Currently, when creating a gdb.FinishBreakpoint in a function
called from an inline frame, it will never be hit:
```
(gdb) py fb=gdb.FinishBreakpoint()
Temporary breakpoint 1 at 0x13f1917b4: file C:/src/repos/binutils-gdb.git/gdb/testsuite/gdb.python/py-finish-breakpoint.c, line 47.
(gdb) c
Continuing.
Thread-specific breakpoint 1 deleted - thread 1 no longer in the thread list.
[Inferior 1 (process 1208) exited normally]
```
The reason is that the frame_id of a breakpoint has to be the
ID of a real frame, ignoring any inline frames.
With this fixed, it's working correctly:
```
(gdb) py fb=gdb.FinishBreakpoint()
Temporary breakpoint 1 at 0x13f5617b4: file C:/src/repos/binutils-gdb.git/gdb/testsuite/gdb.python/py-finish-breakpoint.c, line 47.
(gdb) c
Continuing.
Breakpoint 1, increase_inlined (a=0x40fa5c) at C:/src/repos/binutils-gdb.git/gdb/testsuite/gdb.python/py-finish-breakpoint.c:47
(gdb) py print(fb.return_value)
-8
```
Approved-By: Tom Tromey <tom@tromey.com>
PR29079 shows that pretty printers can be used for an incomplete
type (stub), but only when printing it directly, not if it's
part of another struct:
```
(gdb) p s
$1 = {pp m_i = 5}
(gdb) p s2
$2 = {m_s = <incomplete type>, m_l = 20}
```
The reason is simply that in common_val_print the check for stubs
is before any pretty printer is tried.
It works if the pretty printer is tried before the stub check:
```
(gdb) p s
$1 = {pp m_i = 5}
(gdb) p s2
$2 = {m_s = {pp m_i = 10}, m_l = 20}
```
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29079
Approved-By: Tom Tromey <tom@tromey.com>
This commit makes the gdb.Command.complete methods more verbose when
it comes to error handling.
Previous to this commit if any commands implemented in Python
implemented the complete method, and if there were any errors
encountered when calling that complete method, then GDB would silently
hide the error and continue as if there were no completions.
This makes is difficult to debug any errors encountered when writing
completion methods, and encourages the idea that Python extensions can
be broken, and GDB will just silently work around them.
I don't think this is a good idea. GDB should encourage extensions to
be written correctly, and robustly, and one way in which GDB can (I
think) support this, is by pointing out when an extension goes wrong.
In this commit I've gone through the Python command completion code,
and added calls to gdbpy_print_stack() or gdbpy_print_stack_or_quit()
in places where we were either clearing the Python error, or, in some
cases, just not handling the error at all.
One thing I have not changed is in cmdpy_completer (py-cmd.c) where we
process the list of completions returned from the Command.complete
method; this routine includes a call to gdbpy_is_string to check a
possible completion is a string, if not the completion is ignored.
I was tempted to remove this check, attempt to complete each result to
a string, and display an error if the conversion fails. After all,
returning anything but a string is surely a mistake by the extension
author.
However, the docs clearly say that only strings within the returned
list will be considered as completions. Anything else is ignored. As
such, and to avoid (what I think is pretty unlikely) breakage of
existing code, I've retained the gdbpy_is_string check.
After the gdbpy_is_string check we call python_string_to_host_string,
if this call fails then I do now print the error, where before we
ignored the error. I think this is OK; if GDB thinks something is a
string, but still can't convert it to a string, then I think it's OK
to display the error in that case.
Another case which I was a little unsure about was in
cmdpy_completer_helper, and the call to PyObject_CallMethodObjArgs,
which is when we actually call Command.complete. Previously, if this
call resulted in an exception then we would ignore this and just
pretend there were no completions.
Of all the changes, this is possibly the one with the biggest
potential for breaking existing scripts, but also, is, I think, the
most useful change. If the user code is wrong in some way, such that
an exception is raised, then previously the user would have no obvious
feedback about this breakage. Now GDB will print the exception for
them, making it, I think, much easier to debug their extension. But,
if there is user code in the wild that relies on raising an exception
as a means to indicate there are no completions .... well, that code
is going to break after this commit. I think we can live with this
though, the exceptions means no completions thing was never documented
behaviour.
I also added a new error() call if the PyObject_CallMethodObjArgs call
raises an exception. This causes the completion mechanism within GDB
to stop. Within GDB the completion code is called twice, the first
time to compute the work break characters, and then a second time to
compute the actual completions.
If PyObject_CallMethodObjArgs raises an exception when computing the
word break character, and we print it by calling
gdbpy_print_stack_or_quit(), but then carry on as if
PyObject_CallMethodObjArgs had returns no completions, GDB will
call the Python completion code again, which results in another call
to PyObject_CallMethodObjArgs, which might raise the same exception
again. This results in the Python exception being printed twice.
By throwing a C++ exception after the failed
PyObject_CallMethodObjArgs call, the completion mechanism is aborted,
and no completions are offered. But importantly, the Python exception
is only printed once. I think this gives a much better user
experience.
I've added some tests to cover this case, as I think this is the most
likely case that a user will run into.
Approved-By: Tom Tromey <tom@tromey.com>
GDB's Python API documentation for gdb.Command.complete() says:
The 'complete' method can return several values:
* If the return value is a sequence, the contents of the
sequence are used as the completions. It is up to 'complete'
to ensure that the contents actually do complete the word. A
zero-length sequence is allowed, it means that there were no
completions available. Only string elements of the sequence
are used; other elements in the sequence are ignored.
* If the return value is one of the 'COMPLETE_' constants
defined below, then the corresponding GDB-internal completion
function is invoked, and its result is used.
