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Subject: [Boost-commit] svn:boost r56973 - sandbox/committee/rvalue_ref
From: dave_at_[hidden]
Date: 2009-10-17 22:06:56

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Author: dave
Date: 2009-10-17 22:06:55 EDT (Sat, 17 Oct 2009)
New Revision: 56973
URL: http://svn.boost.org/trac/boost/changeset/56973

Log:
Fix up the standard wording again. Rani was right all along, of
course.

Text files modified:
   sandbox/committee/rvalue_ref/N2983-throwing-move.rst | 100 +++++++++++++++++++++++----------------
   sandbox/committee/rvalue_ref/N2983.html | 94 ++++++++++++++++++++++---------------
   2 files changed, 114 insertions(+), 80 deletions(-)

Modified: sandbox/committee/rvalue_ref/N2983-throwing-move.rst
==============================================================================
--- sandbox/committee/rvalue_ref/N2983-throwing-move.rst (original)
+++ sandbox/committee/rvalue_ref/N2983-throwing-move.rst 2009-10-17 22:06:55 EDT (Sat, 17 Oct 2009)
@@ -82,10 +82,9 @@
move can disturb existing guarantees. We propose that instead of
using ``std::move(x)`` in those cases, thus granting permission for
the compiler to use *any* available move constructor, maintainers of
-these particular operations should use
-``std::legacy_move(x)``, which only grants
-permission to use the non-throwing move constructors of copyable
-types. Unless ``x`` is a move-only type, or is known to have a
+these particular operations should use ``std::legacy_move(x)``, which
+grants permission move *unless* it could throw and the type is
+copyable. Unless ``x`` is a move-only type, or is known to have a
nonthrowing move constructor, the operation would fall back to copying
``x``, just as though ``x`` had never acquired a move constructor at
all.
@@ -132,12 +131,13 @@
 }

-We stress again that the use of ``std::legacy_move`` as opposed to ``move``
-would only be necessary under an *extremely* limited set of
+We stress again that the use of ``std::legacy_move`` as opposed to
+``move`` would only be necessary under an *extremely* limited set of
circumstances. In particular, it would never be required in new code,
which could simply give a *conditional* strong guarantee, e.g. â€œif an
-exception is thrown other than by ``T``\ 's move constructor, there are
-no effects.â€ We recommend that approach as best practice for new code.
+exception is thrown other than by ``T``\ 's move constructor, there
+are no effects.â€ We recommend that approach as best practice for new
+code.

Implementing ``std::legacy_move``
*********************************
@@ -148,7 +148,7 @@
 typename conditional<
 !has_nothrow_move_constructor<T>::value
 && has_copy_constructor<T>::value,
- T&,
+ T const&,
 T&&
>::type
 legacy_move(T& x)
@@ -333,7 +333,7 @@
| ``template <class T> |``T`` has a move |``T`` shall be a complete type. |
| struct has_move_constructor;`` |constructor (17.3.14). | |
+--------------------------------+---------------------------+-----------------------------------+
-| ``template <class T> |``T`` is a type with a move|``has_move_constructor<T>::value`` |
+| ``template <class T> |``T`` is a type with a move|``T`` shall be a complete type. |
| struct |constructor that is known | |
| has_nothrow_move_constructor;``|not to throw any | |
| |exceptions. | |
@@ -341,7 +341,7 @@
| ``template <class T> |``T`` has a move assignment|``T`` shall be a complete type. |
| struct has_move_assign;`` |operator (17.3.13). | |
+--------------------------------+---------------------------+-----------------------------------+
-| ``template <class T> |``T`` is a type with a move|``has_move_assign<T>::value`` |
+| ``template <class T> |``T`` is a type with a move|``T`` shall be a complete type. |
| struct |assignment operator that is| |
| has_nothrow_move_assign;`` |known not to throw any | |
| |exceptions. | |
@@ -365,11 +365,38 @@
23.3.2.3 deque modifiers [deque.modifiers]
==========================================

