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| | + | <noinclude>{{documentation/versioncheck}}</noinclude> |
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| − | Here are some tips to narrow down various issues such as crash, or memory leaks
| + | {{documentation/banner |
| − | | + | | text = [https://slicer.readthedocs.io/en/latest/user_guide/get_help.html#slicer-application-does-not-start This page has been moved to read-the-docs.] |
| − | =Disable features= | + | | background-color = 8FBC8F }} |
| − | Try running Slicer with as few features as possible:
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| − | * Disable Slicer options via the command line
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| − | *: <pre>$ ./Slicer --no-splash --ignore-slicerrc --disable-cli-module --disable-loadable-module --disable-scriptedmodule</pre>
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| − | ** Look at all the possible options
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| − | **: <pre>$ ./Slicer --help</pre>
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| − | * Disable ITK plugins
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| − | *: CLI modules silently load the ITK plugins in lib/Slicer-4.0/ITKFactories. These plugins are used to share the volumes between Slicer and the ITK filter without having to copy them on disk.
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| − | ** rename lib/Slicer-4.0/ITKFactories into lib/Slicer-4.0/ITKFactories-disabled
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| − | * Disable Qt plugins
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| − | ** rename lib/Slicer-4.0/iconengine into lib/Slicer-4.0/iconengine-disabled
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| − | | |
| − | =Track memory leaks=
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| − | <ol>
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| − | <li> Turn ON the VTK_DEBUG_LEAKS CMake variable and build Slicer</li>
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| − | <li> Create a test that reproduces the memory leak systematically </li>
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| − | After execution, the memory leaks are printed automatically by VTK on the standard output:
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| − | 224: vtkDebugLeaks has detected LEAKS!
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| − | 224: Class "vtkProperty2D" has 60 instances still around.
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| − | ...
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| − | <li>Find what specific instance of a class (here vtkProperty2D) leaks.</li>
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| − | If the class is instantiated a large amount of time, it is hard to know what instance is leaking.
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| − | You can edit the constructor and destructor of the class (here vtkProperty2D::vtkProperty2D() and vtkProperty2D::~vtkProperty2D())
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| − | vtkProperty2D::vtkProperty2D()
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| − | {
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| − | ...
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| − | static int count = 0;
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| − | std::cout << "CREATE vtkProperty2D instance #" << count++ << " " << this << std::endl;
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| − | }
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| − |
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| − | vtkProperty2D::~vtkProperty2D()
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| − | {
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| − | ...
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| − | static int count = 0;
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| − | std::cout << "DELETE vtkProperty2D instance #" << count++ << " " << this << std::endl;
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| − | }
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| − | Don't forget to rebuild VTK if the class is from VTK (and not just Slicer inner build)
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| − | After running the test again, you should see a list of
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| − | ...
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| − | CREATE vtkProperty2D instance #0 0x0123456
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| − | ...
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| − | CREATE vtkProperty2D instance #1 0x01234E5
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| − | ...
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| − | DELETE vtkProperty2D instance #0 0x0123456
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| − | ...
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| − | DELETE vtkProperty2D instance #1 0x01234E5
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| − | ...
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| − | CREATE vtkProperty2D instance #2 0x0123A23
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| − | ...
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| − | CREATE vtkProperty2D instance #3 0x0124312
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| − | ...
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| − | Copy/paste the listing in a text editor and ensure that for each CREATE of a pointer (e.g. 0x0123456) it exists a DELETE. If there isn't, you found what instance is leaking. Note the instance # (here instance #2 and #3)
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| − | Run the test with the [[Documentation/4.0/Developers/Tutorials/Debug_Instructions|debugger]], set a breakpoint in the class constructor and ignore the break as many time as the instance number:
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| − | (gdb) break vtkProperty2D::vtkProperty2D()
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| − | Breakpoint 1 at 0x5b22d0e55d04296: file vtkProperty2D.cxx, line 22
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| − | (gdb) ignore 1 2
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| − | When the debugger stops, check the call stack:
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| − | (gdb) backtrace
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| − | By analyzing the trace, you should be able to find the faulty instance.
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| − | </li>
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| − | <li> Analyze the code to see where the leak could be</li>
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| − | Here is a listing of the most common mistakes
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| − | * this->MyXXX = vtkXXX::New();
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| − | ** Is there a matching this->MyXXX->Delete() ?
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| − | ** Are you sure <code>this->MyXXX</code> is <code>0</code> before being assigned a new pointer ? If not, then you need to add
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| − | if (this->MyXXX != 0)
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| − | {
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| − | this->MyXXX->Delete();
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| − | this->MyXXX = 0;
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| − | }
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| − | this->MyXXX = vtkXXX::New();
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| − | </ol>
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| − | {{ombox
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| − | |type=content
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| − | |text=To reduce memory leaks, use the following tools:
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| − | * <code>vtkNew<vtkXXX> myXXX;</code>
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| − | * <code>vtkSmartPointer<vtkXXX> myXXX = vtkSmartPointer<vtkXXX>::New()</code>
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| − | * <code>vtkSmartPointer<vtkXXX> myXXX; myXXX.TakeReference(this->CreateObjAndCallerOwnsReference())</code>.
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| − | }} | |
| − | | |
| − | =Track a crash while accessing already deleted object pointer=
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| − | If the application crashes by accessing an invalid pointer. The goal here is to find when (and why) the pointer is deleted before it is accessed .
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| − | <ol>
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| − | <li>Before the crash, print the value of the pointer:</li>
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| − | Add before the crash (i.e. <code>this->MyObject->update()</code>)
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| − | std::cout << ">>>>>Object pointer: " << this->MyObject << std::endl;
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| − | <li>Add a counter in the destructor:</li>
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| − | Add in the object destructor (it can be in the base class (vtkObject or vtkMRMLNode) if you don't know the type):
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| − | static int count = 0;
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| − | std::cout << "#######Object Destructed: " << this << " " << count++ << std::endl;
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| − | <li>Run the application and make it crash.</li>
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| − | <li>In the logs you shall see something like that:</li>
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| − | #######Object Destructed: 0x12345678 0
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| − | #######Object Destructed: 0x12345679 1
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| − | #######Object Destructed: 0x12345680 2
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| − | >>>>>Object Pointer: 0x12345660
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| − | >>>>>Object Pointer: 0x12345661
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| − | >>>>>Object Pointer: 0x12345662
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| − | #######Object Destructed: 0x12345660 3
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| − | #######Object Destructed: 0x12345661 4
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| − | #######Object Destructed: 0x12345662 5
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| − | #######Object Destructed: 0x12345663 6
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| − | >>>>>Object Pointer: 0x12345670
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| − | >>>>>Object Pointer: 0x12345671
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| − | >>>>>Object Pointer: 0x12345672
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| − | #######Object Destructed: 0x12345660 7
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| − | #######Object Destructed: 0x12345661 8
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| − | #######Object Destructed: 0x12345662 9
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| − | >>>>>Object Pointer: '''0x12345663'''
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| − | Segfault
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| − | <li> Search in the logs when the pointer before crash has been deleted. Set a conditional breakpoint in the debugger:</li>
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| − | (gdb) break MyObj.cxx:103 if count == 6
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| − | or
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| − | (gdb) break MyObj.cxx:103
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| − | (gdb) ignore 1 5
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| − | or if you don't want to use a debugger, you can make it crash the 6th time:
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| − | assert(count != 6);
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| − | <li> Analyze the backtrace to understand why the pointer has been deleted without letting know the object that tries to access it.</li>
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| − | </ol>
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