How a reference address become NULL in C++?
<p>I have a coredump,it shows a reference address is NULL....</p>

<p>details:</p>

<pre><code>(gdb) bt
#0  0xffffe410 in __kernel_vsyscall ()
#1  0x005b6c10 in raise () from /lib/libc.so.6
#2  0x005b8521 in abort () from /lib/libc.so.6
#3  0xf749e641 in Application::fatalSignal () at Application.cc:277
#4  &lt;signal handler called&gt;
#5  SdlProcess::procedureReturn (this=0x0, aSignal=0, aArg1=1, aArg2=0x0)
    at /include/c++/4.1.1/bits/stl_list.h:652
#6  0x08112edb in Sdl::authFailurer (aSdlProcess=@0x0, aLabel=0, aSignal=0, arg2=0x0) at /Mgr/SdlAuth.cc:1781
#7  0x00000000 in ?? ()
================
define:
Sdl::authFailurer(SdlProcess&amp; aSdlProcess, int aLabel, int aSignal, int /*arg1*/, void* arg2)

#5 aSdlProcess.procedureReturn(0, 1, 0);
</code></pre>

<p>and in stl_list.h:652</p>

<pre><code> bool empty() const

      { return this-&gt;_M_impl._M_node._M_next == &amp;this-&gt;_M_impl._M_node; }    ----&gt;652
in procedureReturn()
{
   ...
  if (!mProcedureStack.empty())----&gt;here,mProcedureStack is a datamember of SdlProcess
   ...
  {
  ...}
}
</code></pre>
