<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style>
</head>
<body lang="EN-US" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal">I was planning on waiting a few more days to give more people a chance to chime in. Let's wait till the end of the week?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal" style="margin-left:.5in"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black"><jfbastien@apple.com> on behalf of JF Bastien <jfbastien@apple.com><br>
<b>Date: </b>Tuesday, May 15, 2018 at 1:21 PM<br>
<b>To: </b>James Y Knight <jyknight@google.com><br>
<b>Cc: </b>Shoaib Meenai <smeenai@fb.com>, cfe-dev <cfe-dev@lists.llvm.org><br>
<b>Subject: </b>Re: [cfe-dev] Relaxing format specifier checks<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
</div>
<p class="MsoNormal" style="margin-left:.5in"><a name="_MailOriginalBody"><o:p> </o:p></a></p>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><br>
<br>
<o:p></o:p></span></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody">On May 13, 2018, at 8:18 PM, James Y Knight via cfe-dev <</span><a href="mailto:cfe-dev@lists.llvm.org"><span style="mso-bookmark:_MailOriginalBody">cfe-dev@lists.llvm.org</span><span style="mso-bookmark:_MailOriginalBody"></span></a><span style="mso-bookmark:_MailOriginalBody">>
wrote:<o:p></o:p></span></p>
</div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
<div>
<div>
<div>
<p class="MsoNormal" style="mso-margin-top-alt:0in;margin-right:0in;margin-bottom:12.0pt;margin-left:.5in">
<span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
<div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">On Fri, May 11, 2018, 7:26 PM Shoaib Meenai via cfe-dev <</span></span><a href="mailto:cfe-dev@lists.llvm.org" target="_blank"><span style="mso-bookmark:_MailOriginalBody"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">cfe-dev@lists.llvm.org</span></span><span style="mso-bookmark:_MailOriginalBody"></span></a><span style="mso-bookmark:_MailOriginalBody"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">>
wrote:</span></span><span style="mso-bookmark:_MailOriginalBody"><o:p></o:p></span></p>
</div>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in">
<div>
<div>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.5in">
<span style="mso-bookmark:_MailOriginalBody"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">What are people's thoughts here? Are there preferences for relaxing -Wformat and adding a new option for strict format warnings vs. keeping -Wformat as-is
and adding a new option for relaxed format warnings?</span><o:p></o:p></span></p>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"> <o:p></o:p></span></p>
</div>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">+1 to change the default behavior and put the stricter checks in another flag, for all the reasons discussed
already.</span></span><span style="mso-bookmark:_MailOriginalBody"><o:p></o:p></span></p>
</div>
</div>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody">Sounds like there’s support for doing this.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody">Shoaib, how would you rather proceed?<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
</div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><br>
<br>
<o:p></o:p></span></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<div>
<div>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in">
<div>
<div>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.5in">
<span style="mso-bookmark:_MailOriginalBody"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Of course, we should also ensure that the optimizer doesn't do anything surprising when there's a type mismatch between the specifier and the argument
but both types have the same size and alignment (i.e., the case where the relaxed format warning won't fire), both now and in the future.</span><o:p></o:p></span></p>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"> <o:p></o:p></span></p>
</div>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">I think the concern here would be if clang did calling convention lowering by generating a store of the
outgoing argument with tbaa attached, and then also generated a (potentially mismatched) tbaa-annotated load for the call to va_arg inside the printf function. And then optimized the two functions together.</span></span><span style="mso-bookmark:_MailOriginalBody"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody">I don't believe that can happen, both because the call arguments are not lowered to memory stores (if needed) by clang, but rather by llvm (there's no real possibility
to attach TBAA at that point, even if we wanted to), and also because clang doesn't attach tbaa to the loads generated by va_arg.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><o:p> </o:p></span></p>
</div>
</div>
</div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody">_______________________________________________<br>
cfe-dev mailing list<br>
</span><a href="mailto:cfe-dev@lists.llvm.org"><span style="mso-bookmark:_MailOriginalBody">cfe-dev@lists.llvm.org</span><span style="mso-bookmark:_MailOriginalBody"></span></a><span style="mso-bookmark:_MailOriginalBody"><br>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev<o:p></o:p></span></p>
</div>
</blockquote>
</div>
<p class="MsoNormal" style="margin-left:.5in"><span style="mso-bookmark:_MailOriginalBody"><br>
<br>
</span><o:p></o:p></p>
</div>
</body>
</html>