SUMMARY kwin_x11 crashes when the pressing alt-tab. Doing one alt-tab quickly, releasing both buttons fast, is fine. Holding alt and just clicking tab causes a crash. STEPS TO REPRODUCE 1. Log in to Plasma 2. Open a few applications 3. Hold Alt and click tab. OBSERVED RESULT kwin_x11 crashes (and restarts immediately). EXPECTED RESULT No crash. SOFTWARE/OS VERSIONS Linux/KDE Plasma: (available in About System) KDE Plasma Version: 5.15.4 KDE Frameworks Version: 5.57.0 Qt Version: 5.12.0 ADDITIONAL INFORMATION Distribution: Nixos 19.04 I'm updating the KDE packages for the distribution and testing their stability. $ valgrind kwin_x11 --replace ==26137== Memcheck, a memory error detector ==26137== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==26137== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info ==26137== Command: kwin_x11 --replace ==26137== --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 --26137-- Warning: DWARF2 CFI reader: unhandled DW_OP_ opcode 0x13 ==26137== Warning: set address range perms: large range [0x59c92000, 0xd9c92000) (defined) qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 2707, resource id: 115343413, major code: 3 (GetWindowAttributes), minor code: 0 qt.qpa.xcb: QXcbConnection: XCB error: 9 (BadDrawable), sequence: 2708, resource id: 115343413, major code: 14 (GetGeometry), minor code: 0 ==26137== Thread 5 QQmlThread: ==26137== Invalid read of size 8 ==26137== at 0x589A630: QQmlType::QQmlType(QQmlType const&) (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x574057C: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x57430F7: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x574330D: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x574330D: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x573E663: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x58B29EA: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x58B9FD0: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x58B20CB: QQmlDataBlob::tryDone() (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x58B37FD: QQmlTypeLoader::setData(QQmlDataBlob*, QQmlDataBlob::SourceCodeData const&) (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x58B4069: QQmlTypeLoader::setData(QQmlDataBlob*, QString const&) (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x58B421A: QQmlTypeLoader::loadThread(QQmlDataBlob*) (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== Address 0x0 is not stack'd, malloc'd or (recently) free'd ==26137== Application::crashHandler() called with signal 11; recent crashes: 1 KCrash: Application 'kwin_x11' crashing... ==26137== ==26137== Process terminating with default action of signal 11 (SIGSEGV) ==26137== at 0x65CE6FE: raise (in /nix/store/681354n3k44r8z90m35hm8945vsp95h1-glibc-2.27/lib/libpthread-2.27.so) ==26137== by 0x68E9D1B: KCrash::defaultCrashHandler(int) (in /nix/store/0flfn51m256k9h1y8xfjk9hfgkfy8cnp-kcrash-5.57.0/lib/libKF5Crash.so.5.57.0) ==26137== by 0x80E0C4F: ??? (in /nix/store/681354n3k44r8z90m35hm8945vsp95h1-glibc-2.27/lib/libc-2.27.so) ==26137== by 0x589A62F: ??? (in /nix/store/sr4ilb47rksml5sx5n8za0pk2sc9wb14-qtdeclarative-5.12.0/lib/libQt5Qml.so.5.12.0) ==26137== by 0x1700F4D7: ??? ==26137== by 0xBF8A4CF: ??? ==26137== by 0x179A9BDF: ??? ==26137== ==26137== HEAP SUMMARY: ==26137== in use at exit: 9,859,388 bytes in 79,966 blocks ==26137== total heap usage: 424,540 allocs, 344,574 frees, 128,310,614 bytes allocated ==26137== qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 178, resource id: 115343367, major code: 20 (GetProperty), minor code: 0 qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 179, resource id: 115343367, major code: 20 (GetProperty), minor code: 0 qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 2722, resource id: 52428853, major code: 3 (GetWindowAttributes), minor code: 0 qt.qpa.xcb: QXcbConnection: XCB error: 9 (BadDrawable), sequence: 2723, resource id: 52428853, major code: 14 (GetGeometry), minor code: 0 ==26137== LEAK SUMMARY: ==26137== definitely lost: 480 bytes in 29 blocks ==26137== indirectly lost: 39 bytes in 2 blocks ==26137== possibly lost: 119,027 bytes in 564 blocks ==26137== still reachable: 9,739,842 bytes in 79,371 blocks ==26137== of which reachable via heuristic: ==26137== newarray : 173,192 bytes in 86 blocks ==26137== suppressed: 0 bytes in 0 blocks ==26137== Rerun with --leak-check=full to see details of leaked memory ==26137== ==26137== For counts of detected and suppressed errors, rerun with: -v ==26137== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 24 from 1) Segmentation fault
Can you attach backtrace of the crash?
After upgrading Qt from 5.12.0 to 5.12.3, the bug was gone. Setting to WORKSFORME because I do not know what fixed it.
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