Segmentation Fault and weird errors

Rippanda12 · October 14, 2023, 12:09pm

Code that causes the problem:

    def delete_pages(self, *_) -> None:
        self.main_stk.set_visible_child_name("main_page")
        # remove all pages from stack1
        for page in self.pages:
            page_id = self.get_page_id(page)
            page_child = self.stack1.get_child_by_name(page_id)
            self.stack1.remove(page_child)

can someone suggest a better way to remove all pages from a stack

ebassi · October 14, 2023, 12:41pm

If self.pages is a list model of Gtk.StackPage instances in stack1 then it’s not safe to remove items while iterating over a list.

You have to collect all pages into a separate list, and then remove them:

def delete_pages(self):
    pages = [self.get_page_id(x) for x in self.pages]
    for page_id in pages:
        w = self.stack1.get_child_by_name(page_id)
        self.stack1.remove(w)

Rippanda12 · October 14, 2023, 1:02pm

in the console I still get is it normal or should I ignore it

/Users/panda/sshfs/bakery-gui.py:1599: Warning: instance with invalid (NULL) class pointer
  self.stack1.remove(w)
/Users/panda/sshfs/bakery-gui.py:1599: Warning: g_signal_handlers_disconnect_matched: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
  self.stack1.remove(w)
/Users/panda/sshfs/bakery-gui.py:1599: Warning: instance of invalid non-instantiatable type '(null)'
  self.stack1.remove(w)

ebassi · October 14, 2023, 1:13pm

That’s coming from GTK itself; which version of GTK are you using?

Rippanda12 · October 14, 2023, 1:15pm

ebassi · October 14, 2023, 1:24pm

Could you try this example, and see if it emits the same warning:

import gi

gi.require_version("Gtk", "4.0")
from gi.repository import GLib, Gtk

stack = Gtk.Stack()
stack.add_named(Gtk.Button(label="Hello"), "foo")
stack.add_named(Gtk.Button(label="World"), "bar")
stack.add_named(Gtk.Button(label="Goodbye"), "baz")

pages = stack.get_pages()
assert len(pages) == 3

names = [x.get_name() for x in pages]
assert len(names) == len(pages)

print(names)

for name in names:
    w = stack.get_child_by_name(name)
    stack.remove(w)

assert len(pages) == 0

gwillems · October 15, 2023, 10:05pm

Do you use a Gtk.StackSideBar with the Stack?

If yes, then I’m pretty sure the crash is related to this issue.

Rippanda12 · October 25, 2023, 9:23am

is there any fix it still happens

ebassi · October 25, 2023, 9:50am

You haven’t answered the question from me or @gwillems, so “is there any fix” isn’t really something we can answer.

Rippanda12 · October 25, 2023, 12:55pm

yes I do its called stack1_sidebar in my code

gwillems · October 26, 2023, 7:37pm

OK, so I’m quite sure it’s the same issue I reported.

There is a fix under review, may take a little bit of time till it gets reviewed/integrated/released…

In the meantime, you could tweak your code to keep a reference to the page, to avoid the use-after-free crash.

Maybe something like this should be enough:

        for page in self.pages:
            page_id = self.get_page_id(page)
            page_child = self.stack1.get_child_by_name(page_id)
            self.stack1.remove(page_child)
            page   # does nothing, just here to keep an active reference during remove()

Rippanda12 · October 27, 2023, 12:37am

Thanks will try this when I can
Is there a issue/merge I can track

Rippanda12 · October 29, 2023, 5:57am

It still seg faults even when calling page

gwillems · November 2, 2023, 3:18pm

hmm, now I’m confused…

What about this?

        for page in list(self.pages):
            page_child = page.get_child()
            self.stack1.remove(page_child)

