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<body><span class="vcard"><a class="email" href="mailto:dblaikie@gmail.com" title="David Blaikie <dblaikie@gmail.com>"> <span class="fn">David Blaikie</span></a>
</span> changed
<a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - llvm-cov: wrong code coverage for statements before fork()"
href="https://bugs.llvm.org/show_bug.cgi?id=48264">bug 48264</a>
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<table border="1" cellspacing="0" cellpadding="8">
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Resolution</td>
<td>INVALID
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<td>---
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<td style="text-align:right;">Status</td>
<td>RESOLVED
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<td>REOPENED
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<b><a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - llvm-cov: wrong code coverage for statements before fork()"
href="https://bugs.llvm.org/show_bug.cgi?id=48264#c5">Comment # 5</a>
on <a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - llvm-cov: wrong code coverage for statements before fork()"
href="https://bugs.llvm.org/show_bug.cgi?id=48264">bug 48264</a>
from <span class="vcard"><a class="email" href="mailto:dblaikie@gmail.com" title="David Blaikie <dblaikie@gmail.com>"> <span class="fn">David Blaikie</span></a>
</span></b>
<pre>(In reply to Yibiao Yang from <a href="show_bug.cgi?id=48264#c4">comment #4</a>)
<span class="quote">> (In reply to David Blaikie from <a href="show_bug.cgi?id=48264#c3">comment #3</a>)
> > (In reply to Yibiao Yang from <a href="show_bug.cgi?id=48264#c2">comment #2</a>)
> > > (In reply to David Blaikie from <a href="show_bug.cgi?id=48264#c1">comment #1</a>)
> > > > That sounds correct to me - the program forked, so two processes reached
> > > > those two lines. lldb probably only follows one of those processes.
> > > >
> > > > Try adding a printf/output between line 9 and 10, and you'll see it prints
> > > > out twice.
> > >
> > > Thank you very much. Yes, it is indeed fork. So there is no problem as Line
> > > 9 and Line 10 are marked as executed twice.
> > >
> > > But for Line 3 and Line 4, I was wondering that they should marked as only
> > > executed once since calling to fork is at Line 9. Only at that time, there
> > > are two processes.
> >
> > That's how fork works - a single process runs until fork is called, then
> > that process is cloned into two that continue from the fork call.
> > <a href="https://man7.org/linux/man-pages/man2/fork.2.html">https://man7.org/linux/man-pages/man2/fork.2.html</a>
>
> From this point of view, it also make sense as these two lines are marked as
> executed twice. Gcov behaves differently. I think both are correct. Thank
> you very much.</span >
Sorry, misunderstood your comment and I didn't look at the text closely.
Yeah, it is noteworthy that the early statements show as executed twice - when
they certainly were not. (the fork only executes statements after it twice).
I'd guess LLVM kept the counts in memory/registers that were duplicated when
the process forked, then both sets of values were added to the counts.
That does seem questionable, and gcc/gcov seems more accurate here.</pre>
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