with @value{GDBN} at runtime.
+
+If you are using @value{GDBN} to debug a program that uses this interface, then
+it should work transparently so long as you have not stripped the binary. If
+you are developing a JIT compiler, then the interface is documented in the rest
+of this chapter. At this time, the only known client of this interface is the
+LLVM JIT.
+
+Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
+JIT compiler communicates with @value{GDBN} by writing data into a global
+variable and calling a fuction at a well-known symbol. When @value{GDBN}
+attaches, it reads a linked list of symbol files from the global variable to
+find existing code, and puts a breakpoint in the function so that it can find
+out about additional code.
+
+@menu
+* Declarations:: Relevant C struct declarations
+* Registering Code:: Steps to register code
+* Unregistering Code:: Steps to unregister code
+@end menu
+
+@node Declarations
+@section JIT Declarations
+
+These are the relevant struct declarations that a C program should include to
+implement the interface:
+
+@smallexample
+typedef enum
+@{
+ JIT_NOACTION = 0,
+ JIT_REGISTER_FN,
+ JIT_UNREGISTER_FN
+@} jit_actions_t;
+
+struct jit_code_entry
+@{
+ struct jit_code_entry *next_entry;
+ struct jit_code_entry *prev_entry;
+ const char *symfile_addr;
+ uint64_t symfile_size;
+@};
+
+struct jit_descriptor
+@{
+ uint32_t version;
+ /* This type should be jit_actions_t, but we use uint32_t
+ to be explicit about the bitwidth. */
+ uint32_t action_flag;
+ struct jit_code_entry *relevant_entry;
+ struct jit_code_entry *first_entry;
+@};
+
+/* GDB puts a breakpoint in this function. */
+void __attribute__((noinline)) __jit_debug_register_code() @{ @};
+
+/* Make sure to specify the version statically, because the
+ debugger may check the version before we can set it. */
+struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
+@end smallexample
+
+If the JIT is multi-threaded, then it is important that the JIT synchronize any
+modifications to this global data properly, which can easily be done by putting
+a global mutex around modifications to these structures.
+
+@node Registering Code
+@section Registering Code
+
+To register code with @value{GDBN}, the JIT should follow this protocol:
+
+@itemize @bullet
+@item
+Generate an object file in memory with symbols and other desired debug
+information. The file must include the virtual addresses of the sections.
+
+@item
+Create a code entry for the file, which gives the start and size of the symbol
+file.
+
+@item
+Add it to the linked list in the JIT descriptor.
+
+@item
+Point the relevant_entry field of the descriptor at the entry.
+
+@item
+Set @code{action_flag} to @code{JIT_REGISTER} and call
+@code{__jit_debug_register_code}.
+@end itemize
+
+When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
+@code{relevant_entry} pointer so it doesn't have to walk the list looking for
+new code. However, the linked list must still be maintained in order to allow
+@value{GDBN} to attach to a running process and still find the symbol files.
+
+@node Unregistering Code
+@section Unregistering Code
+
+If code is freed, then the JIT should use the following protocol:
+
+@itemize @bullet
+@item
+Remove the code entry corresponding to the code from the linked list.
+
+@item
+Point the @code{relevant_entry} field of the descriptor at the code entry.
+
+@item
+Set @code{action_flag} to @code{JIT_UNREGISTER} and call
+@code{__jit_debug_register_code}.
+@end itemize
+
+If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
+and the JIT will leak the memory used for the associated symbol files.
+
@node GDB Bugs
@chapter Reporting Bugs in @value{GDBN}
@cindex bugs in @value{GDBN}
@table @code
@kindex maint agent
+@kindex maint agent-eval
@item maint agent @var{expression}
+@itemx maint agent-eval @var{expression}
Translate the given @var{expression} into remote agent bytecodes.
This command is useful for debugging the Agent Expression mechanism
-(@pxref{Agent Expressions}).
+(@pxref{Agent Expressions}). The @samp{agent} version produces an
+expression useful for data collection, such as by tracepoints, while
+@samp{maint agent-eval} produces an expression that evaluates directly
+to a result. For instance, a collection expression for @code{globa +
+globb} will include bytecodes to record four bytes of memory at each
+of the addresses of @code{globa} and @code{globb}, while discarding
+the result of the addition, while an evaluation expression will do the
+addition and return the sum.
@kindex maint info breakpoints
@item @anchor{maint info breakpoints}maint info breakpoints
Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
(@pxref{insert breakpoint or watchpoint packet}).
-@item bc
@cindex @samp{bc} packet
+@anchor{bc}
+@item bc
Backward continue. Execute the target system in reverse. No parameter.
@xref{Reverse Execution}, for more information.
Reply:
@xref{Stop Reply Packets}, for the reply specifications.
-@item bs
@cindex @samp{bs} packet
+@anchor{bs}
+@item bs
Backward single step. Execute one instruction in reverse. No parameter.
@xref{Reverse Execution}, for more information.
Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
@item t
Stop.
-@item T @var{sig}
-Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
@end table
The optional argument @var{addr} normally associated with the
@samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
not supported in @samp{vCont}.
-The @samp{t} and @samp{T} actions are only relevant in non-stop mode
-(@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
+The @samp{t} action is only relevant in non-stop mode
+(@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
A stop reply should be generated for any affected thread not already stopped.
When a thread is stopped by means of a @samp{t} action,
the corresponding stop reply should indicate that the thread has stopped with
@item qCRC:@var{addr},@var{length}
@cindex CRC of memory block, remote request
@cindex @samp{qCRC} packet
-Compute the CRC checksum of a block of memory.
+Compute the CRC checksum of a block of memory using CRC-32 defined in
+IEEE 802.3. The CRC is computed byte at a time, taking the most
+significant bit of each byte first. The initial pattern code
+@code{0xffffffff} is used to ensure leading zeros affect the CRC.
