QML cross ARM SIGSEGV

poucz

Hello,
I build 5.12 from source to ARM platform (imx6).
Running console or qtwidget application is without problem.
When I try to run simply (hello world) qml app, I recieve SIGSEGV. I'm using -platform eglf but sigsegv appear with offscreen platform too.

Here is gdb output...
[0_1548830800410_qml_sigsegv](Uploading 100%)

poucz

(gdb) run
Starting program: /home/root/test3 -platform offscreen
warning: File "/lib/libthread_db-1.0.so" auto-loading has been declined by your auto-load safe-path' set to "$debugdir:$datadir/auto-load". To enable execution of this file add add-auto-load-safe-path /lib/libthread_db-1.0.so line to your configuration file "/home/root/.gdbinit". To completely disable this security protection add set auto-load safe-path / line to your configuration file "/home/root/.gdbinit". For more information about this security protection see the "Auto-loading safe path" section in the GDB manual. E.g., run from the shell: info "(gdb)Auto-loading safe path" warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available. warning: File "/usr/lib/libstdc++.so.6.0.22-gdb.py" auto-loading has been declined by your auto-load safe-path' set to "$debugdir:$datadir/auto-load".
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/var/volatile/tmp/runtime-root'
[New LWP 24680]

Thread 2 "QQmlThread" received signal SIGSEGV, Segmentation fault.
[Switching to LWP 24680]
0x7640d2dc in std::_Function_handler<QV4::CompiledData::QmlUnit* (QV4::CompiledData::QmlUnit*, unsigned int), QmlIR::QmlUnitGenerator::generate(QmlIR::Document&, std::function<bool (QCryptographicHash*)> const&)::{lambda(QV4::CompiledData::QmlUnit*, unsigned int)#2}>::_M_invoke(std::_Any_data const&, QV4::CompiledData::QmlUnit*&&, unsigned int&&) ()
from /home/root/qt/lib/libQt5Qml.so.5
(gdb) bt
#0 0x7640d2dc in std::_Function_handler<QV4::CompiledData::QmlUnit* (QV4::CompiledData::QmlUnit*, unsigned int), QmlIR::QmlUnitGenerator::generate(QmlIR::Document&, std::function<bool (QCryptographicHash*)> const&)::{lambda(QV4::CompiledData::QmlUnit*, unsigned int)#2}>::_M_invoke(std::_Any_data const&, QV4::CompiledData::QmlUnit*&&, unsigned int&&) ()
from /home/root/qt/lib/libQt5Qml.so.5
#1 0x76413dd0 in QmlIR::QmlUnitGenerator::generate(QmlIR::Document&, std::function<bool (QCryptographicHash*)> const&) () from /home/root/qt/lib/libQt5Qml.so.5
#2 0x76431c40 in QQmlTypeCompiler::compile() () from /home/root/qt/lib/libQt5Qml.so.5
#3 0x765a7748 in QQmlTypeData::compile(QQmlRefPointer<QQmlTypeNameCache> const&, QV4::CompiledData::ResolvedTypeReferenceMap const&, std::function<bool (QCryptographicHash*)> const&) () from /home/root/qt/lib/libQt5Qml.so.5
#4 0x765ae5d8 in QQmlTypeData::done() () from /home/root/qt/lib/libQt5Qml.so.5
#5 0x765a6f44 in QQmlDataBlob::tryDone() () from /home/root/qt/lib/libQt5Qml.so.5
#6 0x765a84d0 in QQmlTypeLoader::setData(QQmlDataBlob*, QQmlDataBlob::SourceCodeData const&) () from /home/root/qt/lib/libQt5Qml.so.5
#7 0x765a8e0c in QQmlTypeLoader::setData(QQmlDataBlob*, QString const&) () from /home/root/qt/lib/libQt5Qml.so.5
#8 0x765a90dc in QQmlTypeLoader::loadThread(QQmlDataBlob*) () from /home/root/qt/lib/libQt5Qml.so.5
#9 0x765a9158 in QQmlTypeLoaderThread::loadThread(QQmlDataBlob*) () from /home/root/qt/lib/libQt5Qml.so.5
#10 0x766216dc in QQmlThreadPrivate::threadEvent() () from /home/root/qt/lib/libQt5Qml.so.5
#11 0x76621d44 in QQmlThreadPrivate::event(QEvent*) () from /home/root/qt/lib/libQt5Qml.so.5
#12 0x75eeb4a0 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /home/root/qt/lib/libQt5Core.so.5
#13 0x75eee924 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /home/root/qt/lib/libQt5Core.so.5
#14 0x75f4c418 in postEventSourceDispatch(_GSource*, int ()(void), void*) () from /home/root/qt/lib/libQt5Core.so.5
#15 0x73ae6a4c in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#16 0x73ae6c78 in ?? () from /usr/lib/libglib-2.0.so.0
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

