When using QDebug in Qt5 applications, no output is seen in the application's output view. This is essentially https://bugreports.qt.io/browse/QTCREATORBUG-13828, but applied to KDevelop rather than Qt Creator. A work-around is to set QT_LOGGING_TO_CONSOLE=1 in the execution environment, but many users will not know about this variable, and it is difficult to learn about it without already knowing what is happening.
Happy to receive patches for this!
Created attachment 114450 [details] kdevelop-qdebug-output-working
Is this what the bug is about, because it seems to be working fine for me. here KDevelop is writing the qDebug output to the application output without setting any env vars. I am on KDE Neon unstable, KDevelop v5.2.3 ------- Please excuse any silly mistakes, this is my fist time using Qt or C++, and my first day being evolved with KDE.
Omar, is your test app Qt4 or Qt5? If Qt5, was Qt built with journald support? Qt4 works, Qt5 depends on if it was built with journald support (as e.g. Fedora's package is).
KDevelop spits this while compiling `g++ -Wl,-O1 -o second build/main.o -lQt5Widgets -lQt5Gui -lQt5Core -lGL -lpthread ` so this should be a is a qt5 project I could not find a way of knowing whether Qt was build with journald support or not, so...I might use a little help. I am running KDE Neon Dev edition, if that might help. I suppose that I could just test on a fedora VM just to be sure.
Presumably, if you run your app like `theapp >&- 2>&-` it will write to journald, and thus you could do so and expect that you can see your message in `journalctl`. (For that matter, there should be a bunch of Qt/KDE stuff in there, *if* Qt is using it.)
> Presumably, if you run your app like `theapp >&- 2>&-` it will write to journald Well, I thought that would work, but apparently not. I did confirm, however, that a simple app for me is *not* producing output that is visible in KDevelop (I *do* see the output in journalctl). I also see the output if I run the app from Konsole (i.e. "a real tty"), or if I set QT_LOGGING_TO_CONSOLE=1. In any case, I'm getting at least some output from KDevelop itself in journalctl; if you're running that, and especially if you're running plasma and other KDE apps, it should be pretty obvious if you have QDebug stuff going to journald. If you *don't* see bunches of Qt/KDE stuff in journalctl, you probably don't have QDebug using journald.
Created attachment 131727 [details] [PATCH] Execute Launch: show Qt log output in Run tool view I have spent several hours testing when the output appears or not until I found this bug report. This bug only happens if KDevelop itself is started from a graphical environment rather than from a terminal, and the user launches a Qt application via "Execute Launch" KDevelop action rather than "Debug Launch" action. The issue is inherited by another KDevelop instance Execute-Launched from KDevelop (a recursion of sorts). I just implemented a fix for this issue that sets QT_FORCE_STDERR_LOGGING to 1 in the initial default environment profile and when the user creates a new environment profile: see the attached 0001-Execute-Launch-show-Qt-log-output-in-Run-tool-view.patch. However now I realize that a better fix is possible: add a checkbox on Launch Configuration page with text "Show Qt log messages in Run tool view" and a tooltip "Sets QT_FORCE_STDERR_LOGGING environment variable to 1" (or maybe a more detailed explanation in the tooltip). The checkbox should be checked by default. When KDevelop applies the selected environment profile to a launched program and this new option in its launch configuration is on, it will silently set one more hidden environment variable. This way the fix is retroactively applied to all existing launch configurations without the need to manually add the environment variable to all environment profiles configured in the past. Plus the checkbox provides an opportunity to explain why the environment variable is needed, as opposed to simply specifying it in the unconfigured default and new environment profiles.