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3 <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Appendix B.  Porting and Maintenance</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1" /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      runtime&#10;    , &#10;      library&#10;    " /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="bk01pt04.html" title="Part IV.  Appendices" /><link rel="prev" href="source_design_notes.html" title="Design Notes" /><link rel="next" href="documentation_hacking.html" title="Writing and Generating Documentation" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Appendix B. 
4   Porting and Maintenance
5   
6 </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="source_design_notes.html">Prev</a> </td><th width="60%" align="center">Part IV. 
7   Appendices
8 </th><td width="20%" align="right"> <a accesskey="n" href="documentation_hacking.html">Next</a></td></tr></table><hr /></div><div class="appendix" title="Appendix B.  Porting and Maintenance"><div class="titlepage"><div><div><h1 class="title"><a id="appendix.porting"></a>
9   Porting and Maintenance
10   <a id="idp21971520" class="indexterm"></a>
11 </h1></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="appendix_porting.html#appendix.porting.build_hacking">Configure and Build Hacking</a></span></dt><dd><dl><dt><span class="section"><a href="appendix_porting.html#build_hacking.prereq">Prerequisites</a></span></dt><dt><span class="section"><a href="appendix_porting.html#build_hacking.overview">Overview</a></span></dt><dd><dl><dt><span class="section"><a href="appendix_porting.html#build_hacking.overview.basic">General Process</a></span></dt><dt><span class="section"><a href="appendix_porting.html#build_hacking.overview.map">What Comes from Where</a></span></dt></dl></dd><dt><span class="section"><a href="appendix_porting.html#build_hacking.configure">Configure</a></span></dt><dd><dl><dt><span class="section"><a href="appendix_porting.html#build_hacking.configure.scripts">Storing Information in non-AC files (like configure.host)</a></span></dt><dt><span class="section"><a href="appendix_porting.html#build_hacking.configure.conventions">Coding and Commenting Conventions</a></span></dt><dt><span class="section"><a href="appendix_porting.html#build_hacking.configure.acinclude">The acinclude.m4 layout</a></span></dt><dt><span class="section"><a href="appendix_porting.html#build_hacking.configure.enable"><code class="constant">GLIBCXX_ENABLE</code>, the <code class="literal">--enable</code> maker</a></span></dt></dl></dd><dt><span class="section"><a href="appendix_porting.html#build_hacking.make">Make</a></span></dt></dl></dd><dt><span class="section"><a href="documentation_hacking.html">Writing and Generating Documentation</a></span></dt><dd><dl><dt><span class="section"><a href="documentation_hacking.html#doc.intro">Introduction</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#doc.generation">Generating Documentation</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#doc.doxygen">Doxygen</a></span></dt><dd><dl><dt><span class="section"><a href="documentation_hacking.html#doxygen.prereq">Prerequisites</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#doxygen.rules">Generating the Doxygen Files</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#doxygen.debug">Debugging Generation</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#doxygen.markup">Markup</a></span></dt></dl></dd><dt><span class="section"><a href="documentation_hacking.html#doc.docbook">Docbook</a></span></dt><dd><dl><dt><span class="section"><a href="documentation_hacking.html#docbook.prereq">Prerequisites</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#docbook.rules">Generating the DocBook Files</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#docbook.debug">Debugging Generation</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#docbook.validation">Editing and Validation</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#docbook.examples">File Organization and Basics</a></span></dt><dt><span class="section"><a href="documentation_hacking.html#docbook.markup">Markup By Example</a></span></dt></dl></dd></dl></dd><dt><span class="section"><a href="internals.html">Porting to New Hardware or Operating Systems</a></span></dt><dd><dl><dt><span class="section"><a href="internals.html#internals.os">Operating System</a></span></dt><dt><span class="section"><a href="internals.html#internals.cpu">CPU</a></span></dt><dt><span class="section"><a href="internals.html#internals.char_types">Character Types</a></span></dt><dt><span