I am running multiple instance of the same application. This application is connecting to the database and running stored procedures using ADODB (all code examples are taken from msado15).
The problem is that somehow these two applications are sharing something either with the connection or commands.
For instance if the two instances are in the following function at the same time then they both thow an SEH exception:
Code Snippet
inline _RecordsetPtr Command15::Execute ( VARIANT * RecordsAffected, VARIANT * Parameters, long Options ) {
struct _Recordset * _result = 0;
HRESULT _hr = raw_Execute(RecordsAffected, Parameters, Options, &_result);
if (FAILED(_hr)) _com_issue_errorex(_hr, this, __uuidof(this));
return _RecordsetPtr(_result, false);
}
The exception that occurs is: "First-chance exception ...: 0xC0000005: Access violation reading location 0x00000068."
And afterwords when they go to release the command an error occurs on
First-chance exception at 0x4de4120c in IpsEngine.exe: 0xC0000005: Access violation reading location 0xcccccccc.
Code Snippet
inline void _bstr_t::Data_t::_Free() throw()
{
if (m_wstr != NULL) {
::SysFreeString(m_wstr);
}
if (m_str != NULL) {
delete [] m_str;
}
}
This is being called from.
Code Snippet
inline void Command15::PutRefActiveConnection ( struct _Connection * ppvObject ) {
HRESULT _hr = putref_ActiveConnection(ppvObject);
if (FAILED(_hr)) _com_issue_errorex(_hr, this, __uuidof(this));
}
The exception that occurs: First-chance exception at ...: 0xC0000005: Access violation reading location 0xcccccccc.
Similarly when one instance releases a command using
Code Snippet
inline void Command15::PutRefActiveConnection ( struct _Connection * ppvObject ) {
HRESULT _hr = putref_ActiveConnection(ppvObject);
if (FAILED(_hr)) _com_issue_errorex(_hr, this, __uuidof(this));
}
The second instance of the application fails when running the command at the exact same time.
Code Snippet
inline _RecordsetPtr Command15::Execute ( VARIANT * RecordsAffected, VARIANT * Parameters, long Options ) {
struct _Recordset * _result = 0;
HRESULT _hr = raw_Execute(RecordsAffected, Parameters, Options, &_result);
if (FAILED(_hr)) _com_issue_errorex(_hr, this, __uuidof(this));
return _RecordsetPtr(_result, false);
}
The command and connections are not static and there should be completely seperate instances of these for each instance of the application. Does anybody know why this may be happening. Any help would be appreciated. Thanks in advance.
All of these access issues are with pointers being passed into these functions. As such, we don't have much context with which to help you with these issues. Any issue could be causing these problems including: double freeing, not allocating memory elsewhere or failure to properly initialize memory, failure to check return codes of functions that return memory, etc. In these cases, we need to see the context surrounding the variables that are causing the AV, in for example: for Command15::Execute, RecordsAffected and Parameters would be the variables of interest, we would need to see how they are allocated, initialized, and used prior to this function call in the execution context of a failure, and how they are allocated, initialized, and used prior to this function call in the execution context of success. The most likely cause of this AV is failure to handle error conditions coming back from functions that allocate memory on success.
Thanks,
John
|||But when I run only one instance of the application at a time it works fine, I have been running it already for a long time and never had a problem. How is it that running two seperate instances of the application could cause this error. The memory allocation would not change just because there are two instances? would it?
