Question

I would like to create a program that will run in background as a final product. For debug purpose I want it to display a console.

I learned that there is a ShowWindow( hWnd, SW_HIDE ); function, but if I use it in a ‘standard’ main function the console window still pops up for a moment. I was trying to work it out like this (yes I know it’s crappy):

#define _WIN32_WINNT 0x0500
#include <windows.h>
#include <iostream>
#include <stdio.h>
#include <tchar.h>


#define DEBUG
//#undef DEBUG

#ifndef DEBUG
#pragma comment(linker, "/SUBSYSTEM:WINDOWS")

int APIENTRY _tWinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPTSTR    lpCmdLine,
                     int       nCmdShow)
{
    HWND hWnd = GetConsoleWindow();
    ShowWindow( hWnd, SW_HIDE );    

    while(1);

    return 0;
}
#else
#pragma comment(linker, "/SUBSYSTEM:CONSOLE")
    int main(int argc, int **argv)
    {
        HWND hWnd = GetConsoleWindow();

        while(1);

        return 0;
    }
#endif

Here I managed to prevent the window form popping up, but I can’t pass parameters to the program.

I believe there is a much better solution for this. Can you share?

PS

I don’t want to use .NET.

Answer 1

This is an answer to the first part of the question, “Here I managed to prevent the window form popping up”, i.e. how to set the Windows subsystem for an application in Visual C++.

I will answer the second part of the question, about command line arguments, separately.

// How to create a Windows GUI or console subsystem app with a standard `main`.

#ifndef _MSC_VER
#   error Hey, this is Visual C++ specific source code!
#endif

// Better set this in the project settings, so that it's more easily configured.
#ifdef  NDEBUG
#   pragma comment( linker, "/subsystem:windows /entry:mainCRTStartup" )
#else
#   pragma comment( linker, "/subsystem:console" )
#endif

#undef  UNICODE
#define UNICODE
#undef  NOMINMAX
#define NOMINAX
#undef  STRICT
#define STRICT
#include <windows.h>

int main()
{
    MessageBox( 0, L"Hi!", L"This is the app!", MB_SETFOREGROUND );
}

The NDEBUG standard C++ macro is designed for suppressing the effect of standard assert, so it’s not required to be globally meaningful. However, in practice it is globally meaningful. And then it provides a bit of portability compared to using a Visual C++ macro such as DEBUG.

Anyway, in order to make it easier to configure the subsystem, unless you want to enforce that debug builds should be console and release builds should be GUI, then I recommend doing this in the project settings rather than via a #pragma (note also that e.g. the g++ compiler does not support linker pragmas, so using the project settings is more portable).

If you want you can check the subsystem programmatically instead of just by inspection (i.e. instead of noting whether the above program produces a console or not):

// How to create a Windows GUI or console subsystem app with a standard `main`.

#ifndef _MSC_VER
#   error Hey, this is Visual C++ specific source code!
#endif

// Better set this in the project settings, so that it's more easily configured.
#ifdef  NDEBUG
#   pragma comment( linker, "/subsystem:windows /entry:mainCRTStartup" )
#else
#   pragma comment( linker, "/subsystem:console" )
#endif

#undef  UNICODE
#define UNICODE
#undef  NOMINMAX
#define NOMINAX
#undef  STRICT
#define STRICT
#include <windows.h>

#include <assert.h>         // assert
#include <string>           // std::wstring
#include <sstream>          // std::wostringstream
using namespace std;

template< class Type >
wstring stringFrom( Type const& v )
{
    wostringstream  stream;

    stream << v;
    return stream.str();
}

class S
{
private:
    wstring     s_;

public:
    template< class Type >
    S& operator<<( Type const& v )
    {
        s_ += stringFrom( v );
        return *this;
    }

    operator wstring const& () const { return s_; }
    operator wchar_t const* () const { return s_.c_str(); }
};

IMAGE_NT_HEADERS const& imageHeaderRef()
{
    HMODULE const                   hInstance   =
        GetModuleHandle( nullptr );

    IMAGE_DOS_HEADER const* const   pImageHeader    =
        reinterpret_cast< IMAGE_DOS_HEADER const* >( hInstance );
    assert( pImageHeader->e_magic == IMAGE_DOS_SIGNATURE );     // "MZ"

    IMAGE_NT_HEADERS const* const   pNTHeaders      = reinterpret_cast<IMAGE_NT_HEADERS const*>(
            reinterpret_cast< char const* >( pImageHeader ) + pImageHeader->e_lfanew
            );
    assert( pNTHeaders->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC );    // "PE"

    return *pNTHeaders;
}

int main()
{
    IMAGE_NT_HEADERS const& imageHeader = imageHeaderRef();
    WORD const              subsystem   = imageHeader.OptionalHeader.Subsystem;

    MessageBox(
        0,
        S() << L"Subsystem " << subsystem << L" "
            << (0?0
                : subsystem == IMAGE_SUBSYSTEM_WINDOWS_GUI?     L"GUI"
                : subsystem == IMAGE_SUBSYSTEM_WINDOWS_CUI?     L"Console"
                : L"Other"),
        L"Subsystem info:",
        MB_SETFOREGROUND );
}