class="section"><a href="internals.html#internals.thread_safety">Thread Safety</a></span></dt><dt><span class="section"><a href="internals.html#internals.numeric_limits">Numeric Limits</a></span></dt><dt><span class="section"><a href="internals.html#internals.libtool">Libtool</a></span></dt></dl></dd><dt><span class="section"><a href="test.html">Test</a></span></dt><dd><dl><dt><span class="section"><a href="test.html#test.organization">Organization</a></span></dt><dd><dl><dt><span class="section"><a href="test.html#test.organization.layout">Directory Layout</a></span></dt><dt><span class="section"><a href="test.html#test.organization.naming">Naming Conventions</a></span></dt></dl></dd><dt><span class="section"><a href="test.html#test.run">Running the Testsuite</a></span></dt><dd><dl><dt><span class="section"><a href="test.html#test.run.basic">Basic</a></span></dt><dt><span class="section"><a href="test.html#test.run.variations">Variations</a></span></dt><dt><span class="section"><a href="test.html#test.run.permutations">Permutations</a></span></dt></dl></dd><dt><span class="section"><a href="test.html#test.new_tests">Writing a new test case</a></span></dt><dt><span class="section"><a href="test.html#test.harness">Test Harness and Utilities</a></span></dt><dd><dl><dt><span class="section"><a href="test.html#test.harness.dejagnu">Dejagnu Harness Details</a></span></dt><dt><span class="section"><a href="test.html#test.harness.utils">Utilities</a></span></dt></dl></dd><dt><span class="section"><a href="test.html#test.special">Special Topics</a></span></dt><dd><dl><dt><span class="section"><a href="test.html#test.exception.safety">
12   Qualifying Exception Safety Guarantees
13   
14 </a></span></dt><dd><dl><dt><span class="section"><a href="test.html#test.exception.safety.overview">Overview</a></span></dt><dt><span class="section"><a href="test.html#test.exception.safety.status">
15     Existing tests
16 </a></span></dt><dt><span class="section"><a href="test.html#test.exception.safety.containers">
17 C++11 Requirements Test Sequence Descriptions
18 </a></span></dt></dl></dd></dl></dd></dl></dd><dt><span class="section"><a href="abi.html">ABI Policy and Guidelines</a></span></dt><dd><dl><dt><span class="section"><a href="abi.html#abi.cxx_interface">The C++ Interface</a></span></dt><dt><span class="section"><a href="abi.html#abi.versioning">Versioning</a></span></dt><dd><dl><dt><span class="section"><a href="abi.html#abi.versioning.goals">Goals</a></span></dt><dt><span class="section"><a href="abi.html#abi.versioning.history">History</a></span></dt><dt><span class="section"><a href="abi.html#abi.versioning.prereq">Prerequisites</a></span></dt><dt><span class="section"><a href="abi.html#abi.versioning.config">Configuring</a></span></dt><dt><span class="section"><a href="abi.html#abi.versioning.active">Checking Active</a></span></dt></dl></dd><dt><span class="section"><a href="abi.html#abi.changes_allowed">Allowed Changes</a></span></dt><dt><span class="section"><a href="abi.html#abi.changes_no">Prohibited Changes</a></span></dt><dt><span class="section"><a href="abi.html#abi.impl">Implementation</a></span></dt><dt><span class="section"><a href="abi.html#abi.testing">Testing</a></span></dt><dd><dl><dt><span class="section"><a href="abi.html#abi.testing.single">Single ABI Testing</a></span></dt><dt><span class="section"><a href="abi.html#abi.testing.multi">Multiple ABI Testing</a></span></dt></dl></dd><dt><span class="section"><a href="abi.html#abi.issues">Outstanding Issues</a></span></dt></dl></dd><dt><span class="section"><a href="api.html">API Evolution and Deprecation History</a></span></dt><dd><dl><dt><span class="section"><a href="api.html#api.rel_300"><code class="constant">3.0</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_310"><code class="constant">3.1</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_320"><code class="constant">3.2</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_330"><code class="constant">3.3</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_340"><code class="constant">3.4</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_400"><code class="constant">4.0</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_410"><code class="constant">4.1</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_420"><code class="constant">4.2</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_430"><code class="constant">4.3</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_440"><code class="constant">4.4</code></a></span></dt><dt><span class="section"><a href="api.html#api.rel_450"><code