sierdzio

Can you share config line you used to build Qt?

I suspect you might have turned on JIT but it is not supported on ARM 32 bit.

Looks like the crash happens in QML compiler, that can be turned off, too.

poucz

Thank you for reply.
QT was build with:

./configure -opensource  -confirm-license  -nomake tests -nomake examples -device linux-arm-bustec-g++  -device-option  CROSS_COMPILE=arm-poky-linux-gnueabi-  -sysroot /opt/poky/2.2/sysroots/cortexa9hf-neon-poky-linux-gnueabi/ -recheck-all

and I added file: mkspect/devicelinux-arm-bustec-g++

include(../common/linux_device_pre.conf)
DISTRO_OPTS += hard-float
include(../common/linux_arm_device_post.conf)

IMX6_CFLAGS             = -march=armv7-a -mfpu=neon -DLINUX=1 -DEGL_API_FB=1
QMAKE_CFLAGS           += $$IMX6_CFLAGS
QMAKE_CXXFLAGS         += $$IMX6_CFLAGS

# modifications to g++.conf
QMAKE_CC                = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux/arm-poky-linux-gcc
QMAKE_CXX               = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux/arm-poky-linux-g++
QMAKE_LINK              = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux/arm-poky-linux-g++
QMAKE_LINK_SHLIB        = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux/arm-poky-linux-g++

# modifications to linux.conf
QMAKE_AR                = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux/arm-poky-linux-ar -r
QMAKE_OBJCOPY           = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi-objcopy
QMAKE_NM                = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi-nm
QMAKE_STRIP             = /opt/poky/2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi-strip

load(qt_config)

sierdzio

OK, nothing out of ordinary here.

Please check http://doc.qt.io/qt-5/qtquick-deployment.html to see if:

QML cache location is writable by your application
maybe you enabled QML compiler somehow - then try turning it off CONFIG-=qtquickcompiler
try running the app with QV4_FORCE_INTERPRETER env variable set - it should forcefully disable JIT (https://wiki.qt.io/V4)

Maybe this will help.

poucz

When I compile project with "CONFIG-=qtquickcompiler" - program imediatle crash

When I compile project with "CONFIG+=qtquickcompiler" - program run until I press button and try to gererate graph (ChartView)

So some partial progress is there (with CONFIG+=qtquickcompiler).
I understand this behavior because documentation said:

Your application must load the QML documents via the qrc:/// URL scheme.

So ChartView isn't in qrc. What can I do with this?
I tryed "export QV4_FORCE_INTERPRETER" with same result as above.

Any idea ?

Thank

sierdzio

No more ideas, sorry. Looks like something related to Just in Time compilation, or QML caching, but I don't know how to solve it.

Perhaps you can ask on Qt interest mailing list? https://lists.qt-project.org/ Maybe some core dev would have an idea, maybe there is some "hidden" Qt config flag that would work here.

mozcelikors

I am having the exact same problem with Qt 5.12. The issue remains unresolved. Please give us more clues how to understand the problem.
I suspect this is because of a false configuration, I tried to port Qt 5.12 to a machine (iMX8) that has Qt 5.8 available and working. That might be the cause. But how to solve it is a mystery still.