STYLE: Remove this->MakeOutput(0) calls from constructors in Core
#4654
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Analogue to ITK pull request InsightSoftwareConsortium/ITK#4654 Following C++ Core Guidelines, February 15, 2024, "Don’t call virtual functions in constructors and destructors", https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rc-ctor-virtual
| this->ProcessObject::SetNumberOfRequiredOutputs(1); | ||
| this->ProcessObject::SetNthOutput(0, output.GetPointer()); | ||
| this->ProcessObject::SetNthOutput(0, TOutputImage::New().GetPointer()); |
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Please add comment like: "Generally MakeOutput(n) should be used, but because a virtual method should not be called in a constructor the output is directly constructed."
It is important to note how things should be done, and why they are not done that way for this case. There have been bugs before related to not using MakeOutput.
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Thanks for the suggestion @blowekamp
There have been bugs before related to not using MakeOutput.
Can you possibly still recall what such a bug looked like? Just for my understanding!
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Don't recall the specifics... There are cases when a Process object can have it's outputs removed, and then during execution it needs to make them again.
Maybe f0d570e?
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Interesting! In general, I think this->MakeOutput(i) calls are not necessary, inside a constructor of a class, when the MakeOutput(i) override of this class unconditionally just does the same OutputType::New() call for any index value i.
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I agree they are not necessary. I am just suggestion adding documentation as to why the canonical way of creating a new output is not being used e.g documenting the exception case.
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So that was a "no" to the request for documentation?
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Oh, sorry Bradley, what do you want there? Something like
// Basically equivalent to SetNthOutput(0, MakeOutput(0)).
this->ProcessObject::SetNthOutput(0, TOutputImage::New().GetPointer())
?
I hope it does not need to be longer than one line of comment. This pull request is intended to simplify the code. The idea is: Just call TOutput::New() if that does the job!
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Sorry, I see your suggestion at https://github.com/InsightSoftwareConsortium/ITK/pull/4654/files#r1596759648 As the idea would be to use New(), rather that MakeOutput, in multiple places in the source tree, I would rather have those considerations elsewhere. Maybe in the ITKSoftwareGuide?
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What do you mean "As the idea would be to use New(), rather that MakeOutput, in multiple places in the source tree"?
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Well, this pull request already proposes to replace three MakeOutput calls with TOutput::New(). I don't think it's nice to have an extensive multi-line comment copy-and-pasted multiple times.
Analogue to ITK pull request InsightSoftwareConsortium/ITK#4654 Following C++ Core Guidelines, February 15, 2024, "Don’t call virtual functions in constructors and destructors", https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rc-ctor-virtual
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I think this pull request may also be merged now, as v5.4.0 has been tagged (#4603 (comment)) |
In those cases, `MakeOutput(0)` just did `OutputType::New()` anyway. This commit avoids unnecessary casts and calls to virtual functions. Following C++ Core Guidelines, February 15, 2024, "Don’t call virtual functions in constructors and destructors", https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rc-ctor-virtual
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In those cases,
MakeOutput(0)just didOutputType::New()anyway. This commit avoids unnecessary casts and calls to virtual functions.Following C++ Core Guidelines, February 15, 2024, "Don’t call virtual functions in constructors and destructors",
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rc-ctor-virtual
Intended for after the release of ITK v5.4.0