Compilation of Qt5.3.1 on Ubuntu 20.04.1 - QCommandLineParser addVersionOption() Issue

laurent.c

Hello,

I'm trying to compile Qt5.3.1 on Ubuntu 20.04.1 (see this thread for other issues I encountered with foreach loops : https://forum.qt.io/topic/121528/compilation-of-qt5-3-1-on-ubuntu-20-04-1)

I could compile OK, but then I discovered another issue at runtime, e.g. 'moc--version' gives "Unknown option 'version'" (the same happens with 'rcc' and 'uic').

I actually saw many of those messages during compilation:

QCommandLineParser: option not defined: "version"
QCommandLineParser: option not defined: "help"

Although I felt it was probably not normal, I did not look into it as it did not stop me compiling.

But now, I've been investigating this warnings due to the runtime issue, and here is what I found:

In main.cpp of moc for example, there are calls to parser.addVersionOption() and parser.addHelpOption() so I looked into those methods in src/corelib/tools/qcommandlineparser.cpp.

QCommandLineOption QCommandLineParser::addVersionOption()
{
    QCommandLineOption opt(QStringList() << QStringLiteral("v") << QStringLiteral("version"), tr("Displays version information."));
    addOption(opt);
    d->builtinVersionOption = true;
    return opt;
}

We see that addVersionOption() calls addOption(). So I added some debug and here what I found:

QCommandLineParser: addOptionVersion size = 2       => Correct  size of QStringList (arg 1 of QCommandLineOption)
QCommandLineParser: addOption optionNames size = 1  => Wrong size of QStringList (option.names.size()) !
QCommandLineParser: addOption iterating name = v    => So in the loop (replaced by a for loop instead of foreach!), only 'v' gets parsed, not 'version'

To try, I changed the code to:

QCommandLineOption opt(QStringList() << QStringLiteral("version"), tr("Displays version information."));

Then it works fine, and 'moc --version' returns the expected value (+ QCommandLineParser: option not defined: "version" warning disappears of course).

I'm not able to explain why the QStringList is not passed correctly. So that's where I'm requesting your help trying to understand what's going on !

I'm compiling using GCC 9.3.0.

Thanks in advance.

Christian Ehrlicher

I would take a look in the git history of QCommandLineOption to see if there were fixes/changes to make it work with gcc9

aha_1980

@laurent-c if you really want to keep such an old Qt version (why?), wouldn't it be easier to set up a docker environment for that?

Regards

laurent.c

@Christian-Ehrlicher That's what I've done, and this line is identical in the latest code. Looking at the git log, I could not find anything relevant.

laurent.c

@aha_1980 I'm actually cross-compiling Qt for my embedded device. And I cannot upgrade to latest Qt. I'm cross-compiling for arm (using gcc 4.8 from Linaro toolchain). However, the tools themselves are compiled using the host machine GCC as they have to run on the host machine.