type qualifiers ignored

ckvsoft

Hi

I got a "Warnung: type qualifiers ignored on cast result type [-Wignored-qualifiers]"

response.data is unsigned char data[260];

QByteArray ba;
        Response response = signHash(pin, hash);
         
        for (uint i = 0; i < response.length; i++)
           ba[i] = (const char)response.data[i];

Can i simply remove "(const char)" for same result?

lg Chris

ckvsoft

Hi

I think it was fixed. I need the QByteArray as Base64 and not the int value;
QByteArray doesn't specify either signed or unsigned so

            char ch;
            unsigned char uch;

            ch=231;
            uch=(char) ch;
            QByteArray ba1, ba2;
            ba1[0] = ch;
            ba2[0] = uch;

            qDebug() << (int)ch << "/"<< (int)uch;
            qDebug() << ba1 << "/"<< ba2;
            qDebug() << (signed char)ba1[0] << "/"<< (unsigned char)ba1[0];
            qDebug() << (signed char)ba2[0] << "/"<< (unsigned char)ba2[0];

            QVERIFY(ba1.toBase64() == ba2.toBase64());

QDEBUG : QRK::testBA() -25 / 231
QDEBUG : QRK::testBA() "\xE7" / "\xE7"
QDEBUG : QRK::testBA() -25 / 231
QDEBUG : QRK::testBA() -25 / 231

QVERYFY pass true;

So i can remove (const char)
lg Chris

dheerendra

What is the data type of response.data ?

mrjj

Hi
response.data is unsigned char data[260];
:)
so issue/warning is unsigned char vs char and
it warns that the cast -removes/ignores the sign.

So the big question is about the data.
If it contains negative values, then cast might alter data.
if not, should be fine.

dheerendra

@mrjj It was miss from my side which is exactly at the the top :)

mrjj

@dheerendra
Funny enough, i also didn't see that line first time i read post. :)

aha_1980

@ckvsoft I think the problem is the const, try to remove it, it serves no purpose here.


So either use `append` or search a suitable constructor for ` ba`, like http://doc.qt.io/qt-5/qbytearray.html#QByteArray-1

In that case, you have to `reinterpret_cast< const char *>`

J.Hilk

@aha_1980 said in type qualifiers ignored:

But: this code will crash as ba initially has size zero, so accessing bytes with [] is undefined behavior.

it actually won‘t QByeArray atomatically resizes when you try to access it outside it bounds. It‘s slow, but it won‘t crash.

aha_1980

@J.Hilk ok, that was new for me - will try it.

It's interesting as other Qt containers dont work that way...

Christian Ehrlicher

@aha_1980 said in type qualifiers ignored:

It's interesting as other Qt containers dont work that way...

'interesting' is imo not the correct word here... it's strange. It's similar to the QContainer::value() functions. :/

ckvsoft

@J.Hilk right. It wont't crash. But i fix this now ;-)

ckvsoft

Hi

I think it was fixed. I need the QByteArray as Base64 and not the int value;
QByteArray doesn't specify either signed or unsigned so

            char ch;
            unsigned char uch;

            ch=231;
            uch=(char) ch;
            QByteArray ba1, ba2;
            ba1[0] = ch;
            ba2[0] = uch;

            qDebug() << (int)ch << "/"<< (int)uch;
            qDebug() << ba1 << "/"<< ba2;
            qDebug() << (signed char)ba1[0] << "/"<< (unsigned char)ba1[0];
            qDebug() << (signed char)ba2[0] << "/"<< (unsigned char)ba2[0];

            QVERIFY(ba1.toBase64() == ba2.toBase64());

QDEBUG : QRK::testBA() -25 / 231
QDEBUG : QRK::testBA() "\xE7" / "\xE7"
QDEBUG : QRK::testBA() -25 / 231
QDEBUG : QRK::testBA() -25 / 231

QVERYFY pass true;

So i can remove (const char)
lg Chris

jsulm

@ckvsoft said in type qualifiers ignored:

(char)

Just a note: you should avoid C style casts in C++ and use C++ type casts (like static_cast) instead.