[okular] [Bug 424522] New: dynamic_cast<Okular::ViewerInterface *>(activePart) is null

[12101111]

https://bugs.kde.org/show_bug.cgi?id=424522

            Bug ID: 424522
           Summary: dynamic_cast<Okular::ViewerInterface *>(activePart) is
                    null
           Product: okular
           Version: unspecified
          Platform: Gentoo Packages
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: okular-devel at kde.org
          Reporter: w12101111 at outlook.com
  Target Milestone: ---

SUMMARY

In shell/shell.cpp, Shell::openUrl(),
`dynamic_cast<Okular::ViewerInterface *>(activePart)` is null and cause
segmentation fault.

STEPS TO REPRODUCE
(1)
1. Launch okular
2. Open a pdf file
3. Press ctrl-o to open another pdf
4. Okular crash
(2)
1. Set Okular as default pdf viewer
2. Open a pdf file in Dolphin
3. Okular crash

OBSERVED RESULT

backtrace:

#4  Shell::openUrl (this=0x11b99a0, url=..., serializedOptions=...) at
../okular-20.04.3/shell/shell.cpp:276
#5  0x00000000002195e3 in Shell::fileOpen (this=<optimized out>) at
../okular-20.04.3/shell/shell.cpp:501
#6  0x00007f689c89c8b7 in ?? () from /usr/lib64/libQt5Core.so.5
#7  0x00007f689d2e9b4c in QAction::activate(QAction::ActionEvent) () from
/usr/lib64/libQt5Widgets.so.5
#8  0x00007f689d2e9959 in QAction::event(QEvent*) () from
/usr/lib64/libQt5Widgets.so.5
#9  0x00007f689d2f3260 in QApplicationPrivate::notify_helper(QObject*, QEvent*)
() from /usr/lib64/libQt5Widgets.so.5
#10 0x00007f689d2f46b0 in QApplication::notify(QObject*, QEvent*) () from
/usr/lib64/libQt5Widgets.so.5
#11 0x00007f689c869242 in QCoreApplication::notifyInternal2(QObject*, QEvent*)
() from /usr/lib64/libQt5Core.so.5
#12 0x00007f689cc35015 in QShortcutMap::dispatchEvent(QKeyEvent*) () from
/usr/lib64/libQt5Gui.so.5
#13 0x00007f689cc341f3 in QShortcutMap::tryShortcut(QKeyEvent*) () from
/usr/lib64/libQt5Gui.so.5
#14 0x00007f689cbe4292 in QWindowSystemInterface::handleShortcutEvent(QWindow*,
unsigned long, int, QFlags<Qt::KeyboardModifier>, unsigned int, unsigned int,
unsigned int, QString const&, bool, unsigned short) () from
/usr/lib64/libQt5Gui.so.5
#15 0x00007f689cc04bdd in
QGuiApplicationPrivate::processKeyEvent(QWindowSystemInterfacePrivate::KeyEvent*)
() from /usr/lib64/libQt5Gui.so.5
#16 0x00007f689cbe895a in
QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>)
() from /usr/lib64/libQt5Gui.so.5
#17 0x00007f68983db93a in ?? () from /usr/lib64/libQt5XcbQpa.so.5
#18 0x00007f6899290e39 in g_main_context_dispatch () from
/usr/lib64/libglib-2.0.so.0
#19 0x00007f6899291563 in ?? () from /usr/lib64/libglib-2.0.so.0
#20 0x00007f689929181b in g_main_context_iteration () from
/usr/lib64/libglib-2.0.so.0
#21 0x00007f689c8c1018 in
QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
from /usr/lib64/libQt5Core.so.5
#22 0x00007f689c865076 in
QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from
/usr/lib64/libQt5Core.so.5
#23 0x00007f689c869831 in QCoreApplication::exec() () from
/usr/lib64/libQt5Core.so.5
#24 0x0000000000211c12 in main (argc=1, argv=<optimized out>) at
../okular-20.04.3/shell/main.cpp:113

Add a hack to this function:

diff --git a/shell/shell.cpp b/shell/shell.cpp
index 5d218e28d..f6c84b6d9 100644
--- a/shell/shell.cpp
+++ b/shell/shell.cpp
@@ -257,7 +257,11 @@ void Shell::openUrl(const QUrl &url, const QString
&serializedOptions)
                 applyOptionsToPart(activePart, serializedOptions);
                 activePart->openUrl(url);
             } else {
-                if (dynamic_cast<Okular::ViewerInterface
*>(activePart)->openNewFilesInTabs()) {
+                Okular::ViewerInterface * vi =
dynamic_cast<Okular::ViewerInterface *>(activePart);
+                if ( ! vi) {
+                    printf("vi is null, activePart: %p\n", activePart);
+                }
+                if (vi && vi ->openNewFilesInTabs()) {
                     openNewTab(url, serializedOptions);
                 } else {
                     Shell *newShell = new Shell(serializedOptions);

And recompile it, open some pdfs, the output is:

kf5.kio.kdirmodel: protocol mismatch: "" vs "file"
kf5.kio.kdirmodel: protocol mismatch: "" vs "file"
vi is null, activePart: 0x1d7f840
Settings::instance called after the first use - ignoring
kf5.kio.kdirmodel: protocol mismatch: "" vs "file"
vi is null, activePart: 0x2118470
Settings::instance called after the first use - ignoring
kf5.kio.kdirmodel: protocol mismatch: "" vs "file"
vi is null, activePart: 0x23dcf60
Settings::instance called after the first use - ignoring

So this dynamic_cast is failed.

EXPECTED RESULT

It should not crash

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.19.3
KDE Frameworks Version: 5.72.0
Qt Version: 5.15.0

ADDITIONAL INFORMATION

I have try gentoo ebuild kde-apps/okular-20.04.3 and source code from git
master branch.

I use clang + lld + libc++ as primary toolchain:

CC="clang"
CXX="clang++"
COMMON_FLAGS="-march=skylake -mtune=skylake -O2 -pipe -g"
CFLAGS="${COMMON_FLAGS}"
CXXFLAGS="${COMMON_FLAGS} -stdlib=libc++"
LDFLAGS="-fuse-ld=lld -rtlib=compiler-rt -unwindlib=libunwind"

I think this bug only happend with libcxx and libcxxabi

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