<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office"><head><!--[if gte mso 9]><xml><o:OfficeDocumentSettings><o:AllowPNG/><o:PixelsPerInch>96</o:PixelsPerInch></o:OfficeDocumentSettings></xml><![endif]--></head><body><div style="color:#000; background-color:#fff; font-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:13px"><div id="yui_3_16_0_ym19_1_1515413693521_4159">I'm on macOS Sierra 10.12.6, and using Swift 4.0</div><div id="yui_3_16_0_ym19_1_1515413693521_4299">Tried to access the array concurrently to see whether is it synchronized or no<br></div><div dir="ltr" id="yui_3_16_0_ym19_1_1515413693521_4263"><a href="https://pastebin.com/PnvyM3Qn" class="enhancr2_0af812e8-9a1d-3326-9334-51751140db37" id="yui_3_16_0_ym19_1_1515413693521_4262">import Foundation let global = DispatchQueue.global() var array: [Int] = [ - Pastebin.com</a><br></div><div id="yui_3_16_0_ym19_1_1515413693521_4270"><br></div><div id="enhancr2_0af812e8-9a1d-3326-9334-51751140db37" class="yahoo-link-enhancr-card ymail-preserve-class ymail-preserve-style" style="max-width:400px;font-family:'Helvetica Neue', Helvetica, Arial, sans-serif;" data-url="https://pastebin.com/PnvyM3Qn" data-type="yenhancr" data-category="article" data-embed-url="" data-size="medium" dir="ltr" contenteditable="false"> <a href="https://pastebin.com/PnvyM3Qn" style="text-decoration:none !important; color: #000 !important;" class="yahoo-enhancr-cardlink" target="_blank" rel="noreferrer" id="yui_3_16_0_ym19_1_1515413693521_4318"> <table class="card-wrapper yahoo-ignore-table" style="max-width:400px;" id="yui_3_16_0_ym19_1_1515413693521_4317" cellspacing="0" cellpadding="0" border="0"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4316"><tr id="yui_3_16_0_ym19_1_1515413693521_4315"> <td id="yui_3_16_0_ym19_1_1515413693521_4314" width="400"> <table class="card yahoo-ignore-table" style="max-width:400px;" id="yui_3_16_0_ym19_1_1515413693521_4313" cellspacing="0" cellpadding="0" border="0" width="100%"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4312"><tr id="yui_3_16_0_ym19_1_1515413693521_4311"> <td class="card-primary-image-cell" style="background:#000 url('https://s.yimg.com/vv//api/res/1.2/x_YOsykpk_BPKDNd006jFg--~A/YXBwaWQ9bWFpbDtmaT1maWxsO2g9MjAwO3c9NDAw/https://pastebin.com/i/facebook.png.cf.jpg') no-repeat center center;background-size:cover;height:200px;position:relative;" id="yui_3_16_0_ym19_1_1515413693521_4310" bgcolor="#000000" background="https://s.yimg.com/vv//api/res/1.2/x_YOsykpk_BPKDNd006jFg--~A/YXBwaWQ9bWFpbDtmaT1maWxsO2g9MjAwO3c9NDAw/https://pastebin.com/i/facebook.png.cf.jpg" valign="top"> <!--[if gte mso 9]><v:rect fill="true" stroke="false" style="width:400px;height:218px;position:absolute;top:0;left:0;"><v:fill type="frame" color="#000000" src="https://s.yimg.com/vv//api/res/1.2/x_YOsykpk_BPKDNd006jFg--~A/YXBwaWQ9bWFpbDtmaT1maWxsO2g9MjAwO3c9NDAw/https://pastebin.com/i/facebook.png.cf.jpg"/></v:rect><![endif]--> <table class="yahoo-ignore-table" valign="top" style="width:100%;" id="yui_3_16_0_ym19_1_1515413693521_4309" cellspacing="0" cellpadding="0" border="0"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4308"><tr id="yui_3_16_0_ym19_1_1515413693521_4307"> <td style="background:transparent url('https://s.yimg.com/nq/storm/assets/enhancrV2/12/overlay-tile.png') repeat left top;height:200px;" id="yui_3_16_0_ym19_1_1515413693521_4306" bgcolor="transparent" background="https://s.yimg.com/nq/storm/assets/enhancrV2/12/overlay-tile.png" valign="top"> <!--[if gte mso 9]><v:rect fill="true" stroke="false" style="width:400px;height:218px;position:absolute;top:-18px;left:0;"><v:fill type="pattern" color="#000000" src="https://s.yimg.com/nq/storm/assets/enhancrV2/12/overlay-tile.png"/><v:textbox inset="0,0,20px,0"><![endif]--> <table class="yahoo-ignore-table" style="width:100%;height:185px;min-height:185px;" id="yui_3_16_0_ym19_1_1515413693521_4305" height="185"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4304"><tr id="yui_3_16_0_ym19_1_1515413693521_4303"> <td class="card-richInfo2" style="text-align:left;text-align:left;padding:15px 0 0 15px;vertical-align:top;" id="yui_3_16_0_ym19_1_1515413693521_4302"> </td> <td class="card-actions" style="text-align:right;padding:15px 15px 0 0;vertical-align:top;"> <div class="card-share-container"></div> </td> </tr> </tbody></table> <!