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  1. Qt
  2. QTBUG-92192

Issues calling JSON.stringify() on objects

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    • af1ef35fa0 (qt/qtdeclarative/dev) af1ef35fa0 (qt/tqtc-qtdeclarative/dev) 13a617610a (qt/qtdeclarative/6.3) 13a617610a (qt/tqtc-qtdeclarative/6.3) 13a617610a (qt/qtdeclarative/6.3.2) 13a617610a (qt/tqtc-qtdeclarative/6.3.2)

    Description

      I've been playing around with stuff while trying to figure out if there's a way to control what gets printed when passing a QObject subclass to print()/console.log(). By the way, from reading https://lists.qt-project.org/pipermail/development/2015-November/023713.html, I assume there is no way to do this, but would appreciate confirmation of that.

      #1

      import QtQuick
import QtQuick.Window

Window {
    id: root
    width: 300
    height: 300
    visible: true

    Component.onCompleted: print(JSON.stringify(item))

    Item {
        id: item
    }
}

      prints a very descriptive message:

      qrc:/main.qml:10: TypeError: Type error

      This should probably not be a type error, but if I'm wrong, it should at least say why it is.

      #2

      import QtQuick
import QtQuick.Controls

ApplicationWindow {
    id: root
    width: 300
    height: 300
    visible: true

    Component.onCompleted: print(JSON.stringify(button))

    Button {
        id: button
        text: "Toggle"
        onClicked: fileDialog.visible = !fileDialog.visible
    }
}

      prints a huge string, as is probably expected.

      #3

      This is the interesting one. If I have https://codereview.qt-project.org/c/qt/qtquickcontrols2/+/318565 checked out and run this code

      import QtQuick
import QtQuick.Controls
import QtQuick.Dialogs
import QtQuick.Layouts

ApplicationWindow {
    id: root
    width: 800
    height: 600
    visible: true
//    title: fileDialog.currentFile
    title: "activeFocusItem: " + activeFocusItem

    Component.onCompleted: print(JSON.stringify(button))

    Button {
        id: button
        text: "Toggle"
        onClicked: fileDialog.visible = !fileDialog.visible
    }

    FileDialog {
        id: fileDialog
        title: "Open File"
        currentFolder: "file:///Users/mitch/dev/qt-dev/qtbase/src/corelib"
        nameFilters: ["All files (*)", "Text files (*.txt)", "HTML files (*.html *.htm)"]
        visible: true
    }
}

      I get:

      15:26:02: Starting /Users/mitch/dev/temp/quick-qt_dev_debug_non_fw-Debug/quick.app/Contents/MacOS/quick ...
QML debugging is enabled. Only use this in a safe environment.
AddressSanitizer:DEADLYSIGNAL
=================================================================
==5738==ERROR: AddressSanitizer: stack-overflow on address 0x7ffeecd25e48 (pc 0x0001101dd27f bp 0x7ffeecd26690 sp 0x7ffeecd25e50 T0)
    #0 0x1101dd27f in __asan_memcpy+0x18f (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x4727f)
    #1 0x10e5dc9c9 in int (anonymous namespace)::UnrollTailLoop<2u>::exec<int, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, unsigned long>(unsigned long, int, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, unsigned long) qstring.cpp:244
    #2 0x10e5dc555 in int (anonymous namespace)::UnrollTailLoop<3u>::exec<int, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, unsigned long>(unsigned long, int, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, ucstrncmp(QChar const*, QChar const*, unsigned long)::$_9, unsigned long) qstring.cpp:244
    #3 0x10e5dbe0d in ucstrncmp(QChar const*, QChar const*, unsigned long) qstring.cpp:1005
    #4 0x10e57d4f7 in ucstrcmp(QChar const*, unsigned long, QChar const*, unsigned long) qstring.cpp:1202
    #5 0x10e5804fc in QtPrivate::compareStrings(QStringView, QStringView, Qt::CaseSensitivity) qstring.cpp:1328
    #6 0x109e83a21 in operator==(QString const&, QString const&) qstring.h:847
    #7 0x10a534cb5 in QV4::IdentifierTable::asPropertyKeyImpl(QV4::Heap::String const*) qv4identifiertable.cpp:196
    #8 0x10a4969bd in QV4::IdentifierTable::asPropertyKey(QV4::Heap::String const*) qv4identifiertable_p.h:88
    #9 0x10a530cc5 in QV4::IdentifierTable::asPropertyKey(QV4::String const*) qv4identifiertable_p.h:91
    #10 0x10a7bda02 in QV4::String::createPropertyKeyImpl() const qv4string.cpp:166
    #11 0x10a2b877a in QV4::StringOrSymbol::createPropertyKey() const qv4string_p.h:282
    #12 0x10a2acba0 in QV4::StringOrSymbol::toPropertyKey() const qv4string_p.h:287
    #13 0x10b0a7819 in QQmlValueTypeWrapperOwnPropertyKeyIterator::next(QV4::Object const*, QV4::Property*, QV4::PropertyAttributes*) qqmlvaluetypewrapper.cpp:340
    #14 0x10a5d2c4a in QV4::ObjectIterator::next(QV4::Property*, QV4::PropertyAttributes*) qv4objectiterator.cpp:64
    #15 0x10a5d37c4 in QV4::ObjectIterator::nextPropertyNameAsString(QV4::Value*) qv4objectiterator.cpp:103
    #16 0x10a568a80 in Stringify::JO(QV4::Object*) qv4jsonobject.cpp:798
    #17 0x10a565893 in Stringify::Str(QString const&, QV4::Value const&) qv4jsonobject.cpp:756
    #18 0x10a569db4 in Stringify::makeMember(QString const&, QV4::Value const&) qv4jsonobject.cpp:766
    #19 0x10a568b74 in Stringify::JO(QV4::Object*) qv4jsonobject.cpp:802
    #20 0x10a565893 in Stringify::Str(QString const&, QV4::Value const&) qv4jsonobject.cpp:756
    #21 0x10a569db4 in Stringify::makeMember(QString const&, QV4::Value const&) qv4jsonobject.cpp:766
    #22 0x10a568b74 in Stringify::JO(QV4::Object*) qv4jsonobject.cpp:802
    #23 0x10a565893 in Stringify::Str(QString const&, QV4::Value const&) qv4jsonobject.cpp:756
    #24 0x10a569db4 in Stringify::makeMember(QString const&, QV4::Value const&) qv4jsonobject.cpp:766
    #25 0x10a568b74 in Stringify::JO(QV4::Object*) qv4jsonobject.cpp:802
    #26 0x10a565893 in Stringify::Str(QString const&, QV4::Value const&) qv4jsonobject.cpp:756
    #27 0x10a569db4 in Stringify::makeMember(QString const&, QV4::Value const&) qv4jsonobject.cpp:766
    #28 0x10a568b74 in Stringify::JO(QV4::Object*) qv4jsonobject.cpp:802
    #29 0x10a565893 in Stringify::Str(QString const&, QV4::Value const&) qv4jsonobject.cpp:756
    #30 0x10a569db4 in Stringify::makeMember(QString const&, QV4::Value const&) qv4jsonobject.cpp:766

      I would not expect this to crash. If it's due to recursion, perhaps it should have some limit and just print a warning before hitting it.

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          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-98820 Crash when print delegateModel of Combobox

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed
          relates to

          Suggestion - Public suggestions QTBUG-92194 Use an object's operator<<(QDebug) when passed to print()/console.log()

          • P3: Somewhat important - Should be fixed, but doesn't affect the release in any way.
          • Open
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              ulherman Ulf Hermann
              mitch_curtis Mitch Curtis
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                Created:
                Updated:
                Resolved:

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