Eclipse IDE (Oracle OUAF SDK 25.4 bundle, Eclipse 4.40 / SWT 3.134.0) aborts on Fedora 45 whenever SWT initializes the internal browser. The crash is entirely inside WebKit — no Eclipse or SWT frame is involved beyond the JNI entry point.

The same Eclipse installation, unchanged, worked on Fedora 44.

Source/WTF/wtf/MainThread.cpp:47
RELEASE_ASSERT(!isMainThread() || Thread::currentSingleton().uid() == 1);

42      static std::once_flag initializeKey;
43      std::call_once(initializeKey, [] {
44          initialize();
45          initializeMainThreadPlatform();
46          RunLoop::initializeMain();
47          RELEASE_ASSERT(!isMainThread() || Thread::currentSingleton().uid() == 1);
48      });
49  }

BackTrace:

#0  __pthread_kill_implementation () at pthread_kill.c:44
#1  __pthread_kill_internal () at pthread_kill.c:89
#2  __GI_raise (sig=6) at ../sysdeps/posix/raise.c:26
#3  __GI_abort () at abort.c:77
#4  WTFCrashWithInfo () at WTF/Headers/wtf/Assertions.h:1057
#5  WTF::initializeMainThread()::$_0::operator()() const
      at /usr/src/debug/webkitgtk-2.53.91-1.fc45.x86_64/Source/WTF/wtf/MainThread.cpp:47
#6  std::__invoke_impl<...>   at include/c++/16/bits/invoke.h:63
#7  std::__invoke<...>        at include/c++/16/bits/invoke.h:98
#8  std::call_once<...>       at include/c++/16/mutex:916
#9  std::once_flag::_Prepare_execution<...>  at include/c++/16/mutex:849
#10 std::once_flag::_Prepare_execution<...>::__invoke ()  at include/c++/16/mutex:849
#11 __pthread_once_slow () at pthread_once.c:116
#12 WebKit::webkitInitialize()  (libwebkit2gtk-4.1.so.0)
#13 __pthread_once_slow () at pthread_once.c:116
#14 webkit_web_context_class_intern_init  (libwebkit2gtk-4.1.so.0)
#15 g_type_class_get           (libgobject-2.0.so.0)
#16 g_object_new_with_properties (libgobject-2.0.so.0)
#17 g_object_new               (libgobject-2.0.so.0)
#18 createDefaultWebContext    (libwebkit2gtk-4.1.so.0)
#19 g_once_impl                (libglib-2.0.so.0)
#20 Java_org_eclipse_swt_internal_webkit_WebKitGTK_webkit_1web_1context_1get_1default
      (libswt-webkit-gtk-4973r12.so)

Reproducible: Always

Steps to Reproduce:
1. Install Fedora 45 (branched, upgraded from F44 via dnf system-upgrade)
2. Ensure webkit2gtk4.1-2.53.91-1.fc45 is installed
3. Launch any SWT-based Eclipse IDE (tested: Eclipse 4.40 / SWT 3.134.0)
4. Trigger anything that instantiates an SWT Browser widget — javadoc
   tooltip on hover, Help view, internal browser, or the welcome page
Actual Results:
The JVM aborts (SIGABRT). The crash is inside WebKit, in
WTF::initializeMainThread at Source/WTF/wtf/MainThread.cpp:47:

  RELEASE_ASSERT(!isMainThread() || Thread::currentSingleton().uid() == 1);

Analysis of the core shows the crashing thread is LWP 43927 while the
process's original thread (TID == PID) is LWP 43926. WebKit is being
initialized on the SWT/GTK UI thread, which the JVM creates after process
startup, so it can never have uid 1. This appears structural for any JVM
application: SWT always runs GTK on a thread it creates.

Removing webkit2gtk4.1 lets Eclipse start, but every SWT Browser-based
view is then non-functional. Neither state is a working configuration.

Expected Results:
WebKit initializes successfully when a GTK application calls
webkit_web_context_get_default() from its UI thread, as it did with the
Fedora 44 build of the same code.

Additional Information:
Ruled Out:
JVM version — reproduced identically with the bundled JustJ JRE 21.0.12 and with java-25-openjdk 25.0.4.1.1
SELinux — ausearch -m avc -ts recent returns no matches; reproduced with setenforce 0
WebKit rendering options — reproduced with WEBKIT_DISABLE_COMPOSITING_MODE=1 and WEBKIT_DISABLE_DMABUF_RENDERER=1
SWT browser selection — reproduced with -Dorg.eclipse.swt.browser.DefaultType=none (confirmed present in the crashed process's command line)
WebKit version — reproduced on both 2.53.90-1.fc45 and 2.53.91-1.fc45
LD_PRELOAD of libwebkit2gtk-4.1.so.0 — does not change the outcome