class="constant">4.5</code></a></span></dt></dl></dd><dt><span class="section"><a href="backwards.html">Backwards Compatibility</a></span></dt><dd><dl><dt><span class="section"><a href="backwards.html#backwards.first">First</a></span></dt><dd><dl><dt><span class="section"><a href="backwards.html#backwards.first.ios_base">No <code class="code">ios_base</code></a></span></dt><dt><span class="section"><a href="backwards.html#backwards.first.cout_cin">No <code class="code">cout</code> in <code class="filename">&lt;ostream.h&gt;</code>, no <code class="code">cin</code> in <code class="filename">&lt;istream.h&gt;</code></a></span></dt></dl></dd><dt><span class="section"><a href="backwards.html#backwards.second">Second</a></span></dt><dd><dl><dt><span class="section"><a href="backwards.html#backwards.second.std">Namespace <code class="code">std::</code> not supported</a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.iterators">Illegal iterator usage</a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.isspace"><code class="code">isspace</code> from <code class="filename">&lt;cctype&gt;</code> is a macro
19   </a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.at">No <code class="code">vector::at</code>, <code class="code">deque::at</code>, <code class="code">string::at</code></a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.eof">No <code class="code">std::char_traits&lt;char&gt;::eof</code></a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.stringclear">No <code class="code">string::clear</code></a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.ostreamform_istreamscan">
20   Removal of <code class="code">ostream::form</code> and <code class="code">istream::scan</code>
21   extensions
22 </a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.stringstreams">No <code class="code">basic_stringbuf</code>, <code class="code">basic_stringstream</code></a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.wchar">Little or no wide character support</a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.iostream_templates">No templatized iostreams</a></span></dt><dt><span class="section"><a href="backwards.html#backwards.second.thread_safety">Thread safety issues</a></span></dt></dl></dd><dt><span class="section"><a href="backwards.html#backwards.third">Third</a></span></dt><dd><dl><dt><span class="section"><a href="backwards.html#backwards.third.headers">Pre-ISO headers moved to backwards or removed</a></span></dt><dt><span class="section"><a href="backwards.html#backwards.third.hash">Extension headers hash_map, hash_set moved to ext or backwards</a></span></dt><dt><span class="section"><a href="backwards.html#backwards.third.nocreate_noreplace">No <code class="code">ios::nocreate/ios::noreplace</code>.
23 </a></span></dt><dt><span class="section"><a href="backwards.html#backwards.third.streamattach">
24 No <code class="code">stream::attach(int fd)</code>
25 </a></span></dt><dt><span class="section"><a href="backwards.html#backwards.third.support_cxx98">
26 Support for C++98 dialect.
27 </a></span></dt><dt><span class="section"><a href="backwards.html#backwards.third.support_tr1">
28 Support for C++TR1 dialect.
29 </a></span></dt><dt><span class="section"><a href="backwards.html#backwards.third.support_cxx11">
30 Support for C++11 dialect.
31 </a></span></dt><dt><span class="section"><a href="backwards.html#backwards.third.iterator_type">
32   <code class="code">Container::iterator_type</code> is not necessarily <code class="code">Container::value_type*</code>
33 </a></span></dt></dl></dd></dl></dd></dl></div><div class="section" title="Configure and Build Hacking"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="appendix.porting.build_hacking"></a>Configure and Build Hacking</h2></div></div></div><div class="section" title="Prerequisites"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.prereq"></a>Prerequisites</h3></div></div></div><p>
34     As noted <a class="link" href="http://gcc.gnu.org/install/prerequisites.html" target="_top">previously</a>,
35     certain other tools are necessary for hacking on files that
36     control configure (<code class="code">configure.ac</code>,
37     <code class="code">acinclude.m4</code>) and make
38     (<code class="code">Makefile.am</code>). These additional tools
39     (<code class="code">automake</code>, and <code class="code">autoconf</code>) are further
40     described in detail in their respective manuals. All the libraries
41     in GCC try to stay in sync with each other in terms of versions of
42     the auto-tools used, so please try to play nicely with the
43     neighbors.