Rippanda12 · November 2, 2023, 7:11pm

Traceback (most recent call last):
  File "/home/panda/Bakery/bakery-gui.py", line 278, in delete_pages
    page_child = page.get_child()
                 ^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'get_child'

github.com

BredOS/Bakery/blob/e54a367e1503eddd9b92422838d1633ec1fbdbab/bakery-gui.py#L276


      
                  self.next_btn.set_sensitive(self.current_page < num_pages - 1)
                  self.back_btn.set_sensitive(self.current_page > 0)
          
          def on_cancel_clicked(self, button) -> None:
              # connect the yes button to the delete_pages function
              self.cancel_dialog.present()
          
          def delete_pages(self, dialog, resp) -> None:
              if resp == "yes":
                  self.main_stk.set_visible_child(self.main_page.get_child())
                  # remove all pages from stack1
          
                  pages = [self.get_page_id(x) for x in self.pages]
                  for page_id in pages:
                      w = self.stack1.get_child_by_name(page_id)
                      self.stack1.remove(w)
              self.cancel_dialog.hide()
          
          def get_page_id(self, page_name) -> str:
              return page_name

here’s the code if u wanna take a deeper look

gwillems · November 3, 2023, 5:12pm

Ah OK, thanks, I see, I thought self.pages was a list model of Gtk.StackPages…

Can you please try this?

        for page in self.pages:
            page_id = self.get_page_id(page)
            page_child = self.stack1.get_child_by_name(page_id)
            stackpage = self.stack1.get_page(page_child)
            self.stack1.remove(page_child)
            stackpage   # does nothing, just used to keep an active reference during remove()

Rippanda12 · December 10, 2023, 9:24am

it does not, on another note now i have a segfault in a different place


(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.832: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.832: pango_layout_line_unref: assertion 'private->ref_count > 0' failed
malloc(): unaligned fastbin chunk detected
Fatal Python error: Aborted

Thread 0x0000ffff53fff120 (most recent call first):
  File "/home/panda/Bakery/./bakery-gui.py", line 671 in run
  File "/usr/lib/python3.11/threading.py", line 1038 in _bootstrap_inner
  File "/usr/lib/python3.11/threading.py", line 995 in _bootstrap

Thread 0x0000ffff51fbf120 (most recent call first):
  File "/usr/lib/python3.11/concurrent/futures/thread.py", line 81 in _worker
  File "/usr/lib/python3.11/threading.py", line 975 in run
  File "/usr/lib/python3.11/threading.py", line 1038 in _bootstrap_inner
  File "/usr/lib/python3.11/threading.py", line 995 in _bootstrap

Thread 0x0000ffff957bf120 (most recent call first):
  File "/usr/lib/python3.11/concurrent/futures/thread.py", line 81 in _worker
  File "/usr/lib/python3.11/threading.py", line 975 in run
  File "/usr/lib/python3.11/threading.py", line 1038 in _bootstrap_inner
  File "/usr/lib/python3.11/threading.py", line 995 in _bootstrap

Current thread 0x0000ffff99017020 (most recent call first):
  File "/usr/lib/python3.11/site-packages/gi/overrides/Gio.py", line 42 in run
  File "/home/panda/Bakery/./bakery-gui.py", line 1042 in <module>

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.832: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.833: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.833: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.833: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.833: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.833: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

Extension modules: gi._gi
(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.834: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.834: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed

(bakery-gui.py:67328): Pango-CRITICAL **: 11:21:21.835: pango_layout_line_unref: assertion 'private->ref_count > 0' failed
 (total: 1)
fish: Job 1, 'python ./bakery-gui.py' terminated by signal SIGABRT (Abort)

when trying to present a dialog im doing it from a different thread

class InstallThread(threading.Thread):
    def __init__(self, window, install_window):
        threading.Thread.__init__(self)
        self.window = window
        self.install_window = install_window

    def run(self):
        install_data = self.window.collect_data()
        lp("Starting install with data: " + str(install_data))
        res = bakery.install(install_data, do_deferred=False)
        if res == 0:
            # Change to finish page
          .... *Code here works*
        else:
            sleep(2.5)
            self.window.err_dialog.present()

gwillems · December 10, 2023, 1:32pm

Hi,

don’t call Gtk APIs outside of the main thread, they’re not thread-safe.

Instead of:

sleep(2.5)
self.window.err_dialog.present()

better do:

GLib.timeout_add(2500, self.window.err_dialog.present)

that will call “present” asynchronously from the main gtk thread.

system · January 24, 2024, 1:32pm

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