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29db1eb339
If the user implements a TUI window in Python, and this window
responds to GDB events and then redraws its window contents then there
is currently an edge case which can lead to problems.
The Python API documentation suggests that calling methods like erase
or write on a TUI window (from Python code) will raise an exception if
the window is not valid.
And the description for is_valid says:
This method returns True when this window is valid. When the user
changes the TUI layout, windows no longer visible in the new layout
will be destroyed. At this point, the gdb.TuiWindow will no longer
be valid, and methods (and attributes) other than is_valid will
throw an exception.
From this I, as a user, would expect that if I did 'tui disable' to
switch back to CLI mode, then the window would no longer be valid.
However, this is not the case.
When the TUI is disabled the windows in the TUI are not deleted, they
are simply hidden. As such, currently, the is_valid method continues
to return true.
This means that if the users Python code does something like:
def event_handler (e):
global tui_window_object
if tui_window_object->is_valid ():
tui_window_object->erase ()
tui_window_object->write ("Hello World")
gdb.events.stop.connect (event_handler)
Then when a stop event arrives GDB will try to draw the TUI window,
even when the TUI is disabled.
This exposes two bugs. First, is_valid should be returning false in
this case, second, if the user forgot to add the is_valid call, then I
believe the erase and write calls should be throwing an
exception (when the TUI is disabled).
The solution to both of these issues is I think bound together, as it
depends on having a working 'is_valid' check.
There's a rogue assert added into tui-layout.c as part of this
commit. While working on this commit I managed to break GDB such that
TUI_CMD_WIN was nullptr, this was causing GDB to abort. I'm leaving
the assert in as it might help people catch issues in the future.
This patch is inspired by the work done here:
https://sourceware.org/pipermail/gdb-patches/2020-December/174338.html
gdb/ChangeLog:
* python/py-tui.c (gdbpy_tui_window) <is_valid>: New member
function.
(REQUIRE_WINDOW): Call is_valid member function.
(REQUIRE_WINDOW_FOR_SETTER): New define.
(gdbpy_tui_is_valid): Call is_valid member function.
(gdbpy_tui_set_title): Call REQUIRE_WINDOW_FOR_SETTER instead.
* tui/tui-data.h (struct tui_win_info) <is_visible>: Check
tui_active too.
* tui/tui-layout.c (tui_apply_current_layout): Add an assert.
* tui/tui.c (tui_enable): Move setting of tui_active earlier in
the function.
gdb/doc/ChangeLog:
* python.texinfo (TUI Windows In Python): Extend description of
TuiWindow.is_valid.
gdb/testsuite/ChangeLog:
* gdb.python/tui-window-disabled.c: New file.
* gdb.python/tui-window-disabled.exp: New file.
* gdb.python/tui-window-disabled.py: New file.
90 lines
3.3 KiB
Python
90 lines
3.3 KiB
Python
# Copyright (C) 2021 Free Software Foundation, Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# A TUI window implemented in Python that responds to, and displays,
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# stop and exit events.
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import gdb
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# When an event arrives we ask the window to redraw itself. We should
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# only do this if the window is valid. When this flag is true we
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# perform the is_valid check. When this flag is false
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perform_valid_check = True
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update_title = False
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cleanup_properly = False
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# A global place into which we can write the window title.
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titles_at_the_close = {}
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class EventWindow:
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def __init__ (self, win):
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self._win = win
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self._count = 0
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win.title = "This Is The Event Window"
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self._stop_listener = lambda e : self._event ('stop', e)
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gdb.events.stop.connect (self._stop_listener)
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self._exit_listener = lambda e : self._event ('exit', e)
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gdb.events.exited.connect (self._exit_listener)
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self._events = []
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# Ensure we can erase and write to the window from the
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# constructor, the window should be valid by this point.
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self._win.erase ()
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self._win.write ("Hello world...")
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def close (self):
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global cleanup_properly
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global titles_at_the_close
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# Ensure that window properties can be read within the close method.
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titles_at_the_close[self._win.title] = dict (width=self._win.width,
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height=self._win.height)
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# The following calls are pretty pointless, but this ensures
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# that we can erase and write to a window from the close
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# method, the last moment a window should be valid.
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self._win.erase ()
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self._win.write ("Goodbye cruel world...")
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if cleanup_properly:
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# Disconnect the listeners and delete the lambda functions.
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# This removes cyclic references to SELF, and so alows SELF to
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# be deleted.
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gdb.events.stop.disconnect (self._stop_listener)
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gdb.events.exited.disconnect (self._exit_listener)
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self._stop_listener = None
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self._exit_listener = None
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def _event (self, type, event):
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global perform_valid_check
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global update_title
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self._count += 1
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self._events.insert (0, type)
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if not perform_valid_check or self._win.is_valid ():
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if update_title:
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self._win.title = "This Is The Event Window (" + str (self._count) + ")"
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else:
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self.render ()
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def render (self):
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self._win.erase ()
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w = self._win.width
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h = self._win.height
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for i in range (min (h, len (self._events))):
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self._win.write (self._events[i] + "\n")
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gdb.register_window_type("events", EventWindow)
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