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Diffstat (limited to 'doc/html/align/vocabulary.html')
| -rw-r--r-- | doc/html/align/vocabulary.html | 132 |
1 files changed, 56 insertions, 76 deletions
diff --git a/doc/html/align/vocabulary.html b/doc/html/align/vocabulary.html index 71f1cb4fc3..e05189a65d 100644 --- a/doc/html/align/vocabulary.html +++ b/doc/html/align/vocabulary.html @@ -32,63 +32,55 @@ <span class="phrase"><a name="align.vocabulary.basic_align"></a></span><a class="link" href="vocabulary.html#align.vocabulary.basic_align">[basic.align]</a> </h4> <p> - Object types have <span class="bold"><strong>alignment requirements</strong></span> which - place restrictions on the addresses at which an object of that type may be - allocated. An <span class="bold"><strong>alignment</strong></span> is an implementation-defined - integer value representing the number of bytes between successive addresses - at which a given object can be allocated. An object type imposes an alignment - requirement on every object of that type; stricter alignment can be requested - using the alignment specifier. + Object types have <span class="emphasis"><em>alignment requirements</em></span> which place restrictions + on the addresses at which an object of that type may be allocated. An <span class="emphasis"><em>alignment</em></span> + is an implementation-defined integer value representing the number of bytes + between successive addresses at which a given object can be allocated. An object + type imposes an alignment requirement on every object of that type; stricter + alignment can be requested using the alignment specifier. </p> <p> - A <span class="bold"><strong>fundamental alignment</strong></span> is represented by - an alignment less than or equal to the greatest alignment supported by the - implementation in all contexts, which is equal to <code class="computeroutput"><span class="keyword">alignof</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">max_align_t</span><span class="special">)</span></code>. + A <span class="emphasis"><em>fundamental alignment</em></span> is represented by an alignment + less than or equal to the greatest alignment supported by the implementation + in all contexts, which is equal to <code class="computeroutput"><span class="keyword">alignof</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">max_align_t</span><span class="special">)</span></code>. The alignment required for a type might be different when it is used as the - type of a complete object and when it is used as the type of a subobject. + type of a complete object and when it is used as the type of a subobject. [<span class="emphasis"><em>Example:</em></span> </p> -<div class="tip"><table border="0" summary="Tip"> -<tr> -<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../doc/src/images/tip.png"></td> -<th align="left">Tip</th> -</tr> -<tr><td align="left" valign="top"> -<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">B</span> <span class="special">{</span> <span class="keyword">long</span> <span class="keyword">double</span> <span class="identifier">d</span><span class="special">;</span> <span class="special">};</span> -<span class="keyword">struct</span> <span class="identifier">D</span> <span class="special">:</span> <span class="keyword">virtual</span> <span class="identifier">B</span> <span class="special">{</span> <span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span> <span class="special">};</span> -</pre> -<p> - When <code class="computeroutput"><span class="identifier">D</span></code> is the type of a complete - object, it will have a subobject of type <code class="computeroutput"><span class="identifier">B</span></code>, - so it must be aligned appropriately for a <code class="computeroutput"><span class="keyword">long</span> - <span class="keyword">double</span></code>. If <code class="computeroutput"><span class="identifier">D</span></code> - appears as a subobject of another object that also has <code class="computeroutput"><span class="identifier">B</span></code> - as a virtual base class, the <code class="computeroutput"><span class="identifier">B</span></code> - subobject might be part of a different subobject, reducing the alignment - requirements on the <code class="computeroutput"><span class="identifier">D</span></code> subobject. - </p> -</td></tr> -</table></div> +<div class="orderedlist"><ol class="orderedlist" type="1"> +<li class="listitem"> + <code class="computeroutput"><span class="keyword">struct</span> <span class="identifier">B</span> + <span class="special">{</span> <span class="keyword">long</span> + <span class="keyword">double</span> <span class="identifier">d</span><span class="special">;</span> <span class="special">};</span></code> + </li> +<li class="listitem"> + <code class="computeroutput"><span class="keyword">struct</span> <span class="identifier">D</span> + <span class="special">:</span> <span class="keyword">virtual</span> + <span class="identifier">B</span> <span class="special">{</span> + <span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span> <span class="special">};</span></code> + </li> +</ol></div> <p> - The result of the <code class="computeroutput"><span class="keyword">alignof</span></code> operator - reflects the alignment requirement of the type in the complete-object case. + When <code class="computeroutput"><span class="identifier">D</span></code> is the type of a complete + object, it will have a subobject of type <code class="computeroutput"><span class="identifier">B</span></code>, + so it must be aligned appropriately for a <code class="computeroutput"><span class="keyword">long</span> + <span class="keyword">double</span></code>. If <code class="computeroutput"><span class="identifier">D</span></code> + appears