From wchar_t* to QString: QString::fromUtf16 or QString::fromWCharArray?

Bart_Vandewoestyne

Today, my CppDepend complained about the following code:

wchar_t* buffer = _wgetenv(L"USERNAME");
if (buffer != NULL)
{
    userId = QString::fromUtf16(buffer).toLower();
}

The problem is that buffer is wchar_t*, while QString::fromUtf16 expects a const ushort *.

As I wasn't quite sure whether to replace the fromUtf16 function call with

userId = QString::fromUtf16(reinterpret_cast<const ushort*>(buffer)).toLower();

or with

userId = QString::fromWCharArray(buffer).toLower();

I wrote this little test program:

https://github.com/BartVandewoestyne/Qt/blob/master/tests/qstring_from_wchar_t_array.cpp

On Linux, wchar_t seems to be 4 bytes and there seems to be a difference between the two functions:

sizeof(wchar_t) =  4 
QString::fromUtf16(reinterpret_cast<const ushort*>(text)) => "F" 
QString::fromWCharArray(text) => "FooBar"

on Windows, wchar_t seems to be 2 bytes and there seems to be no difference:

sizeof(wchar_t) =  2 
QString::fromUtf16(reinterpret_cast<const ushort*>(text)) => "FooBar" 
QString::fromWCharArray(text) => "FooBar"

My conclusion would be that in this case, where I have to create a QString out of a wchar_t*, the safest and most portable way is to use QString::fromWCharArray(text). Is my conclusion correct, or am I overlooking something?

Kind regards,
Bart