From cb1e6af53d48aeb32c3c41314763e781e9859599 Mon Sep 17 00:00:00 2001
From: "Pavel A. Lebedev" <cygnus@michiru.ru>
Date: Wed, 30 Dec 2020 08:28:06 +0300
Subject: [PATCH] Add conditional noexcept forwarding from free to member swap
 functions.

This allows std::is_nothrow_swappable{,_with} to work properly.
This only touches user-facing classes, with the following exceptions:
- map,set: only doc changes (with a drive-by missing semicolon fix),
  detail::tree which they derive from already forwards noexcept for swap.
- flat_set: only doc changes for flat_set and a change for
  detail::flat_tree, which it derives from to get swap.
- static_vector: while this adds the forwarding, member static_vector::swap
  is currently never noexcept, although it could be for noexcept-swappable
  and noexcept-move-constructible elements.
- small_vector: there is no free swap, and member swap is never noexcept,
  although it could be for noexcept-swappable and noexcept-move-
  constructible elements. Swapping small_vectors of exact same type goes
  through std::swap, which seems to get noexcept right, and small_vectors
  of different sizes use swap for boost::container::vector, which fails
  to detect when such swap could be noexcept. This patch doesn't touch
  small_vector.
- scoped_allocator: neither member nor free swap are noexcept, although
  they should be, and all other constructions/assignments/comparisons too,
  as they only forward these operations to underlying allocators, which
  are required to not throw exceptions for them. Only static_vector's
  static_storage_allocator might throw for these and it shouldn't appear
  in scoped_allocator. Unsure of the scope of changes needed or whether it
  is even worth it, this patch doesn't touch scoped_allocator.
---
 include/boost/container/deque.hpp            |  1 +
 include/boost/container/detail/flat_tree.hpp |  1 +
 include/boost/container/devector.hpp         |  2 ++
 include/boost/container/flat_map.hpp         |  2 ++
 include/boost/container/flat_set.hpp         |  8 ++++++--
 include/boost/container/list.hpp             |  1 +
 include/boost/container/map.hpp              | 10 +++++++---
 include/boost/container/set.hpp              |  8 ++++++--
 include/boost/container/slist.hpp            |  1 +
 include/boost/container/stable_vector.hpp    |  1 +
 include/boost/container/static_vector.hpp    |  5 ++++-
 include/boost/container/string.hpp           |  1 +
 include/boost/container/vector.hpp           |  1 +
 13 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/include/boost/container/deque.hpp b/include/boost/container/deque.hpp
index e94ea7b..d95314e 100644
--- a/include/boost/container/deque.hpp
+++ b/include/boost/container/deque.hpp
@@ -1910,6 +1910,7 @@ class deque : protected deque_base<typename real_allocator<T, Allocator>::type,
    //!
    //! <b>Complexity</b>: Constant.
    BOOST_CONTAINER_FORCEINLINE friend void swap(deque& x, deque& y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {  x.swap(y);  }
 
    #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
diff --git a/include/boost/container/detail/flat_tree.hpp b/include/boost/container/detail/flat_tree.hpp
index 8debd6f..2dc4230 100644
--- a/include/boost/container/detail/flat_tree.hpp
+++ b/include/boost/container/detail/flat_tree.hpp
@@ -1448,6 +1448,7 @@ class flat_tree
       {  return !(x < y);  }
 
    BOOST_CONTAINER_FORCEINLINE friend void swap(flat_tree& x, flat_tree& y)
+          BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
       {  x.swap(y);  }
 
    private:
diff --git a/include/boost/container/devector.hpp b/include/boost/container/devector.hpp
index 84d48e4..e16a79d 100644
--- a/include/boost/container/devector.hpp
+++ b/include/boost/container/devector.hpp
@@ -2000,6 +2000,8 @@ class devector
    {  return !(x < y);  }
 