* All other results are treated as though there were no
available completions.
So, returning a non-sequence, and non-integer from a complete method
should be fine; it should just be treated as though there are no
completions.
However, if I write a complete method that returns None, I see this
behaviour:
(gdb) complete completefilenone x
Python Exception <class 'TypeError'>: 'NoneType' object is not iterable
warning: internal error: Unhandled Python exception
(gdb)
Which is caused because we currently assume that anything that is not
an integer must be iterable, and we call PyObject_GetIter on it. When
this call fails a Python exception is set, but instead of
clearing (and therefore ignoring) this exception as we do everywhere
else in the Python completion code, we instead just return with the
exception set.
In this commit I add a PySequence_Check call. If this call returns
false (and we've already checked the integer case) then we can assume
there are no completion results.
I've added a test which checks returning a non-sequence.
Approved-By: Tom Tromey <tom@tromey.com>
I ran test-case gdb.python/tui-window-disabled.exp on a configuration without
python support, and ran into:
...
PASS: $exp: cleanup_properly=True: initial restart: set pagination off
UNSUPPORTED: $exp: cleanup_properly=True: couldn't restart GDB
PASS: $exp: cleanup_properly=False: initial restart: set pagination off
UNSUPPORTED: $exp: cleanup_properly=False: couldn't restart GDB
...
After looking into the test-case, I realized that this is a consequence of
!allow_python_tests.
Handle this instead by requiring allow_python_tests, such that we get the usual
and more clear:
...
UNSUPPORTED: $exp: require failed: allow_python_tests
...
Also fix a return without value in clean_restart_and_setup, which if triggered
would cause:
...
ERROR: expected boolean value but got ""
...
Tested on x86_64-linux.
'runtest' complains about a path in a test name, from the new test
case py-missing-debug.exp.
This patch fixes the problem by providing an explicit test name to
gdb_test. I chose something very basic because the block in question
is already wrapped in with_test_prefix.
This commit builds on the previous commit, and implements the
extension_language_ops::handle_missing_debuginfo function for Python.
This hook will give user supplied Python code a chance to help find
missing debug information.
The implementation of the new hook is pretty minimal within GDB's C++
code; most of the work is out-sourced to a Python implementation which
is modelled heavily on how GDB's Python frame unwinders are
implemented.
The following new commands are added as commands implemented in
Python, this is similar to how the Python unwinder commands are
implemented:
info missing-debug-handlers
enable missing-debug-handler LOCUS HANDLER
disable missing-debug-handler LOCUS HANDLER
To make use of this extension hook a user will create missing debug
information handler objects, and registers these handlers with GDB.
When GDB encounters an objfile that is missing debug information, each
handler is called in turn until one is able to help. Here is a
minimal handler that does nothing useful:
import gdb
import gdb.missing_debug
class MyFirstHandler(gdb.missing_debug.MissingDebugHandler):
def __init__(self):
super().__init__("my_first_handler")
def __call__(self, objfile):
# This handler does nothing useful.
return None
gdb.missing_debug.register_handler(None, MyFirstHandler())
Returning None from the __call__ method tells GDB that this handler
was unable to find the missing debug information, and GDB should ask
any other registered handlers.
By extending the __call__ method it is possible for the Python
extension to locate the debug information for objfile and return a
value that tells GDB how to use the information that has been located.
Possible return values from a handler:
- None: This means the handler couldn't help. GDB will call other
registered handlers to see if they can help instead.
- False: The handler has done all it can, but the debug information
for the objfile still couldn't be found. GDB will not call
any other handlers, and will continue without the debug
information for objfile.
- True: The handler has installed the debug information into a
location where GDB would normally expect to find it. GDB
should look again for the debug information.
- A string: The handler can return a filename, which is the file
containing the missing debug information. GDB will load
this file.
When a handler returns True, GDB will look again for the debug
information, but only using the standard built-in build-id and
.gnu_debuglink based lookup strategies. It is not possible for an
extension to trigger another debuginfod lookup; the assumption is that
the debuginfod server is remote, and out of the control of extensions
running within GDB.
Handlers can be registered globally, or per program space. GDB checks
the handlers for the current program space first, and then all of the
global handles. The first handler that returns a value that is not
None, has "handled" the objfile, at which point GDB continues.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>
Add a gdb.Value.bytes attribute. This attribute contains the bytes of
the value (assuming the complete bytes of the value are available).
If the bytes of the gdb.Value are not available then accessing this
attribute raises an exception.
The bytes object returned from gdb.Value.bytes is cached within GDB so
that the same bytes object is returned each time. The bytes object is
created on-demand though to reduce unnecessary work.
For some values we can of course obtain the same information by
reading inferior memory based on gdb.Value.address and
gdb.Value.type.sizeof, however, not every value is in memory, so we
don't always have an address.
The gdb.Value.bytes attribute will convert any value to a bytes
object, so long as the contents are available. The value can be one
created purely in Python code, the value could be in a register,
or (of course) the value could be in memory.
The Value.bytes attribute can also be assigned too. Assigning to this
attribute is similar to calling Value.assign, the value of the
underlying value is updated within the inferior. The value assigned
to Value.bytes must be a buffer which contains exactly the correct
number of bytes (i.e. unlike value creation, we don't allow oversized
buffers).
To support this assignment like behaviour I've factored out the core
of valpy_assign. I've also updated convert_buffer_and_type_to_value
so that it can (for my use case) check the exact buffer length.
