C / C++ / MFC

Re: unique_ptr and make_unique -- [SOLVED]

28-Jul-18 6:00

Now that you understand it, how about writing an article for the rest of us?

Richard Andrew x6428-Jul-18 11:06

Richard Andrew x64

28-Jul-18 11:06

Thanks for the vote of confidence, Richard! Big Grin | :-D

I can't say that I completely understand it. Getting it to work was partly just trying different things until I hit upon the magic combination!

I do understand some parts of it better now, but hardly well enough to write an article. Smile | :)

The difficult we do right away...
...the impossible takes slightly longer.

Where I can learn about using wsprintf?

GESY26-Jul-18 8:01

26-Jul-18 8:01

Where I can learn about using wsprintf? I using Visual Studio 12 with plain C Code Lines.

For examples, this lines give me 2 different results depending on the
formatting I believe but I can't find any practical info about it.

For example what the " >>6" or " >>12" do?

Thanks, check the code below and you see what I mean

DWORD DVALE=19542016;

wsprintf(BUFF, "Version is %d \n Good Night",DVALE >>6 & 0xff);
MessageBox(hWndMain,BUFF,"The Value",MB_OK); // Display 192

wsprintf(BUFF, "Version is %d \n Good Night",DVALE >> 12 & 0xff);
MessageBox(hWndMain,BUFF,"The Value",MB_OK); // Display 163

Victor Nijegorodov26-Jul-18 8:25

Victor Nijegorodov

26-Jul-18 8:25

Did you try to pass the L"Version is %d \n Good Night" rather than "Version is %d \n Good Night"?
" >>6" or " >>12" just do what they must do according to the https://msdn.microsoft.com/en-us/library/336xbhcz.aspx?f=255&MSPPError=-2147217396

Joe Woodbury26-Jul-18 8:26

Joe Woodbury

26-Jul-18 8:26

The greater-than signs are shift operators (https://msdn.microsoft.com/en-us/library/336xbhcz.aspx?f=255&MSPPError=-2147217396). The result is then truncated using a bitwise and operator (Bitwise AND Operator: &[^])

GESY26-Jul-18 16:25

26-Jul-18 16:25

Auch, you think I can remember those days?

That's a lot of math, if I start experimenting I may get it back.
But for now, that page got me hungry!!!
But I did catch the idea of shifting, all this because
a code that I posted here, that some one tested and said works correctly
and got the right values, however I don't, I do not see how may code
works correctly on his computer, but on mine I get big numbers, far for what
I am looking for. Go ahead and check it, and tell me what you think if you please....
Thanks

Look for "No-Errors-but-wrong-values-on-return"

Joe Woodbury26-Jul-18 17:45

Joe Woodbury

26-Jul-18 17:45

Sorry, I can't diagnose what happens on your computer.

(And whatever you are doing elsewhere is pointless and bad practice. Errors in your code have been identified. Just check the windows version and end it there.

To clarify: DON'T check the versions of system DLLs. There are multiple versions of many DLLs and you have no idea which DLL is actually being used.)

modified 26-Jul-18 23:55pm.

GESY27-Jul-18 4:05

27-Jul-18 4:05

But you can tell the studio whichone too look for or use, I think.

GESY27-Jul-18 4:07

27-Jul-18 4:07

Thank you very much I got the idea now, 100000 of thanks.

Richard MacCutchan26-Jul-18 22:13

Return nothing from a function having return type

26-Jul-18 22:13

wsprintf is not the issue, it is how you are extracting the numbers from the version structure. Check the version documentation again.

meerokh26-Jul-18 0:40

meerokh

26-Jul-18 0:40

I have a class PackageSingleton and got a function getPackage whose return type is another class Package. This function iterates over a queue and retrieves a package and executes it. If a queue is empty i want to return nothing and keep looping the queue until a package is found. In C++ NULL cant be returned and returning a nullptr is giving an error

no viable conversion from returned value of type 'nullptr_t' to function return type 'Package

. Any idea how should i handle this situation.

c++

modified 26-Jul-18 6:58am.

Re: Return nothing from a function having return type

Richard MacCutchan26-Jul-18 1:28

Re: Return nothing from a function having return type

26-Jul-18 1:28

You can only return a nullptr if the defined return type is a pointer to something. If the return type is some sort of object then you must return an actual object of that type. You could solve this by changing the function to return a pointer to the relevant Package object.

Member 1392860827-Jul-18 11:43

Member 13928608

27-Jul-18 11:43

If we didn't define the return type a pointer then how we will get nullptr. I have so far used char, int return type from Bitdefender Error 1020

what is the relevant package for returning pointer type?

modified 27-Jul-18 17:49pm.

