core/doc/uncaught_exceptions.qbk
Andrey Semashev 82957de970 Extracted uncaught_exceptions function from Boost.Log.
The uncaught_exceptions function is functionally equivalent to
unhandled_exceptions_count in Boost.Log and implements functionality
similar to the same named C++17 standard function. Tests and docs are
also included.

One notable difference from std::uncaught_exceptions is that the return
type is unsigned rather than signed. This is deliberate as uncaught_exceptions
must never return a negative value and unsigned int better documents that.
Theoretically, as a counter, it may also overflow.
2018-11-10 17:44:13 +03:00

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[/
/ Copyright (c) 2018 Andrey Semashev
/
/ Distributed under the Boost Software License, Version 1.0. (See accompanying
/ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
/]
[section:uncaught_exceptions uncaught_exceptions]
[simplesect Authors]
* Andrey Semashev
[endsimplesect]
[section Header <boost/core/uncaught_exceptions.hpp>]
The header `<boost/core/uncaught_exceptions.hpp>` defines the `boost::core::uncaught_exceptions` function,
which is a more portable implementation of the same named function introduced in C++17. The function
returns the number of the currently pending exceptions. When that function returns a value greater than 0,
throwing an exception from a destructor can terminate the program.
Unfortunately, the function cannot be implemented on every pre-C++17 compiler, although the most commonly
used compilers are supported. When the compiler does not provide the necessary functionality,
`boost::core::uncaught_exceptions` returns a non-zero value if at least one exception is pending (i.e. not
necessarily the number of pending exceptions), and `BOOST_CORE_UNCAUGHT_EXCEPTIONS_EMULATED` macro
is defined.
[section Example]
``
class my_class
{
private:
const unsigned int m_exception_count;
public:
my_class() : m_exception_count(boost::core::uncaught_exceptions())
{
}
~my_class() noexcept(false)
{
if (m_exception_count == boost::core::uncaught_exceptions())
do_something_potentially_throwing();
}
};
``
[endsect]
[endsect]
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