as a subobject of another object that also has <code class="computeroutput"><span class="identifier">B</span></code> + as a virtual base class, the <code class="computeroutput"><span class="identifier">B</span></code> + subobject might be part of a different subobject, reducing the alignment requirements + on the <code class="computeroutput"><span class="identifier">D</span></code> subobject. —<span class="emphasis"><em>end + example</em></span>] The result of the <code class="computeroutput"><span class="keyword">alignof</span></code> + operator reflects the alignment requirement of the type in the complete-object + case. </p> <p> - An <span class="bold"><strong>extended alignment</strong></span> is represented by an - alignment greater than <code class="computeroutput"><span class="keyword">alignof</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">max_align_t</span><span class="special">)</span></code>. - It is implementation-defined whether any extended alignments are supported - and the contexts in which they are supported. A type having an extended alignment - requirement is an <span class="bold"><strong>over-aligned type</strong></span>. + An <span class="emphasis"><em>extended alignment</em></span> is represented by an alignment greater + than <code class="computeroutput"><span class="keyword">alignof</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">max_align_t</span><span class="special">)</span></code>. It is implementation-defined whether any + extended alignments are supported and the contexts in which they are supported. + A type having an extended alignment requirement is an <span class="emphasis"><em>over-aligned + type</em></span>. [<span class="emphasis"><em>Note:</em></span> Every over-aligned type is or + contains a class type to which extended alignment applies (possibly through + a non-static data member). —<span class="emphasis"><em>end note</em></span>] </p> -<div class="note"><table border="0" summary="Note"> -<tr> -<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> -<th align="left">Note</th> -</tr> -<tr><td align="left" valign="top"><p> - Every over-aligned type is or contains a class type to which extended alignment - applies (possibly through a non-static data member). - </p></td></tr> -</table></div> <p> Alignments are represented as values of the type <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span></code>. Valid alignments include only those values returned by an <code class="computeroutput"><span class="keyword">alignof</span></code> @@ -97,28 +89,20 @@ integral power of two. </p> <p> - Alignments have an order from <span class="bold"><strong>weaker</strong></span> to <span class="bold"><strong>stronger</strong></span> or <span class="bold"><strong>stricter</strong></span> - alignments. Stricter alignments have larger alignment values. An address that - satisfies an alignment requirement also satisfies any weaker valid alignment - requirement. + Alignments have an order from <span class="emphasis"><em>weaker</em></span> to <span class="emphasis"><em>stronger</em></span> + or <span class="emphasis"><em>stricter</em></span> alignments. Stricter alignments have larger + alignment values. An address that satisfies an alignment requirement also satisfies + any weaker valid alignment requirement. </p> <p> The alignment requirement of a complete type can be queried using an <code class="computeroutput"><span class="keyword">alignof</span></code> expression. Furthermore, the types <code class="computeroutput"><span class="keyword">char</span></code>, <code class="computeroutput"><span class="keyword">signed</span> <span class="keyword">char</span></code>, and <code class="computeroutput"><span class="keyword">unsigned</span> <span class="keyword">char</span></code> shall have the weakest alignment - requirement. + requirement. [<span class="emphasis"><em>Note:</em></span> This enables the character types to + be used as the underlying type for an aligned memory area. —<span class="emphasis"><em>end + note</em></span>] </p> -<div class="note"><table border="0" summary="Note"> -<tr> -<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> -<th align="left">Note</th> -</tr> -<tr><td align="left" valign="top"><p> - This enables the character types to be used as the underlying type for an - aligned memory area. - </p></td></tr> -</table></div> <p> Comparing alignments is meaningful and provides the obvious results: </p> @@ -133,17 +117,12 @@ When an alignment is larger than another it represents a stricter alignment. </li> </ul></div> -<div class="note"><table border="0" summary="Note"> -<tr> -<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> -<th align="left">Note</th> -</tr> -<tr><td align="left" valign="top"><p> - The runtime pointer alignment function can be used to obtain an aligned pointer - within a buffer; the aligned-storage templates in the library can be used - to obtain aligned storage. - </p></td></tr> -</table></div> +<p> + [<span class="emphasis"><em>Note:</em></span> The runtime pointer alignment function can be used + to obtain an aligned pointer within a buffer; the aligned-storage templates + in the library can be used to obtain aligned storage. —<span class="emphasis"><em>end + note</em></span>] + </p> <p> If a request for a specific extended alignment in a specific context is not supported by an implementation, the program is ill-formed. Additionally, a @@ -153,7 +132,8 @@ </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> -<td align="right"><div class="copyright-footer">Copyright © 2014-2016 Glen Joseph Fernandes<p> +<td align="right"><div class="copyright-footer">Copyright © 2014-2017 Glen + Joseph Fernandes<p> Distributed under the Boost Software License, Version 1.0. </p> </div></td> |