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Propagate noexcept specification in boost::swap.

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Mark boost::swap noexcept if the type supports non-throwing swap
implementation.
This commit is contained in:
Andrey Semashev
2023-01-07 01:52:02 +03:00
parent 99f9654f18
commit 8a8738a981
5 changed files with 88 additions and 25 deletions
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include/boost/core/swap.hpp
+22 -7
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@@ -13,10 +13,10 @@
// - swap_impl is put outside the boost namespace, to avoid infinite
// recursion (causing stack overflow) when swapping objects of a primitive
// type.
// - swap_impl has a using-directive, rather than a using-declaration,
// because some compilers (including MSVC 7.1, Borland 5.9.3, and
// Intel 8.1) don't do argument-dependent lookup when it has a
// using-declaration instead.
// - std::swap is imported with a using-directive, rather than
// a using-declaration, because some compilers (including MSVC 7.1,
// Borland 5.9.3, and Intel 8.1) don't do argument-dependent lookup
// when it has a using-declaration instead.
// - boost::swap has two template arguments, instead of one, to
// avoid ambiguity when swapping objects of a Boost type that does
// not have its own boost::swap overload.
@@ -30,6 +30,13 @@
#endif
#include <cstddef> // for std::size_t
#if defined(BOOST_GCC) && (BOOST_GCC < 40700)
// gcc 4.6 ICEs on noexcept specifications below
#define BOOST_CORE_SWAP_NOEXCEPT_IF(x)
#else
#define BOOST_CORE_SWAP_NOEXCEPT_IF(x) BOOST_NOEXCEPT_IF(x)
#endif
namespace boost_swap_impl
{
// we can't use type_traits here
@@ -37,17 +44,22 @@ namespace boost_swap_impl
template<class T> struct is_const { enum _vt { value = 0 }; };
template<class T> struct is_const<T const> { enum _vt { value = 1 }; };
// Use std::swap if argument dependent lookup fails.
// We need to have this at namespace scope to be able to use unqualified swap() call
// in noexcept specification.
using namespace std;
template<class T>
BOOST_GPU_ENABLED
void swap_impl(T& left, T& right)
void swap_impl(T& left, T& right) BOOST_CORE_SWAP_NOEXCEPT_IF(BOOST_NOEXCEPT_EXPR(swap(left, right)))
{
using namespace std;//use std::swap if argument dependent lookup fails
swap(left,right);
swap(left, right);
}
template<class T, std::size_t N>
BOOST_GPU_ENABLED
void swap_impl(T (& left)[N], T (& right)[N])
BOOST_CORE_SWAP_NOEXCEPT_IF(BOOST_NOEXCEPT_EXPR(::boost_swap_impl::swap_impl(left[0], right[0])))
{
for (std::size_t i = 0; i < N; ++i)
{
@@ -62,9 +74,12 @@ namespace boost
BOOST_GPU_ENABLED
typename enable_if_c< !boost_swap_impl::is_const<T1>::value && !boost_swap_impl::is_const<T2>::value >::type
swap(T1& left, T2& right)
BOOST_CORE_SWAP_NOEXCEPT_IF(BOOST_NOEXCEPT_EXPR(::boost_swap_impl::swap_impl(left, right)))
{
::boost_swap_impl::swap_impl(left, right);
}
}
#undef BOOST_CORE_SWAP_NOEXCEPT_IF
#endif