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<p class="MsoNormal">A bug was introduced with revision <span style="font-size:9.0pt;font-family:"Courier New"">
02ec546246ad</span> with the aim of fixing compiler warnings.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none">In the function <span style="font-size:9.5pt;font-family:Consolas">
SAO::processSaoUnitAll()</span> in sao.cpp, <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas">
<span style="color:blue">int</span> i;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> uint32_t edgeType;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal">was changed to<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> uint32_t i;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> uint32_t edgeType;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal">This change caused a segmentation fault (on a particular test case) here:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas">
<span style="color:blue">for</span> (i = 0; i < (1 << X265_DEPTH); i++)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"> offsetBo[i] = m_clipTable[i + offset[m_tableBo[i]]];<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal">The problem is that the expression “i + offset[m_tableBo[i]” is converted to unsigned type by the compiler. When this expression would otherwise be negative, the conversion results in a very big positive number, which causes the segmentation
fault.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The lesson is to be very careful when changing between signed and unsigned types when the compiler displays a warning. Editing code to remove warnings sometimes do more harm than good. Perhaps the better approach to fixing type mismatch
warnings is to convert the unsigned variables to signed or with type casting.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none">Similar code exists in <span style="font-size:9.5pt;font-family:Consolas">
SAO::processSaoUnitRow()</span> so the same fix should be applied to this function as well.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best regards,<o:p></o:p></p>
<p class="MsoNormal">- Dzung Hoang<o:p></o:p></p>
<p class="MsoNormal">Zenverge, Inc.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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