After updating to qt 5.13.2, all of my qt based applications are now segfaulting immediately after launch. Downgrading back to qt 5.12.5 fixes the problem.
[33728.522284] kdiff3: segfault at 0 ip 0000000000000000 sp 00007ffd5899e1e8 error 14 in kdiff3[561d78d5e000+30000]
[33728.522288] Code: Bad RIP value.
[33867.037107] wireshark: segfault at 0 ip 0000000000000000 sp 00007ffc93b3bd38 error 14 in wireshark[561b0f621000+a5000]
[33867.037112] Code: Bad RIP value.
[33930.700740] kdiff3: segfault at 0 ip 0000000000000000 sp 00007ffc1bf57de8 error 14 in kdiff3[558b10a23000+30000]
[33930.700745] Code: Bad RIP value.
[33934.307967] qdirstat: segfault at 0 ip 0000000000000000 sp 00007fff59358278 error 14 in qdirstat[56249dee3000+2b000]
[33934.307972] Code: Bad RIP value.
Because this cropped up after a 17.1 profile migration, I did an "emerge -e @world" out of an abundance of caution, but that didn't help.
This is only happening on one of my two Gentoo installs.
* My installation running natively on hardware (Thinkpad p50) is fine.
* The affected install is running virtualized in virtualBox 6.0.14 on Windows 10.
Created attachment 602096 [details]
Debug information (gdb backtraces, emerge --info, package information)
Not sure how could I help, but I am having the same issue.
I am on a different (source-based) distribution, though, which may suggest an upstream bug.
There have indeed been some reports with issues like this when using VirtualBox, though the version numbers don't quite match...
See for example: https://forums.gentoo.org/viewtopic-t-1106432.html
QT based applications experienced the same failures after updating inside a virtual container (VirtualBox). A symptom was Plasma experienced a black screen with a cursor after launched from SDDM login or called directly from inside a startx environment, QT applications failed inside other DE's such as MATE.
The fix was GCC flag adjustment to Portage in make.conf and rebuilding all of the QT and KDE/Plasma packages. Removing the -MARCH="NATIVE" flag in make.conf solved this issue, it would seem CPU features are being compiled in which aren't supported.
This was tested on an i7 6700HQ
Good catch. I can confirm that removing "-march=native" fixes Qt applications for me.
I took it a step further and found that qtgui is actually the only package with this problem. All other dev-qt/*, kde-frameworks/*, and kde-plasma/* packages work perfectly fine with "-march=native" - at least for what I have installed for kdiff3/keepassxc/qdirstat/wireshark.
And even a step further, qtgui also appears to work with "-march=native -mno-avx2". I noticed qtgui has a patch for "-march=native" and AVX2 in Bug 672946, so this might be rearing its head again in a different way.
Verified on i7-6820HQ, which does have AVX2 support. So I suppose that means there's a few options:
* GCC is doing something wrong - but I have everything in world built with "-march=native" so that's unlikely.
* VirtualBox has been broken all along, but Qt 5.13 introduced new AVX2 code triggering this bug.
* Qt has a bug in its AVX2 code, or is incorrectly handling CPU feature detection.
*** Bug 718764 has been marked as a duplicate of this bug. ***
I can confirm, that i have exactly the same issue with dev-qt/qtgui-5.15.1-r1.
The whole system installed with -match=native, and re-installing qtgui with "-march=native -mno-avx2" - makes KDE to work again!