The restrictions for when the Value.bytes can or cannot be written too
are exactly the same as for Value.assign.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=13267
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>
Clang doesn't use CFA information for variable locations. This makes it
so software breakpoints get a false hit when rbp gets popped, causing
a FAIL in gdb.python/py-watchpoint.exp. Since this is nothing wrong with
GDB itself, add an xfail to reduce noise.
Approved-By: Tom Tromey <tom@tromey.com>
The test gdb.python/py-explore-cc.exp was showing one unexpected
failure. This was due to how clang mapped instructions to lines,
resulting in the inferior seemingly stopping at a different location.
This patch adds a nop line in the relevant location so we don't need to
add XFAILs for existing clang releases, if this gets solved in future
versions.
Approved-By: Tom Tromey <tom@tromey.com>
This commit adds a new Python function, gdb.notify_mi, that can be used
to emit custom async notification to MI channel. This can be used, among
other things, to implement notifications about events MI does not support,
such as remote connection closed or register change.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Andrew Burgess <aburgess@redhat.com>
Reformat a Python file with black after this commit:
commit 59912fb2d2
Date: Tue Sep 19 11:45:36 2023 +0100
gdb: add Python events for program space addition and removal
There should be no functional change with this commit.
Initially I just wanted a Python event for when GDB removes a program
space, I'm writing a Python extension that caches information for each
program space, and need to know when I should discard entries for a
particular program space.
But, it seemed easy enough to also add an event for when GDB adds a
new program space, so I went ahead and added both new events.
Of course, we don't currently have an observable for program space
addition or removal, so I first needed to add these. After that it's
pretty simple to add two new Python events and have these trigger.
The two new event registries are:
events.new_progspace
events.free_progspace
These emit NewProgspaceEvent and FreeProgspaceEvent objects
respectively, each of these new event types has a 'progspace'
attribute that contains the relevant gdb.Progspace object.
There's a couple of things to be mindful of.
First, it is not possible to catch the NewProgspaceEvent for the very
first program space, the one that is created when GDB first starts, as
this program space is created before any Python scripts are sourced.
In order to allow this event to be caught we would need to defer
creating the first program space, and as a consequence the first
inferior, until some later time. But, existing scripts could easily
depend on there being an initial inferior, so I really don't think we
should change that -- and so, we end up with the consequence that we
can't catch the event for the first program space.
The second, I think minor, issue, is that GDB doesn't clean up its
program spaces upon exit -- or at least, they are not cleaned up
before Python is shut down. As a result, any program spaces in use at
the time GDB exits don't generate a FreeProgspaceEvent. I'm not
particularly worried about this for my use case, I'm using the event
to ensure that a cache doesn't hold stale entries within a single GDB
session. It's also easy enough to add a Python at-exit callback which
can do any final cleanup if needed.
Finally, when testing, I did hit a slightly weird issue with some of
the remote boards (e.g. remote-stdio-gdbserver). As a consequence of
this issue I see some output like this in the gdb.log:
(gdb) PASS: gdb.python/py-progspace-events.exp: inferior 1
step
FreeProgspaceEvent: <gdb.Progspace object at 0x7fb7e1d19c10>
warning: cannot close "target:/lib64/libm.so.6": Cannot execute this command while the target is running.
Use the "interrupt" command to stop the target
and then try again.
warning: cannot close "target:/lib64/libc.so.6": Cannot execute this command while the target is running.
Use the "interrupt" command to stop the target
and then try again.
warning: cannot close "target:/lib64/ld-linux-x86-64.so.2": Cannot execute this command while the target is running.
Use the "interrupt" command to stop the target
and then try again.
do_parent_stuff () at py-progspace-events.c:41
41 ++global_var;
(gdb) PASS: gdb.python/py-progspace-events.exp: step
The 'FreeProgspaceEvent ...' line is expected, that's my test Python
extension logging the event. What isn't expected are all the blocks
like:
warning: cannot close "target:/lib64/libm.so.6": Cannot execute this command while the target is running.
Use the "interrupt" command to stop the target
and then try again.
It turns out that this has nothing to do with my changes, this is just
a consequence of reading files over the remote protocol. The test
forks a child process which GDB stays attached too. When the child
exits, GDB cleans up by calling prune_inferiors, which in turn can
result in GDB trying to close some files that are open because of the
inferior being deleted.
If the prune_inferiors call occurs when the remote target is
running (and in non-async mode) then GDB will try to send a fileio
packet while the remote target is waiting for a stop reply, and the
remote target will throw an error, see remote_target::putpkt_binary in
remote.c for details.
I'm going to look at fixing this, but, as I said, this is nothing to
do with this change, I just mention it because I ended up needing to
account for these warning messages in one of my tests, and it all
looks a bit weird.
Approved-By: Tom Tromey <tom@tromey.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
I ran across this site:
https://no-color.org/
... which lobbies for tools to recognize the NO_COLOR environment
variable and disable any terminal styling when it is seen.
This patch implements this for gdb.
Regression tested on x86-64 Fedora 38.
Co-Authored-By: Andrew Burgess <aburgess@redhat.com>
Reviewed-by: Kevin Buettner <kevinb@redhat.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Andrew Burgess <aburgess@redhat.com>
This commit fixes an issue that was discovered while writing the tests
for the previous commit.
