string转wstring

方法一：（str从函数传参时可能出问题）

#include <codecvt>
#include <string>

std::wstring_convert<std::codecvt_utf8<wchar_t>> converter;
std::wstring &wstr = converter.from_bytes(str);

转回 to_bytes

方法二：

#include <comutil.h>  
#pragma comment(lib, "comsuppw.lib")

string to wstring:

_bstr_t t = str.c_str();  
wchar_t* pwchar = (wchar_t*)t;  
wstring result = pwchar; 

wstring to string:

_bstr_t t = wstring.c_str();  
char* pchar = (char*)t;  
string result = pchar;