C++ _tmain would not start running - c++

Question

I have an mfc project which is process spawned by a windows service. For some reason the process dies before it starts. Global values get created but the process would not start the _tmain. This issue raised while moving from VC6 to VS2012.
Here is a code sample, I can place a break point and stop at this line CWinApp theApp; but I can't stop at the first line of _tmain. The program just can't find the entry point and exists.
// prog.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
/////////////////////////////////////////////////////////////////////////////
// The one and only application object
CWinApp theApp;
using namespace std;
int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
try {
SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOGPFAULTERRORBOX | SEM_NOOPENFILEERRORBOX);
int nRetCode = 0;
// initialize MFC and print and error on failure
if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0))
{
// TODO: change error code to suit your needs
nRetCode = 1;
}
else
{
//Some propietry code which runs here
}
return nRetCode;
}
catch(...) {
return 147;
}
}
initially I thought this issue is caused due to the MFC which accompanies VS2012. I noticed however that our development version just before the move has the same affect. This seems strange enough because the previous version has the same code and it finds the entry point just fine.
I was able to start the program by doing the following:
// prog.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
/////////////////////////////////////////////////////////////////////////////
// The one and only application object
using namespace std;
class MyApp : public CWinApp {
public:
MyApp() : CWinApp(_T("VCP")){}
int init(LPTSTR CommandLine);
virtual int Run()
{
return init(m_lpCmdLine);
}
};
MyApp theApp;
//int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
int MyApp::init(LPTSTR CommandLine)
{
int argc = 2;
TCHAR* argv[] = {_T(""),_T("")};
argv[1]= CommandLine;
try {
SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOGPFAULTERRORBOX | SEM_NOOPENFILEERRORBOX);
int nRetCode = 0;
// initialize MFC and print and error on failure
int r=1;
if (r>1)//(!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0))
{
// TODO: change error code to suit your needs
nRetCode = 1;
}
else
{
// some propietry code
}
return nRetCode;
}
catch(...) {
return 147;
}
}
To summarize I have 3 versions of code. a release version of code which works just fine. Two development version on different Visual studios which have the same affect of not finding the entry point. a fresh mfc project contains code similar to the faulty code and it finds the _tmain.
My questions are :
Why is this happening?
How can I run with _tmain?

Answer 1

Your original code can only work if the EXE is linked as a console mode app. Pretty unusual for MFC apps, but it is supported. Getting MFC initialized with a call AfxWinInit() is indeed required.
But clearly your EXE isn't being linked as a console mode app or your 2nd snippet would not work. Which relies on the WinMain() implementation embedded inside MFC. The normal way that MFC apps are done.
Linker + System, SubSystem setting. It needs to be set to "Console" if a console mode app is indeed intended and you want your own main() function to be the entrypoint.