<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 Sep 25, 2019, at 15:19, Nico Weber <<a href="mailto:thakis@chromium.org" class="">thakis@chromium.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><div dir="ltr" class="">On Wed, Sep 25, 2019 at 12:11 PM Louis Dionne via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org" class="">libcxx-dev@lists.llvm.org</a>> wrote:<br class=""></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;"><div style="overflow-wrap: break-word;" class=""><br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Sep 23, 2019, at 15:15, Shoaib Meenai via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank" class="">libcxx-dev@lists.llvm.org</a>> wrote:</div><br class=""><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Ah, sorry – my apologies.<u class=""></u><u class=""></u></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><u class=""></u> <u class=""></u></div><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(181, 196, 223); padding: 3pt 0in 0in;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span style="font-size: 12pt;" class="">From:<span class=""> </span></span></b><span style="font-size: 12pt;" class="">Marshall Clow <<a href="mailto:mclow.lists@gmail.com" target="_blank" class="">mclow.lists@gmail.com</a>><br class=""><b class="">Date:<span class=""> </span></b>Monday, September 23, 2019 at 12:14 PM<br class=""><b class="">To:<span class=""> </span></b>Shoaib Meenai <<a href="mailto:smeenai@fb.com" target="_blank" class="">smeenai@fb.com</a>><br class=""><b class="">Cc:<span class=""> </span></b>"<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank" class="">libcxx-dev@lists.llvm.org</a>" <<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank" class="">libcxx-dev@lists.llvm.org</a>><br class=""><b class="">Subject:<span class=""> </span></b>Re: [libcxx-dev] Non-merged type info name comparison<u class=""></u><u class=""></u></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">On Mon, Sep 23, 2019 at 12:02 PM Shoaib Meenai via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank" style="color: purple; text-decoration: underline;" class="">libcxx-dev@lists.llvm.org</a>> wrote:<u class=""></u><u class=""></u></div></div><div class=""><blockquote style="border-style: none none none solid; border-left-width: 1pt; border-left-color: rgb(204, 204, 204); padding: 0in 0in 0in 6pt; margin-left: 4.8pt; margin-right: 0in;" class=""><div class=""><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">In<span class=""> </span><a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_rL361913&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=zXNo5HfpEBs2AeK5MYbybBHSXRWS2rfFR2LYPo1zuhA&s=5In-WOhspL-mxLcgsafyIl0_G_S9IkKnfaj3lVT6y44&e=" target="_blank" style="color: purple; text-decoration: underline;" class="">https://reviews.llvm.org/rL361913</a>, libc++ gained the option to make type info comparisons use a strcmp on the type info name, which is useful for when we can’t guarantee RTTI uniqueness. I believe libstdc++ also defaults to strcmp comparisons. However, libstdc++ doesn’t perform the string comparison when the type info name begins with the * character [1], which is the case for e.g. types defined in anonymous namespaces. Should libc++’s implementation be changed to match, at least when targeting Linux?</div></div></div></blockquote></div></div></div></div></blockquote><div class="">Actually, in what cases can we guarantee that RTTI has been fully duplicated? For example, I don't think anything prevents users from using a shared library that redefines the RTTI for a type, no?</div></div></div></blockquote><div class=""><br class=""></div><div class="">Do you mean deduplicated?</div></div></div></div></blockquote><div><br class=""></div><div>Yes, sorry!</div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><div class="gmail_quote"><div class=""><br class=""></div><div class="">If so, then in binaries that have everything (including libc++) statically linked, this is guaranteed.</div></div></div></div></blockquote></div><div class=""><br class=""></div><div class="">Right. So some platforms (I guess Android) have this property, and other platforms (like Apple platforms, where we don't link libc++ statically into applications) do not. I guess it's then a choice to be made by vendors, and the status quo is OK.</div><div class=""><br class=""></div><div class="">Louis</div><div class=""><br class=""></div></body></html>