gcc/libstdc++-v3/doc/html/manual/bk01pt03ch28s02.html

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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Implementation</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_concurrency.html" title="Chapter 28. Concurrency" /><link rel="prev" href="ext_concurrency.html" title="Chapter 28. Concurrency" /><link rel="next" href="bk01pt03ch28s03.html" title="Use" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Implementation</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_concurrency.html">Prev</a> </td><th width="60%" align="center">Chapter 28. Concurrency</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch28s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Implementation"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.impl"></a>Implementation</h2></div></div></div><div class="sect2" title="Using Builtin Atomic Functions"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.concurrency.impl.atomic_fallbacks"></a>Using Builtin Atomic Functions</h3></div></div></div><p>The functions for atomic operations described above are either
implemented via compiler intrinsics (if the underlying host is
capable) or by library fallbacks.</p><p>Compiler intrinsics (builtins) are always preferred.  However, as
the compiler builtins for atomics are not universally implemented,
using them directly is problematic, and can result in undefined
function calls. (An example of an undefined symbol from the use
of <code class="code">__sync_fetch_and_add</code> on an unsupported host is a
missing reference to <code class="code">__sync_fetch_and_add_4</code>.)
</p><p>In addition, on some hosts the compiler intrinsics are enabled
conditionally, via the <code class="code">-march</code> command line flag. This makes
usage vary depending on the target hardware and the flags used during
compile.
</p><p>
If builtins are possible for bool-sized integral types,
<code class="code">_GLIBCXX_ATOMIC_BUILTINS_1</code> will be defined.
If builtins are possible for int-sized integral types,
<code class="code">_GLIBCXX_ATOMIC_BUILTINS_4</code> will be defined.
</p><p>For the following hosts, intrinsics are enabled by default.
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>alpha</p></li><li class="listitem"><p>ia64</p></li><li class="listitem"><p>powerpc</p></li><li class="listitem"><p>s390</p></li></ul></div><p>For others, some form of <code class="code">-march</code> may work. On
non-ancient x86 hardware, <code class="code">-march=native</code> usually does the
trick.</p><p> For hosts without compiler intrinsics, but with capable
hardware, hand-crafted assembly is selected. This is the case for the following hosts:
</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>cris</p></li><li class="listitem"><p>hppa</p></li><li class="listitem"><p>i386</p></li><li class="listitem"><p>i486</p></li><li class="listitem"><p>m48k</p></li><li class="listitem"><p>mips</p></li><li class="listitem"><p>sparc</p></li></ul></div><p>And for the rest, a simulated atomic lock via pthreads.
</p><p> Detailed information about compiler intrinsics for atomic operations can be found in the GCC <a class="ulink" href="http://gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html" target="_top"> documentation</a>.
</p><p> More details on the library fallbacks from the porting <a class="link" href="internals.html#internals.thread_safety" title="Thread Safety">section</a>.
</p></div><div class="sect2" title="Thread Abstraction"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.concurrency.impl.thread"></a>Thread Abstraction</h3></div></div></div><p>A thin layer above IEEE 1003.1 (i.e. pthreads) is used to abstract
the thread interface for GCC. This layer is called "gthread," and is
comprised of one header file that wraps the host's default thread layer with
a POSIX-like interface.
</p><p> The file &lt;gthr-default.h&gt; points to the deduced wrapper for
the current host. In libstdc++ implementation files,
&lt;bits/gthr.h&gt; is used to select the proper gthreads file.
</p><p>Within libstdc++ sources, all calls to underlying thread functionality
use this layer. More detail as to the specific interface can be found in the source <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00883_source.html" target="_top">documentation</a>.
</p><p>By design, the gthread layer is interoperable with the types,
functions, and usage found in the usual &lt;pthread.h&gt; file,
including <code class="code">pthread_t</code>, <code class="code">pthread_once_t</code>, <code class="code">pthread_create</code>,
etc.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_concurrency.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_concurrency.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt03ch28s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 28. Concurrency </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Use</td></tr></table></div></body></html>
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2010-04-22  Jonathan Wakely  <jwakely.gcc@gmail.com>

	* doc/xml/faq.xml: Link to manual.
	* doc/xml/manual/using.xml: Expand dynamic libraries section.
	* doc/xml/manual/strings.xml: Mention shrink_to_fit() member.
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	* doc/xml/manual/appendix_contributing.xml: Update Bash version.
	* doc/html/*: Regenerate.

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+								<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Implementation</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_concurrency.html" title="Chapter 28. Concurrency" /><link rel="prev" href="ext_concurrency.html" title="Chapter 28. Concurrency" /><link rel="next" href="bk01pt03ch28s03.html" title="Use" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Implementation</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_concurrency.html">Prev</a> </td><th width="60%" align="center">Chapter 28. Concurrency</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch28s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Implementation"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.impl"></a>Implementation</h2></div></div></div><div class="sect2" title="Using Builtin Atomic Functions"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.concurrency.impl.atomic_fallbacks"></a>Using Builtin Atomic Functions</h3></div></div></div><p>The functions for atomic operations described above are either
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+								implemented via compiler intrinsics (if the underlying host is
 								capable) or by library fallbacks.</p><p>Compiler intrinsics (builtins) are always preferred.  However, as
 								the compiler builtins for atomics are not universally implemented,
 								using them directly is problematic, and can result in undefined
 								function calls. (An example of an undefined symbol from the use
 								of <code class="code">__sync_fetch_and_add</code> on an unsupported host is a
 								missing reference to <code class="code">__sync_fetch_and_add_4</code>.)
 								</p><p>In addition, on some hosts the compiler intrinsics are enabled
 								conditionally, via the <code class="code">-march</code> command line flag. This makes
 								usage vary depending on the target hardware and the flags used during
 								compile.
-												faq.xml: Link to manual.

