<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 5:09 PM, Argyrios Kyrtzidis <<a href="mailto:kyrtzidis@apple.com">kyrtzidis@apple.com</a>> wrote:<br><div><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div><blockquote type="cite" class=""><div class="">On Oct 1, 2014, at 4:52 PM, John McCall <<a href="mailto:rjmccall@apple.com" class="">rjmccall@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; 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; float: none; display: inline !important;" class="">On Oct 1, 2014, at 4:34 PM, Argyrios Kyrtzidis <</span><a href="mailto:kyrtzidis@apple.com" style="font-family: Helvetica; font-size: 12px; 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;" class="">kyrtzidis@apple.com</a><span style="font-family: Helvetica; font-size: 12px; 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; float: none; display: inline !important;" class="">> wrote:</span><br style="font-family: Helvetica; font-size: 12px; 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;" class=""><div style="font-family: Helvetica; font-size: 12px; 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;" class=""><blockquote type="cite" class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="">+ John</div><div class=""><br class=""></div><div class="">John, could you advice here ?</div><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Oct 1, 2014, at 4:20 PM, Marshall Clow <<a href="mailto:mclow.lists@gmail.com" class="">mclow.lists@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="" 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" class="">mclow.lists@gmail.com</a>> wrote:<br class=""><div class=""><blockquote type="cite" class=""><div class="" 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 class=""></div><div class="" 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 class="" 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 class=""></div><div class="" 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 class=""></div><div class="">Richard also pointed me to: <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html#retainable-object-pointers" class="">http://clang.llvm.org/docs/AutomaticReferenceCounting.html#retainable-object-pointers</a></div><div class=""><br class=""></div><div class="">So, while I agree with <font face="LucidaGrande" class="">Argyrios that this changed the behavior of is_trivially_destructible for forward-declared objective-C classes,</font></div><div class=""><font face="LucidaGrande" class="">I am now convinced that the old behavior was incorrect, and the new behavior is “better”.</font></div><div class=""><font face="LucidaGrande" class=""><br class=""></font></div><div class=""><font face="LucidaGrande" class="">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></div></blockquote></div></div></blockquote><div class=""><br class=""></div>Pointers to forward-declared Objective-C classes are still complete types. They should be both destructible and (outside of ARC) non-trivially destructible.</div><div style="font-family: Helvetica; font-size: 12px; 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;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; 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;" class="">I assume the problem here is ObjC property syntax, which usually looks like “foo.prop” where foo has ObjC pointer type. Type-checking a property access really does require the type to be complete. However, pseudo-destructor calls are not property accesses, and should not require the pointee type to be complete.</div><div style="font-family: Helvetica; font-size: 12px; 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;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; 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;" class="">Does that answer your question?</div></div></blockquote><div><br class=""></div><div>Are you suggesting that we make compiler changes to accept the pseudo-destructor call for ObjC pointers</div></div></div></blockquote><div><br></div><div>Yes. We already accept the pseudo-destructor call if the interface type is complete, presumably without actually looking anything up in the interface. We just unnecessarily bail out early if the interface is incomplete, despite it being a pseudo-destructor call.</div><br><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div><div>, and if yes, what would the codegen behavior be for ARC ?</div></div></div></blockquote><div><br></div></div>That doesn’t need to change.<div><br></div><div>John.</div></body></html>