-Change paragraph 2 as follows:
+Context::

- 2 Remarks: If an exception is thrown other than by the copy constructor,
- :ins:`move constructor, move assignment operator`
- or assignment operator of ``T`` there are no effects.
+ iterator insert(const_iterator position, const T& x);
+ iterator insert(const_iterator position, T&& x);
+ void insert(const_iterator position, size_type n, const T& x);
+ template <class InputIterator>;
+ void insert(const_iterator position, ;
+ InputIterator first, InputIterator last);
+
+ template <class... Args> void emplace_front(Args&&... args);
+ template <class... Args> void emplace_back(Args&&... args);
+ template <class... Args> iterator emplace(const_iterator position, Args&&... args);
+ void push_front(const T& x);
+ void push_front(T&& x);
+ void push_back(const T& x);
+ void push_back(T&& x);`
+
+Change Paragraph 2 as follows:
+
+ 2 Remarks: If an exception is thrown other than by the copy
+ constructor\ :ins:`, move constructor, move assignment operator` or
+ assignment operator of ``T`` there are no effects. :raw-html:`If an exception is thrown by the move constructor of a
+ non-CopyConstructible <code>T</code>, the effects are
+ unspecified.`
+
+-----
+
+Context::
+
+ iterator erase(const_iterator position);
+ iterator erase(const_iterator first, const_iterator last);

Change paragraph 6 as follows:

@@ -391,7 +418,7 @@

Change paragraph 3 as follows:

- Effects: A directive that informs a vector of a planned change in
+ :del:`3`:ins:`2` Effects: A directive that informs a vector of a planned change in
 size, so that it can manage the storage allocation
 accordingly. After ``reserve()``, ``capacity()`` is greater or
 equal to the argument of reserve if reallocation happens; and
@@ -426,37 +453,26 @@
 void insert(const_iterator position, size_type n, const T& x);
 template <class InputIterator>
 void insert(const_iterator position, InputIterator first, InputIterator last);
- :del:`template <class... Args> void emplace_back(Args&&... args);`
- template <class... Args> iterator emplace(const_iterator position, Args&&... args);
- :del:`void push_back(const T& x);
- void push_back(T&& x);`
+ template <class... Args> void emplace_back(Args&&... args);
+ template <class... Args> iterator emplace(const_iterator position, Args&&... args);
+ void push_back(const T& x);
+ void push_back(T&& x);

 :del:`1 Requires: If value_type has a move constructor, that constructor shall
 not throw any exceptions.`

- :del:`2`:ins:`1` Remarks: Causes reallocation if the new size is greater than the
- old capacity. If no reallocation happens, all the iterators and
- references before the insertion point remain valid. If an exception
- is thrown other than by the copy constructor :ins:`move constructor,
- move assignment operator,` or assignment operator of ``T`` or by any
- InputIterator operation there are no effects.
-
- :del:`3`:ins:`2` Complexity: The complexity is linear in the number of elements
- inserted plus the distance to the end of the vector.
-
- .. parsed-literal::
-
- :ins:`void push_back(const T& x);
- void push_back(T&& x);
- template <class... Args> void emplace_back(Args&&... args);`
-
- :ins:`2 Remarks: Causes reallocation if the new size is greater than
- the old capacity. If no reallocation happens, all iterators and
- references remain valid. Otherwise, if an exception is thrown by
- the move constructor of a non-CopyConstructible type, the effects
- are unspecified.`
+ :del:`2`:ins:`1` Remarks: Causes reallocation if the new size is
+ greater than the old capacity. If no reallocation happens, all the
+ iterators and references before the insertion point remain valid.
+ If an exception is thrown other than by the copy constructor
+ :ins:`move constructor, move assignment operator,` or assignment
+ operator of ``T`` or by any InputIterator operation there are no
+ effects. :raw-html:`if an exception is thrown by
+ the move constructor of a non-CopyConstructible <code>T</code>, the
+ effects are unspecified.`

- :ins:`Complexity: O(1)`
+ :del:`3`:ins:`2` Complexity: The complexity is linear in the number
+ of elements inserted plus the distance to the end of the vector.

