QString to wchar_t* conversion

[sogo]

Hi,
I am having some confusion regarding conversion from QString to wchar_t* using QString::toWCharArray(wchar_t* inputFileLocation). I am doing this conversion to get location of a file and reading it using C api "_wfopen" and "fread" but it sometimes it is not able to open and read file. Here is a little snipper of my code of what I am doing:

QString inFile = "<Some file location is OS dir>";
wchar_t* iFile = new wchar_t[inFile.size()];
inFile.toWCharArray(iFile);
FILE* openFile = _wfopen(iFile, L"rb");
if (openFile == NULL) { qDebug() << "Can not open input file"; throw 2; }

Now this behavior was happening very randomly as in sometimes it will open and sometimes it doesn't so I looked online and saw this forum post
conversion issue from QString-wchar_t - stackoverflow
and saw the third post from jake_w that this conversion does not terminate the array with null. I just wanted to confirm whether this conversion terminates the array with null or do I have to do it manually like below:

QString inFile = "<Some file location is OS dir>";
wchar_t* iFile = new wchar_t[inFile.size()+1];
inFile.toWCharArray(iFile);
iFile[inFile.size()] = '\0'; //Manually terminate array
FILE* openFile = _wfopen(iFile, L"rb");
if (openFile == NULL) { qDebug() << "Can not open input file"; throw 2; }

[jsulm]

@sogo said in QString to wchar_t* conversion:

I just wanted to confirm whether this conversion terminates the array with null or do I have to do it manually like below:

It's mentioned in the documentation: https://doc.qt.io/qt-5/qstring.html#toWCharArray
"Note: This function does not append a null character to the array."...

[sogo]

Oh, I missed that line. I will then append it manually. Thanks and let me close this issue.

[JonB]

@sogo
Given that you are using Qt, why do you want the conversion to wchar_t? You are using it in order to use the FILE type and do your I/O with calls like _wfopen(), doubtless under Windows. I cannot see any reason you would want to do that. Given that you are writing a Qt application, you would be much better off using Qt file access functions, for all sorts of reasons.

[sogo]

@JonB Good point, we have kind of big project and almost all parts of it uses C styles api and we recently started with Qt so to have consistency, just going for IO using c style. In the future we port it to qt or c++. probably.

[Bonnie]

Wouldn't inFile.toStdWString().c_str() be a better choice even if you need to call _wfopen()?

[sogo]

@Bonnie Hi Bonnie, how will that work? Wouldn't be return type of inFile.toStdWString().c_str() be char* array and _wfopen does not take that as argument. Plus it will not serve purpose of storing array characters in 2 byte.

[Bonnie]

@sogo
It is toStdWString, not toStdString :)