Cross-compile Qt for specific arm target from 64bits Linux

Question

I'm currently trying to compile a project and port it to a 32bit target deploying a Linux based system.

My host machine runs x86_64 Debian Stretch and my target is an Atmel SAMA5d2 running a custom Linux. My cross toolchain is generated from buildroot.

At the moment I'm able to cross compile applications for the target using the buildroot generated toolchain. However, I would like to integrate Qt and build Qt apps for the target.

To be able to build my applications for the targetted platform I need to compile Qt for my target. To do so I have to tell Qt to use the buildroot toolchain instead of the native one.

From what I found I either have to provide -device <device> --device-option CROSS_COMPILE=$TOOLCHAIN_PATH or -xplatform <mkspec> to configure Qt with the expected toolchain.

Obviously my target is not in the device list under qtbase/mkspecs/devices so I think the best solution is to create a mkspec for my target.

My command should look like this :

./configure -xplatform <my_mkspec> -embedded arm -prefix <customQtPath>

However I'm kinda lost and I don't know how to do it only from documentation and what I found by googling my problem.
Also do I need to specify the target is 32bit as armv7 is only 32bits?

I would be glad to have some help on this. Thanks.

Luca Carlon · Accepted Answer · 2017-09-20 16:14:42Z

1

Your assumptions are correct. You can read similar specs and create your own, those are pretty simple. For instance Pi2 is an armv7 device, you can start from this qmake.conf. Then, pass to configure:

-device <given_name> -device-option CROSS_COMPILE=<path_and_prefix> -sysroot <your_sysroot>

just change paths, tune cflags if needed etc... Then follow build tutorials.

answered Sep 20, 2017 at 16:14

Luca Carlon

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3 Comments

Arkaik Over a year ago

I thought the device has to be in the list under qtbase/mkspecs/devices as it's said in documentation : italic_The device is selected through the configure tool's -device parameter. The name that follows after this argument must, at least partially, match one of the subdirectories under devices._italic So should I give the create the spec at this location? Also, where could I find documentation about the meaning and use of all those qmake variables?

Luca Carlon Over a year ago

Yes, place yours in there. There is a qmake manual but most are not documented. Read the specs for other chips and experiment.

Arkaik Over a year ago

Thanks, I'll try it and come back to tell you if I succeeded, however it can take a while as I have modifications to do to add Qt in buildroot.

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