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fixed defaulted moves on older compilers

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This commit is contained in:
Andrzej Krzemienski
2017-11-06 20:15:15 +01:00
parent 40f7c97292
commit 7541076cf1
4 changed files with 12 additions and 10 deletions
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2
doc/1A_on_performance.qbk
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@ -19,7 +19,7 @@ Lifetime of the `T` inside `_storage` is manually controlled with placement-`new
T _storage;
};
We call it a ['direct] storage. This makes `optional<T>` a trivially-copyable type for scalar `T`s. This only works for compilers that support defaulted functions. On compilers without defaulted functions we still use the direct storage, but `optional<T>` is no longer recognized as trivially-copyable. Apart from scalar types, we leave the programmer a way of customizing her type, so that it is reconized by `optional` as candidate for optimized storage, by specializing type trait `boost::opitonal_config::optional_uses_direct_storage_for`:
We call it a ['direct] storage. This makes `optional<T>` a trivially-copyable type for scalar `T`s. This only works for compilers that support defaulted functions (including defaulted move assignment and constructor). On compilers without defaulted functions we still use the direct storage, but `optional<T>` is no longer recognized as trivially-copyable. Apart from scalar types, we leave the programmer a way of customizing her type, so that it is reconized by `optional` as candidate for optimized storage, by specializing type trait `boost::opitonal_config::optional_uses_direct_storage_for`:
struct X // not trivial
{

12
include/boost/optional/detail/optional_config.hpp
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@ -114,14 +114,16 @@
#endif
// Detection of correctly implemented defaulted functions
// Detect suport for defaulting move operations
// (some older compilers implement rvalue references,
// defaulted funcitons but move operations are not special members and cannot be defaulted)
#ifdef BOOST_NO_CXX11_DEFAULTED_FUNCTIONS
# define BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_FUNCTIONS
# define BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
#elif BOOST_WORKAROUND(BOOST_MSVC, < 1900)
// on MSVC 12.0 move constructor and move assignment are not reconized as special functions
// and they cannot be defaulted
# define BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_FUNCTIONS
# define BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
#elif BOOST_WORKAROUND(BOOST_GCC_VERSION, < 40600)
# define BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
#endif

4
test/optional_test_experimental_traits.cpp
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@ -20,7 +20,7 @@
#include "boost/type_traits/is_base_of.hpp"
#include "boost/optional/detail/experimental_traits.hpp"
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_FUNCTIONS
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
struct PrivDefault
{
@ -144,7 +144,7 @@ void test_trivial_copyability()
int main()
{
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_FUNCTIONS
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
test_type_traits();
test_trivial_copyability();
#endif

4
test/optional_test_static_properties.cpp
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@ -20,7 +20,7 @@
#include "boost/type_traits/is_base_of.hpp"
#include "boost/optional/detail/experimental_traits.hpp"
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_FUNCTIONS
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
struct PrivDefault
{
@ -138,7 +138,7 @@ void test_trivial_copyability()
int main()
{
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_FUNCTIONS
#ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
test_type_traits();
test_trivial_copyability();
#endif