I noticed that, when GDB restarts an inferior, the executable_changed
event would trigger twice. The first notification would originate
from:
#0 exec_file_attach (filename=0x4046680 "/tmp/hello.x", from_tty=0) at ../../src/gdb/exec.c:513
#1 0x00000000006f3adb in reopen_exec_file () at ../../src/gdb/corefile.c:122
#2 0x0000000000e6a3f2 in generic_mourn_inferior () at ../../src/gdb/target.c:3682
#3 0x0000000000995121 in inf_child_target::mourn_inferior (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/inf-child.c:192
#4 0x0000000000995cff in inf_ptrace_target::mourn_inferior (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/inf-ptrace.c:125
#5 0x0000000000a32472 in linux_nat_target::mourn_inferior (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/linux-nat.c:3609
#6 0x0000000000e68a40 in target_mourn_inferior (ptid=...) at ../../src/gdb/target.c:2761
#7 0x0000000000a323ec in linux_nat_target::kill (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/linux-nat.c:3593
#8 0x0000000000e64d1c in target_kill () at ../../src/gdb/target.c:924
#9 0x00000000009a19bc in kill_if_already_running (from_tty=1) at ../../src/gdb/infcmd.c:328
#10 0x00000000009a1a6f in run_command_1 (args=0x0, from_tty=1, run_how=RUN_STOP_AT_MAIN) at ../../src/gdb/infcmd.c:381
#11 0x00000000009a20a5 in start_command (args=0x0, from_tty=1) at ../../src/gdb/infcmd.c:527
#12 0x000000000068dc5d in do_simple_func (args=0x0, from_tty=1, c=0x35c7200) at ../../src/gdb/cli/cli-decode.c:95
While the second originates from:
#0 exec_file_attach (filename=0x3d7a1d0 "/tmp/hello.x", from_tty=0) at ../../src/gdb/exec.c:513
#1 0x0000000000dfe525 in reread_symbols (from_tty=1) at ../../src/gdb/symfile.c:2517
#2 0x00000000009a1a98 in run_command_1 (args=0x0, from_tty=1, run_how=RUN_STOP_AT_MAIN) at ../../src/gdb/infcmd.c:398
#3 0x00000000009a20a5 in start_command (args=0x0, from_tty=1) at ../../src/gdb/infcmd.c:527
#4 0x000000000068dc5d in do_simple_func (args=0x0, from_tty=1, c=0x35c7200) at ../../src/gdb/cli/cli-decode.c:95
In the first case the call to exec_file_attach first passes through
reopen_exec_file. The reopen_exec_file performs a modification time
check on the executable file, and only calls exec_file_attach if the
executable has changed on disk since it was last loaded.
However, in the second case things work a little differently. In this
case GDB is really trying to reread the debug symbol. As such, we
iterate over the objfiles list, and for each of those we check the
modification time, if the file on disk has changed then we reload the
debug symbols from that file.
However, there is an additional check, if the objfile has the same
name as the executable then we will call exec_file_attach, but we do
so without checking the cached modification time that indicates when
the executable was last reloaded, as a result, we reload the
executable twice.
In this commit I propose that reread_symbols be changed to
unconditionally call reopen_exec_file before performing the objfile
iteration. This will ensure that, if the executable has changed, then
the executable will be reloaded, however, if the executable has
already been recently reloaded, we will not reload it for a second
time.
After handling the executable, GDB can then iterate over the objfiles
list and reload them in the normal way.
With this done I now see the executable reloaded only once when GDB
restarts an inferior, which means I can remove the kfail that I added
to the gdb.python/py-exec-file.exp test in the previous commit.
Approved-By: Tom Tromey <tom@tromey.com>
This commit makes the executable_changed observable available through
the Python API as an event. There's nothing particularly interesting
going on here, it just follows the same pattern as many of the other
Python events we support.
The new event registry is called events.executable_changed, and this
emits an ExecutableChangedEvent object which has two attributes, a
gdb.Progspace called 'progspace', this is the program space in which
the executable changed, and a Boolean called 'reload', which is True
if the same executable changed on disk and has been reloaded, or is
False when a new executable has been loaded.
One interesting thing did come up during testing though, you'll notice
the test contains a setup_kfail call. During testing I observed that
the executable_changed event would trigger twice when GDB restarted an
inferior. However, the ExecutableChangedEvent object is identical for
both calls, so the wrong information is never sent out, we just see
one too many events.
I tracked this down to how the reload_symbols function (symfile.c)
takes care to also reload the executable, however, I've split fixing
this into a separate commit, so see the next commit for details.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>
Add a new Progspace.executable_filename attribute that contains the
path to the executable for this program space, or None if no
executable is set.
The path within this attribute will be set by the "exec-file" and/or
"file" commands.
Accessing this attribute for an invalid program space will raise an
exception.
This new attribute is similar too, but not the same as the existing
gdb.Progspace.filename attribute. If I could change the past, I'd
change the 'filename' attribute to 'symbol_filename', which is what it
actually represents. The old attribute will be set by the
'symbol-file' command, while the new attribute is set by the
'exec-file' command. Obviously the 'file' command sets both of these
attributes.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>
Add a new Progspace.symbol_file attribute. This attribute holds the
gdb.Objfile object that corresponds to Progspace.filename, or None if
there is no main symbol file currently set.
Currently, to get this gdb.Objfile, a user would need to use
Progspace.objfiles, and then search for the objfile with a name that
matches Progspace.filename -- which should work just fine, but having
direct access seems a little nicer.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>
This bug points out that if one uses -var-set-visualizer with "None"
-- to disable a pretty-printer for a varobj -- then
-var-evaluate-expression will still use pretty-printing.
This is a combination of bugs. First, setting the visualizer does not
update the display text; and second, computing the display text should
use "raw" when Python is available but no visualizer is desired.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=11738
Reviewed-by: Keith Seitz <keiths@redhat.com>
A user noticed that, while a pretty-printer can return Python strings
from its "children" method, this does not really work for MI. I
tracked this down to my_value_of_variable calling into
c_value_of_variable, which specially handles arrays and structures --
not using the actual contents of the string.
