Using "CreateProcess()" gives error C2664

Question

I am trying to open an application from my .cpp file. I did some research and found that using CreateProcess() would be the best option. Doing this resulted in the following code:

 //Below has the purpose of starting up the server: -----------------------------------------------
    LPWSTR command = (LPWSTR)"C:\\Users\\CCRT\\Documents\\UPDATED\\FINALSERVER\\FINALSERVER\\Debug\\FINALSERVER.exe";
    // Start the child process.
    LPSTARTUPINFOA si;
    PROCESS_INFORMATION pi;
   
    if (!CreateProcess(NULL,   // No module name (use command line)
        command,        // Command line
        NULL,           // Process handle not inheritable
        NULL,           // Thread handle not inheritable
        FALSE,          // Set handle inheritance to FALSE
        0,              // No creation flags
        NULL,           // Use parent's environment block
        NULL,           // Use parent's starting directory
        &si,            // Pointer to STARTUPINFO structure
        &pi)           // Pointer to PROCESS_INFORMATION structure
        )
    {
        printf("CreateProcess failed (%d).\n", GetLastError());
    }
     else {
         std::cout << "Command success\n";
     }

However, i get the following error when i try to build my solution:

cannot convert argument 9 from 'LPSTARTUPINFOA *' to 'LPSTARTUPINFOW' 

The error is on the CreateProcess() function.

I am wondering if anybody can explain the error to me and tell me how to fix it as i am so confused about what is going wrong.

Answer 1

cannot convert argument 9 from 'LPSTARTUPINFOA *' to 'LPSTARTUPINFOW'

You are giving the function a pointer to a STARTUPINFOA pointer but the function expects a STARTUPINFOW pointer (which is what LPSTARTUPINFOW is typedefined as).

The correct way is therefore to define si like so:

STARTUPINFOW si{sizeof(STARTUPINFOW)}; // not LPSTARTUPINFOW

The sizeof(STARTUPINFOW) part sets the cb member of si to the size of the structure.

Also: LPWSTR command = (LPWSTR)"C:\\U... is wrong. It should be

wchar_t command[] = L"C:\\U...";
//                  ^

The L makes the string literal a const wchar_t[N] (where N is the length of the string + 1), but since the command may be altered by CreateProcessW, you need to put it in a mutable wchar_t array.

It's also best to be consistent. Use the "wide" functions explicitly, like CreateProcessW, unless you plan on building for Ansi too, then be consistent and use STARTUPINFO (without A or W) and use the TEXT macro to define strings.