Cent0S 7 best Qt5 version and xcb fix

qDebug

Hey guys!

Just try to figures out what Qt5 version will compile with CentOS7 DevTools 7. So far i testet some, from 5.9.1 to 5.14.0. 5.14 seems to be the latest i can theoretically with my CentOS 7 setup.

Theoretically because there still is the xcb error and other error like audio libs. I installed all xcb libs and dev-packs yum can find, also did compile xcb-lib from source. My best guess is an error in the config files.

Did check, all libs are in place, configure log told me ld can't find them. pkg-config is ok with it.

When i google CentOS and Qt5, there are a lot of unsolved questions about this.

In the configure options there is an option to use qt's own xcb, but i did't even manage to get tis option typed in correct, always error unkown command. -xcb xcb-qt, -xcb-qt, -xcb -xcb-qt, -xcb -xcb-qt and even silly -xcb-xcb-qt. No luck so far :(

Did anyone ever solve this?

Thaks :)

Axel Spoerl

@qDebug

Did anyone ever solve this?

-xcbis the right option and if the right configure is called, it will not complain. For the records, it's not Qt's own XCB.
For the rest, included required packages, I suggest to read the manual.

qDebug

@Axel-Spoerl

From 5.14.0 configure script:

-xcb-xlib............. Enable Xcb-Xlib support [auto]

  Platform backends:
    -direct2d .......... Enable Direct2D support [auto] (Windows only)
    -directfb .......... Enable DirectFB support [no] (Unix only)
    -eglfs ............. Enable EGLFS support [auto; no on Android and Windows]
    -gbm ............... Enable backends for GBM [auto] (Linux only)
    -kms ............... Enable backends for KMS [auto] (Linux only)
    -linuxfb ........... Enable Linux Framebuffer support [auto] (Linux only)
    -xcb ............... Enable X11 support. Select used xcb-* libraries [system/qt/no]
                         (-qt-xcb still uses system version of libxcb itself)

-xcb ............... Enable X11 support. Select used xcb-* libraries [system/qt/no]

What exactly does this selector do: system, qt or no and how to use it? Because as i wrote -xcb-qt does not work ... "xcb-*"

Surprise: I did read the manual. Does not work on CentOS7 (at least for me and lots of guys on google, github, ...). I know, thats a big Linux problem, distribution between different distributions, thats the reason i ask here, if anyone ever solved the distributions/compiler/lib - problem(s).

For clarity: I did manage to compile serveral version of Qt on CentOS without xcb and audio libs, both shared and static with static libstdc and static glibc libs. So my only issue is xcb. Also tested on CentOS 9 and latest Qt 5, same issues with xcb.

Axel Spoerl

@qDebug
If compiling with XCB fails, most likely there’s a library/header missing and the configure output should tell you what it is. Even though Centos is not amongst the supported platforms for Qt 5.15, I should work. I’ve done it myself.

qDebug

@Axel-Spoerl

After some more testing, it looks like my main issues are static libs and the compiler lib prefix so ld won't find the static ones.

Do you know an easy way to change the compiler command from -lname.a to -lname? Did poke around in some conf files but got lost there very fast.

Only found QMAKE_LFLAGS_RELEASE but no idea where and when Qt may or may not add ...

qDebug

Well, i did figure it out, kinda ...

For CentOS 7 - DevTools 7 - the best Qt version are 5.8 to 5.12. Depends on what you want to do. I wrote a script and did compile all of them in with all or nothing, shared and static.

Kind like alchemy (-;

I knwo there are docs and feature update news but it is still most of the time unclear what version will work at all.