**Note to proposal reader:** The strong guarantee of ``push_back`` for
CopyConstructible ``T``\ s is maintained by virtue of 23.2.1

Modified: sandbox/committee/rvalue_ref/N2983.html
==============================================================================
--- sandbox/committee/rvalue_ref/N2983.html (original)
+++ sandbox/committee/rvalue_ref/N2983.html 2009-10-17 22:06:55 EDT (Sat, 17 Oct 2009)
@@ -398,10 +398,9 @@
move can disturb existing guarantees. We propose that instead of
using <tt class="docutils literal">std::move(x)</tt> in those cases, thus granting permission for
the compiler to use any available move constructor, maintainers of
-these particular operations should use
-<tt class="docutils literal">std::legacy_move(x)</tt>, which only grants
-permission to use the non-throwing move constructors of copyable
-types. Unless <tt class="docutils literal">x</tt> is a move-only type, or is known to have a
+these particular operations should use <tt class="docutils literal">std::legacy_move(x)</tt>, which
+grants permission move unless it could throw and the type is
+copyable. Unless <tt class="docutils literal">x</tt> is a move-only type, or is known to have a
nonthrowing move constructor, the operation would fall back to copying
<tt class="docutils literal">x</tt>, just as though <tt class="docutils literal">x</tt> had never acquired a move constructor at
all.
@@ -444,12 +443,13 @@
 }
}
</pre>
-We stress again that the use of <tt class="docutils literal">std::legacy_move</tt> as opposed to <tt class="docutils literal">move</tt>
-would only be necessary under an extremely limited set of
+We stress again that the use of <tt class="docutils literal">std::legacy_move</tt> as opposed to
+<tt class="docutils literal">move</tt> would only be necessary under an extremely limited set of
circumstances. In particular, it would never be required in new code,
which could simply give a conditional strong guarantee, e.g. â€œif an
-exception is thrown other than by <tt class="docutils literal">T</tt>'s move constructor, there are
-no effects.â€ We recommend that approach as best practice for new code.
+exception is thrown other than by <tt class="docutils literal">T</tt>'s move constructor, there
+are no effects.â€ We recommend that approach as best practice for new
+code.
</div>
<div class="section" id="implementing-std-legacy-move">
<h1><a class="toc-backref" href="#id9">Implementing <tt class="docutils literal">std::legacy_move</tt></a></h1>
@@ -459,7 +459,7 @@
typename conditional<
 !has_nothrow_move_constructor<T>::value
 && has_copy_constructor<T>::value,
- T&,
+ T const&,
 T&&
>::type
legacy_move(T& x)
@@ -630,7 +630,7 @@
constructor that is known
not to throw any
exceptions.</td>
-<td><tt class="docutils literal">has_move_constructor<T>::value</tt></td>
+<td><tt class="docutils literal">T</tt> shall be a complete type.</td>
</tr>
<tr><td><tt class="docutils literal">template <class T>
struct has_move_assign;</tt></td>
@@ -645,7 +645,7 @@
assignment operator that is
known not to throw any
exceptions.</td>
-<td><tt class="docutils literal">has_move_assign<T>::value</tt></td>
+<td><tt class="docutils literal">T</tt> shall be a complete type.</td>
</tr>
<tr><td><tt class="docutils literal">template <class T>
struct has_copy_constructor;</tt></td>
@@ -677,11 +677,37 @@
</div>
<div class="section" id="deque-modifiers-deque-modifiers">
<h2><a class="toc-backref" href="#id18">23.3.2.3 deque modifiers [deque.modifiers]</a></h2>
-Change paragraph 2 as follows:
+Context:
+<pre class="literal-block">
+iterator insert(const_iterator position, const T& x);
+iterator insert(const_iterator position, T&& x);
+void insert(const_iterator position, size_type n, const T& x);
+template <class InputIterator>;
+ void insert(const_iterator position, ;
+ InputIterator first, InputIterator last);
+
+template <class... Args> void emplace_front(Args&&... args);
+template <class... Args> void emplace_back(Args&&... args);
+template <class... Args> iterator emplace(const_iterator position, Args&&... args);