2010-04-22  Jonathan Wakely  <jwakely.gcc@gmail.com>

	* doc/xml/faq.xml: Link to manual.
	* doc/xml/manual/using.xml: Expand dynamic libraries section.
	* doc/xml/manual/strings.xml: Mention shrink_to_fit() member.
	* doc/xml/manual/prerequisites.xml: Link to doxygen requirements.
	* doc/xml/manual/appendix_contributing.xml: Update Bash version.
	* doc/html/*: Regenerate.

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+								</p><p>
-												parallel_mode.xml: Clarify use of explicit parallel algorithms.

2008-06-24  Benjamin Kosnik  <bkoz@redhat.com>

	* doc/xml/manual/parallel_mode.xml: Clarify use of explicit
	parallel algorithms.
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	* doc/html/*: Regenerate.

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+								If builtins are possible for bool-sized integral types,
 								<code class="code">_GLIBCXX_ATOMIC_BUILTINS_1</code> will be defined.
 								If builtins are possible for int-sized integral types,
 								<code class="code">_GLIBCXX_ATOMIC_BUILTINS_4</code> will be defined.
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+								</p><p>For the following hosts, intrinsics are enabled by default.
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+								</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>alpha</p></li><li class="listitem"><p>ia64</p></li><li class="listitem"><p>powerpc</p></li><li class="listitem"><p>s390</p></li></ul></div><p>For others, some form of <code class="code">-march</code> may work. On
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+								non-ancient x86 hardware, <code class="code">-march=native</code> usually does the
 								trick.</p><p> For hosts without compiler intrinsics, but with capable
 								hardware, hand-crafted assembly is selected. This is the case for the following hosts:
-												evolution.xml: Update for 4.4 and 4.5 releases.

2010-01-05  Benjamin Kosnik  <bkoz@redhat.com>

	* doc/xml/manual/evolution.xml: Update for 4.4 and 4.5 releases.
	* doc/html: Regenerate.

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+								</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>cris</p></li><li class="listitem"><p>hppa</p></li><li class="listitem"><p>i386</p></li><li class="listitem"><p>i486</p></li><li class="listitem"><p>m48k</p></li><li class="listitem"><p>mips</p></li><li class="listitem"><p>sparc</p></li></ul></div><p>And for the rest, a simulated atomic lock via pthreads.
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+								</p><p> Detailed information about compiler intrinsics for atomic operations can be found in the GCC <a class="ulink" href="http://gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html" target="_top"> documentation</a>.
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	* doc/xml/faq.xml: Remove redundant xreflabel entities.
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+								</p><p> More details on the library fallbacks from the porting <a class="link" href="internals.html#internals.thread_safety" title="Thread Safety">section</a>.
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2010-01-05  Benjamin Kosnik  <bkoz@redhat.com>

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	* doc/html: Regenerate.

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+								</p></div><div class="sect2" title="Thread Abstraction"><div class="titlepage"><div><div><h3 class="title"><a id="manual.ext.concurrency.impl.thread"></a>Thread Abstraction</h3></div></div></div><p>A thin layer above IEEE 1003.1 (i.e. pthreads) is used to abstract
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+								the thread interface for GCC. This layer is called "gthread," and is
 								comprised of one header file that wraps the host's default thread layer with
 								a POSIX-like interface.
 								</p><p> The file &lt;gthr-default.h&gt; points to the deduced wrapper for
 								the current host. In libstdc++ implementation files,
 								&lt;bits/gthr.h&gt; is used to select the proper gthreads file.
 								</p><p>Within libstdc++ sources, all calls to underlying thread functionality
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2010-01-07  Benjamin Kosnik  <bkoz@redhat.com>

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+								use this layer. More detail as to the specific interface can be found in the source <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a00883_source.html" target="_top">documentation</a>.
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+								</p><p>By design, the gthread layer is interoperable with the types,
 								functions, and usage found in the usual &lt;pthread.h&gt; file,
 								including <code class="code">pthread_t</code>, <code class="code">pthread_once_t</code>, <code class="code">pthread_create</code>,
 								etc.
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2010-04-22  Jonathan Wakely  <jwakely.gcc@gmail.com>

	* doc/xml/faq.xml: Link to manual.
	* doc/xml/manual/using.xml: Expand dynamic libraries section.
	* doc/xml/manual/strings.xml: Mention shrink_to_fit() member.
	* doc/xml/manual/prerequisites.xml: Link to doxygen requirements.
	* doc/xml/manual/appendix_contributing.xml: Update Bash version.
	* doc/html/*: Regenerate.

From-SVN: r158624

											
										
										
											2010-04-22 01:33:44 +02:00
+								</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_concurrency.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_concurrency.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt03ch28s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 28. Concurrency </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Use</td></tr></table></div></body></html>