44   </p></div><div class="section" title="Overview"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.overview"></a>Overview</h3></div></div></div><div class="section" title="General Process"><div class="titlepage"><div><div><h4 class="title"><a id="build_hacking.overview.basic"></a>General Process</h4></div></div></div><p>
45   The configure process begins the act of building libstdc++, and is
46   started via:
47 </p><pre class="screen">
48 <code class="computeroutput">
49 configure
50 </code>
51 </pre><p>
52 The <code class="filename">configure</code> file is a script generated (via
53 <span class="command"><strong>autoconf</strong></span>) from the file
54 <code class="filename">configure.ac</code>.
55 </p><p>
56   After the configure process is complete, 
57 </p><pre class="screen">
58 <code class="computeroutput">
59 make all
60 </code>
61 </pre><p>
62 in the build directory starts the build process. The <code class="literal">all</code> target comes from the <code class="filename">Makefile</code> file, which is  generated via <span class="command"><strong>configure</strong></span> from the <code class="filename">Makefile.in</code> file, which is in turn generated (via
63 <span class="command"><strong>automake</strong></span>) from the file
64 <code class="filename">Makefile.am</code>.
65 </p></div><div class="section" title="What Comes from Where"><div class="titlepage"><div><div><h4 class="title"><a id="build_hacking.overview.map"></a>What Comes from Where</h4></div></div></div><div class="figure"><a id="idp21998848"></a><p class="title"><strong>Figure B.1. Configure and Build File Dependencies</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="../images/confdeps.png" align="middle" alt="Dependency Graph for Configure and Build Files" /></div></div></div><br class="figure-break" /><p>
66     Regenerate all generated files by using the command 
67     <code class="code">autoreconf</code> at the top level of the libstdc++ source
68     directory.
69   </p></div></div><div class="section" title="Configure"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.configure"></a>Configure</h3></div></div></div><div class="section" title="Storing Information in non-AC files (like configure.host)"><div class="titlepage"><div><div><h4 class="title"><a id="build_hacking.configure.scripts"></a>Storing Information in non-AC files (like configure.host)</h4></div></div></div><p>
70     Until that glorious day when we can use AC_TRY_LINK with a
71     cross-compiler, we have to hardcode the results of what the tests
72     would have shown if they could be run.  So we have an inflexible
73     mess like crossconfig.m4.
74   </p><p>
75     Wouldn't it be nice if we could store that information in files
76     like configure.host, which can be modified without needing to
77     regenerate anything, and can even be tweaked without really
78     knowing how the configury all works?  Perhaps break the pieces of
79     crossconfig.m4 out and place them in their appropriate
80     config/{cpu,os} directory.
81   </p><p>
82     Alas, writing macros like
83     "<code class="code">AC_DEFINE(HAVE_A_NICE_DAY)</code>" can only be done inside
84     files which are passed through autoconf.  Files which are pure
85     shell script can be source'd at configure time.  Files which
86     contain autoconf macros must be processed with autoconf.  We could
87     still try breaking the pieces out into "config/*/cross.m4" bits,
88     for instance, but then we would need arguments to aclocal/autoconf
89     to properly find them all when generating configure.  I would
90     discourage that.
91 </p></div><div class="section" title="Coding and Commenting Conventions"><div class="titlepage"><div><div><h4 class="title"><a id="build_hacking.configure.conventions"></a>Coding and Commenting Conventions</h4></div></div></div><p>
92     Most comments should use {octothorpes, shibboleths, hash marks,
93     pound signs, whatever} rather than "dnl".  Nearly all comments in
94     configure.ac should.  Comments inside macros written in ancilliary
95     .m4 files should.  About the only comments which should
96     <span class="emphasis"><em>not</em></span> use #, but use dnl instead, are comments
97     <span class="emphasis"><em>outside</em></span> our own macros in the ancilliary
98     files.  The difference is that # comments show up in
99     <code class="code">configure</code> (which is most helpful for debugging),
100     while dnl'd lines just vanish.  Since the macros in ancilliary
101     files generate code which appears in odd places, their "outside"
102     comments tend to not be useful while reading
103     <code class="code">configure</code>.