--[if gte mso 9]></v:textbox></v:rect><![endif]--> </td> </tr> </tbody></table> </td> </tr> <tr id="yui_3_16_0_ym19_1_1515413693521_4405"> <td id="yui_3_16_0_ym19_1_1515413693521_4404"> <table class="card-info yahoo-ignore-table" style="background:#fff;position:relative;z-index:2;width:95%;max-width:380px;border:1px solid #e0e4e9;border-bottom:3px solid #000000;margin-top:-40px;margin-left:auto;margin-right:auto;" id="yui_3_16_0_ym19_1_1515413693521_4403" cellspacing="0" cellpadding="0" border="0" align="center"> <tbody><tr> <td style="background-color:#ffffff;padding:16px 0 16px 12px;vertical-align:top;"> </td> <td style="vertical-align:middle;padding:16px 12px;width:99%;"> <h2 class="card-title" style="font-size: 16px; line-height:19px; margin:0 0 4px 0;font-family:'Helvetica Neue', Helvetica, Arial, sans-serif;word-break:break-word;">import Foundation let global = DispatchQueue.global() var array: [Int...</h2> <div class="card-description" style="font-size:11px;line-height:15px;color:#999;word-break:break-word;"></div> </td> <td style="text-align:right;padding:16px 12px 16px 0;"> </td> </tr> </tbody></table> </td> </tr> </tbody></table> </td> </tr> </tbody></table> </a></div><div id="yui_3_16_0_ym19_1_1515413693521_4408"><br></div><div id="yui_3_16_0_ym19_1_1515413693521_4409">When tried to run it using the terminal</div><div id="yui_3_16_0_ym19_1_1515413693521_4416">This crash happened</div><div id="yui_3_16_0_ym19_1_1515413693521_4417"><br></div><div id="yui_3_16_0_ym19_1_1515413693521_4418" dir="ltr"><a href="https://pastebin.com/vrdKTfrP" class="enhancr2_5a98714b-dace-156a-89c6-8e3af06f6ea3" id="yui_3_16_0_ym19_1_1515413693521_4424">swift(69836,0x700002dc2000) malloc: *** error for object 0x7ffe4be237e0: pointer - Pastebin.com</a></div><div><br></div><div id="enhancr2_5a98714b-dace-156a-89c6-8e3af06f6ea3" class="yahoo-link-enhancr-card ymail-preserve-class ymail-preserve-style" style="max-width:400px;font-family:'Helvetica Neue', Helvetica, Arial, sans-serif;" data-url="https://pastebin.com/vrdKTfrP" data-type="yenhancr" data-category="article" data-embed-url="" data-size="medium" dir="ltr" contenteditable="false"> <a href="https://pastebin.com/vrdKTfrP" style="text-decoration:none !important; color: #000 !important;" class="yahoo-enhancr-cardlink" target="_blank" rel="noreferrer" id="yui_3_16_0_ym19_1_1515413693521_4442"> <table class="card-wrapper yahoo-ignore-table" style="max-width:400px;" id="yui_3_16_0_ym19_1_1515413693521_4441" cellspacing="0" cellpadding="0" border="0"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4440"><tr id="yui_3_16_0_ym19_1_1515413693521_4439"> <td id="yui_3_16_0_ym19_1_1515413693521_4438" width="400"> <table class="card yahoo-ignore-table" style="max-width:400px;" id="yui_3_16_0_ym19_1_1515413693521_4437" cellspacing="0" cellpadding="0" border="0" width="100%"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4436"><tr id="yui_3_16_0_ym19_1_1515413693521_4645"> <td class="card-primary-image-cell" style="background:#000 url('https://s.yimg.com/vv//api/res/1.2/x_YOsykpk_BPKDNd006jFg--~A/YXBwaWQ9bWFpbDtmaT1maWxsO2g9MjAwO3c9NDAw/https://pastebin.com/i/facebook.png.cf.jpg') no-repeat center center;background-size:cover;height:200px;position:relative;" id="yui_3_16_0_ym19_1_1515413693521_4644" bgcolor="#000000" background="https://s.yimg.com/vv//api/res/1.2/x_YOsykpk_BPKDNd006jFg--~A/YXBwaWQ9bWFpbDtmaT1maWxsO2g9MjAwO3c9NDAw/https://pastebin.com/i/facebook.png.cf.jpg" valign="top"> <!