Declare unsigned char[] with Q_DECLARE_METATYPE

Question

I'm trying to set up some unit tests with QtTest and i'd like to use QFETCH.

I am testing the following function :

static std::vector<bool> FrameHandler::getBitsFromFrame(unsigned char* data, unsigned char length);

It simply converts a array of char into a vector of bits.

So, I set up my test class like this :

#include <QtTest/QtTest>
#include <vector>
#include "FrameHandler.h"

class BusTester : public QObject {
    Q_OBJECT

private slots:

    void bytesToVector_data() {
        QTest::addColumn<unsigned char[]>("Tested");
        QTest::addColumn<unsigned char>("Length");
        QTest::addColumn< std::vector<bool> >("Reference");

        // Test for one byte
        std::vector<bool> oneByte(8, false);
        oneByte[0] = true;
        oneByte[1] = true;
        oneByte[3] = true;
        oneByte[4] = true;

        unsigned char oneByteInput[1]{
            0b11011000
        };

        QTest::newRow("One byte") << oneByteInput << 1 << oneByte;
    }

    void bytesToVector() {
        QFETCH(unsigned char[], tested);
        QFETCH(unsigned char, length);
        QFETCH(std::vector<bool>, reference);

        QCOMPARE(FrameHandler::getBitsFromFrame(tested, length), reference);
    }
};

QTEST_MAIN(BusTester)
#include "bustester.moc"

When I do this, the compiler says :

expected unqualified-id before ‘[’ token
         QFETCH(unsigned char[], tested);

And also :

On line `QTest::addColumn<unsigned char[]>("Tested");`, Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system

I thought the two errors were linked, so i added Q_DECLARE_METATYPE(unsigned char[]); before the class declaration, but then I get this :

In qmetatype.h, expected '>' before '*' token (line 1695)

Is it possible to declare unsigned char[] to Qt's QMetaType system ? Thanks

arturx64 · Accepted Answer · 2017-08-11T14:39:42.713

2

Q_DECLARE_METATYPE(T) Type T must be constructable, copiable and destructable. Array doesn match this rules, but you can create wrapper around.

struct Arr
{
    unsigned char arr[SIZE];
};
Q_DECLARE_METATYPE( Arr );

or

typedef std::array<unsigned char, SIZE> TArr;
Q_DECLARE_METATYPE( TArr );

But there is one difficulties - SIZE, You have-to declare it

edited Aug 11 '17 at 14:39

answered Aug 11 '17 at 14:35

arturx64

943
4
12

Or just use an `unsigned char *` – dtech Aug 11 '17 at 14:39
Yes. But in this case, You have to hold somewhere pointed object to avoid access violation. This this test data, so it could static constants to achieve that. – arturx64 Aug 11 '17 at 14:43
Presumably the OP knows what he is doing and now to avoid out of bounds access. – dtech Aug 11 '17 at 14:44
@arturx64 your answer looks reasonable, i'll try it out as soon as possible ! – Xatyrian Aug 11 '17 at 14:50

Declare unsigned char[] with Q_DECLARE_METATYPE

1 Answers1