Now, this part of MI seems bad to me, but rather than change that,
this applies the fix to only dynamic varobjs, which is the only
scenario where a string like this can really be returned.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18282
Reviewed-by: Keith Seitz <keiths@redhat.com>
This commit extends the breakpoint mechanism to allow for inferior
specific breakpoints (but not watchpoints in this commit).
As GDB gains better support for multiple connections, and so for
running multiple (possibly unrelated) inferiors, then it is not hard
to imagine that a user might wish to create breakpoints that apply to
any thread in a single inferior. To achieve this currently, the user
would need to create a condition possibly making use of the $_inferior
convenience variable, which, though functional, isn't the most user
friendly.
This commit adds a new 'inferior' keyword that allows for the creation
of inferior specific breakpoints.
Inferior specific breakpoints are automatically deleted when the
associated inferior is removed from GDB, this is similar to how
thread-specific breakpoints are deleted when the associated thread is
deleted.
Watchpoints are already per-program-space, which in most cases mean
watchpoints are already inferior specific. There is a small window
where inferior-specific watchpoints might make sense, which is after a
vfork, when two processes are sharing the same address space.
However, I'm leaving that as an exercise for another day. For now,
attempting to use the inferior keyword with a watchpoint will give an
error, like this:
(gdb) watch a8 inferior 1
Cannot use 'inferior' keyword with watchpoints
A final note on the implementation: currently, inferior specific
breakpoints, like thread-specific breakpoints, are inserted into every
inferior, GDB then checks once the inferior stops if we are in the
correct thread or inferior, and resumes automatically if we stopped in
the wrong thread/inferior.
An obvious optimisation here is to only insert breakpoint locations
into the specific program space (which mostly means inferior) that
contains either the inferior or thread we are interested in. This
would reduce the number times GDB has to stop and then resume again in
a multi-inferior setup.
I have a series on the mailing list[1] that implements this
optimisation for thread-specific breakpoints. Once this series has
landed I'll update that series to also handle inferior specific
breakpoints in the same way. For now, inferior specific breakpoints
are just slightly less optimal, but this is no different to
thread-specific breakpoints in a multi-inferior debug session, so I
don't see this as a huge problem.
[1] https://inbox.sourceware.org/gdb-patches/cover.1685479504.git.aburgess@redhat.com/
I ran into a test failure on gdb.python/py-thread-exited.c. The test
creates two threads and then catches the thread exits in Python. The
test expects the threads to exit in a specific order.
As the test is currently written, it is _likely_, but not guaranteed,
that the threads will exit in the same order they are created, which
is what the test expects.
When running on a loaded system I ran into a case where the threads
exited in the reverse creation order, which caused the test to fail.
I could fix this by having the .exp file not care about the thread
order, or by changing the C file to force the order. I chose the
later, and added a pthread_barrier_t to ensure the threads exit in the
correct order.
There should be no change in what is tested after this commit.
gdbserver does not notify gdb of new threads when they are created.
I'm not sure if this is documented anywhere, but it is mentioned on
this page:
https://sourceware.org/gdb/wiki/LocalRemoteFeatureParity
Search for "Finding new threads in the inferior".
This behavior is a bit unfortunate -- I would think that it would be
better to arrange for such notification if something on the gdb side
is interested.
Meanwhile, this patch fixes py-thread-exited.exp to work around this
problem.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30677
Two fixes in gdb.python/py-thread-exited.exp:
- fix the copyright notice validity range (PR testsuite/30687):
2022-202 -> 2022-2023, and
- add missing "require allow_python_tests".
Tested on x86_64-linux.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30687
This adds a new objfile_for_address method to gdb.Progspace. This
makes it easy to find the objfile for a given address.
There's a related PR; and while this change would have been sufficient
for my original need, it's not clear to me whether I should close the
bug. Nevertheless I think it makes sense to at least mention it here.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=19288
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Andrew reported that the previous change to gdb.Inferior.read_memory &
friends introducing scoped_restore_current_inferior_for_memory broke
gdb.dap/stop-at-main.exp. This is also reported as PR dap/30644.
The root of the problem is that all the methods that now use
scoped_restore_current_inferior_for_memory cause GDB to crash with a
failed assert if they are run on an inferior that is not yet started.
E.g.:
(gdb) python i = gdb.selected_inferior ()
(gdb) python i.read_memory (4,4)
gdb/thread.c:626: internal-error: any_thread_of_inferior: Assertion `inf->pid != 0' failed.
This patch fixes the problem by removing
scoped_restore_current_inferior_for_memory's ctor ptid parameter and
the any_thread_of_inferior calls completely, and making
scoped_restore_current_inferior_for_memory switch inferior_ptid to a
pid ptid.
I was a little worried that some port might be assuming inferior_ptid
points at a thread in the xfer_partial memory access routines. We
know that anything that supports forks must not assume that, due to
how detach_breakpoints works. I looked at a number of xfer_partial
implementations, and didn't see anything that is looking at
inferior_ptid in a way that would misbehave. I'm thinking that we
could go forward with this and just fix ports if they break.
While on some ports like on AMD GPU we have thread-specific address
spaces, and so when accessing memory for those address spaces, we must
have the right thread context (via inferior_ptid) selected, in
Inferior.read_memory, we only have the inferior to work with, so this
API as is can't be used to access thread-specific address spaces.
IOW, it can only be used to access the global address space that is
visible to both the CPU and the GPUs.
In proc-service.c:ps_xfer_memory, the other spot using
scoped_restore_current_inferior_for_memory, we're always accessing
per-inferior memory.
If we end up using scoped_restore_current_inferior_for_memory later to
set up the context to read memory from a specific thread, then we can
add an alternative ctor that takes a thread_info pointer, and make
inferior_ptid point to the thread, for example.
