<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div>On Jul 16, 2012, at 1:06 PM, Richard Smith <<a href="mailto:richard@metafoo.co.uk">richard@metafoo.co.uk</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div class="gmail_quote">On Mon, Jul 16, 2012 at 12:55 PM, Ted Kremenek <span dir="ltr"><<a href="mailto:kremenek@apple.com" target="_blank">kremenek@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word"><div class="im"><br><div><div>On Jul 15, 2012, at 10:14 PM, Richard Smith <<a href="mailto:richard@metafoo.co.uk" target="_blank">richard@metafoo.co.uk</a>> wrote:</div><br><blockquote type="cite">
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The patch replaces the 'track the last DeclRefExpr we saw' technique with a separate pass to classify the DeclRefExprs as use or initialization. Fixing this exposed some "false" positives on some benchmarking code which looks like:</div>
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void f() {</div><div style="font-family:Helvetica;font-size:medium;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
volatile int n;</div><div style="font-family:Helvetica;font-size:medium;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
for (int i = 0; i < N; ++i)</div><div style="font-family:Helvetica;font-size:medium;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
n += f();</div><div style="font-family:Helvetica;font-size:medium;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
}</div><div style="font-family:Helvetica;font-size:medium;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
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... so the patch classifies compound-assignments as neither initialization nor use (it leaves the variable uninitialized if it was before, and leaves it initialized if it was before).</div><br></blockquote></div><br></div>
<div>Hi Richard,</div><div><br></div><div>One comment on this last point. We tend to like avoiding the uninitialized value taint propagating after the first use to avoid a cascade of warnings. Your last comment here implies that were we to flag a warning at "n += f()" we might also flag another warning later if 'n' is used again. Is that true?</div>
</div></blockquote><div><br></div><div>-Wuninitialized only produces one warning per variable. That's handled in the Sema layer; the Analysis layer reports all uninitialized uses. My patch doesn't change that side of things.</div>
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</blockquote></div><br><div>Right, makes sense. Overall, this patch looks good to me, and is a nice cleanup.</div></body></html>