[AGENT++] crash in Vb::set_value

[Loridon, Martin]

Hello all,

 

Sometimes my (multi-threaded) agent running on a Win32 platform in VC++6.0
debug environment crashes. (access violation)

This happens when I try to change a MibLeaf value. See the code parts below
gathered from snmp++ sources.

agent++ version is 3.5.19 and snmp++ 3.2.13

 

/**

   * Get the value of the receiver.

   * 

   * @param i - A reference to a long the receiver's value will be copied
in.  

   * @return SNMP_ERROR_SUCCESS on success.

   */

  virtual int                    get_value(long& i) const 

                                                             { return
get_value().get_value(i); }

 

 

 

 

Vbx MibLeaf::get_value() const

{

            Vbx vb(get_oid());

            if (value)

                        vb.set_value(*value);

 

            return vb;

}

 

  /**

   * Set the value using any SnmpSyntax object.

   */

  void set_value(const SnmpSyntax &val)

    { free_vb(); iv_vb_value = val.clone(); };

 

169:    void set_value(const SnmpSyntax &val)

170:      { free_vb(); iv_vb_value = val.clone(); };

004240B0   push        ebp

004240B1   mov         ebp,esp

004240B3   sub         esp,44h

004240B6   push        ebx

004240B7   push        esi

004240B8   push        edi

004240B9   push        ecx

004240BA   lea         edi,[ebp-44h]

004240BD   mov         ecx,11h

004240C2   mov         eax,0CCCCCCCCh

004240C7   rep stos    dword ptr [edi]

004240C9   pop         ecx

004240CA   mov         dword ptr [ebp-4],ecx

004240CD   mov         ecx,dword ptr [ebp-4]

004240D0   call        Vb::free_vb (0042dc40)

004240D5   mov         eax,dword ptr [ebp+8]

004240D8   mov         edx,dword ptr [eax]

004240DA   mov         esi,esp

004240DC   mov         ecx,dword ptr [ebp+8]

004240DF   call        dword ptr [edx+8]

004240E2   cmp         esi,esp

004240E4   call        __chkesp (004b8d70)

004240E9   mov         ecx,dword ptr [ebp-4]

004240EC   mov         dword ptr [ecx+14h],eax

004240EF   pop         edi

004240F0   pop         esi

004240F1   pop         ebx

004240F2   add         esp,44h

004240F5   cmp         ebp,esp

004240F7   call        __chkesp (004b8d70)

004240FC   mov         esp,ebp

004240FE   pop         ebp

004240FF   ret         4

004240DF   call        dword ptr [edx+8] edx register contains rubbish

I wonder if this could have something to do with the return of vb in Vbx
MibLeaf::get_value() const

which is in fact a local variable and also be destructed by leaving the
function.

Is this a bug or am I wrong?

Martin Loridon 
Software Development Engineer 
Barco Digital Cinema 
Noordlaan 5 
B-8520 Kuurne, Belgium 
Tel:  +32 (0)56 36 87 17 
Fax: +32 (0)56 36 88 62 
mailto:martin.loridon at barco.com <mailto:martin.loridon at barco.com>  
www.d-cine.barco.com 
www.barco.com 

 

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