New test added to gdb.python/py-inferior.exp, exercising
Inferior.read_memory without execution.
No regressions on native and extended-gdbserver x86_64 GNU/Linux.
Reviewed-By: Tom Tromey <tom@tromey.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30644
Change-Id: I11309c5ddbbb51a4594cf63c21b3858bfd9aed19
A user noticed that Inferior.read_memory and a few other Python APIs
will always use the currently selected inferior, not the one passed to
the call.
This patch fixes the bug by arranging to switch to the inferior. I
found this same issue in several APIs, so this fixes them all.
I also added a few missing calls to INFPY_REQUIRE_VALID to these
methods.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30615
Approved-By: Pedro Alves <pedro@palves.net>
py-inferior.exp creates a Python variable named 'str'. This clashes
with the built-in type of the same name and can be confusing when
trying to evaluate Python code when debugging the test case. This
patch renames it.
Approved-By: Pedro Alves <pedro@palves.net>
This changes py-inferior.exp to make it a bit more robust when adding
new inferiors during the course of the test.
Approved-By: Pedro Alves <pedro@palves.net>
While working on this series, I noticed a some oddities in
py-inferior.exp. One is an obviously incorrect comment, and the
others are confusing test names. This patch fixes these.
Approved-By: Pedro Alves <pedro@palves.net>
I wrote a TUI window in Python, and I noticed that setting its title
did not result in a refresh, so the new title did not appear. This
patch corrects this problem.
Only a few types in the Python API currently have __repr__()
implementations. This patch adds a few more of them. specifically: it
adds __repr__() implementations to gdb.Symbol, gdb.Architecture,
gdb.Block, gdb.Breakpoint, gdb.BreakpointLocation, and gdb.Type.
This makes it easier to play around the GDB Python API in the Python
interpreter session invoked with the 'pi' command in GDB, giving more
easily accessible tipe information to users.
An example of how this would look like:
(gdb) pi
>> gdb.lookup_type("char")
<gdb.Type code=TYPE_CODE_INT name=char>
>> gdb.lookup_global_symbol("main")
<gdb.Symbol print_name=main>
The gdb.Block.__repr__() method shows the first 5 symbols from the
block, and then a message to show how many more were elided (if any).
v6:
Fix comments.
Fix copyright
Remove unnecessary test suite stuff. save_var had to stay, as it mutates
some test suite state that otherwise fails.
v5:
Did what Tom Tromey requested in v4; which can be found here: https://pi.simark.ca/gdb-patches/87pmjm0xar.fsf@tromey.com/
v4:
Doc formatting fixed.
v3:
Eli:
Updated docs & NEWS to reflect new changes. Added
a reference from the .ptid attribute of the ThreadExitedEvent
to the ptid attribute of InferiorThread. To do this,
I've added an anchor to that attribute.
Tom:
Tom requested that I should probably just emit the thread object;
I ran into two issues for this, which I could not resolve in this patch;
1 - The Thread Object (the python type) checks it's own validity
by doing a comparison of it's `thread_info* thread` to nullptr. This
means that any access of it's attributes may (probably, since we are
in "async" land) throw Python exceptions because the thread has been
removed from the thread object. Therefore I've decided in v3 of this
patch to just emit most of the same fields that gdb.InferiorThread has, namely
global_num, name, num and ptid (the 3-attribute tuple provided by
gdb.InferiorThread.ptid).
2 - A python user can hold a global reference to an exiting thread. Thus
in order to have a ThreadExit event that can provide attribute access
reliably (both as a global reference, but also inside the thread exit
handler, as we can never guarantee that it's executed _before_ the
thread_info pointer is removed from the gdbpy thread object),
the `thread_info *` thread pointer must not be null. However, this
comes at the cost of gdb.InferiorThread believing it is "valid" - which means,
that if a user holds takes a global reference to that
exiting event thread object, they can some time later do `t.switch()` at which
point GDB will 'explode' so to speak.
v2:
Fixed white space issues and NULL/nullptr stuff,
as requested by Tom Tromey.
v1:
Currently no event is emitted for a thread exit.
This adds this functionality by emitting a new gdb.ThreadExitedEvent.
It currently provides four attributes:
- global_num: The GDB assigned global thread number
- num: the per-inferior thread number
- name: name of the thread or none if not set
- ptid: the PTID of the thread, a 3-attribute tuple, identical to
InferiorThread.ptid attribute
Added info to docs & the NEWS file as well.
Added test to test suite.
Fixed formatting.
Feedback wanted and appreciated.
on openSUSE Leap 42.3, with python 3.4, I run into a
"SyntaxError: invalid syntax" due to usage of an f-string in test-case
gdb.python/py-unwind.py.
Fix this by using string concatenation using '+' instead.
Tested on x86_64-linux.
This adds an 'assign' method to gdb.Value. This allows for assignment
without requiring the use of parse_and_eval.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
With a gdb 13.2 based package on SLE-15 aarch64, I run into:
...
(gdb) PASS: gdb.python/py-rbreak.exp: nosharedlibrary
py sl = gdb.rbreak("^[^_]",minsyms=False)^M
Breakpoint 2 at 0x4004ac: file ../sysdeps/aarch64/crti.S, line 63.^M
...
(gdb) py print(len(sl))^M
12^M
(gdb) FAIL: gdb.python/py-rbreak.exp: check number of returned breakpoints is 11
...
The FAIL is due to:
- the glibc object crti.o containing debug information for function
call_weak_fn, and
- the test-case not expecting this.
