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Revert "Add new build-time configuration feature."
This reverts commit dad7bc5b30.
Conflicts:
checks/config.jam
This commit is contained in:
jzmaddock
@@ -1,65 +0,0 @@
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[section:build_config Build Time Configuration]
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There are times when you want to control whether a build target gets built or not, based
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on what features the compiler supports. For example, suppose you have a test file
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"test_constexpr_128.cpp" which requires three key features in order to build:
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* The `constexpr` keyword as detected by BOOST_NO_CXX11_CONSTEXPR.
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* User defined literals, as detected by BOOST_NO_CXX11_USER_DEFINED_LITERALS.
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* The `__int128` data type, as detected by BOOST_HAS_INT128.
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Clearly we know that if these features are not supported by the compiler, then
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there's simply no point in even trying to build the test program. The main advantages being:
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* Faster compile times - build configuration uses lightweight tests the results of which are also cached.
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* Less noise in build output - there's no reason to be faced with pages of template
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instantiation backtrace if we know the file can never compile anyway.
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* Less noise in the online test results - the test will show up as blank, rather than as a fail
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in the online test matrix.
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* A better experience for end users building all of Boost, if those libraries which can not be built
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for the current target compiler are simply skipped, rather than generating pages of error output.
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Returning to our example, the test case is probably executed in it's Jamfile via the "run" rule:
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run test_constexpr_128.cpp ;
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We now need to make this target conditional on the necessary features.
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We can do that by first importing the necessary rule at the start of the Jamfile:
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import path-to-config-lib/checks/config : requires ;
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Assuming that the test case is in the usual directory:
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libs/yourlib/test
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then the import rule will actually be:
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import ../../config/checks/config : requires ;
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Then add a "requires" rule invocation to the requirements section of the target:
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run test_constexpr_128.cpp
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: : : #requirements:
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[ requires cxx11_constexpr cxx11_user_defined_literals int128 ] ;
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Notice that multiple arguments can be added to the requires rule, and that these are
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always the same as the Boost.Config macro name, but in lower case and with the ['boost_no_]
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or ['boost_has_] prefix removed.
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When building the above example, you will see at the start of the build process the results
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of the configuration, for example GCC in C++11 mode gives:
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- Boost.Config Feature Check: int128 : yes
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- Boost.Config Feature Check: cxx11_constexpr : yes
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- Boost.Config Feature Check: cxx11_user_defined_literals : yes
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That's all there is to this handy feature, should at any time you be unsure of the feature-test
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names you can pass to the "requires" rule, then search for the Boost.Config macro of interest in
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libs/config/checks/Jamfiles.v2, and the name of the feature check will follow it.
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And finally, this feature is built around the Boost.Build built in rule ['check-target-builds]
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which can be used to perform more generalized build-time feature testing. The checks in this
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library are provided as a convenient shorthand without the need for you to write the test cases yourself.
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[endsect]
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@@ -50,7 +50,6 @@ Distributed under the Boost Software License, Version 1.0.
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[include configuring_boost.qbk]
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[include macro_reference.qbk]
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[include build_time.qbk]
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[include cstdint.qbk]
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[include guidelines.qbk]
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[include rationale.qbk]
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@@ -7,7 +7,7 @@
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<link rel="home" href="../index.html" title="Boost.Config">
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@@ -20,7 +20,7 @@
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@@ -5613,7 +5613,7 @@
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@@ -1,144 +0,0 @@
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
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<title>Build Time Configuration</title>
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<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="boost_config.build_config"></a><a class="link" href="build_config.html" title="Build Time Configuration">Build Time Configuration</a>
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</h2></div></div></div>
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<p>
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There are times when you want to control whether a build target gets built
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or not, based on what features the compiler supports. For example, suppose
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you have a test file "test_constexpr_128.cpp" which requires three
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key features in order to build:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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The <code class="computeroutput"><span class="keyword">constexpr</span></code> keyword as detected
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by BOOST_NO_CXX11_CONSTEXPR.
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</li>
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<li class="listitem">
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User defined literals, as detected by BOOST_NO_CXX11_USER_DEFINED_LITERALS.
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</li>
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<li class="listitem">
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The <code class="computeroutput"><span class="identifier">__int128</span></code> data type,
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as detected by BOOST_HAS_INT128.
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</li>
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</ul></div>
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<p>
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Clearly we know that if these features are not supported by the compiler, then
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there's simply no point in even trying to build the test program. The main
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advantages being:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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Faster compile times - build configuration uses lightweight tests the results
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of which are also cached.
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</li>
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<li class="listitem">
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Less noise in build output - there's no reason to be faced with pages of
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template instantiation backtrace if we know the file can never compile
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anyway.
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</li>
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<li class="listitem">
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Less noise in the online test results - the test will show up as blank,
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rather than as a fail in the online test matrix.
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</li>
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<li class="listitem">
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A better experience for end users building all of Boost, if those libraries
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which can not be built for the current target compiler are simply skipped,
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rather than generating pages of error output.
