or loading and unloading shared objects in memory. As such, using
caching allocators on systems that do not support
<code class="function">abi::__cxa_atexit</code> is not recommended.
or loading and unloading shared objects in memory. As such, using
caching allocators on systems that do not support
<code class="function">abi::__cxa_atexit</code> is not recommended.
- </p></div><div class="section" title="Implementation"><div class="titlepage"><div><div><h4 class="title"><a id="allocator.impl"></a>Implementation</h4></div></div></div><div class="section" title="Interface Design"><div class="titlepage"><div><div><h5 class="title"><a id="id577681"></a>Interface Design</h5></div></div></div><p>
+ </p></div><div class="section" title="Implementation"><div class="titlepage"><div><div><h4 class="title"><a id="allocator.impl"></a>Implementation</h4></div></div></div><div class="section" title="Interface Design"><div class="titlepage"><div><div><h5 class="title"><a id="id608091"></a>Interface Design</h5></div></div></div><p>
The only allocator interface that
is supported is the standard C++ interface. As such, all STL
containers have been adjusted, and all external allocators have
The only allocator interface that
is supported is the standard C++ interface. As such, all STL
containers have been adjusted, and all external allocators have
</p><p>
The base class that <code class="classname">allocator</code> is derived from
may not be user-configurable.
</p><p>
The base class that <code class="classname">allocator</code> is derived from
may not be user-configurable.
It's difficult to pick an allocation strategy that will provide
maximum utility, without excessively penalizing some behavior. In
fact, it's difficult just deciding which typical actions to measure
It's difficult to pick an allocation strategy that will provide
maximum utility, without excessively penalizing some behavior. In
fact, it's difficult just deciding which typical actions to measure
The current default choice for
<code class="classname">allocator</code> is
<code class="classname">__gnu_cxx::new_allocator</code>.
The current default choice for
<code class="classname">allocator</code> is
<code class="classname">__gnu_cxx::new_allocator</code>.
In use, <code class="classname">allocator</code> may allocate and
deallocate using implementation-specified strategies and
heuristics. Because of this, every call to an allocator object's
In use, <code class="classname">allocator</code> may allocate and
deallocate using implementation-specified strategies and
heuristics. Because of this, every call to an allocator object's
A high-performance allocator that uses a bit-map to keep track
of the used and unused memory locations. It has its own
documentation, found <a class="link" href="bitmap_allocator.html" title="bitmap_allocator">here</a>.
A high-performance allocator that uses a bit-map to keep track
of the used and unused memory locations. It has its own
documentation, found <a class="link" href="bitmap_allocator.html" title="bitmap_allocator">here</a>.
- </p></li></ol></div></div><div class="bibliography" title="Bibliography"><div class="titlepage"><div><div><h4 class="title"><a id="allocator.biblio"></a>Bibliography</h4></div></div></div><div class="biblioentry" title="ISO/IEC 14882:1998 Programming languages - C++"><a id="id566591"></a><p><span class="title"><i>
+ </p></li></ol></div></div><div class="bibliography" title="Bibliography"><div class="titlepage"><div><div><h4 class="title"><a id="allocator.biblio"></a>Bibliography</h4></div></div></div><div class="biblioentry" title="ISO/IEC 14882:1998 Programming languages - C++"><a id="id669051"></a><p><span class="title"><i>
<a class="ulink" href="http://www.drdobbs.com/cpp/184403759" target="_top">
<em class="citetitle">
The Standard Librarian: What Are Allocators Good For?
<a class="ulink" href="http://www.drdobbs.com/cpp/184403759" target="_top">
<em class="citetitle">
The Standard Librarian: What Are Allocators Good For?
