Exe crashes after coming out of the method in c++ - c++

Question

I have a method FormatOutPut() that internally calls a "callBack" method MyFunct() in C++. There is a crash, when the control comes out the FormatOutPut(). The callback method MyFunct() just prints the output on the screen. When I debugged the code using windbg I got the following traces,
(1250.1270): Stack buffer overflow - code c0000409 (!!! second chance !!!)
What I am guessing is that,the return address on the stack for the FormatOutPut(), is corrupted by the callback method. So when control is shifted back to the calling method it crashes.
When I comment out the callback method everything works fine. Any inputs on this will be great help.
Callback method prototype is as below,
typedef void(__stdcall *MyCallBack)(char*,char*,char*,char*,char*,char*,char*,char*,char*,char*,int, int );
Body:-
void MyCallbackRoutine(char* GetFeature,char* GetVersion,char* GetStartDate, char* GetExpireDate, char* GetUsers,char* GetKey,char* GetVendorString, char* GetHostID,char* GetErrorMsg,char* GetLicense,int GetCheckOutStatus, int nCount)
{
if ( nCount == 0 )
{
_strtime_s( timeCallbackstart, 10 );
time(&startCallbackstart);
bOnlyOnce = true;
}
cout << endl;
cout << "-------------------------------------------------------" << endl;
cout << "GetCheckOutStatus: " << GetCheckOutStatus << endl;
cout << "GetErrorMsg: " << GetErrorMsg << endl;
cout << endl;
cout << "GetFeature: " << GetFeature << endl;
cout << "GetVersion: " << GetVersion << endl;
cout << "GetStartDate: " << GetStartDate << endl;
cout << "GetExpireDate: " << GetExpireDate << endl;
cout << "GetUsers: " << GetUsers << endl;
cout << "GetKey: " << GetKey << endl;
cout << "GetVendorString: " << GetVendorString << endl;
cout << "GetHostID: " << GetHostID << endl;
cout << "GetLicense: " << GetLicense << endl;
cout << endl;
cout << "Licenscounter: " << nCount << endl;
cout << "------------------------------------------------------" << endl;
cout << endl;
}
Thanks and Regards,
AKJ

Answer 1

The issue that I see is that your calling convention of __stdcall for the typedef of the function prototype and the callback function itself does not match. If the calling convention does not match up, stack issues can arise when returning from the called function.
More on calling conventions here.
The typedef for the function is as follows:
typedef void(__stdcall *MyCallBack)(char*,char*,char*,char*,char*,char*,char*,
char*,char*,char*,int, int );
but the function that is assigned as the callback has this:
void MyCallbackRoutine(char* GetFeature,char* GetVersion,char* GetStartDate,
char* GetExpireDate, char* GetUsers,char* GetKey,
char* GetVendorString, char* GetHostID,
char* GetErrorMsg,char* GetLicense,
int GetCheckOutStatus, int nCount)
The number and type of parameters match up, the return type void matches, but the key element that doesn't match is that __stdcall is missing. By default, The calling convention is __cdecl if not specified. The correction should be:
void __stdcall MyCallbackRoutine(char* GetFeature,char* GetVersion,char* GetStartDate,
char* GetExpireDate, char* GetUsers,char* GetKey,
char* GetVendorString, char* GetHostID,
char* GetErrorMsg,char* GetLicense,
int GetCheckOutStatus, int nCount)
Note that the compiler should have picked up the issue when assigning a function who's definition doesn't match the prototype as this small example demonstrates (If this compiler error occurs, do not try to fix it by applying a C-style cast to shut the compiler up -- that is not a fix).