    BOOST_CONTAINER_FORCEINLINE friend void swap(devector& x, devector& y)
+      BOOST_NOEXCEPT_IF( allocator_traits_type::propagate_on_container_swap::value
+                        || allocator_traits_type::is_always_equal::value)
    {  x.swap(y);  }
 
    private:
diff --git a/include/boost/container/flat_map.hpp b/include/boost/container/flat_map.hpp
index 4cf41af..5cb35d5 100644
--- a/include/boost/container/flat_map.hpp
+++ b/include/boost/container/flat_map.hpp
@@ -1602,6 +1602,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    BOOST_CONTAINER_FORCEINLINE friend void swap(flat_map& x, flat_map& y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {  x.swap(y);  }
 
    #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
@@ -2959,6 +2960,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    BOOST_CONTAINER_FORCEINLINE friend void swap(flat_multimap& x, flat_multimap& y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {  x.swap(y);  }
 };
 
diff --git a/include/boost/container/flat_set.hpp b/include/boost/container/flat_set.hpp
index 7af8395..fe44fe5 100644
--- a/include/boost/container/flat_set.hpp
+++ b/include/boost/container/flat_set.hpp
@@ -1084,7 +1084,9 @@ class flat_set
    //! <b>Effects</b>: x.swap(y)
    //!
    //! <b>Complexity</b>: Constant.
-   friend void swap(flat_set& x, flat_set& y);
+   friend void swap(flat_set& x, flat_set& y)
+      BOOST_NOEXCEPT_IF(  allocator_traits_type::is_always_equal::value
+                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value );
 
    //! <b>Effects</b>: Extracts the internal sequence container.
    //!
@@ -1817,7 +1819,9 @@ class flat_multiset
    //! <b>Effects</b>: x.swap(y)
    //!
    //! <b>Complexity</b>: Constant.
-   friend void swap(flat_multiset& x, flat_multiset& y);
+   friend void swap(flat_multiset& x, flat_multiset& y)
+      BOOST_NOEXCEPT_IF(  allocator_traits_type::is_always_equal::value
+                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value );
 
    //! <b>Effects</b>: Extracts the internal sequence container.
    //!
diff --git a/include/boost/container/list.hpp b/include/boost/container/list.hpp
index 33270cf..67ee962 100644
--- a/include/boost/container/list.hpp
+++ b/include/boost/container/list.hpp
@@ -1439,6 +1439,7 @@ class list
    //!
    //! <b>Complexity</b>: Constant.
    BOOST_CONTAINER_FORCEINLINE friend void swap(list& x, list& y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {  x.swap(y);  }
 
    #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
diff --git a/include/boost/container/map.hpp b/include/boost/container/map.hpp
index 84270e9..03d761e 100644
--- a/include/boost/container/map.hpp
+++ b/include/boost/container/map.hpp
@@ -1062,7 +1062,7 @@ class map
    //! <b>Complexity</b>: Constant.
    void swap(map& x)
       BOOST_NOEXCEPT_IF(  allocator_traits_type::is_always_equal::value
-                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value )
+                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value );
 
    //! <b>Effects</b>: erase(begin(),end()).
    //!
@@ -1283,7 +1283,9 @@ class map
    //! <b>Effects</b>: x.swap(y)
    //!
    //! <b>Complexity</b>: Constant.
-   friend void swap(map& x, map& y);
+   friend void swap(map& x, map& y)
+      BOOST_NOEXCEPT_IF(  allocator_traits_type::is_always_equal::value
+                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value );
 
    #endif   //#if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
 
@@ -2218,7 +2220,9 @@ class multimap
    //! <b>Effects</b>: x.swap(y)
    //!
    //! <b>Complexity</b>: Constant.
-   friend void swap(multimap& x, multimap& y);
+   friend void swap(multimap& x, multimap& y)
+      BOOST_NOEXCEPT_IF(  allocator_traits_type::is_always_equal::value
+                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value );
 
    #endif   //#if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
 };
diff --git a/include/boost/container/set.hpp b/include/boost/container/set.hpp
index 14b5b6b..0a39f2e 100644
--- a/include/boost/container/set.hpp
+++ b/include/boost/container/set.hpp
@@ -945,7 +945,9 @@ class set
    //! <b>Effects</b>: x.swap(y)
    //!
    //! <b>Complexity</b>: Constant.
-   friend void swap(set& x, set& y);
+   friend void swap(set& x, set& y)
+      BOOST_NOEXCEPT_IF(  allocator_traits_type::is_always_equal::value
+                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value );
 
