How to convert string to LPWSTR in c++

Question

Can anyone help in converting string to LPWSTR

string command=obj.getInstallationPath()+"<some string appended>"

Now i wat to pass it as parameter for CreateProcessW(xx,command,x...)

But createProcessW() accepts only LPWSTR so i need to cast string to LPWSTR

Thanks in Advance

http://stackoverflow.com/questions/27220/how-to-convert-stdstring-to-lpcwstr-in-c-unicode — Arsen Mkrtchyan, Jul 29 '09 at 08:06
@ArsenMkrt: this question is wider than the one you refer to. — xtofl, Jul 29 '09 at 08:40

score 12 · Answer 1 · answered Jul 29 '09 at 08:01

12

If you have an ANSI string, then have you considered calling CreateProcessA instead? If there is a specific reason you need to call CreateProcessW then you will need to convert the string. Try the MultiByteToWideChar function.

answered Jul 29 '09 at 08:01

Greg Hewgill

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score 6 · Answer 2 · edited May 23 '17 at 11:54

6

Another way:

mbstowcs_s

use with string.c_str(), you can find example here or here

OR

USES_CONVERSION_EX;

std::string text = "text";
LPWSTR lp = A2W_EX(text.c_str(), text.length());

OR

{
    std::string str = "String to LPWSTR";
    BSTR b = _com_util::ConvertStringToBSTR(str.c_str());
    LPWSTR lp = b;
    Use lp before SysFreeString...
    SysFreeString(b);
}

edited May 23 '17 at 11:54

Community

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answered May 10 '12 at 19:15

Cobaia

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Isn't that the same thing as in @gbjbaanb's answer? http://stackoverflow.com/a/1198822/6610 – xtofl May 11 '12 at 10:19
I had to change it a little to get it working : CComBSTR bstrDomain(csDomain); LPWSTR pszServerName = bstrDomain; NetWkstaGetInfo(pszServerName,dwLevel,(LPBYTE *)&pBuf); – Nitin Chaudhari Nov 09 '12 at 06:09
`SysFreeString` deallocates the memory, you cannot use `lp` afterwards – M.M Aug 15 '14 at 11:32
@MattMcNabb added your consideration. – Cobaia Aug 15 '14 at 21:27

gbjbaanb · Answer 3 · 2021-01-19T11:04:53.840

5

The easiest way to convert an ansi string to a wide (unicode) string is to use the string conversion macros.

To use these, put USES_CONVERSION at the top of your function, then you can use macros like A2W() to perform the conversion very easily.

eg.

char* sz = "tadaaa";
CreateProcessW(A2W(sz), ...);

The macros allocate space on the stack, perform the conversion and return the converted string.

edited Jan 19 '21 at 11:04

answered Jul 29 '09 at 08:43

gbjbaanb

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The documentation you refer to also says you don't need the USES_CONVERSION for ATL7.0 and up. – xtofl Jul 29 '09 at 11:20
yeah, but I've been using it for so long I add that automatically :) – gbjbaanb Jul 29 '09 at 12:16

score 3 · Answer 4 · answered Jul 29 '09 at 09:08

Also, you might want to consider using TCHAR throughout... If I'm correct, the idea would be something like this:

typedef std::basic_string<TCHAR> tstring

// Make any methods you control return tstring values. Thus, you could write:
tstring command = obj.getInstallationPath();
CreateProcess(x, command.c_str(), ...);

Note that we use CreateProcess instead of CreateProcessW or CreateProcessA. The idea is that if UNICODE is defined, then TCHAR is typedefed to WCHAR and CreateProcess is #defined to be CreateProcessW, which accepts a LPWSTR; but if UNICODE is not defined, then TCHAR becomes char, and CreateProcess becomes CreateProcessA, which accepts a LPSTR. But I might not have the details right here... this stuff seems somewhat needlessly complicated :(.

Only use TCHAR for converting ancient windows software. The only ones having good reason to keep using it are microsoft documentation writers, when they have both an A and a W function. — Deduplicator, Aug 15 '14 at 11:32

score 1 · Answer 5 · answered Aug 28 '12 at 23:13

1

Here is another option. I've been using this function to do the conversion.

//C++ string to WINDOWS UNICODE string
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;
}

And wrap your string like this. s2ws( volume.c_str())

answered Aug 28 '12 at 23:13

Joel

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If that has an exception, it will create a memory leak. – Jonathan Jan 25 '13 at 23:59
@Jonathan The memory leak can be fixed by using `std::vector buf(len);` instead of the `new` line. – M.M Aug 15 '14 at 11:29
also there is a problem that if `s.size() > INT_MAX - 1` you'll get bogus results at best ; to make this function robust it should check for that and throw an exception or take some other well-defined action – M.M Aug 15 '14 at 11:30

How to convert string to LPWSTR in c++

5 Answers5