<div dir="ltr">Hi Francois,<div><br></div><div>Maybe I misunderstood, but I disagree with your statement that "you cannot use the keyword auto with these other methods"</div><div><br></div><div>Attached is a screenshot showing a small ITK test program in a Visual Studio debugging session. </div><div><br></div><div>The program is very simple; an AddImages() function is called, which itself calls a CreateImage() function twice before adding the created images and returning the result.</div><div>Note that I have used <font face="monospace"><b>auto</b></font> when storing the image pointers returned by the CreateImage and AddImage functions.</div><div><br></div><div>On the right of the image you can see snapshots of the memory usage as the program executes, and I have also annotated which lines of the program were executed immediately before taking the snapshot.</div><div><br></div><div>The first snapshot show that on line 22, very little memory has been allocated, since we have not yet created any images.</div><div>On line 23 ~16MB of memory is used when the first image is created.</div><div>On line 24 ~32MB is used after the 2nd image is created.</div><div>On line 30 the two images are added together and the result is returned from the function. At this point ~48MB is used because all 3 image still exist in memory.</div><div>On line 31 we exit from the AddImages() function and can see that the memory for two temporary images has been correctly deallocated, since the <font face="monospace"><b>im1</b></font> and <font face="monospace"><b>im2</b></font> pointers have gone out of scope.</div><div>Finally on line 38 we exit the main() function and see that the memory usage returns to ~0MB, since the <font face="monospace"><b>image</b></font> variable also goes out of scope and the memory associated with it is deallocated.</div><div><br></div><div>Based on this simple test I think that it is probably safe to use <font face="monospace"><b>auto</b></font> to store the output from filters. It does not look like it interferes with the reference counting or leads to memory leaks, as Yann was worried about.</div><div><br></div><div>Let me know if you see any mistakes in my tests!</div><div>Kiran</div><div><br></div><img src="cid:15af1551a065f63678a1" alt="ITKPointerTest.png" class="" style="max-width: 100%; opacity: 1;"><div><br></div><br><div class="gmail_quote"><div dir="ltr">On Tue, 21 Mar 2017 at 12:38 Francois Budin <<a href="mailto:francois.budin@kitware.com">francois.budin@kitware.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg">Hello Yann,<br class="gmail_msg"><br class="gmail_msg"></div>Indeed, you are correct. New() will return a smart pointer, but other methods will return a pointer, so you cannot use the keyword "auto" with these other methods.<br class="gmail_msg"></div>The two following links give some insight in why ITK is implemented this way:<br class="gmail_msg"><a href="https://itk.org/Wiki/ITK/Examples/Utilities/ReturnObjectFromFunction" class="gmail_msg" target="_blank">https://itk.org/Wiki/ITK/Examples/Utilities/ReturnObjectFromFunction</a><br class="gmail_msg"><a href="https://itk.org/pipermail/insight-developers/2011-April/018011.html" class="gmail_msg" target="_blank">https://itk.org/pipermail/insight-developers/2011-April/018011.html</a><br class="gmail_msg"><br class="gmail_msg"></div>Hope this helps,<br class="gmail_msg"></div>Francois<br class="gmail_msg"></div><div class="gmail_extra gmail_msg"><br class="gmail_msg"><div class="gmail_quote gmail_msg">On Tue, Mar 21, 2017 at 6:45 AM, asertyuio via Insight-users <span dir="ltr" class="gmail_msg"><<a href="mailto:insight-users@itk.org" class="gmail_msg" target="_blank">insight-users@itk.org</a>></span> wrote:<br class="gmail_msg"><blockquote class="gmail_quote gmail_msg" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF" class="gmail_msg">
<div class="m_-3661160424353991923m_4393718566787835312markdown-here-wrapper gmail_msg">
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">Hi Hans,</p>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">Thanks for your
answer !</p>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">I was asking that
because when I use auto keyword with a filter output, it seems
like is result in a normal point type, not a smart pointer, so a
code with</p>
<pre style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;font-size:1em;line-height:1.2em;margin:1.2em 0px" class="gmail_msg"><code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline;white-space:pre-wrap;overflow:auto;border-radius:3px;border:1px solid rgb(204,204,204);padding:0.5em 0.7em;display:block!important" class="gmail_msg">auto testOutput = testFilter->GetOutput();
</code></pre>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">has not the same
behavior as</p>
<pre style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;font-size:1em;line-height:1.2em;margin:1.2em 0px" class="gmail_msg"><code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline;white-space:pre-wrap;overflow:auto;border-radius:3px;border:1px solid rgb(204,204,204);padding:0.5em 0.7em;display:block!important" class="gmail_msg"> FilterOutputType::Pointer testOutput = testFilter->GetOutput();
</code></pre>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg"><code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="gmail_msg">testOutput</code>
is a smart pointer in the second case, and a normal pointer in
the first one.</p>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">I was wondering if
it could interfere with the smart pointer role (for example
causing memory leak, or wrong reference count).</p>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">After a deeper look,
<code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="gmail_msg">New()</code>
return a smart pointer (so with auto =, no problem) and <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="gmail_msg">GetOutput()</code>
a pointer. So the second code snipset just creates another
instance of a smart pointer.</p>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">I hope what was my
question is now clearer !<br class="gmail_msg">
Yann</p><span class="gmail_msg">
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">Le 21/03/2017 à
01:43, Johnson, Hans J a écrit :</p>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg"></p>
<div class="m_-3661160424353991923m_4393718566787835312markdown-here-exclude gmail_msg">
<p class="gmail_msg"></p>
<blockquote type="cite" class="gmail_msg">
<pre class="gmail_msg">Yann,
It will work only if you are compiling with C++11, and you have no intention of sharing your code with others who may not use C++11 syntax.
ITK proper currently maintains backwards compatibility with older versions of C++.
Hans
</pre>
</blockquote>
<p class="gmail_msg"></p>
</div>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg"></p>
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