<a class="ulink" href="http://www.cs.umass.edu/~emery/hoard/" target="_top">
<em class="citetitle">
The Hoard Memory Allocator
</em>
</a>
<a class="ulink" href="http://www.cs.umass.edu/~emery/hoard/" target="_top">
<em class="citetitle">
The Hoard Memory Allocator
</em>
</a>
<a class="ulink" href="http://www.cs.umass.edu/~emery/pubs/berger-oopsla2002.pdf" target="_top">
<em class="citetitle">
Reconsidering Custom Memory Allocation
</em>
</a>
<a class="ulink" href="http://www.cs.umass.edu/~emery/pubs/berger-oopsla2002.pdf" target="_top">
<em class="citetitle">
Reconsidering Custom Memory Allocation
</em>
</a>
- . </span><span class="author"><span class="firstname">Emery</span> <span class="surname">Berger</span>. </span><span class="author"><span class="firstname">Ben</span> <span class="surname">Zorn</span>. </span><span class="author"><span class="firstname">Kathryn</span> <span class="surname">McKinley</span>. </span><span class="copyright">Copyright © 2002 OOPSLA. </span></p></div><div class="biblioentry"><a id="id618584"></a><p><span class="biblioid">
+ . </span><span class="author"><span class="firstname">Emery</span> <span class="surname">Berger</span>. </span><span class="author"><span class="firstname">Ben</span> <span class="surname">Zorn</span>. </span><span class="author"><span class="firstname">Kathryn</span> <span class="surname">McKinley</span>. </span><span class="copyright">Copyright © 2002 OOPSLA. </span></p></div><div class="biblioentry"><a id="id560587"></a><p><span class="biblioid">
- . </span></span></p></div><div class="biblioentry" title="The C++ Programming Language"><a id="id573163"></a><p><span class="title"><i>The C++ Programming Language</i>. </span><span class="author"><span class="firstname">Bjarne</span> <span class="surname">Stroustrup</span>. </span><span class="copyright">Copyright © 2000 . </span><span class="pagenums">19.4 Allocators. </span><span class="publisher"><span class="publishername">
+ . </span></span></p></div><div class="biblioentry" title="The C++ Programming Language"><a id="id558562"></a><p><span class="title"><i>The C++ Programming Language</i>. </span><span class="author"><span class="firstname">Bjarne</span> <span class="surname">Stroustrup</span>. </span><span class="copyright">Copyright © 2000 . </span><span class="pagenums">19.4 Allocators. </span><span class="publisher"><span class="publishername">
- . </span></span></p></div><div class="biblioentry" title="Yalloc: A Recycling C++ Allocator"><a id="id598393"></a><p><span class="title"><i>Yalloc: A Recycling C++ Allocator</i>. </span><span class="author"><span class="firstname">Felix</span> <span class="surname">Yen</span>. </span></p></div></div></div><div class="section" title="auto_ptr"><div class="titlepage"><div><div><h3 class="title"><a id="std.util.memory.auto_ptr"></a>auto_ptr</h3></div></div></div><div class="section" title="Limitations"><div class="titlepage"><div><div><h4 class="title"><a id="auto_ptr.limitations"></a>Limitations</h4></div></div></div><p>Explaining all of the fun and delicious things that can
+ . </span></span></p></div><div class="biblioentry" title="Yalloc: A Recycling C++ Allocator"><a id="id644475"></a><p><span class="title"><i>Yalloc: A Recycling C++ Allocator</i>. </span><span class="author"><span class="firstname">Felix</span> <span class="surname">Yen</span>. </span></p></div></div></div><div class="section" title="auto_ptr"><div class="titlepage"><div><div><h3 class="title"><a id="std.util.memory.auto_ptr"></a>auto_ptr</h3></div></div></div><div class="section" title="Limitations"><div class="titlepage"><div><div><h4 class="title"><a id="auto_ptr.limitations"></a>Limitations</h4></div></div></div><p>Explaining all of the fun and delicious things that can
happen with misuse of the <code class="classname">auto_ptr</code> class
template (called <acronym class="acronym">AP</acronym> here) would take some
time. Suffice it to say that the use of <acronym class="acronym">AP</acronym>
happen with misuse of the <code class="classname">auto_ptr</code> class
template (called <acronym class="acronym">AP</acronym> here) would take some
time. Suffice it to say that the use of <acronym class="acronym">AP</acronym>
Derived classes override those functions to destroy resources in a context
where the correct dynamic type is known. This is an application of the
technique known as type erasure.