+void push_front(const T& x);
+void push_front(T&& x);
+void push_back(const T& x);
+void push_back(T&& x);`
+</pre>
+Change Paragraph 2 as follows:
<blockquote>
-2 Remarks: If an exception is thrown other than by the copy constructor,
-move constructor, move assignment operator
-or assignment operator of <tt class="docutils literal">T</tt> there are no effects.</blockquote>
+2 Remarks: If an exception is thrown other than by the copy
+constructor, move constructor, move assignment operator or
+assignment operator of <tt class="docutils literal">T</tt> there are no effects. If an exception is thrown by the move constructor of a
+non-CopyConstructible <code>T</code>, the effects are
+unspecified.</blockquote>
+<hr class="docutils" />
+Context:
+<pre class="literal-block">
+iterator erase(const_iterator position);
+iterator erase(const_iterator first, const_iterator last);
+</pre>
Change paragraph 6 as follows:
<blockquote>
6 Throws: Nothing unless an exception is thrown by the copy constructor,
@@ -700,7 +726,7 @@
not throw any exceptions.</blockquote>
Change paragraph 3 as follows:
<blockquote>
-Effects: A directive that informs a vector of a planned change in
+32 Effects: A directive that informs a vector of a planned change in
size, so that it can manage the storage allocation
accordingly. After <tt class="docutils literal">reserve()</tt>, <tt class="docutils literal">capacity()</tt> is greater or
equal to the argument of reserve if reallocation happens; and
@@ -731,32 +757,24 @@
void insert(const_iterator position, size_type n, const T& x);
template <class InputIterator>
 void insert(const_iterator position, InputIterator first, InputIterator last);
-template <class... Args> void emplace_back(Args&&... args);
+template <class... Args> void emplace_back(Args&&... args);
template <class... Args> iterator emplace(const_iterator position, Args&&... args);
-void push_back(const T& x);
-void push_back(T&& x);
+void push_back(const T& x);
+void push_back(T&& x);
</pre>
1 Requires: If value_type has a move constructor, that constructor shall
not throw any exceptions.
-21 Remarks: Causes reallocation if the new size is greater than the
-old capacity. If no reallocation happens, all the iterators and
-references before the insertion point remain valid. If an exception
-is thrown other than by the copy constructor move constructor,
-move assignment operator, or assignment operator of <tt class="docutils literal">T</tt> or by any
-InputIterator operation there are no effects.
-32 Complexity: The complexity is linear in the number of elements
-inserted plus the distance to the end of the vector.
-<pre class="literal-block">
-void push_back(const T& x);
-void push_back(T&& x);
-template <class... Args> void emplace_back(Args&&... args);
-</pre>
-2 Remarks: Causes reallocation if the new size is greater than
-the old capacity. If no reallocation happens, all iterators and
-references remain valid. Otherwise, if an exception is thrown by
-the move constructor of a non-CopyConstructible type, the effects
-are unspecified.
-Complexity: O(1)
+21 Remarks: Causes reallocation if the new size is
+greater than the old capacity. If no reallocation happens, all the
+iterators and references before the insertion point remain valid.
+If an exception is thrown other than by the copy constructor
+move constructor, move assignment operator, or assignment
+operator of <tt class="docutils literal">T</tt> or by any InputIterator operation there are no
+effects. if an exception is thrown by
+the move constructor of a non-CopyConstructible <code>T</code>, the
+effects are unspecified.
+32 Complexity: The complexity is linear in the number
+of elements inserted plus the distance to the end of the vector.
</blockquote>
Note to proposal reader: The strong guarantee of <tt class="docutils literal">push_back</tt> for
CopyConstructible <tt class="docutils literal">T</tt>s is maintained by virtue of 23.2.1

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