104   </p><p>
105     Do not use any <code class="code">$target*</code> variables, such as
106     <code class="code">$target_alias</code>.  The single exception is in
107     configure.ac, for automake+dejagnu's sake.
108   </p></div><div class="section" title="The acinclude.m4 layout"><div class="titlepage"><div><div><h4 class="title"><a id="build_hacking.configure.acinclude"></a>The acinclude.m4 layout</h4></div></div></div><p>
109     The nice thing about acinclude.m4/aclocal.m4 is that macros aren't
110     actually performed/called/expanded/whatever here, just loaded.  So
111     we can arrange the contents however we like.  As of this writing,
112     acinclude.m4 is arranged as follows:
113   </p><pre class="programlisting">
114     GLIBCXX_CHECK_HOST
115     GLIBCXX_TOPREL_CONFIGURE
116     GLIBCXX_CONFIGURE
117   </pre><p>
118     All the major variable "discovery" is done here.  CXX, multilibs,
119     etc.
120   </p><pre class="programlisting">
121     fragments included from elsewhere
122   </pre><p>
123     Right now, "fragments" == "the math/linkage bits".
124   </p><pre class="programlisting">
125     GLIBCXX_CHECK_COMPILER_FEATURES
126     GLIBCXX_CHECK_LINKER_FEATURES
127     GLIBCXX_CHECK_WCHAR_T_SUPPORT
128 </pre><p>
129   Next come extra compiler/linker feature tests.  Wide character
130   support was placed here because I couldn't think of another place
131   for it.  It will probably get broken apart like the math tests,
132   because we're still disabling wchars on systems which could actually
133   support them.
134 </p><pre class="programlisting">
135     GLIBCXX_CHECK_SETRLIMIT_ancilliary
136     GLIBCXX_CHECK_SETRLIMIT
137     GLIBCXX_CHECK_S_ISREG_OR_S_IFREG
138     GLIBCXX_CHECK_POLL
139     GLIBCXX_CHECK_WRITEV
140
141     GLIBCXX_CONFIGURE_TESTSUITE
142 </pre><p>
143   Feature tests which only get used in one place.  Here, things used
144   only in the testsuite, plus a couple bits used in the guts of I/O.
145 </p><pre class="programlisting">
146     GLIBCXX_EXPORT_INCLUDES
147     GLIBCXX_EXPORT_FLAGS
148     GLIBCXX_EXPORT_INSTALL_INFO
149 </pre><p>
150   Installation variables, multilibs, working with the rest of the
151   compiler.  Many of the critical variables used in the makefiles are
152   set here.
153 </p><pre class="programlisting">
154     GLIBGCC_ENABLE
155     GLIBCXX_ENABLE_C99
156     GLIBCXX_ENABLE_CHEADERS
157     GLIBCXX_ENABLE_CLOCALE
158     GLIBCXX_ENABLE_CONCEPT_CHECKS
159     GLIBCXX_ENABLE_CSTDIO
160     GLIBCXX_ENABLE_CXX_FLAGS
161     GLIBCXX_ENABLE_C_MBCHAR
162     GLIBCXX_ENABLE_DEBUG
163     GLIBCXX_ENABLE_DEBUG_FLAGS
164     GLIBCXX_ENABLE_LONG_LONG
165     GLIBCXX_ENABLE_PCH
166     GLIBCXX_ENABLE_SJLJ_EXCEPTIONS
167     GLIBCXX_ENABLE_SYMVERS
168     GLIBCXX_ENABLE_THREADS
169 </pre><p>
170   All the features which can be controlled with enable/disable
171   configure options.  Note how they're alphabetized now?  Keep them
172   like that.  :-)
173 </p><pre class="programlisting">
174     AC_LC_MESSAGES
175     libtool bits
176 </pre><p>
177   Things which we don't seem to use directly, but just has to be
178   present otherwise stuff magically goes wonky.