--[if gte mso 9]><v:rect fill="true" stroke="false" style="width:400px;height:218px;position:absolute;top:0;left:0;"><v:fill type="frame" color="#000000" src="https://s.yimg.com/vv//api/res/1.2/x_YOsykpk_BPKDNd006jFg--~A/YXBwaWQ9bWFpbDtmaT1maWxsO2g9MjAwO3c9NDAw/https://pastebin.com/i/facebook.png.cf.jpg"/></v:rect><![endif]--> <table class="yahoo-ignore-table" valign="top" style="width:100%;" id="yui_3_16_0_ym19_1_1515413693521_4643" cellspacing="0" cellpadding="0" border="0"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4642"><tr id="yui_3_16_0_ym19_1_1515413693521_4641"> <td style="background:transparent url('https://s.yimg.com/nq/storm/assets/enhancrV2/12/overlay-tile.png') repeat left top;height:200px;" id="yui_3_16_0_ym19_1_1515413693521_4640" bgcolor="transparent" background="https://s.yimg.com/nq/storm/assets/enhancrV2/12/overlay-tile.png" valign="top"> <!--[if gte mso 9]><v:rect fill="true" stroke="false" style="width:400px;height:218px;position:absolute;top:-18px;left:0;"><v:fill type="pattern" color="#000000" src="https://s.yimg.com/nq/storm/assets/enhancrV2/12/overlay-tile.png"/><v:textbox inset="0,0,20px,0"><![endif]--> <table class="yahoo-ignore-table" style="width:100%;height:185px;min-height:185px;" id="yui_3_16_0_ym19_1_1515413693521_4639" height="185"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4638"><tr id="yui_3_16_0_ym19_1_1515413693521_4637"> <td class="card-richInfo2" style="text-align:left;text-align:left;padding:15px 0 0 15px;vertical-align:top;" id="yui_3_16_0_ym19_1_1515413693521_4636"> </td> <td class="card-actions" style="text-align:right;padding:15px 15px 0 0;vertical-align:top;"> <div class="card-share-container"></div> </td> </tr> </tbody></table> <!--[if gte mso 9]></v:textbox></v:rect><![endif]--> </td> </tr> </tbody></table> </td> </tr> <tr id="yui_3_16_0_ym19_1_1515413693521_4435"> <td id="yui_3_16_0_ym19_1_1515413693521_4434"> <table class="card-info yahoo-ignore-table" style="background:#fff;position:relative;z-index:2;width:95%;max-width:380px;border:1px solid #e0e4e9;border-bottom:3px solid #000000;margin-top:-40px;margin-left:auto;margin-right:auto;" id="yui_3_16_0_ym19_1_1515413693521_4433" cellspacing="0" cellpadding="0" border="0" align="center"> <tbody id="yui_3_16_0_ym19_1_1515413693521_4491"><tr id="yui_3_16_0_ym19_1_1515413693521_4490"> <td style="background-color:#ffffff;padding:16px 0 16px 12px;vertical-align:top;"> </td> <td style="vertical-align:middle;padding:16px 12px;width:99%;" id="yui_3_16_0_ym19_1_1515413693521_4489"> <h2 class="card-title" style="font-size: 16px; line-height:19px; margin:0 0 4px 0;font-family:'Helvetica Neue', Helvetica, Arial, sans-serif;word-break:break-word;">swift(69836,0x700002dc2000) malloc: *** error for object 0x7ffe4be237e0: po...</h2> <div class="card-description" style="font-size:11px;line-height:15px;color:#999;word-break:break-word;"></div> </td> <td style="text-align:right;padding:16px 12px 16px 0;"> </td> </tr> </tbody></table> </td> </tr> </tbody></table> </td> </tr> </tbody></table> </a></div><div id="yui_3_16_0_ym19_1_1515413693521_4432"><br></div><div id="yui_3_16_0_ym19_1_1515413693521_4484">Avoided this crash using Serial Dispatch Queue</div><div id="yui_3_16_0_ym19_1_1515413693521_4485"><br></div><div id="yui_3_16_0_ym19_1_1515413693521_4488" dir="ltr">let otherDispatch = DispatchQueue(label: "another.dispatch.com",<br id="yui_3_16_0_ym19_1_1515413693521_4600"> qos: .default)<br id="yui_3_16_0_ym19_1_1515413693521_4601">func appending(_ i: Int) {<br id="yui_3_16_0_ym19_1_1515413693521_4602"> otherDispatch.sync { array.append(i) }<br id="yui_3_16_0_ym19_1_1515413693521_4603">}<br></div><div id="yui_3_16_0_ym19_1_1515413693521_4523"><br></div><div id="yui_3_16_0_ym19_1_1515413693521_4530"><br></div><div dir="ltr" id="yui_3_16_0_ym19_1_1515413693521_4460"><br></div><div dir="ltr" id="yui_3_16_0_ym19_1_1515413693521_4687">Also tried to file this issue on bugs.swift.org, and it appears your site is down (under maintainence)</div><div dir="ltr" id="yui_3_16_0_ym19_1_1515413693521_4691"><br></div><div dir="ltr">Sorry<br></div></div></body></html>