The debug information is there due to compiling glibc using a binutils which
contains commit 591cc9fbbf ("gas/Dwarf: record functions").
I've run into a similar issue before, see commit 3fbbcf473a ("[gdb/testsuite]
Fix regexp in py-rbreak.exp").
The fix I applied there was to use a regexp "^[^_]" to filter out
__libc_csu_fini and __libc_csu_init, but that doesn't work for call_weak_fn.
Fix this by:
- reverting the regexp to "", and
- rewriting the check to require at least 11 functions, rather than a precise
match.
Tested on x86_64-linux.
PR testsuite/30538
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30538
While working on PR tui/30526, I noticed a bug in test-case
gdb.python/tui-window-disabled.exp.
Here we send "tui enable" to gdb, but don't wait for it to arrive before
checking for a window box:
...
send_gdb "tui enable\n"
Term::check_box "check for python window" 0 0 80 16
...
Fix this by waiting for the prompt to be issued in TUI before doing the check.
Tested on x86_64-linux.
History Of This Patch
=====================
This commit aims to address PR gdb/21699. There have now been a
couple of attempts to fix this issue. Simon originally posted two
patches back in 2021:
https://sourceware.org/pipermail/gdb-patches/2021-July/180894.htmlhttps://sourceware.org/pipermail/gdb-patches/2021-July/180896.html
Before Pedro then posted a version of his own:
https://sourceware.org/pipermail/gdb-patches/2021-July/180970.html
After this the conversation halted. Then in 2023 I (Andrew) also took
a look at this bug and posted two versions:
https://sourceware.org/pipermail/gdb-patches/2023-April/198570.htmlhttps://sourceware.org/pipermail/gdb-patches/2023-April/198680.html
The approach taken in my first patch was pretty similar to what Simon
originally posted back in 2021. My second attempt was only a slight
variation on the first.
Pedro then pointed out his older patch, and so we arrive at this
patch. The GDB changes here are mostly Pedro's work, but updated by
me (Andrew), any mistakes are mine.
The tests here are a combinations of everyone's work, and the commit
message is new, but copies bits from everyone's earlier work.
Problem Description
===================
Bug PR gdb/21699 makes the observation that using $_as_string with
GDB's printf can cause GDB to print unexpected data from the
inferior. The reproducer is pretty simple:
#include <stddef.h>
static char arena[100];
/* Override malloc() so value_coerce_to_target() gets a known
pointer, and we know we"ll see an error if $_as_string() gives
a string that isn't null terminated. */
void
*malloc (size_t size)
{
memset (arena, 'x', sizeof (arena));
if (size > sizeof (arena))
return NULL;
return arena;
}
int
main ()
{
return 0;
}
And then in a GDB session:
$ gdb -q test
Reading symbols from /tmp/test...
(gdb) start
Temporary breakpoint 1 at 0x4004c8: file test.c, line 17.
Starting program: /tmp/test
Temporary breakpoint 1, main () at test.c:17
17 return 0;
(gdb) printf "%s\n", $_as_string("hello")
"hello"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
(gdb) quit
The problem above is caused by how value_cstring is used within
py-value.c, but once we understand the issue then it turns out that
value_cstring is used in an unexpected way in many places within GDB.
Within py-value.c we have a null-terminated C-style string. We then
pass a pointer to this string, along with the length of this
string (so not including the null-character) to value_cstring.
In value_cstring GDB allocates an array value of the given character
type, and copies in requested number of characters. However
value_cstring does not add a null-character of its own. This means
that the value created by calling value_cstring is only
null-terminated if the null-character is included in the passed in
length. In py-value.c this is not the case, and indeed, in most uses
of value_cstring, this is not the case.
When GDB tries to print one of these strings the value contents are
pushed to the inferior, and then read back as a C-style string, that
is, GDB reads inferior memory until it finds a null-terminator. For
the py-value.c case, no null-terminator is pushed into the inferior,
so GDB will continue reading inferior memory until a null-terminator
is found, with unpredictable results.
Patch Description
=================
The first thing this patch does is better define what the arguments
for the two function value_cstring and value_string should represent.
The comments in the header file are updated to describe whether the
length argument should, or should not, include a null-character.
Also, the data argument is changed to type gdb_byte. The functions as
they currently exist will handle wide-characters, in which case more
than one 'char' would be needed for each character. As such using
gdb_byte seems to make more sense.
To avoid adding casts throughout GDB, I've also added an overload that
still takes a 'char *', but asserts that the character type being used
is of size '1'.
The value_cstring function is now responsible for adding a null
character at the end of the string value it creates.
However, once we start looking at how value_cstring is used, we
realise there's another, related, problem. Not every language's
strings are null terminated. Fortran and Ada strings, for example,
are just an array of characters, GDB already has the function
value_string which can be used to create such values.
Consider this example using current GDB:
(gdb) set language ada
(gdb) p $_gdb_setting("arch")
$1 = (97, 117, 116, 111)
(gdb) ptype $
type = array (1 .. 4) of char
(gdb) p $_gdb_maint_setting("test-settings string")
$2 = (0)
(gdb) ptype $
type = array (1 .. 1) of char
This shows two problems, first, the $_gdb_setting and
$_gdb_maint_setting functions are calling value_cstring using the
builtin_char character, rather than a language appropriate type. In
the first call, the 'arch' case, the value_cstring call doesn't
include the null character, so the returned array only contains the
expected characters. But, in the $_gdb_maint_setting example we do
end up including the null-character, even though this is not expected
for Ada strings.
This commit adds a new language method language_defn::value_string,
this function takes a pointer and length and creates a language
appropriate value that represents the string. For C, C++, etc this
will be a null-terminated string (by calling value_cstring), and for
Fortran and Ada this can be a bounded array of characters with no null
terminator. Additionally, this new language_defn::value_string
function is responsible for selecting a language appropriate character
type.
