<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">On Oct 1, 2014, at 3:36 PM, Marshall Clow <<a href="mailto:mclow.lists@gmail.com">mclow.lists@gmail.com</a>> wrote:<br><div><blockquote type="cite"><div style="font-family: LucidaGrande; font-size: 11px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br></div><div style="font-family: LucidaGrande; font-size: 11px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Richard Smith pointed out that destroying a pointer to an objective-C class might require an ARC call, and so the compiler needs to see the type to figure out if it is_destructible.</div><div style="font-family: LucidaGrande; font-size: 11px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br></div><div style="font-family: LucidaGrande; font-size: 11px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Note that is_destructible<ObjCForwardClass**>::value is true, so it’s just pointers to objective-C objects, not pointers in general.</div></blockquote><br></div><div>Richard also pointed me to: <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html#retainable-object-pointers">http://clang.llvm.org/docs/AutomaticReferenceCounting.html#retainable-object-pointers</a></div><div><br></div><div>So, while I agree with <font face="LucidaGrande">Argyrios that this changed the behavior of is_trivially_destructible for forward-declared objective-C classes,</font></div><div><font face="LucidaGrande">I am now convinced that the old behavior was incorrect, and the new behavior is “better”.</font></div><div><font face="LucidaGrande"><br></font></div><div><font face="LucidaGrande">One could argue that a forward-declared objective-C class is not a complete type, since the compiler doesn’t know how to destroy it, and if so, then is_destructible is not required to give any answer at all ("T shall be a complete type”).</font></div><div><font face="LucidaGrande"><br></font></div><div><font face="LucidaGrande">— Marshall</font></div><div><font face="LucidaGrande"><br></font></div><br></body></html>