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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Another alternative is to copy the pointer and not the whole array (as it done in C)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Eli Friedman [mailto:eli.friedman@gmail.com]
<br>
<b>Sent:</b> Wednesday, June 19, 2013 20:46<br>
<b>To:</b> Adler, Arik<br>
<b>Cc:</b> cfe-dev@cs.uiuc.edu<br>
<b>Subject:</b> Re: [cfe-dev] Question about arrays in blocks<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Wed, Jun 19, 2013 at 2:53 AM, Adler, Arik <<a href="mailto:arik.adler@intel.com" target="_blank">arik.adler@intel.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">I am now testing blocks usage in OpenCL.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">I noticed that Clang forbids using an arrays within blocks (Clang forbid array capturing)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">For Example, the following code will fail to compile because there is a reference to an array within a block.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">But if the line referring to block will comment out and the line with reference to integer pointer ('j') will comment in, the code will pass.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D"> </span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas;color:blue">void</span><span style="font-size:9.5pt;font-family:Consolas"> block_arr()</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas">{</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> <span style="color:blue">int</span> res = 0;</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> <span style="color:blue">int</span> i[4] = { 3, 4, 4, 1 };</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> <span style="color:blue">int</span>* j = i;</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:1.0in;text-autospace:none">
<span style="font-size:9.5pt;font-family:Consolas"> <span style="color:blue">int</span> (^test_block )(<span style="color:blue">int</span>) = ^(<span style="color:blue">int</span> num)</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> {</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> <span style="color:blue">
return</span> num + i[1]; <span style="color:green">// This is an error: "error: cannot refer to declaration with an array type inside block"</span></span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas;color:green">// return num + j[1]; // This would work</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> };</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> </span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas"> res = test_block(7);</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:Consolas">}</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">Do you know what is the reason behind this limitation?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D">And why it is possible to use a regular pointers but arrays are forbidden?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">IIRC, it's just so that people don't accidentally make implicit copies of large arrays.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-Eli <o:p></o:p></p>
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