Error while making example file

ferocito

Hey,
I need to use Qt for a school project, so I downloaded the 6.4.2 version and tried to build the example project the teacher gave us, but I struggled with this error :

./glwidget.h:3:10: fatal error: 'QOpenGLWidget' file not found

Note that the error is related to a

#include  <QOpenGLWidget>

in a .h file of the project.

I succeed to resolve this error by adding

INCLUDEPATH += /path/to/header/file

to the .pro file, but another error came up :

ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1

I tried to add this (with ChatGPT help) on the .pro file :

QMAKE_MACOSX_DEPLOYMENT_TARGET = 12.5
QMAKE_APPLE_DEVICE_ARCHS = arm64
LIBS += -framework QtWidgets -framework QtOpenGL

but it didn't change anything...

When changing arm64 to x86_64, same error :

ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1

In my despair, I tried to build one of the examples the 6.4.2 Qt version provides :

cd /path/to/Qt/examples/6.4.2/widgets/tools/plugandpaint/app
qmake
make -config release

And as i was expecting, another error :

ld: library not found for -lpnp_basictools
clang: error: linker command failed with exit code 1

I have

QT += openglwidgets

in my .pro file, so the problem is not related to this.

After hours spent on ChatGPT and hours trying to explain my problem to the course assistants, this forum is my last hope before resetting my Mac.

If this can help, I'm on a M2 Macbook Air, version 12.5.

Thank you if you made it this far, hope someone will be able to help me.

jsulm

@ferocito said in Error while making example file:

QOpenGLWidget

It should be enough to add

QT += openglwidgets

to your pro file like shown in https://doc.qt.io/qt-6/qopenglwidget.html

ferocito

@jsulm Hey! Thank you for your response, I already have
QT += openglwidgets in my .pro file, that's why this error surprises me...

SGaist

@ferocito hi,

Did you check that the Qt version you use is a universal build ?

Did you use the online installer to install it ?

ferocito

This post is deleted!

ferocito

@SGaist Hey! Yes I used the online installer to install it.
I juste reinstalled the 6.4.2 version and I made sure in the online installer that it was the universal build, but the error's still here...

JonB

@ferocito
I don't know, but https://doc.qt.io/qt-6/qtopengl-index.html#building-with-qmake documenting changes from Qt 5 to 6 says you need:

QT += opengl

Try that as well as/instead of QT += openglwidgets, any help? Don't forget to re-run qmake when changing the .pro file!

ferocito

@JonB Still the same error... A friend tried to do the same routine as mine on his mac, and same errors too...

SGaist

Can you provide a minimal example that triggers this error ?

ferocito

@ferocito When running any type of project...

The last error i mentioned in my post comes from an example project directly provided by Qt and findable at

/Users/{UserName}/Qt/Examples/Qt-6.4.2/widgets/tools/plugandpaint

However, when i create a simple project with just an empty window, it works perfectly...

ChrisW67

The plug and Paint example should be built from this folder
/path/to/Qt/examples/6.4.2/widgets/tools/plugandpaint
not
/path/to/Qt/examples/6.4.2/widgets/tools/plugandpaint/app

Using the latter folder will not build the plugin libraries, one of which is the subject of the complaint:

ld: library not found for -lpnp_basictools
clang: error: linker command failed with exit code 1

ferocito

@ChrisW67 I did this and still the same error...

I searched the "lpnp_basictools" library in my computer, and i didn't find it. Maybe Qt doesn't find this library because it simply doesn't exist on my computer.

It's weird because I installed Qt with the Qt online installer...

Maybe one thing that can help : I only installed the MacOS version, and didn't install the IOS modules (they weight 17 GB and I don't need to make apps for IOS).

However, I tried to build and run another example :

/path/to/Qt/Examples/Qt-6.4.2/statemachine

and it works perfectly.

It's weird because the example my teacher gave me is a simple colored triangle display, without any animation and interaction, and I can't run it, while the statemachine example seems way more complicated, with interaction and animations...

jsulm

@ferocito said in Error while making example file:

I searched the "lpnp_basictools" library in my computer, and i didn't find it

The name of the library should be: libpnp_basictools.so.*
-lpnp_basictools means: -l is the parameter telling linker to link libpnp_basictools.so library.

ferocito

@jsulm Can't find this file in my computer.

ChrisW67

@ferocito The file is built as one of the plugins in the Plug & Paint example.
The example code is here and the specific sub-project that builds the library is at plugins/basictools/basictools.pro

$ cd ~/Qt/Examples/Qt-6.4.2/widgets/tools/plugandpaint
$ qmake
$ make
...
$ ls -F . plugins
.:
app/  CMakeLists.txt  Makefile  plugandpaint*  plugandpaint.pro  plugins/

plugins:
basictools/  CMakeLists.txt  extrafilters/  libpnp_basictools.a  libpnp_extrafilters.so*  Makefile  plugins.pro