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</li>
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</ul></div>
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<p>
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Returning to our example, the test case is probably executed in it's Jamfile
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via the "run" rule:
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</p>
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<pre class="programlisting"><span class="identifier">run</span> <span class="identifier">test_constexpr_128</span><span class="special">.</span><span class="identifier">cpp</span> <span class="special">;</span>
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</pre>
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<p>
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We now need to make this target conditional on the necessary features. We can
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do that by first importing the necessary rule at the start of the Jamfile:
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</p>
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<pre class="programlisting"><span class="identifier">import</span> <span class="identifier">path</span><span class="special">-</span><span class="identifier">to</span><span class="special">-</span><span class="identifier">config</span><span class="special">-</span><span class="identifier">lib</span><span class="special">/</span><span class="identifier">checks</span><span class="special">/</span><span class="identifier">config</span> <span class="special">:</span> <span class="identifier">requires</span> <span class="special">;</span>
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</pre>
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<p>
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Assuming that the test case is in the usual directory:
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</p>
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<pre class="programlisting"><span class="identifier">libs</span><span class="special">/</span><span class="identifier">yourlib</span><span class="special">/</span><span class="identifier">test</span>
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</pre>
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<p>
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then the import rule will actually be:
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</p>
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<pre class="programlisting"><span class="identifier">import</span> <span class="special">../../</span><span class="identifier">config</span><span class="special">/</span><span class="identifier">checks</span><span class="special">/</span><span class="identifier">config</span> <span class="special">:</span> <span class="identifier">requires</span> <span class="special">;</span>
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</pre>
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<p>
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Then add a "requires" rule invocation to the requirements section
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of the target:
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</p>
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<pre class="programlisting"><span class="identifier">run</span> <span class="identifier">test_constexpr_128</span><span class="special">.</span><span class="identifier">cpp</span>
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<span class="special">:</span> <span class="special">:</span> <span class="special">:</span> <span class="special">#</span><span class="identifier">requirements</span><span class="special">:</span>
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<span class="special">[</span> <span class="identifier">requires</span> <span class="identifier">cxx11_constexpr</span> <span class="identifier">cxx11_user_defined_literals</span> <span class="identifier">int128</span> <span class="special">]</span> <span class="special">;</span>
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</pre>
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<p>
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Notice that multiple arguments can be added to the requires rule, and that
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these are always the same as the Boost.Config macro name, but in lower case
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and with the <span class="emphasis"><em>boost_no_</em></span> or <span class="emphasis"><em>boost_has_</em></span>
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prefix removed.
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</p>
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<p>
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When building the above example, you will see at the start of the build process
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the results of the configuration, for example GCC in C++11 mode gives:
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</p>
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<pre class="programlisting"><span class="special">-</span> <span class="identifier">Boost</span><span class="special">.</span><span class="identifier">Config</span> <span class="identifier">Feature</span> <span class="identifier">Check</span><span class="special">:</span> <span class="identifier">int128</span> <span class="special">:</span> <span class="identifier">yes</span>
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<span class="special">-</span> <span class="identifier">Boost</span><span class="special">.</span><span class="identifier">Config</span> <span class="identifier">Feature</span> <span class="identifier">Check</span><span class="special">:</span> <span class="identifier">cxx11_constexpr</span> <span class="special">:</span> <span class="identifier">yes</span>
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<span class="special">-</span> <span class="identifier">Boost</span><span class="special">.</span><span class="identifier">Config</span> <span class="identifier">Feature</span> <span class="identifier">Check</span><span class="special">:</span> <span class="identifier">cxx11_user_defined_literals</span> <span class="special">:</span> <span class="identifier">yes</span>
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</pre>
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<p>
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That's all there is to this handy feature, should at any time you be unsure
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of the feature-test names you can pass to the "requires" rule, then
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search for the Boost.Config macro of interest in libs/config/checks/Jamfiles.v2,
|
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and the name of the feature check will follow it.
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</p>
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<p>
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And finally, this feature is built around the Boost.Build built in rule <span class="emphasis"><em>check-target-builds</em></span>
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which can be used to perform more generalized build-time feature testing. The
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checks in this library are provided as a convenient shorthand without the need
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for you to write the test cases yourself.
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</p>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2001-2007 Beman Dawes, Vesa Karvonen, John
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Maddock<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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@@ -77,7 +77,6 @@
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<dt><span class="section"><a href="boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_for_libraries_with_separate_source_code">Macros
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for libraries with separate source code</a></span></dt>
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</dl></dd>
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<dt><span class="section"><a href="boost_config/build_config.html">Build Time Configuration</a></span></dt>
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<dt><span class="section"><a href="boost_config/cstdint.html">Standard Integer Types</a></span></dt>
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<dd><dl>
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<dt><span class="section"><a href="boost_config/cstdint.html#boost_config.cstdint.overview">Overview</a></span></dt>
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@@ -968,7 +967,7 @@
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"><p><small>Last revised: June 05, 2014 at 17:41:22 GMT</small></p></td>
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<td align="left"><p><small>Last revised: June 01, 2014 at 09:50:01 GMT</small></p></td>
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