Crash using a big string in QML Qt 5.5.0 (no crash in 5.4)

frankiefrank

I have some QML code which is running alright in Qt 5.4 but crashes in my later 5.5.0.

The original code in 5.4 was a log-to-file mechanism. Instead of writing to a file at each logging call, I would append to a string, then a timer would occasionally get the string, write the string to a file (via C++/QML integration) and clear the string.

After switching to 5.5 I noticed a crash. I eventually reduced the code to be just QML, no C++ call at all.

property string logBuffer = ""

// Place this in some rectangle you can click
MouseArea {
anchors.fill: parent
onClicked: {
    console.log("Started constructing long string.");
    var str = "Something worthy of logging. For the sake of the test, I make the string a bit longer than usual, to see if there is an effect..."
    // You can increase / decrease the number of iterations
    for (var i = 0; i < 3000; i++) {
        logBuffer = logBuffer + str + i + "\n";
    }
    console.log("Long string constructed.")

    console.log("Clear buffer of length " + logBuffer.length);
    if (logBuffer.length > 0) {
        logBuffer = "";
    }
}

After several calls I get a crash "R6010 abort() has been called".

I'm not even sure if this a QTBUG or I'm really misusing the QML here, mainly not sure why the newer version behaves differently.

xargs1

It works ok for me with 5.4.2 and 5.5.1 on Linux. The behavior is better with 5.5.1; 5.4.2 uses over 1GB of RAM after a few clicks.