Avoiding the main (entry point) in a C program

Question

Is it possible to avoid the entry point (main) in a C program. In the below code, is it possible to invoke the func() call without calling via main()

Answer 1

The solution depends on the compiler and linker which you use. Always is that not main is the real entry point of the application. The real entry point makes some initializations and call for example main. If you write programs for Windows using Visual Studio, you can use /ENTRY switch of the linker to overwrite the default entry point mainCRTStartup and call func() instead of main():

#ifdef NDEBUG
void mainCRTStartup()
{
    ExitProcess (func());
}
#endif

If is a standard practice if you write the most small application. In the case you will receive restrictions in the usage of C-Runtime functions. You should use Windows API function instead of C-Runtime function. For example instead of printf("This is func \n") you should use OutputString(TEXT("This is func \n")) where OutputString are implemented only with respect of WriteFile or WriteConsole:

static HANDLE g_hStdOutput = INVALID_HANDLE_VALUE;
static BOOL g_bConsoleOutput = TRUE;

BOOL InitializeStdOutput()
{
    g_hStdOutput = GetStdHandle (STD_OUTPUT_HANDLE);
    if (g_hStdOutput == INVALID_HANDLE_VALUE)
        return FALSE;

    g_bConsoleOutput = (GetFileType (g_hStdOutput) & ~FILE_TYPE_REMOTE) != FILE_TYPE_DISK;
#ifdef UNICODE
    if (!g_bConsoleOutput && GetFileSize (g_hStdOutput, NULL) == 0) {
        DWORD n;

        WriteFile (g_hStdOutput, "\xFF\xFE", 2, &n, NULL);
    }
#endif

    return TRUE;
}

void Output (LPCTSTR pszString, UINT uStringLength)
{
    DWORD n;

    if (g_bConsoleOutput) {
#ifdef UNICODE
        WriteConsole (g_hStdOutput, pszString, uStringLength, &n, NULL);
#else
        CHAR szOemString[MAX_PATH];
        CharToOem (pszString, szOemString);
        WriteConsole (g_hStdOutput, szOemString, uStringLength, &n, NULL);
#endif
    }
    else
#ifdef UNICODE
        WriteFile (g_hStdOutput, pszString, uStringLength * sizeof (TCHAR), &n, NULL);
#else
    {
        //PSTR pszOemString = _alloca ((uStringLength + sizeof(DWORD)));
        CHAR szOemString[MAX_PATH];
        CharToOem (pszString, szOemString);
        WriteFile (g_hStdOutput, szOemString, uStringLength, &n, NULL);
    }
#endif
}

void OutputString (LPCTSTR pszString)
{
    Output (pszString, lstrlen (pszString));
}