<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">The 'format' attribute already states whether or not it takes 'printf' or 'scanf' format strings. That's not really the issue here. The issue is whether or not the function is a no-op given an empty format string. For a 'scanf' format string, it's clearly a no-op given no format string. For a 'printf' format string, that's not necessarily the case.<div><div><br><div><div>On Sep 30, 2011, at 11:07 AM, Ahmed Charles wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><meta content="text/html; charset=utf-8" http-equiv="Content-Type"><div><div><div style="font-family: Calibri,sans-serif; font-size: 11pt;">Without knowing the context perfectly, is it possible to annotate the function in a way that expresses which set of format strings it accepts? Of there are two sets of behaviors from format strings, then having a way to identify each makes sense.<br>
</div></div><hr><span style="font-family: Tahoma,sans-serif; font-size: 10pt; font-weight: bold;">From: </span><span style="font-family: Tahoma,sans-serif; font-size: 10pt;">Ted Kremenek</span><br><span style="font-family: Tahoma,sans-serif; font-size: 10pt; font-weight: bold;">Sent: </span><span style="font-family: Tahoma,sans-serif; font-size: 10pt;">9/30/2011 12:45 AM</span><br>
<span style="font-family: Tahoma,sans-serif; font-size: 10pt; font-weight: bold;">To: </span><span style="font-family: Tahoma,sans-serif; font-size: 10pt;">Joerg Sonnenberger</span><br><span style="font-family: Tahoma,sans-serif; font-size: 10pt; font-weight: bold;">Cc: </span><span style="font-family: Tahoma,sans-serif; font-size: 10pt;">llvm cfe</span><br>
<span style="font-family: Tahoma,sans-serif; font-size: 10pt; font-weight: bold;">Subject: </span><span style="font-family: Tahoma,sans-serif; font-size: 10pt;">Re: [cfe-commits] r140777 - in /cfe/trunk: lib/Sema/SemaChecking.cpp test/Sema/format-strings.c</span><br>
<br></div><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div>On Sep 30, 2011, at 12:38 AM, Ted Kremenek wrote:</div><br class="Apple-interchange-newline">
<blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div>On Sep 29, 2011, at 11:51 PM, Joerg Sonnenberger wrote:</div><br class="Apple-interchange-newline">
<blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; ">On Thu, Sep 29, 2011 at 04:01:39PM -0700, Ted Kremenek wrote:<br>
<blockquote type="cite">This isn't just about printf and scanf, but any function with the format attribute. There are functions with that attribute where this isn't a no-op even when the format string is empty. I saw such a case, which was the motivation for this change.<br>
</blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">That said, the warning definitely is useful for printf and friends when there are no data arguments. I'd like the warning to be the strictest when it can be.<br>
</blockquote><br>Why not support -W(no-)format-zero-length like GCC then?<br></span></blockquote></div><br><div>Clang does support that, and I don't think it is so simple.</div><div><br></div><div>Passing -Wno-format-zero-length means the warning never fires at all, even in legit cases (like the ones you pointed out).</div>
<div><br></div><div>Using pragmas to silence the warning within smaller blocks of code is also not user friendly, as it requires using it on every callsite that the warning triggers.</div></div></blockquote></div><br><div>
Along the pragmas line, the only solution that I know of that would work without silencing the warning outright would be to wrap the original function in a macro that surrounded the function call with _Pragmas that silenced the warning. That's obviously not a great experience.</div>
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