After this commit the only calls to value_cstring are from the C
expression evaluator and from the default language_defn::value_string.
And the only calls to value_string are from Fortan, Ada, and ObjectC
related code.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=21699
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Co-Authored-By: Andrew Burgess <aburgess@redhat.com>
Co-Authored-By: Pedro Alves <pedro@palves.net>
Approved-By: Simon Marchi <simon.marchi@efficios.com>
This adds two new attributes and three new methods to gdb.Inferior.
The attributes let Python code see the command-line arguments and the
name of "main". Argument setting is also supported.
The methods let Python code manipulate the inferior's environment
variables.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
This adds a 'global_context' parse_and_eval to gdb.parse_and_eval.
This lets users request a parse that is done at "global scope".
I considered letting callers pass in a block instead, with None
meaning "global" -- but then there didn't seem to be a clean way to
express the default for this parameter.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
This adds a new Python function, gdb.execute_mi, that can be used to
invoke an MI command but get the output as a Python object, rather
than a string. This is done by implementing a new ui_out subclass
that builds a Python object.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=11688
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
It was pointed out on the mailing list that the new tests added in
this commit:
commit 4de4e48514
Date: Tue Jan 24 15:35:45 2023 +0000
gdb/python: extend the Python Disassembler API to allow for styling
will fail when GDB is built with Python 3.6 or earlier. This is
because the error that is emitted when a function argument is missing
changed in Python 3.7, instead of an error like this:
Python Exception <class 'TypeError'>: function missing required argument 'style' (pos 1)
earlier versions of Python emit:
Python Exception <class 'TypeError'>: Required argument 'style' (pos 1) not found
and the new tests didn't allow for this.
This commit fixes this by allowing either pattern. I've tested this
building GDB against Python 3.7.9 and 3.6.15, with this commit all
tests in gdb.python/py-disasm.exp now pass.
This commit extends the Python Disassembler API to allow for styling
of the instructions.
Before this commit the Python Disassembler API allowed the user to do
two things:
- They could intercept instruction disassembly requests and return a
string of their choosing, this string then became the disassembled
instruction, or
- They could call builtin_disassemble, which would call back into
libopcode to perform the disassembly. As libopcode printed the
instruction GDB would collect these print requests and build a
string. This string was then returned from the builtin_disassemble
call, and the user could modify or extend this string as needed.
Neither of these approaches allowed for, or preserved, disassembler
styling, which is now available within libopcodes for many of the more
popular architectures GDB supports.
This commit aims to fill this gap. After this commit a user will be
able to do the following things:
- Implement a custom instruction disassembler entirely in Python
without calling back into libopcodes, the custom disassembler will
be able to return styling information such that GDB will display
the instruction fully styled. All of GDB's existing style
settings will affect how instructions coming from the Python
disassembler are displayed in the expected manner.
- Call builtin_disassemble and receive a result that represents how
libopcode would like the instruction styled. The user can then
adjust or extend the disassembled instruction before returning the
result to GDB. Again, the instruction will be styled as expected.
To achieve this I will add two new classes to GDB,
DisassemblerTextPart and DisassemblerAddressPart.
Within builtin_disassemble, instead of capturing the print calls from
libopcodes and building a single string, we will now create either a
text part or address part and store these parts in a vector.
The DisassemblerTextPart will capture a small piece of text along with
the associated style that should be used to display the text. This
corresponds to the disassembler calling
disassemble_info::fprintf_styled_func, or for disassemblers that don't
support styling disassemble_info::fprintf_func.
The DisassemblerAddressPart is used when libopcodes requests that an
address be printed, and takes care of printing the address and
associated symbol, this corresponds to the disassembler calling
disassemble_info::print_address_func.
These parts are then placed within the DisassemblerResult when
builtin_disassemble returns.
Alternatively, the user can directly create parts by calling two new
methods on the DisassembleInfo class: DisassembleInfo.text_part and
DisassembleInfo.address_part.
Having created these parts the user can then pass these parts when
initializing a new DisassemblerResult object.
Finally, when we return from Python to gdbpy_print_insn, one way or
another, the result being returned will have a list of parts. Back in
GDB's C++ code we walk the list of parts and call back into GDB's core
to display the disassembled instruction with the correct styling.
The new API lives in parallel with the old API. Any existing code
that creates a DisassemblerResult using a single string immediately
creates a single DisassemblerTextPart containing the entire
instruction and gives this part the default text style. This is also
what happens if the user calls builtin_disassemble for an architecture
that doesn't (yet) support libopcode styling.
This matches up with what happens when the Python API is not involved,
an architecture without disassembler styling support uses the old
libopcodes printing API (the API that doesn't pass style info), and
GDB just prints everything using the default text style.
The reason that parts are created by calling methods on
DisassembleInfo, rather than calling the class constructor directly,
is DisassemblerAddressPart. Ideally this part would only hold the
address which the part represents, but in order to support backwards
compatibility we need to be able to convert the
DisassemblerAddressPart into a string. To do that we need to call
GDB's internal print_address function, and to do that we need an
gdbarch.
What this means is that the DisassemblerAddressPart needs to take a
gdb.Architecture object at creation time. The only valid place a user
can pull this from is from the DisassembleInfo object, so having the
DisassembleInfo act as a factory ensures that the correct gdbarch is
passed over each time. I implemented both solutions (the one
presented here, and an alternative where parts could be constructed
directly), and this felt like the cleanest solution.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: Tom Tromey <tom@tromey.com>
