How to convert std::string to LPCWSTR in C++ (Unicode)

Question

Thanks for the link to the MSDN article. This is exactly what I was looking for.

std::wstring s2ws(const std::string& s)
{
    int len;
    int slength = (int)s.length() + 1;
    len = MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength, 0, 0); 
    wchar_t* buf = new wchar_t[len];
    MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength, buf, len);
    std::wstring r(buf);
    delete[] buf;
    return r;
}

std::wstring stemp = s2ws(myString);
LPCWSTR result = stemp.c_str();

The solution is actually a lot easier than any of the other suggestions:

std::wstring stemp = std::wstring(s.begin(), s.end());
LPCWSTR sw = stemp.c_str();

Best of all, it's platform independent.

If you are in an ATL/MFC environment, You can use the ATL conversion macro:

#include <atlbase.h>
#include <atlconv.h>

. . .

string myStr("My string");
CA2W unicodeStr(myStr);

You can then use unicodeStr as an LPCWSTR. The memory for the unicode string is created on the stack and released then the destructor for unicodeStr executes.

I prefer using standard converters:

#include <codecvt>

std::string s = "Hi";
std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> converter;
std::wstring wide = converter.from_bytes(s);
LPCWSTR result = wide.c_str();

Please find more details in this answer: https://stackoverflow.com/a/18597384/592651

---

Update 12/21/2020 : My answer was commented on by @Andreas H . I thought his comment is valuable, so I updated my answer accordingly:

1. codecvt_utf8_utf16 is deprecated in C++17.
2. Also the code implies that source encoding is UTF-8 which it usually isn't.
3. In C++20 there is a separate type std::u8string for UTF-8 because of that.

But it worked for me because I am still using an old version of C++ and it happened that my source encoding was UTF-8 .

Same as Toran Billups's answer, except that we should know:

The C++-standard has rules for .c_str() method, which allows us to use const_cast (instead of the unnecessary allocation and deletion).

std::wstring s2ws(const std::string &s)
{
    int len;
    int slength = (int)s.length() + 1;
    len = MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength, 0, 0);
    std::wstring buf;
    buf.resize(len);
    MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength,
           const_cast<wchar_t *>(buf.c_str()), len);
    return buf;
}

std::wstring wrapper = s2ws("My UTF8 string!");
LPCWSTR result = wrapper.c_str();