Dll returning a String

[DaoK]

Is that normal that I got an error like that :

error C2679: binary '=' : no operator defined which takes a right-hand operand of type
'class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > (__cdecl *)(void)'
(or there is no acceptable conversion)

The code look like :

std::string a;
a = (*returnMyString);

[jim mcnamara]

First answer: NO not normal

If it is an external (usually MS) dll - you are dealing with null-terminated char *.

If it's OLE , then you've likely got BSTR *.

Not <string>
as in std::string

[parksie]

If you're calling between C++ DLLs from the same compiler, you can return strings quite happily...the best thing if you're making a C DLL is to get them to supply a buffer and a length, then fill it up a la strncpy().

Watch for the buffer overruns, though!

[DaoK]

Well you are both too good in C for me because I think you have answer my question with too much hard word because I do not understand what to change to have no error...


And can we put whole class in a DLL ?

[DaoK]

I call the dll to the string like that :

	std::string sPass;
	sPass =(*PasswordMaker);

and I got :

error C2679: binary '=' : no operator defined which takes a right-hand operand of type 'class std::basic_string<char,st
ruct std::char_traits<char>,class std::allocator<char> > (__cdecl *)(void)' (or there is no acceptable conversion)

warning C4550: expression evaluates to a function which is missing an argument list

[abdul]

Maybe try this:

std::string sPass;
sPass =(*PasswordMaker)(); 

[DaoK]

THX but that produce that error now :

[DaoK]

THX but that produce that error now :

[DaoK]

THX but that produce that error now :


I have that when the exe close.

[abdul]

How is your DLL written? What's the code for PasswordMaker()?

[abdul]

Oh, are you freeing the DLL when you have used it? Use FreeLibrary() to unload the DLL before quitting the program.

//Use the DLL
//...........
//Free the DLL
FreeLibrary(hDLL); 

[DaoK]

C++ doesn't have something like in vb unload() or a function who is exectuted when the program close ?

[DaoK]

C++ doesn't have something like in vb unload() or a function who is exectuted when the program close ?

Here is in the dll the code of the password function, the freelibrary didn't solve the problem.

std::string __declspec( dllexport )PasswordMaker()
{
    char cChar;                    //Contain the character that the user have pressed
    std::string sPass;            //Contain all character
    int iNombreChar = 0;        //Number of character that the user have pressed
    //Loop until the user press enter            
    while(true) 
    {
        //Get character one by one
        cChar = getch();

        //Only if the number that the user put is bigger than 1 you can erase
        if (iNombreChar > 0)
        {
            if( cChar == 8)
            {
                //Erase the character in the String
                sPass = sPass.substr(0,sPass.length() -1);
                //Erase the character at the screen
                std::cout << (char)(8) << char(32) << char(8);
                iNombreChar--;
            }//End if
        }//End if
        
        //Put stars and not the character
        if (cChar != 13 && cChar != 8)
        {
            sPass += cChar;
            std::cout << "*";
            iNombreChar ++;
        }//End if
        //If the user press ENTER than we have done with the password creation
        else if (cChar == 13)
            break;
    }//End for while(true)
    return sPass;
}//End PasswordMaker 

[DaoK]

C++ doesn't have something like in vb unload() or a function who is exectuted when the program close ?

Here is in the dll the code of the password function, the freelibrary didn't solve the problem.

std::string __declspec( dllexport )PasswordMaker()
{
    char cChar;                    //Contain the character that the user have pressed
    std::string sPass;            //Contain all character
    int iNombreChar = 0;        //Number of character that the user have pressed
    //Loop until the user press enter            
    while(true) 
    {
        //Get character one by one
        cChar = getch();

        //Only if the number that the user put is bigger than 1 you can erase
        if (iNombreChar > 0)
        {
            if( cChar == 8)
            {
                //Erase the character in the String
                sPass = sPass.substr(0,sPass.length() -1);
                //Erase the character at the screen
                std::cout << (char)(8) << char(32) << char(8);
                iNombreChar--;
            }//End if
        }//End if
        
        //Put stars and not the character
        if (cChar != 13 && cChar != 8)
        {
            sPass += cChar;
            std::cout << "*";
            iNombreChar ++;
        }//End if
        //If the user press ENTER than we have done with the password creation
        else if (cChar == 13)
            break;
    }//End for while(true)
    return sPass;
}//End PasswordMaker