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Renamed boost::swap to boost::core::invoke_swap, deprecated boost::swap.

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The rename allows to avoid forming an infinite recursion in compile time
(because of noexcept specification that needs to resolve the unqualified call
to swap) or run time (in case if the boost::swap function is the only one
suitable for the passed arguments).

To avoid the compile-time recursion, removed noexcept specification from
boost::swap. The specification is still present in boost::core::invoke_swap.

Deprecated boost::swap and associated headers. boost::core::invoke_swap
is defined in a new boost/core/invoke_swap.hpp header.

Updated docs and tests. Removed tests that check inclusion of deprecated
headers.

Fixes https://github.com/boostorg/core/issues/148.
This commit is contained in:
Andrey Semashev
2023-07-12 12:17:07 +03:00
parent 216999e552
commit 9fc2a2f1ac
34 changed files with 214 additions and 192 deletions
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doc/changes.qbk
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@@ -1,12 +1,29 @@
[/
Copyright 2021 Peter Dimov
Copyright 2022 Andrey Semashev
Copyright 2022-2023 Andrey Semashev
Distributed under the Boost Software License, Version 1.0.
https://boost.org/LICENSE_1_0.txt)
]
[section Revision History]
[section Changes in 1.84.0]
* `boost::swap` utility function has been renamed to `boost::core::invoke_swap` to
avoid forming a potential infinite recursion when the arguments are not swappable.
The new function is defined in `boost/core/invoke_swap.hpp` and is functionally equivalent
to `boost::swap`. The old `boost::swap` name is preserved for backward compatibility
but deprecated and will be removed in a future release. Its `noexcept` specification
has been removed to avoid compile errors caused by compile-time recursion.
`BOOST_ALLOW_DEPRECATED_SYMBOLS` or `BOOST_ALLOW_DEPRECATED` can be defined to suppress
deprecation warnings for the transition period. ([@https://github.com/boostorg/core/issues/148 #148])
* Headers `boost/swap.hpp`, `boost/utility/swap.hpp` and `boost/core/swap.hpp` are
deprecated and will be removed. Please, switch to `boost/core/invoke_swap.hpp`.
`BOOST_ALLOW_DEPRECATED_HEADERS` or `BOOST_ALLOW_DEPRECATED` can be defined to suppress
deprecation warnings.
[endsect]
[section Changes in 1.83.0]
* Added support for incomplete types to [link core.type_name `boost::core::type_name`].
doc/swap.qbk
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@@ -20,17 +20,17 @@
[endsimplesect]
[section Header <boost/core/swap.hpp>]
[section Header <boost/core/invoke_swap.hpp>]
[^template<class T> void swap(T& left, T& right) noexcept(['see below]);]
[^template<class T> void invoke_swap(T& left, T& right) noexcept(['see below]);]
[endsect]
[section Introduction]
The template function `boost::swap` allows the values of two
variables to be swapped, using argument dependent lookup to
select a specialized swap function if available. If no
The template function `boost::core::invoke_swap` allows the
values of two variables to be swapped, using argument dependent
lookup to select a specialized swap function if available. If no
specialized swap function is available, `std::swap` is used.
[endsect]
@@ -56,9 +56,9 @@ Although this is legal C++, no Boost libraries use this method,
whereas many Boost libraries provide specialized swap functions
in their own namespaces.
`boost::swap` also supports swapping built-in arrays. Note that
`std::swap` originally did not do so, but a request to add an
overload of `std::swap` for built-in arrays has been accepted
`boost::core::invoke_swap` also supports swapping built-in arrays.
Note that `std::swap` originally did not do so, but a request to
add an overload of `std::swap` for built-in arrays has been accepted
by the C++ Standards Committee[footnote
[@http://open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#809
LWG Defect Report 809: std::swap should be overloaded for array
@@ -68,14 +68,15 @@ by the C++ Standards Committee[footnote
[section Exception Safety]
`boost::swap` provides the same exception guarantee as the
underlying swap function used, with one exception; for an array
`boost::core::invoke_swap` provides the same exception guarantee as
the underlying swap function used, with one exception; for an array
of type `T[n]`, where `n > 1` and the underlying swap function
for `T` provides the strong exception guarantee, `boost::swap`
provides only the basic exception guarantee.
for `T` provides the strong exception guarantee,
`boost::core::invoke_swap` provides only the basic exception guarantee.
In C++11 and later, `boost::swap` propagates the same `noexcept`
specification as the one specified in the underlying swap function.
In C++11 and later, `boost::core::invoke_swap` propagates the same
`noexcept` specification as the one specified in the underlying swap
function.
[endsect]
@@ -104,7 +105,7 @@ Or:
[section Portability]
Several older compilers do not support argument dependent
lookup. On these compilers `boost::swap` will call
lookup. On these compilers `boost::core::invoke_swap` will call
`std::swap`, ignoring any specialized swap functions that
could be found as a result of argument dependent lookup.
@@ -118,7 +119,9 @@ could be found as a result of argument dependent lookup.
tests, and documentation
* *Steven Watanabe* - for the idea to make `boost::swap` less
specialized than `std::swap`, thereby allowing the function
to have the name 'swap' without introducing ambiguity
to have the name 'swap' without introducing ambiguity. However,
later the function was renamed to `boost::core::invoke_swap`
to avoid potential infinite recursion.
[endsect]