<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Hi All,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">  I debug a Release build LLVM crash, and find the culprit. The code snippet below,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">    llvm::ArrayRef<<span style="font-variant-ligatures:no-common-ligatures">SDValue> Ops = { Lo, Hi }; // should be `SDValue Ops[2] </span></font><span style="font-family:arial,helvetica,sans-serif;font-variant-ligatures:no-common-ligatures">= { Lo, Hi };</span><span style="font-variant-ligatures:no-common-ligatures;font-family:arial,helvetica,sans-serif">`</span></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><span style="font-variant-ligatures:no-common-ligatures">    </span><span style="font-variant-ligatures:no-common-ligatures">return DAG.getMergeValues(Ops, dl);</span></font></div><div class="gmail_default"><span style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif"><br></font></span></div><div class="gmail_default"><span style="font-variant-ligatures:no-common-ligatures"><font face="arial, helvetica, sans-serif">Turns out a nullptr is dereferenced in </font></span><span style="font-family:arial,helvetica,sans-serif;font-variant-ligatures:no-common-ligatures">DAG.getMergeValues, thus I have segfault.</span></div><div class="gmail_default"><span style="font-family:arial,helvetica,sans-serif;font-variant-ligatures:no-common-ligatures"><br></span></div><div class="gmail_default"><span style="font-family:arial,helvetica,sans-serif;font-variant-ligatures:no-common-ligatures">From the comment on [1], it says:</span></div><div class="gmail_default"><br></div><div class="gmail_default">    This class does not own the underlying data, it is expected to be used in situations</div><div class="gmail_default">    where the data resides in some other buffer, whose lifetime extends past that of the</div><div class="gmail_default">    ArrayRef. For this reason, it is not in general safe to store an ArrayRef.<br></div><div class="gmail_default"><br></div><div class="gmail_default">I feel somehow the comment explain why I get the segfault, but not sure about that.</div><div class="gmail_default">Would someone kindly explain why?</div><div class="gmail_default"><br></div><div class="gmail_default">  Thanks.</div>















<div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">[1] <a href="http://llvm.org/doxygen/classllvm_1_1ArrayRef.html">http://llvm.org/doxygen/classllvm_1_1ArrayRef.html</a></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Regards,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">chenwj</div><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div>Wei-Ren Chen (陳韋任)<br>Homepage: <a href="https://people.cs.nctu.edu.tw/~chenwj" target="_blank">https://people.cs.nctu.edu.tw/~chenwj</a></div></div></div>
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