Derived classes override those functions to destroy resources in a context
where the correct dynamic type is known. This is an application of the
technique known as type erasure.
- </p></div><div class="section" title="Implementation"><div class="titlepage"><div><div><h4 class="title"><a id="shared_ptr.impl"></a>Implementation</h4></div></div></div><div class="section" title="Class Hierarchy"><div class="titlepage"><div><div><h5 class="title"><a id="id663376"></a>Class Hierarchy</h5></div></div></div><p>
+ </p></div><div class="section" title="Implementation"><div class="titlepage"><div><div><h4 class="title"><a id="shared_ptr.impl"></a>Implementation</h4></div></div></div><div class="section" title="Class Hierarchy"><div class="titlepage"><div><div><h5 class="title"><a id="id580941"></a>Class Hierarchy</h5></div></div></div><p>
A <code class="classname">shared_ptr<T></code> contains a pointer of
type <span class="type">T*</span> and an object of type
<code class="classname">__shared_count</code>. The shared_count contains a
A <code class="classname">shared_ptr<T></code> contains a pointer of
type <span class="type">T*</span> and an object of type
<code class="classname">__shared_count</code>. The shared_count contains a
Unlike the other <code class="classname">_Sp_counted_*</code> classes, this one is parameterized on the
type of object, not the type of pointer; this is purely a convenience
that simplifies the implementation slightly.
Unlike the other <code class="classname">_Sp_counted_*</code> classes, this one is parameterized on the
type of object, not the type of pointer; this is purely a convenience
that simplifies the implementation slightly.
The interface of <code class="classname">tr1::shared_ptr</code> was extended for C++0x
with support for rvalue-references and the other features from
N2351. As with other libstdc++ headers shared by TR1 and C++0x,
The interface of <code class="classname">tr1::shared_ptr</code> was extended for C++0x
with support for rvalue-references and the other features from
N2351. As with other libstdc++ headers shared by TR1 and C++0x,
shared_ptr in libstdc++ the compiler and library are fixed, which
makes things much simpler: we have an atomic CAS or we don't, see Lock
Policy below for details.
shared_ptr in libstdc++ the compiler and library are fixed, which
makes things much simpler: we have an atomic CAS or we don't, see Lock
Policy below for details.
</p><p>
There is a single <code class="classname">_Sp_counted_base</code> class,
which is a template parameterized on the enum
</p><p>
There is a single <code class="classname">_Sp_counted_base</code> class,
which is a template parameterized on the enum
<code class="filename">ext/atomicity.h</code>, which detect if the program
is multi-threaded. If only one thread of execution exists in
the program then less expensive non-atomic operations are used.
<code class="filename">ext/atomicity.h</code>, which detect if the program
is multi-threaded. If only one thread of execution exists in
the program then less expensive non-atomic operations are used.
The classes derived from <code class="classname">_Sp_counted_base</code> (see Class Hierarchy
below) and <code class="classname">__shared_count</code> are implemented separately for C++0x
and TR1, in <code class="filename">bits/boost_sp_shared_count.h</code> and
The classes derived from <code class="classname">_Sp_counted_base</code> (see Class Hierarchy
below) and <code class="classname">__shared_count</code> are implemented separately for C++0x
and TR1, in <code class="filename">bits/boost_sp_shared_count.h</code> and
change unless bug fixes require it. If the code that is common to both
C++0x and TR1 modes needs to diverge further then it might be necessary to
duplicate additional classes and only make changes to the C++0x versions.
change unless bug fixes require it. If the code that is common to both
C++0x and TR1 modes needs to diverge further then it might be necessary to
duplicate additional classes and only make changes to the C++0x versions.
