<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Dylan,<div class=""><br class=""></div><div class="">I worked with Lang Hames on this back in July when this change was made. I don’t recall the exact details off the top of my head, but one key points of the thinking was you could not use this without handling the Error. I’ll seem to recall the only case one of the default constructors was allowed was for a sentinel value.</div><div class=""><br class=""></div><div class="">I’ll try to grab Lang today and try to look at this and get back to you. Sorry the details are not fresh on my mind as we did make these changes over 2 months ago.</div><div class=""><br class=""></div><div class="">Kev</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Oct 3, 2016, at 6:48 PM, Dylan McKay <<a href="mailto:dylanmckay34@gmail.com" class="">dylanmckay34@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="markdown-here-wrapper" style=""><p style="margin:0px 0px 1.2em!important" class="">r276686 introduced a regression into the object archive writer.</p><p style="margin:0px 0px 1.2em!important" class=""><a href="http://276686/" class="">r276686</a> on Phabricator</p><p style="margin:0px 0px 1.2em!important" class="">It causes the constructor <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="">Archive::Child(Parent, Data, StartOfFile)</code> to segfault if it is given a parent equalling NULL.</p><p style="margin:0px 0px 1.2em!important" class="">LLVM does this in a few places. The most prominent example is the <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="">Archive::child_iterator</code> default constructor. This will never execute without causing a segfault.</p><p style="margin:0px 0px 1.2em!important" class="">I’m in the process of updating Rust to LLVM 4.0. We are currently using <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="">Archive::child_iterator</code>, and it causes us to segfault when writing object files.</p>
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