Bug report #21270

QGIS crashes when createInstance() uses wrong constructor in a QgsProcessingAlgorithm subclass

Added by Reino Ruusu almost 5 years ago. Updated almost 5 years ago.

Assignee:Alessandro Pasotti
Affected QGIS version:3.5(master) Regression?:No
Operating System:Any Easy fix?:No
Pull Request or Patch supplied:Yes Resolution:fixed/implemented
Crashes QGIS or corrupts data:Yes Copied to github as #:29088



QGIS makes a hard crash when the createInstance() method calls a non-existent constructor in a python processing script class (QgsProcessingAlgorithm).

This is an easy error to make after creating a new script from a template.


  • Create a new script in the Processing Toolbox using 'Create New Script from Template...'
  • Rename class ExampleProcessingAlgorithm to anything else (such as MyProcessingAlgorithm). Leave reference to ExampleProcessingAlgorithm() in createInstance().
  • Save template script
  • Execute script by double-clicking it in Scripts/Example scripts/My script
  • ':( QGIS Crashed' dialog


Crash ID: 4e33457d15a27ee43b8270be864ceb43b1208535

Stack Trace

QgsProcessingAlgorithm::setProvider :
QgsProcessingAlgorithm::create :
PyInit__core :
PyMethodDef_RawFastCallKeywords :
PyMethodDef_RawFastCallKeywords :
PyEval_EvalFrameDefault :
PyFunction_FastCallDict :
PyMethodDef_RawFastCallDict :
PyObject_Call :
PyInit_QtCore :
PyInit_QtCore :
PyInit_QtCore :
PyInit_QtCore :
PyInit_QtCore :
QMetaObject::activate :
QAbstractItemView::doubleClicked :
QTreeView::mouseDoubleClickEvent :
QWidget::event :
QFrame::event :
QAbstractItemView::viewportEvent :
QCoreApplicationPrivate::sendThroughObjectEventFilters :
QApplicationPrivate::notify_helper :
QApplication::notify :
QgsApplication::notify :
QCoreApplication::notifyInternal2 :
QApplicationPrivate::sendMouseEvent :
QSizePolicy::QSizePolicy :
QSizePolicy::QSizePolicy :
QApplicationPrivate::notify_helper :
QApplication::notify :
QgsApplication::notify :
QCoreApplication::notifyInternal2 :
QGuiApplicationPrivate::processMouseEvent :
QWindowSystemInterface::sendWindowSystemEvents :
QEventDispatcherWin32::processEvents :
CallWindowProcW :
DispatchMessageW :
QEventDispatcherWin32::processEvents :
qt_plugin_query_metadata :
QEventLoop::exec :
QCoreApplication::exec :
main :
BaseThreadInitThunk :
RtlUserThreadStart :

QGIS Version: 3.4.4-Madeira
QGIS code revision: f6ddc62fdb
Compiled against Qt: 5.11.2
Running against Qt: 5.11.2
Compiled against GDAL: 2.4.0
Running against GDAL: 2.4.0

System Info
CPU Type: x86_64
Kernel Type: winnt
Kernel Version: 10.0.17134

Associated revisions

Revision 8db38afb
Added by Alessandro Pasotti almost 5 years ago

Processing: fix crash in alg runner task with bad scripts

Fixes #21270

With test


#1 Updated by Giovanni Manghi almost 5 years ago

  • Priority changed from Normal to High

#2 Updated by Alessandro Pasotti almost 5 years ago

  • Assignee set to Alessandro Pasotti
  • Operating System changed from Windows 10 Pro - build 17134.523 to Any
  • Affected QGIS version changed from 3.4.4 to 3.5(master)

#3 Updated by Alessandro Pasotti almost 5 years ago

  • Status changed from Open to In Progress
  • Resolution set to fixed/implemented
  • Pull Request or Patch supplied changed from No to Yes

PR https://github.com/qgis/QGIS/pull/9193

Btw, there are endless ways to crash QGIS from bad python code, we will never be able to prevent this to happen: http://enki-editor.org/2014/08/23/Pyqt_mem_mgmt.html

#4 Updated by Alessandro Pasotti almost 5 years ago

  • % Done changed from 0 to 100
  • Status changed from In Progress to Closed

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