Store std::exception_ptr in QUnhandledException

For historical reasons Qt Concurrent reports QUnhandledException in
case if an exception that is not derived from QException is thrown
from a worker thread. Changing this behavior may not be a good idea,
since the existing user code may rely on it. Changed QUnhandledException
to wrap the std::exception_ptr to the actual exception, so that the
users can obtain the information about the thrown exception if needed.

[ChangeLog][QtCore][QUnhandledException] Improved QUnhandledException to
store the std::exception_ptr to the actual exception thrown from a
QtCocnurrent worker thread.

Change-Id: I30e7c1d3e01aff6e1ed9938c421da0a888f12066
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/corelib/doc/snippets/code/src_corelib_thread_qexception.cpp b/src/corelib/doc/snippets/code/src_corelib_thread_qexception.cpp
index 723c1630f6..08bbee7dd3 100644
--- a/src/corelib/doc/snippets/code/src_corelib_thread_qexception.cpp
+++ b/src/corelib/doc/snippets/code/src_corelib_thread_qexception.cpp
@@ -83,3 +83,19 @@ void MyException::raise() const { throw *this; }
 MyException *MyException::clone() const { return new MyException(*this); }
 
 //! [3]
+
+//! [4]
+
+try {
+    auto f = QtConcurrent::run([] { throw MyException {}; });
+    // ...
+} catch (const QUnhandledException &e) {
+    try {
+        if (e.exception())
+            std::rethrow_exception(e.exception());
+    } catch (const MyException &ex) {
+        // Process 'ex'
+    }
+}
+
+//! [4]