Re: Return nothing from a function having return type

Richard MacCutchan27-Jul-18 21:54

Re: Return nothing from a function having return type

27-Jul-18 21:54

I don't understand what you are saying. If the return type of your getPackage function is a Package object, then that is what you must return. If the function fails then you must find some other way to signal that failure, perhaps by throwing an exception. If you want the possibility of returning nullptr to indicate failure, then the function must return a pointer to a Package object, thus:

C++

Package* getPackage()
{
    Package* pPackage;

    // code to create a new package ...
    pPackage = new Package();
    // ...
    if (some problem with creating the object)
        pPackage = nullptr;

    return pPackage;
}

Jochen Arndt26-Jul-18 1:48

Jochen Arndt

26-Jul-18 1:48

The common solution is to return an empty object. But this requires that the class supports such (usually by the default constructor without arguments creating such an empty object and providing a member function that checks for the object being empty).

An example is the std::string class:

C++

std::string somefunc()
{
    // An empty string
    std::string str();
    
    // Optionally set the string here
    
    // Might return an empty string
    return str;
    // May also use 
    //return std::string();
}

std::string str = somefunc();
if (!str.empty())
{
    // String is not empty
}

Re: Return nothing from a function having return type

Joe Woodbury26-Jul-18 5:44

Joe Woodbury

26-Jul-18 5:44

If you are using C++17, there is std::optional designed just for this situation. You could return a raw pointer (assuming the collection outlives the use of its objects), a unique_ptr (construct a new object) or shared_ptr (and store the Packages as shared_ptr objects).

Another option is to pass a non-const reference to a Package and have the method return a bool indicating success or failure.

As has been pointed out, you could also return an empty object. This is the only choice if your design is constrained to return just an instance.

No Errors but wrong values on return?

GESY25-Jul-18 16:02

25-Jul-18 16:02

I trying to get the Version of the ComCtl32.dll library, according to what I had read
the version number for the ony on System 32 is 5.82 for legacy.

This is the code I have created, and cant get any close to that, you will see extra
lines of code for testing purposes, I maybe not even doing right the creation of the
string for the dialog box, check it out please teach me /give some tips why I get wrong values.

The Code ( Noticed the return 1 or 0 in case of no or errors ) and 1000 of thanks in advance.

char NFILE[255]; DWORD dwSize, dwHandle = 0; VS_FIXEDFILEINFO * pvi;

// Set the Path and file name
strcpy(NFILE,"C:\\Windows\\System32\\ComCtl32.dll");
MessageBox(hWndMain,NFILE,"",MB_OK); // Testing

// Check if we can reach the library.
if(LoadLibrary(NFILE)==NULL) return 1; // If NULL there is an error

// Check if Version info can retrieve and returns the size, in bytes, of that information.
dwSize = GetFileVersionInfoSize( NFILE, NULL ); // Link the Version.lib Library first
if(dwSize==0) MessageBox(hwnd,"Error","",MB_OK); // 0 means an Error

// Get the file Information
char *FDBUF = new char[dwSize];
if ( !GetFileVersionInfo( NFILE, dwHandle, dwSize, &FDBUF[ 0 ] ) )
{ delete FDBUF; return 1; } // If not true, delete the buffer and return

// Get the information into the VS_FIXEDFILEINFO Structure
dwSize = sizeof(VS_FIXEDFILEINFO);
if ( !VerQueryValue( & FDBUF[ 0 ], "\\", (LPVOID*)&pvi, (unsigned int*)&dwSize ) )
{ delete FDBUF; return 1; } // Error processing the information structure.

// Original values according to windows File Version is 5.82 on System32 for legacy
// The 6.0 version lives in %SystemRoot%\winsxs.

wsprintf(BUFF, "Version is %d",LOBYTE(LOWORD(pvi->dwProductVersionLS)),HIBYTE(LOWORD(pvi->dwProductVersionMS)));

MessageBox(hwnd,BUFF,"The Value",MB_OK); // Display the value

delete FDBUF; return 0;

Victor Nijegorodov25-Jul-18 20:52

Victor Nijegorodov

25-Jul-18 20:52

You could get some ideas from this discussion:
c++ - Why does GetFileVersionInfo on kernel32.dll in windows 10 returns version 6.2? - Stack Overflow
and this Chris Maunder's article:
Determining the version number of the Windows system libraries

GESY26-Jul-18 7:58

26-Jul-18 7:58

I had see many examples on getting the windows version, this is not the case.

Even Microsoft on on a web page show a funtion that does not work as it shows.

Thank

Victor Nijegorodov26-Jul-18 8:20

Victor Nijegorodov

26-Jul-18 8:20

GESY wrote:
I had see many examples on getting the windows version, this is not the case.

But you try at least some of them?

GESY27-Jul-18 3:55