1// Copyright (C) 2016 The Qt Company Ltd.
2// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
3
4#include "qexception.h"
5#include "QtCore/qshareddata.h"
6
7#if !defined(QT_NO_EXCEPTIONS) || defined(Q_QDOC)
8
9QT_BEGIN_NAMESPACE
10
11/*!
12 \class QException
13 \inmodule QtCore
14 \brief The QException class provides a base class for exceptions that can be transferred across threads.
15 \since 5.0
16
17 Qt Concurrent supports throwing and catching exceptions across thread
18 boundaries, provided that the exception inherits from QException
19 and implements two helper functions:
20
21 \snippet code/src_corelib_thread_qexception.cpp 0
22
23 QException subclasses must be thrown by value and
24 caught by reference:
25
26 \snippet code/src_corelib_thread_qexception.cpp 1
27
28 If you throw an exception that is not a subclass of QException,
29 the \l{Qt Concurrent} functions will throw a QUnhandledException
30 in the receiver thread.
31
32 When using QFuture, transferred exceptions will be thrown when calling the following functions:
33 \list
34 \li QFuture::waitForFinished()
35 \li QFuture::result()
36 \li QFuture::resultAt()
37 \li QFuture::results()
38 \endlist
39*/
40
41/*!
42 \fn QException::raise() const
43 In your QException subclass, reimplement raise() like this:
44
45 \snippet code/src_corelib_thread_qexception.cpp 2
46*/
47
48/*!
49 \fn QException::clone() const
50 In your QException subclass, reimplement clone() like this:
51
52 \snippet code/src_corelib_thread_qexception.cpp 3
53*/
54
55/*!
56 \class QUnhandledException
57 \inmodule QtCore
58
59 \brief The QUnhandledException class represents an unhandled exception in a
60 Qt Concurrent worker thread.
61 \since 5.0
62
63 If a worker thread throws an exception that is not a subclass of QException,
64 the \l{Qt Concurrent} functions will throw a QUnhandledException on the receiver
65 thread side. The information about the actual exception that has been thrown
66 will be saved in the QUnhandledException class and can be obtained using the
67 exception() method. For example, you can process the exception held by
68 QUnhandledException in the following way:
69
70 \snippet code/src_corelib_thread_qexception.cpp 4
71
72 Inheriting from this class is not supported.
73*/
74
75/*!
76 \fn QUnhandledException::raise() const
77 \internal
78*/
79
80/*!
81 \fn QUnhandledException::clone() const
82 \internal
83*/
84
85/*!
86 Destroys this QException object.
87*/
88QException::~QException() noexcept
89{
90}
91
92/*!
93 \fn QException::QException()
94
95 Constructs a QException object.
96*/
97
98/*!
99 \fn QException::QException(const QException &other)
100
101 Creates a copy of \a other.
102
103 \note Be careful when using this function, as you risk slicing.
104
105 \sa clone()
106*/
107
108/*!
109 \fn QException &QException::operator=(const QException &other)
110
111 Copy-assigns \a other over this object.
112
113 \note Be careful when using this function, as you risk slicing.
114*/
115
116void QException::raise() const
117{
118 QException e = *this;
119 throw e;
120}
121
122QException *QException::clone() const
123{
124 return new QException(*this);
125}
126
127class QUnhandledExceptionPrivate : public QSharedData
128{
129public:
130 QUnhandledExceptionPrivate(std::exception_ptr exception) noexcept : exceptionPtr(exception) { }
131 std::exception_ptr exceptionPtr;
132};
133
134/*!
135 \fn QUnhandledException::QUnhandledException(std::exception_ptr exception = nullptr) noexcept
136 \since 6.0
137
138 Constructs a new QUnhandledException object. Saves the pointer to the actual
139 exception object if \a exception is passed.
140
141 \sa exception()
142*/
143QUnhandledException::QUnhandledException(std::exception_ptr exception) noexcept
144 : d(new QUnhandledExceptionPrivate(exception))
145{
146}
147
148/*!
149 Move-constructs a QUnhandledException, making it point to the same
150 object as \a other was pointing to.
151*/
152QUnhandledException::QUnhandledException(QUnhandledException &&other) noexcept
153 : d(std::exchange(obj&: other.d, new_val: {}))
154{
155}
156
157/*!
158 Constructs a QUnhandledException object as a copy of \a other.
159*/
160QUnhandledException::QUnhandledException(const QUnhandledException &other) noexcept
161 : d(other.d)
162{
163}
164
165/*!
166 Assigns \a other to this QUnhandledException object and returns a reference
167 to this QUnhandledException object.
168*/
169QUnhandledException &QUnhandledException::operator=(const QUnhandledException &other) noexcept
170{
171 d = other.d;
172 return *this;
173}
174
175/*!
176 \fn void QUnhandledException::swap(QUnhandledException &other)
177 \since 6.0
178 \memberswap{unhandled exception object}
179*/
180
181/*!
182 \since 6.0
183
184 Returns a \l{https://en.cppreference.com/w/cpp/error/exception_ptr}{pointer} to
185 the actual exception that has been saved in this QUnhandledException. Returns a
186 \c null pointer, if it does not point to an exception object.
187*/
188std::exception_ptr QUnhandledException::exception() const
189{
190 return d->exceptionPtr;
191}
192
193QUnhandledException::~QUnhandledException() noexcept
194{
195}
196
197void QUnhandledException::raise() const
198{
199 QUnhandledException e = *this;
200 throw e;
201}
202
203QUnhandledException *QUnhandledException::clone() const
204{
205 return new QUnhandledException(*this);
206}
207
208#if !defined(Q_QDOC)
209
210namespace QtPrivate {
211
212void ExceptionStore::setException(const QException &e)
213{
214 Q_ASSERT(!hasException());
215 try {
216 e.raise();
217 } catch (...) {
218 exceptionHolder = std::current_exception();
219 }
220}
221
222void ExceptionStore::setException(std::exception_ptr e)
223{
224 Q_ASSERT(!hasException());
225 exceptionHolder = e;
226}
227
228bool ExceptionStore::hasException() const
229{
230 return !!exceptionHolder;
231}
232
233std::exception_ptr ExceptionStore::exception() const
234{
235 return exceptionHolder;
236}
237
238void ExceptionStore::throwPossibleException()
239{
240 if (hasException())
241 std::rethrow_exception(exceptionHolder);
242}
243
244void ExceptionStore::rethrowException() const
245{
246 Q_ASSERT(hasException());
247 std::rethrow_exception(exceptionHolder);
248}
249
250} // namespace QtPrivate
251
252#endif //Q_QDOC
253
254QT_END_NAMESPACE
255
256#endif // QT_NO_EXCEPTIONS
257

source code of qtbase/src/corelib/thread/qexception.cpp