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| ==ReturnObjectFromFunction.cxx==
| | {{warning|1=The media wiki content on this page is no longer maintained. The examples presented on the https://itk.org/Wiki/* pages likely require ITK version 4.13 or earlier releases. In many cases, the examples on this page no longer conform to the best practices for modern ITK versions.}} |
| <source lang="cpp">
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| #include "itkImage.h"
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| typedef itk::Image<unsigned char, 2> ImageType;
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| ImageType::Pointer ReturnSmartPointer()
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| { | |
| ImageType::Pointer image = ImageType::New();
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| itk::Index<2> corner = {{0,0}};
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| itk::Size<2> size = {{10,10}};
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| itk::ImageRegion<2> region(corner, size);
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| image->SetRegions(region);
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| image->Allocate();
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| return image;
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| }
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| ImageType* ReturnPointer()
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| {
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| ImageType::Pointer image = ImageType::New();
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| itk::Index<2> corner = {{0,0}};
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| itk::Size<2> size = {{10,10}};
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| itk::ImageRegion<2> region(corner, size);
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| image->SetRegions(region);
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| image->Allocate();
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| return image;
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| }
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| int main(int argc, char *argv[])
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| {
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| {
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| // This is how it should be done.
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| ImageType::Pointer smartPointer = ReturnSmartPointer();
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| std::cout << smartPointer->GetLargestPossibleRegion() << std::endl;
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| }
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| {
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| ImageType* pointer = ReturnPointer();
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| // This crashes the program because the smart pointer created in the function goes out of scope and gets deleted
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| // because it is returned as a normal pointer.
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| // std::cout << pointer->GetLargestPossibleRegion() << std::endl;
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| }
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| | |
| {
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| ImageType* pointer = ReturnSmartPointer();
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| // This crashes the program because though the function returned a ::Pointer, it was not stored
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| // anywhere so the reference count was not increased, so it got deleted.
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| // std::cout << pointer->GetLargestPossibleRegion() << std::endl;
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| }
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| {
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| // I thought this might also work, but it does not (crash).
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| // My reasoning was that even though you don't return a smart pointer, you assign the object to a smart | |
| // pointer at return time, so it still has a reference count of 1.
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| //ImageType::Pointer smartPointer = ReturnPointer(); // this line causes a 'glibc error'
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| // std::cout << smartPointer->GetLargestPossibleRegion() << std::endl;
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| }
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|
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| return 0;
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| }
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| </source>
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| {{ITKCMakeLists|ReturnObjectFromFunction}}
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