179 </p></div><div class="section" title="GLIBCXX_ENABLE, the --enable maker"><div class="titlepage"><div><div><h4 class="title"><a id="build_hacking.configure.enable"></a><code class="constant">GLIBCXX_ENABLE</code>, the <code class="literal">--enable</code> maker</h4></div></div></div><p>
180     All the <code class="literal">GLIBCXX_ENABLE_FOO</code> macros use a common
181     helper, <code class="literal">GLIBCXX_ENABLE</code>.  (You don't have to use
182     it, but it's easy.)  The helper does two things for us:
183   </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
184      Builds the call to the <code class="literal">AC_ARG_ENABLE</code> macro, with --help text
185      properly quoted and aligned.  (Death to changequote!)
186    </p></li><li class="listitem"><p>
187      Checks the result against a list of allowed possibilities, and
188      signals a fatal error if there's no match.  This means that the
189      rest of the <code class="literal">GLIBCXX_ENABLE_FOO</code> macro doesn't need to test for
190      strange arguments, nor do we need to protect against
191      empty/whitespace strings with the <code class="code">"x$foo" = "xbar"</code>
192      idiom.
193    </p></li></ol></div><p>Doing these things correctly takes some extra autoconf/autom4te code,
194    which made our macros nearly illegible.  So all the ugliness is factored
195    out into this one helper macro.
196 </p><p>Many of the macros take an argument, passed from when they are expanded
197    in configure.ac.  The argument controls the default value of the
198    enable/disable switch.  Previously, the arguments themselves had defaults.
199    Now they don't, because that's extra complexity with zero gain for us.
200 </p><p>There are three "overloaded signatures".  When reading the descriptions
201    below, keep in mind that the brackets are autoconf's quotation characters,
202    and that they will be stripped.  Examples of just about everything occur
203    in acinclude.m4, if you want to look.
204 </p><pre class="programlisting">
205     GLIBCXX_ENABLE (FEATURE, DEFAULT, HELP-ARG, HELP-STRING)
206     GLIBCXX_ENABLE (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, permit a|b|c)
207     GLIBCXX_ENABLE (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, SHELL-CODE-HANDLER)
208 </pre><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
209      FEATURE is the string that follows --enable.  The results of the
210      test (such as it is) will be in the variable $enable_FEATURE,
211      where FEATURE has been squashed.  Example:
212      <code class="code">[extra-foo]</code>, controlled by the --enable-extra-foo
213      option and stored in $enable_extra_foo.
214    </p></li><li class="listitem"><p>
215      DEFAULT is the value to store in $enable_FEATURE if the user does
216      not pass --enable/--disable.  It should be one of the permitted
217      values passed later.  Examples: <code class="code">[yes]</code>, or
218      <code class="code">[bar]</code>, or <code class="code">[$1]</code> (which passes the
219      argument given to the <code class="literal">GLIBCXX_ENABLE_FOO</code> macro
220      as the default).
221    </p><p>
222      For cases where we need to probe for particular models of things,
223      it is useful to have an undocumented "auto" value here (see
224      <code class="literal">GLIBCXX_ENABLE_CLOCALE</code> for an example).
225    </p></li><li class="listitem"><p>
226      HELP-ARG is any text to append to the option string itself in the
227      --help output.  Examples: <code class="code">[]</code> (i.e., an empty string,
228      which appends nothing), <code class="code">[=BAR]</code>, which produces
229      <code class="code">--enable-extra-foo=BAR</code>, and
230      <code class="code">[@&lt;:@=BAR@:&gt;@]</code>, which produces
231      <code class="code">--enable-extra-foo[=BAR]</code>.  See the difference?  See
232      what it implies to the user?
233    </p><p>
234      If you're wondering what that line noise in the last example was,
235      that's how you embed autoconf special characters in output text.
