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
85QException::~QException() noexcept
86{
87}
88
89void QException::raise() const
90{
91 QException e = *this;
92 throw e;
93}
94
95QException *QException::clone() const
96{
97 return new QException(*this);
98}
99
100class QUnhandledExceptionPrivate : public QSharedData
101{
102public:
103 QUnhandledExceptionPrivate(std::exception_ptr exception) noexcept : exceptionPtr(exception) { }
104 std::exception_ptr exceptionPtr;
105};
106
107/*!
108 \fn QUnhandledException::QUnhandledException(std::exception_ptr exception = nullptr) noexcept
109 \since 6.0
110
111 Constructs a new QUnhandledException object. Saves the pointer to the actual
112 exception object if \a exception is passed.
113
114 \sa exception()
115*/
116QUnhandledException::QUnhandledException(std::exception_ptr exception) noexcept
117 : d(new QUnhandledExceptionPrivate(exception))
118{
119}
120
121/*!
122 Move-constructs a QUnhandledException, making it point to the same
123 object as \a other was pointing to.
124*/
125QUnhandledException::QUnhandledException(QUnhandledException &&other) noexcept
126 : d(std::exchange(obj&: other.d, new_val: {}))
127{
128}
129
130/*!
131 Constructs a QUnhandledException object as a copy of \a other.
132*/
133QUnhandledException::QUnhandledException(const QUnhandledException &other) noexcept
134 : d(other.d)
135{
136}
137
138/*!
139 Assigns \a other to this QUnhandledException object and returns a reference
140 to this QUnhandledException object.
141*/
142QUnhandledException &QUnhandledException::operator=(const QUnhandledException &other) noexcept
143{
144 d = other.d;
145 return *this;
146}
147
148/*!
149 \fn void QUnhandledException::swap(QUnhandledException &other)
150 \since 6.0
151
152 Swaps this QUnhandledException with \a other. This function is very fast and
153 never fails.
154*/
155
156/*!
157 \since 6.0
158
159 Returns a \l{https://en.cppreference.com/w/cpp/error/exception_ptr}{pointer} to
160 the actual exception that has been saved in this QUnhandledException. Returns a
161 \c null pointer, if it does not point to an exception object.
162*/
163std::exception_ptr QUnhandledException::exception() const
164{
165 return d->exceptionPtr;
166}
167
168QUnhandledException::~QUnhandledException() noexcept
169{
170}
171
172void QUnhandledException::raise() const
173{
174 QUnhandledException e = *this;
175 throw e;
176}
177
178QUnhandledException *QUnhandledException::clone() const
179{
180 return new QUnhandledException(*this);
181}
182
183#if !defined(Q_QDOC)
184
185namespace QtPrivate {
186
187void ExceptionStore::setException(const QException &e)
188{
189 Q_ASSERT(!hasException());
190 try {
191 e.raise();
192 } catch (...) {
193 exceptionHolder = std::current_exception();
194 }
195}
196
197void ExceptionStore::setException(std::exception_ptr e)
198{
199 Q_ASSERT(!hasException());
200 exceptionHolder = e;
201}
202
203bool ExceptionStore::hasException() const
204{
205 return !!exceptionHolder;
206}
207
208std::exception_ptr ExceptionStore::exception() const
209{
210 return exceptionHolder;
211}
212
213void ExceptionStore::throwPossibleException()
214{
215 if (hasException())
216 std::rethrow_exception(exceptionHolder);
217}
218
219void ExceptionStore::rethrowException() const
220{
221 Q_ASSERT(hasException());
222 std::rethrow_exception(exceptionHolder);
223}
224
225} // namespace QtPrivate
226
227#endif //Q_QDOC
228
229QT_END_NAMESPACE
230
231#endif // QT_NO_EXCEPTIONS
232

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