+
+@emph{Note:} This is the same CRC used in validating separate debug
+files (@pxref{Separate Debug Files, , Debugging Information in Separate
+Files}). However the algorithm is slightly different. When validating
+separate debug files, the CRC is computed taking the @emph{least}
+significant bit of each byte first, and the final result is inverted to
+detect trailing zeros.
+
Reply:
@table @samp
@item E @var{NN}
@tab @samp{-}
@tab No
+@item @samp{ConditionalTracepoints}
+@tab No
+@tab @samp{-}
+@tab No
+
+@item @samp{ReverseContinue}
+@tab No
+@tab @samp{-}
+@tab No
+
+@item @samp{ReverseStep}
+@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:osdata:read} packet
((@pxref{qXfer osdata read}).
+@item ConditionalTracepoints
+The remote stub accepts and implements conditional expressions defined
+for tracepoints (@pxref{Tracepoint Conditions}).
+
+@item ReverseContinue
+The remote stub accepts and implements the reverse continue packet
+(@pxref{bc}).
+
+@item ReverseStep
+The remote stub accepts and implements the reverse step packet
+(@pxref{bs}).
+
@end table
@item qSymbol::
@table @samp
-@item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
+@item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:X@var{len},@var{bytes}]@r{[}-@r{]}
Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
the tracepoint is disabled. @var{step} is the tracepoint's step
-count, and @var{pass} is its pass count. If the trailing @samp{-} is
+count, and @var{pass} is its pass count. If an @samp{X} is present,
+it introduces a tracepoint condition, which consists of a hexadecimal
+length, followed by a comma and hex-encoded bytes, in a manner similar
+to action encodings as described below. If the trailing @samp{-} is
present, further @samp{QTDP} packets will follow to specify this
tracepoint's actions.
@cindex interrupts (remote protocol)
When a program on the remote target is running, @value{GDBN} may
-attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
-control of which is specified via @value{GDBN}'s @samp{remotebreak}
-setting (@pxref{set remotebreak}).
+attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
+a @code{BREAK} followed by @code{g},
+control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
The precise meaning of @code{BREAK} is defined by the transport
mechanism and may, in fact, be undefined. @value{GDBN} does not
(@pxref{X packet}), used for binary downloads, may include an unescaped
@code{0x03} as part of its packet.
+@code{BREAK} followed by @code{g} is also known as Magic SysRq g.
+When Linux kernel receives this sequence from serial port,
+it stops execution and connects to gdb.
+
Stubs are not required to recognize these interrupt mechanisms and the
precise meaning associated with receipt of the interrupt is
implementation defined. If the target supports debugging of multiple
Target descriptions can identify the architecture of the remote target
and (for some architectures) provide information about custom register
-sets. @value{GDBN} can use this information to autoconfigure for your
+sets. They can also identify the OS ABI of the remote target.
+@value{GDBN} can use this information to autoconfigure for your
target, or to warn you if you connect to an unsupported target.
Here is a simple target description:
<!DOCTYPE target SYSTEM "gdb-target.dtd">
<target version="1.0">
@r{[}@var{architecture}@r{]}
+ @r{[}@var{osabi}@r{]}
+ @r{[}@var{compatible}@r{]}
@r{[}@var{feature}@dots{}@r{]}
</target>
@end smallexample
<architecture>@var{arch}</architecture>
@end smallexample
-@var{arch} is an architecture name from the same selection
-accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
-Debugging Target}).
+@var{arch} is one of the architectures from the set accepted by
+@code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
+
+@subsection OS ABI
+@cindex @code{<osabi>}
+
+This optional field was introduced in @value{GDBN} version 7.0.
+Previous versions of @value{GDBN} ignore it.
+
+An @samp{<osabi>} element has this form:
+
+@smallexample
+ <osabi>@var{abi-name}</osabi>
+@end smallexample
+
+@var{abi-name} is an OS ABI name from the same selection accepted by
+@w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
+
+@subsection Compatible Architecture
+@cindex @code{<compatible>}
+
+This optional field was introduced in @value{GDBN} version 7.0.
+Previous versions of @value{GDBN} ignore it.
+
+A @samp{<compatible>} element has this form:
+
+@smallexample
+ <compatible>@var{arch}</compatible>
+@end smallexample
+
+@var{arch} is one of the architectures from the set accepted by
+@code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
+
+A @samp{<compatible>} element is used to specify that the target
+is able to run binaries in some other than the main target architecture
+given by the @samp{<architecture>} element. For example, on the
+Cell Broadband Engine, the main architecture is @code{powerpc:common}
+or @code{powerpc:common64}, but the system is able to run binaries
+in the @code{spu} architecture as well. The way to describe this
+capability with @samp{<compatible>} is as follows:
+
+@smallexample
+ <architecture>powerpc:common</architecture>
+ <compatible>spu</compatible>
+@end smallexample
@subsection Features
@cindex <feature>
@samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
@samp{wCSSF}, and @samp{wCASF} registers are optional.
+The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
+should contain at least registers @samp{d0} through @samp{d15}. If
+they are present, @samp{d16} through @samp{d31} should also be included.
+@value{GDBN} will synthesize the single-precision registers from
+halves of the double-precision registers.
+
+The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
+need to contain registers; it instructs @value{GDBN} to display the
+VFP double-precision registers as vectors and to synthesize the
+quad-precision registers from pairs of double-precision registers.
+If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
+be present and include 32 double-precision registers.
+
@node MIPS Features
@subsection MIPS Features
@cindex target descriptions, MIPS features
projects / deliverable / binutils-gdb.git / blobdiff