libstdc++-v3/doc/html/manual/appendix_porting.html

   1 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
   2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
   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>