<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Nov 27, 2018, at 10:16 AM, David Blaikie via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" class="">cfe-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><br class=""><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Mon, Nov 26, 2018 at 6:55 PM Reid Kleckner <<a href="mailto:rnk@google.com" class="">rnk@google.com</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class=""><div class="gmail_quote"><div dir="ltr" class="">On Mon, Nov 26, 2018 at 6:43 PM Kostya Serebryany via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank" class="">cfe-dev@lists.llvm.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class=""><div class="gmail_quote"><div dir="ltr" class="">On Sat, Nov 17, 2018 at 9:00 AM David Blaikie via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank" class="">cfe-dev@lists.llvm.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class="">Would it be that drastic to have this require a code change/compiler rebuild to enable? It could be designed so the change is small/easy (changing a constant) but that the default compilers we all ship around (& especially not the official releases) don't allow access to this functionality.<br class=""><br class="">Anyone wanting to gather data would have to make this small change, rebuild their compiler, build their target with this feature & gatehr results from there.</div></blockquote><div class=""><br class=""></div><div class="">This will cripple our ability to do measurements because in many cases we can only build things with whatever is the production compiler. </div><div class="">I'd rather just rename the flag to something like -ftrivial-auto-var-init=zero-SCARY-WARNING-ABOUT-VOID-WARRANTY-GOES-HERE</div></div></div></blockquote><div class=""><br class=""></div></div></div><div dir="ltr" class=""><div class="gmail_quote"><div class="">Reminds me of -fheinous-gnu-extensions. ;-)</div></div></div></blockquote><div class=""><br class="">Pretty much - and I don't think any choice of spelling is bad enough that it'd make it substantially less likely that people would end up depending on the behavior in their non-buggy codepaths. Once the flag is written into someone's build system, there it is... even if it's absurdly long/verbose/angry/whatever, generally it'll slip under the radar after it's written into the build system.<br class=""></div></div></div></div></blockquote></div><br class=""><div class="">I’d like to get us to a point where we all agree to a solution. I think these statements are true:</div><div class=""><br class=""></div><div class="">0. We want to minimize the size / perf hit because that’ll maximize adoption.</div><div class="">1. We need to gather size / perf data of uninit versus zero-init versus pattern-init.</div><div class="">2. The easier it is to gather data, the faster it’ll be to find and address regressions we don’t know about (likely in other people’s codebases).</div><div class="">3. We don’t want to have zero-init long term, and we don’t want people to rely on it.</div><div class="">4. Giving the flag / attribute an ugly name won’t prevent people from using them.</div><div class=""><br class=""></div><div class="">These seem at odds because we don’t usually remove flags. Can we purposefully change the name of the zero-init flag / attribute on every release, until we finally remove it? Or is the only option to give up on 2. And add friction when trying to collect data?</div></body></html>