Cannot convert 'const char*' to 'WCHAR

问题:

I have documentation where written that username, IP and password must be const char* and when I'm putting varaibles in const char, I'm getting this error message.

This is my code:

#include <cstdlib>
#include <iostream>
#include <stdio.h>
#include <windows.h>

using namespace std;

typedef int (__cdecl *MYPROC)(LPWSTR);

int main()
{
    HINSTANCE hinstDLL;
    MYPROC ProcAdd;   
    hinstDLL = LoadLibrary("LmServerAPI.dll");
    if(hinstDLL != NULL){
        ProcAdd = (MYPROC) GetProcAddress(hinstDLL,"LmServer_Login");            
        if(ProcAdd != NULL){
            const char* IP = "xxx.177.xxx.23";
            const char* name = "username";
            const char* pass = "password";
            int port = 888;
            ProcAdd(IP,port,name,pass);
            system ("pause");          
        }          
    }
}

And I got this error:

cannot convert const char*' toWCHAR*' in argument passing

Which kind of variable must I use for those arguments and how?

回答1:

You are most likely using one of the Visual Studio compilers, where in Project Settings, there is a Character set choice. Choose from:

• Unicode character set (UTF-16), default
• Multi-Byte character set (UTF-8)
• Not Set

Calling functions that accept strings in the Unicode setting requires you to make Unicode string literals:

"hello"

Is of type const char*, whereas:

L"hello"

is of type const wchar_t*. So either change your configuration to Not set or change your string literals to wide ones.

回答2:

For literals, you want to use L on the string as in:

L"My String"

If you may compile in wide character or not, then you may want to consider using the _T() macro instead:

_T("My String")

Wide string characters under MS-Windows make use of the UTF-16 format. For more information about Unicode formats, look on the Unicode website.

To dynamically convert a string, you need to know the format of your char * string. In most cases, under Windows it is a Win1252, but definitively not always. Microsoft Windows supports many 8 bit formats, including UTF-8 and ISO-8859-1.

If you trust the locale setup, you could use the mbstowc_s() functions.

For other conversions, you may want to look at the MultiByteToWideChar() function