Hello group!<br><br>We are experiencing problems with boost::weak_ptr in a multi-threaded environment. It looks that the lock on the ref counting doesn't work well with weak_ptr in release build.<br><br>configuration : <br>
Windows 2000 SP4<br>VC6 SP5<br>boost 1.33.1<br><br>In summary, it seems that add_ref_lock in sp_counted_base_w32.hpp has a bug in release. In disassemblies, we observe : <br><br>01&nbsp;&nbsp; lea&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; esi,[eax+4]<br>02&nbsp;&nbsp; mov&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; eax,dword ptr [esi]
<br>03&nbsp;&nbsp; test&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; eax,eax<br>04&nbsp;&nbsp; je&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; TestWeakPtr+0E4h (00401244)<br>05&nbsp;&nbsp; lea&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ecx,[eax+1]<br>06&nbsp;&nbsp; mov&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; edx,esi<br>07&nbsp;&nbsp; lock cmpxchg dword ptr [edx],ecx<br><span style="font-weight: bold;">08&nbsp;&nbsp; mov&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ecx,eax
</span><br style="font-weight: bold;"><span style="font-weight: bold;">09&nbsp;&nbsp; cmp&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ecx,eax</span><br>10&nbsp;&nbsp; je&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; TestWeakPtr+7Dh (004011dd)<br><br>At line 08, you'll see that we move eax into ecx and after (line 09) we compare ecx and eax that are obviously the same which will destruct prematurely our pointer. In attachement, I send a complete program reproducing the bug with VC6 in release.
<br><br>It is probably a bug in VC6. But is it caused by a bad use? is it simply a &quot;bug&quot; in boost 
1.33.1? <br><br>By the way,  we can remove the &quot;bug&quot; by simply &quot;patching&quot; add_ref_lock implementation like this : <br><br>bool add_ref_lock() // true on success<br>{<br>&nbsp;&nbsp;&nbsp; for( ;; )<br>&nbsp;&nbsp;&nbsp; {<br>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; long tmp = static_cast&lt; long const volatile&amp; &gt;( use_count_ );
<br>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; if( tmp == 0 ) return false;<br>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <span style="font-weight: bold;">long tmp2 = tmp + 1;</span><br>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; if(InterlockedCompareExchange ( &amp;use_count_, <span style="font-weight: bold;">tmp2</span>, tmp ) == 
<span style="font-weight: bold;">tmp2 - 1</span> ) <br>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return true;<br>&nbsp;&nbsp;&nbsp; }<br>}<br><br>Thank you for any suggestion!<br clear="all"><br>-- <br>Alain Cormier<br><a href="mailto:alain.work@gmail.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
alain.work@gmail.com</a><br>