    #endif   //#if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
 
@@ -1608,7 +1610,9 @@ class multiset
    //! <b>Effects</b>: x.swap(y)
    //!
    //! <b>Complexity</b>: Constant.
-   friend void swap(multiset& x, multiset& y);
+   friend void swap(multiset& x, multiset& y)
+      BOOST_NOEXCEPT_IF(  allocator_traits_type::is_always_equal::value
+                                 && boost::container::dtl::is_nothrow_swappable<Compare>::value );
 
    #endif   //#if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
 
diff --git a/include/boost/container/slist.hpp b/include/boost/container/slist.hpp
index d142744..f08c4b8 100644
--- a/include/boost/container/slist.hpp
+++ b/include/boost/container/slist.hpp
@@ -1629,6 +1629,7 @@ class slist
    //!
    //! <b>Complexity</b>: Constant.
    friend void swap(slist& x, slist& y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {  x.swap(y);  }
 
    #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
diff --git a/include/boost/container/stable_vector.hpp b/include/boost/container/stable_vector.hpp
index b5906bd..4a26ee5 100644
--- a/include/boost/container/stable_vector.hpp
+++ b/include/boost/container/stable_vector.hpp
@@ -1840,6 +1840,7 @@ class stable_vector
    //!
    //! <b>Complexity</b>: Constant.
    BOOST_CONTAINER_FORCEINLINE friend void swap(stable_vector& x, stable_vector& y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {  x.swap(y);  }
 
    #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
diff --git a/include/boost/container/static_vector.hpp b/include/boost/container/static_vector.hpp
index 6408c22..3678947 100644
--- a/include/boost/container/static_vector.hpp
+++ b/include/boost/container/static_vector.hpp
@@ -1169,6 +1169,7 @@ public:
 #else
 
    BOOST_CONTAINER_FORCEINLINE friend void swap(static_vector &x, static_vector &y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {
       x.swap(y);
    }
@@ -1275,13 +1276,15 @@ bool operator>= (static_vector<V, C1, O1> const& x, static_vector<V, C2, O2> con
 //! @par Complexity
 //!   Linear O(N).
 template<typename V, std::size_t C1, std::size_t C2, class O1, class O2>
-inline void swap(static_vector<V, C1, O1> & x, static_vector<V, C2, O2> & y);
+inline void swap(static_vector<V, C1, O1> & x, static_vector<V, C2, O2> & y)
+    BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)));
 
 #else
 
 template<typename V, std::size_t C1, std::size_t C2, class O1, class O2>
 inline void swap(static_vector<V, C1, O1> & x, static_vector<V, C2, O2> & y
       , typename dtl::enable_if_c< C1 != C2>::type * = 0)
+    BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
 {
    x.swap(y);
 }
diff --git a/include/boost/container/string.hpp b/include/boost/container/string.hpp
index bd1381b..b6c0aaf 100644
--- a/include/boost/container/string.hpp
+++ b/include/boost/container/string.hpp
@@ -3399,6 +3399,7 @@ operator>=( const basic_string<CharT,Traits,Allocator>& x, BasicStringView<CharT
 // Swap.
 template <class CharT, class Traits, class Allocator>
 inline void swap(basic_string<CharT,Traits,Allocator>& x, basic_string<CharT,Traits,Allocator>& y)
+    BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
 {  x.swap(y);  }
 
 #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
diff --git a/include/boost/container/vector.hpp b/include/boost/container/vector.hpp
index 83b2aeb..0d7f837 100644
--- a/include/boost/container/vector.hpp
+++ b/include/boost/container/vector.hpp
@@ -2197,6 +2197,7 @@ private:
    //!
    //! <b>Complexity</b>: Constant.
    BOOST_CONTAINER_FORCEINLINE friend void swap(vector& x, vector& y)
+       BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT(x.swap(y)))
    {  x.swap(y);  }
 
    #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED