Better integration of faulthandler. See #1853

Instead of writing the stacktrace to stderr, write it to
~/.quodlibet/faultdump and on the next start raise an
exception with the content.

Slightly adjust the exception dialog to use a text view for the
exception message instead of a tree view header since the passed
text from the faulthandler stack trace can be quite long.

quodlibet/quodlibet/_init.py

@@ -38,14 +38,6 @@ def _override_exceptions():
     if not no_excepthook:
         GLib.idle_add(_override_exceptions)
 
-    # faulthandler gives a python stacktrace on segfaults..
-    try:
-        import faulthandler
-    except ImportError:
-        pass
-    else:
-        faulthandler.enable()
-
 
 def is_init():
     """Returns if init() was called"""

quodlibet/quodlibet/_main.py

@@ -16,6 +16,7 @@
 from quodlibet.util import cached_func, windows, set_process_title
 from quodlibet.util.dprint import print_d
 from quodlibet.util.path import mkdir
+from quodlibet.util import faulthandling
 
 
 PLUGIN_DIRS = ["editing", "events", "playorder", "songsmenu", "playlist",
@@ -272,7 +273,7 @@ def application_openFile_(self, sender, filename):
 
 def run(window, before_quit=None):
     print_d("Entering quodlibet.main")
-    from gi.repository import Gtk, Gdk
+    from gi.repository import Gtk, Gdk, GLib
     from quodlibet._init import is_init
 
     assert is_init()
@@ -319,6 +320,17 @@ def quit_gtk(window):
         # if we don't show a window, startup isn't completed, so call manually
         Gdk.notify_startup_complete()
 
+    try:
+        faulthandling.enable(os.path.join(get_user_dir(), "faultdump"))
+        crash_message = faulthandling.check_and_clear_error()
+    except IOError:
+        util.print_exc()
+    else:
+        if crash_message is not None:
+            def trigger_crash_exception():
+                raise Exception(crash_message)
+            GLib.idle_add(trigger_crash_exception)
+
     # set QUODLIBET_START_PERF to measure startup time until the
     # windows is first shown.
     if "QUODLIBET_START_PERF" in environ:
@@ -328,6 +340,8 @@ def quit_gtk(window):
     else:
         Gtk.main()
 
+    faulthandling.disable()
+
     print_d("Gtk.main() done.")
 
 

quodlibet/quodlibet/qltk/debugwindow.py

@@ -183,11 +183,18 @@ def __init__(self, type_, value, traceback):
         label.set_line_wrap(True)
         box = Gtk.VBox(spacing=6)
         buttons = Gtk.HButtonBox()
+
+        viewbox = Gtk.VBox(spacing=4)
+        buf = Gtk.TextBuffer()
+        buf.set_text(text_type(value))
+        viewbox.add(Gtk.TextView(buffer=buf, editable=False))
         view = Gtk.TreeView()
+        viewbox.add(view)
+        view.set_headers_visible(False)
         sw = Gtk.ScrolledWindow()
         sw.set_policy(Gtk.PolicyType.AUTOMATIC, Gtk.PolicyType.ALWAYS)
         sw.set_shadow_type(Gtk.ShadowType.IN)
-        sw.add(view)
+        sw.add(viewbox)
         model = Gtk.ListStore(object, object, object)
         self.__fill_list(view, model, value, traceback)
         view.set_model(model)
@@ -236,7 +243,7 @@ def cdf(column, cell, model, iter, data):
                     util.escape(function), line, util.escape(filename)))
 
         render = Gtk.CellRendererText()
-        col = Gtk.TreeViewColumn(text_type(value).replace("_", "__"), render)
+        col = Gtk.TreeViewColumn(u"", render)
         col.set_cell_data_func(render, cdf)
         col.set_visible(True)
         col.set_expand(True)

quodlibet/quodlibet/util/faulthandling.py

@@ -0,0 +1,110 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 Christoph Reiter
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation
+
+"""
+Interface around faulthandler to save and restore segfault info for the
+next program invocation.
+"""
+
+import os
+import ctypes
+import errno
+
+try:
+    import faulthandler
+except ImportError:
+    faulthandler = None
+
+
+_fileobj = None
+_enabled = False
+
+
+def enable(path):
+    """Enable crash reporting and create empty target file
+
+    Args:
+        path (pathlike): the location of the crash log target path
+    Raises:
+        IOError: In case the location is not writable
+    """
+
+    global _fileobj, _enabled
+
+    if _fileobj is not None:
+        raise Exception("already enabled")
+
+    _enabled = True
+
+    if faulthandler is None:
+        return
+
+    try:
+        _fileobj = open(path, "rb+")
+    except IOError as e:
+        if e.errno == errno.ENOENT:
+            _fileobj = open(path, "wb+")
+
+    faulthandler.enable(_fileobj)
+
+
+def disable():
+    """Disable crash reporting and removes the target file
+
+    Does not raise.
+    """
+
+    global _fileobj, _enabled
+
+    assert _enabled
+    _enabled = False
+
+    if _fileobj is None:
+        return
+
+    faulthandler.disable()
+
+    try:
+        _fileobj.close()
+        os.unlink(_fileobj.name)
+    except IOError:
+        pass
+    _fileobj = None
+
+
+def check_and_clear_error():
+    """Returns an error message or None. Calling this will clear the error
+    so a second call will always return None.
+
+    enable() needs to be called first.
+
+    Returns:
+        text or None
+    Raises:
+        IOError: In case the file couldn't be read
+    """
+
+    global _fileobj, _enabled
+
+    assert _enabled
+
+    if _fileobj is None:
+        return
+
+    _fileobj.seek(0)
+    text = _fileobj.read().decode("utf-8", "replace").strip()
+    _fileobj.seek(0)
+    _fileobj.truncate()
+
+    if text:
+        return text
+
+
+def crash():
+    """Makes the process segfault. For testing purposes"""
+
+    ctypes.string_at(0)

quodlibet/tests/helper.py

@@ -11,6 +11,7 @@
 import sys
 import shutil
 import locale
+import errno
 
 from gi.repository import Gtk, Gdk
 from senf import fsnative, environ
@@ -269,7 +270,11 @@ def temp_filename(*args, **kwargs):
 
     yield filename
 
-    os.remove(filename)
+    try:
+        os.remove(filename)
+    except OSError as e:
+        if e.errno != errno.ENOENT:
+            raise
 
 
 def get_temp_copy(path):

quodlibet/tests/test_util_faulthandling.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 Christoph Reiter
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation
+
+from tests import TestCase
+from .helper import temp_filename
+
+from quodlibet.util import faulthandling
+
+
+class Tfaulthandling(TestCase):
+
+    def test_basic(self):
+        with temp_filename() as filename:
+            faulthandling.enable(filename)
+            assert faulthandling.check_and_clear_error() is None
+            faulthandling.disable()