-</p></div><div class="section" title="Related functions and classes"><div class="titlepage"><div><div><h5 class="title"><a id="id650024"></a>Related functions and classes</h5></div></div></div><div class="variablelist"><dl><dt><span class="term"><code class="code">dynamic_pointer_cast</code>, <code class="code">static_pointer_cast</code>,
+</p></div><div class="section" title="Related functions and classes"><div class="titlepage"><div><div><h5 class="title"><a id="id614202"></a>Related functions and classes</h5></div></div></div><div class="variablelist"><dl><dt><span class="term"><code class="code">dynamic_pointer_cast</code>, <code class="code">static_pointer_cast</code>,
<code class="code">const_pointer_cast</code></span></dt><dd><p>
As noted in N2351, these functions can be implemented non-intrusively using
the alias constructor. However the aliasing constructor is only available
<code class="code">const_pointer_cast</code></span></dt><dd><p>
As noted in N2351, these functions can be implemented non-intrusively using
the alias constructor. However the aliasing constructor is only available
As well as the extra constructors, this implementation also needs some
members of _Sp_counted_deleter to be protected where they could otherwise
be private.
As well as the extra constructors, this implementation also needs some
members of _Sp_counted_deleter to be protected where they could otherwise
be private.
- </p></dd></dl></div></div></div><div class="section" title="Use"><div class="titlepage"><div><div><h4 class="title"><a id="shared_ptr.using"></a>Use</h4></div></div></div><div class="section" title="Examples"><div class="titlepage"><div><div><h5 class="title"><a id="id597398"></a>Examples</h5></div></div></div><p>
+ </p></dd></dl></div></div></div><div class="section" title="Use"><div class="titlepage"><div><div><h4 class="title"><a id="shared_ptr.using"></a>Use</h4></div></div></div><div class="section" title="Examples"><div class="titlepage"><div><div><h5 class="title"><a id="id616991"></a>Examples</h5></div></div></div><p>
Examples of use can be found in the testsuite, under
<code class="filename">testsuite/tr1/2_general_utilities/shared_ptr</code>.
Examples of use can be found in the testsuite, under
<code class="filename">testsuite/tr1/2_general_utilities/shared_ptr</code>.
The resolution to C++ Standard Library issue <a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#674" target="_top">674</a>,
"shared_ptr interface changes for consistency with N1856" will
need to be implemented after it is accepted into the working
The resolution to C++ Standard Library issue <a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#674" target="_top">674</a>,
"shared_ptr interface changes for consistency with N1856" will
need to be implemented after it is accepted into the working
code to work with, Peter Dimov in particular for his help and
invaluable advice on thread safety. Phillip Jordan and Paolo
Carlini for the lock policy implementation.
code to work with, Peter Dimov in particular for his help and
invaluable advice on thread safety. Phillip Jordan and Paolo
Carlini for the lock policy implementation.
<a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2351.htm" target="_top">
<em class="citetitle">
Improving shared_ptr for C++0x, Revision 2
<a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2351.htm" target="_top">
<em class="citetitle">
Improving shared_ptr for C++0x, Revision 2
<a class="ulink" href="http://open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2456.html" target="_top">
<em class="citetitle">
C++ Standard Library Active Issues List
<a class="ulink" href="http://open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2456.html" target="_top">
<em class="citetitle">
C++ Standard Library Active Issues List
<a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2461.pdf" target="_top">
<em class="citetitle">
Working Draft, Standard for Programming Language C++
<a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2461.pdf" target="_top">
<em class="citetitle">
Working Draft, Standard for Programming Language C++
<a class="ulink" href="http://boost.org/libs/smart_ptr/shared_ptr.htm" target="_top">shared_ptr
<em class="citetitle">
Boost C++ Libraries documentation, shared_ptr
<a class="ulink" href="http://boost.org/libs/smart_ptr/shared_ptr.htm" target="_top">shared_ptr
<em class="citetitle">
Boost C++ Libraries documentation, shared_ptr