236      They're called <a class="link" href="http://www.gnu.org/software/autoconf/manual/autoconf.html#Quadrigraphs" target="_top"><span class="emphasis"><em>quadrigraphs</em></span></a>
237      and you should use them whenever necessary.
238  </p></li><li class="listitem"><p>HELP-STRING is what you think it is.  Do not include the
239    "default" text like we used to do; it will be done for you by
240    GLIBCXX_ENABLE.  By convention, these are not full English
241    sentences.  Example: [turn on extra foo]
242    </p></li></ul></div><p>
243   With no other arguments, only the standard autoconf patterns are
244   allowed: "<code class="code">--{enable,disable}-foo[={yes,no}]</code>" The
245   $enable_FEATURE variable is guaranteed to equal either "yes" or "no"
246   after the macro.  If the user tries to pass something else, an
247   explanatory error message will be given, and configure will halt.
248 </p><p>
249   The second signature takes a fifth argument, "<code class="code">[permit
250   a | b | c | ...]</code>"
251   This allows <span class="emphasis"><em>a</em></span> or <span class="emphasis"><em>b</em></span> or
252   ... after the equals sign in the option, and $enable_FEATURE is
253   guaranteed to equal one of them after the macro.  Note that if you
254   want to allow plain --enable/--disable with no "=whatever", you must
255   include "yes" and "no" in the list of permitted values.  Also note
256   that whatever you passed as DEFAULT must be in the list.  If the
257   user tries to pass something not on the list, a semi-explanatory
258   error message will be given, and configure will halt.  Example:
259   <code class="code">[permit generic|gnu|ieee_1003.1-2001|yes|no|auto]</code>
260 </p><p>
261   The third signature takes a fifth argument.  It is arbitrary shell
262   code to execute if the user actually passes the enable/disable
263   option.  (If the user does not, the default is used.  Duh.)  No
264   argument checking at all is done in this signature.  See
265   GLIBCXX_ENABLE_CXX_FLAGS for an example of handling, and an error
266   message.
267 </p></div></div><div class="section" title="Make"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.make"></a>Make</h3></div></div></div><p>
268     The build process has to make all of object files needed for
269     static or shared libraries, but first it has to generate some
270     include files. The general order is as follows:
271   </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
272      make include files, make pre-compiled headers
273    </p></li><li class="listitem"><p>
274      make libsupc++
275    </p><p>
276      Generates a libtool convenience library,
277      <code class="filename">libsupc++convenience</code> with language-support
278      routines. Also generates a freestanding static library,
279      <code class="filename">libsupc++.a</code>.
280    </p></li><li class="listitem"><p>
281      make src
282    </p><p>
283      Generates two convenience libraries, one for C++98 and one for
284      C++11, various compability files for shared and static
285      libraries, and then collects all the generated bits and creates
286      the final libstdc++ libraries.
287   </p><div class="orderedlist"><ol class="orderedlist" type="a"><li class="listitem"><p>
288      make src/c++98
289    </p><p>
290      Generates a libtool convenience library,
291      <code class="filename">libc++98convenience</code> with language-support
292      routines. Uses the <code class="literal">-std=gnu++98</code> dialect.
293    </p></li><li class="listitem"><p>
294      make src/c++11
295    </p><p>
296      Generates a libtool convenience library,
297      <code class="filename">libc++11convenience</code> with language-support
298      routines. Uses the <code class="literal">-std=gnu++11</code> dialect.
299    </p></li><li class="listitem"><p>
300      make src
301    </p><p>
302      Generates needed compatibility objects for shared and static
303      libraries. Shared-only code is seggregated at compile-time via
304      the macro <code class="literal">_GLIBCXX_SHARED</code>.
305    </p><p>
306      Then, collects all the generated convenience libraries, adds in
307      any required compatibility objects, and creates the final shared
308      and static libraries: <code class="filename">libstdc++.so</code> and
309      <code class="filename">libstdc++.a</code>.
310    </p></li></ol></div></li></ol></div></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="source_design_notes.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt04.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="documentation_hacking.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Design Notes </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Writing and Generating Documentation</td></tr></table></div></body></html>