qDebug not displaying anything

Question

Often when I need to debug something it's easier to print something using qDebug() instead of debugging step-by-step using a debugger. The problem is that from time to time the output of qDebug() isn't displayed at all! The same with qWarning and qCritical. What's strange, it only occurs when running the project normally (Ctrl+R), while when debugging (F5) the output shows up.

Solution 1

The solution is simple: add CONFIG += console to your .pro file and rebuild the whole project.

Solution 2

Solution for me, As stated in https://bugzilla.redhat.com/show_bug.cgi?id=1227295#c10 was :

1. look for qtlogging.ini in /etc/xdg/QtProject/ .
2. edit the current (or create the file qtlogging.ini if missing)

[Rules]
*.debug=false

to

[Rules]
*.debug=true
qt.*.debug=false

3. recompile and check!

Solution 3

If you are running multiple instances of Qt Creator, qDebug does not work properly.

Solution 4

I had the same problem and none of the answers here did help me. I found the solution here: https://lists.fedoraproject.org/archives/list/[email protected]/thread/SB6QJZGVDLWWBZCMTNKMVZSSPPNREOYJ/

I had to set QT_ASSUME_STDERR_HAS_CONSOLE=1. This can be done in code:

qputenv("QT_ASSUME_STDERR_HAS_CONSOLE", "1");

Or better in the "Kits" settings under "Environment".

Solution 5

My solution for this problem using

Windows 10 Education
Qt Creator (5.x)
Developing a Qt widget.

Problem:

So my issue was whenever I added a QDebug message it didn't show up in the application output although my code was 100% the same as in the tutorial and compiled fine.

Solution:

Right click on the file where you added the QDebug message, for me it was main.cpp. Click build. Press the green arrow on the bottom.

If this still doesn't work go to "Build"->"CleanAll", "Build"->"qMake" and go for the green arrow again.

Of course you have to #include <QDebug> and check that it is well spelled inside your code.

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Comments

[Mayank]

its not working for me...I used the statement qDebug("test"); and added CONFIG += console to my .pro file.

[Lukasz Czerwinski]

Did you try to rebuild the whole project? It worked for me then.

[bobbaluba]

@LukaszCzerwinski I did this, and it didn't work for me either. My problem is slightly different from OP, though, as I don't see debug output in neither debugging mode nor regular run.

[Pandrei]

maybe off topic, but why are you answering your own question? :)

[Lukasz Czerwinski]

That's a good question. I answered it because... Stackoverflow encourages people to do so (yes! :) )

[Lukasz Czerwinski]

1. There is a checkbox "Answer your own question" when you write the question (see: stackoverflow.com/questions/ask)

[Lukasz Czerwinski]

2. They also explicitly say that "It’s OK to Ask and Answer Your Own Questions" (see their blog: blog.stackoverflow.com/2011/07/…)

[Lukasz Czerwinski]

HTH. Happy stackoverflowing! :)

[recycler]

is working for me - seems that this entry is disabling the QDebug in recent systems like ubuntu 18.xx

[Nicolas C. R.]

im not sure if thats the cause, but i forgot to mention that i was on Ubuntu 17.10 and Qt 5.9

[user240515]

Also works if I put it in ~/.config/QtProject/qtlogging.ini

[Som Pra]

The #include <QDebug> helped me... Thanks

[Damon Jenkins]

Thankyou so much omg