error C2679: binary '=' in VC++

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Hi friends,

Old Code:

extern "C" __declspec(dllexport) int ReturnSize()
{
    return KbReceived;
}

New Code:

extern "C" __declspec(dllexport) int ReturnSize(char *PortName)
{
     PortName =Re;
     return KbReceived;
}

Here Re = Port No.KbReceived -- file Size

when i run this new code i got this error:
"error C2679: binary '=' : no operator defined which takes a right-hand operand of type 'class CString' (or there is no acceptable conversion) MFCDLL.cpp"

How can i Solve this? Please Help me.
Regards,
Lakshmi Narayanan.S

Posted 1-Aug-11 19:50pm

naraayanan

Updated 1-Aug-11 20:02pm

tolw

v3

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tolw 2-Aug-11 2:04am

Edited for readability

2 solutions

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Resmi Anna · Answer 1 · 2011-08-01T20:21:00

Solution 1

Re is of type CString rt?U need to copy the string using the function strcpy()
like

strcpy( PortName, Re );

Also ensure that you have allocated enogh memory for PortName before passing its refrence to the function ReturnSize().

Posted 1-Aug-11 20:21pm

Resmi Anna

Olivier Levrey · Answer 2 · 2011-08-01T21:49:00

As Resmi Anna guessed, I suppose Re is a CString.

I am pretty sure the problem comes from string encoding: your are expecting your CString object to hold a string as char* array, but it is (in your project) a wchar* array (2 bytes per character).

There are 2 solutions to fix your issue:

1- Change your function declaration to make it accept wide chars:

C++

extern "C" __declspec(dllexport) int ReturnSize(TCHAR* PortName)
{
     PortName =Re;
     return KbReceived;
}

But be carefull after to use wide character strings in the application that uses the dll.

2- If you want to force your CString to hold char, go to the Project Properties page, in the General tab, set Character set to Not set (and do it for both Release and Debug configurations).

I must now ask what you want to achieve with your function?
Because if you want to return a string object to the caller, you can't do it this way: the pointer your are setting will not be returned to the caller.

If you want to return the string just do something like that:

C++

extern "C" __declspec(dllexport) LPCTSTR GetString()
{
     return Re;
}