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 Stylesheets V1.75.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><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="internals.html" title="Porting to New Hardware or Operating Systems" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Appendix B.
4 Porting and Maintenance
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.
8 </th><td width="20%" align="right"> <a accesskey="n" href="internals.html">Next</a></td></tr></table><hr /></div><div class="appendix" title="Appendix B. Porting and Maintenance"><div class="titlepage"><div><div><h2 class="title"><a id="appendix.porting"></a>Appendix B.
9 Porting and Maintenance
10 <a id="id559270" class="indexterm"></a>
11 </h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="appendix_porting.html#appendix.porting.build_hacking">Configure and Build Hacking</a></span></dt><dd><dl><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.prereq">Prerequisites</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.map">Overview: What Comes from Where</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.scripts">Storing Information in non-AC files (like configure.host)</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.conventions">Coding and Commenting Conventions</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.acinclude">The acinclude.m4 layout</a></span></dt><dt><span class="sect2"><a href="appendix_porting.html#build_hacking.enable"><code class="constant">GLIBCXX_ENABLE</code>, the <code class="literal">--enable</code> maker</a></span></dt></dl></dd><dt><span class="sect1"><a href="internals.html">Porting to New Hardware or Operating Systems</a></span></dt><dd><dl><dt><span class="sect2"><a href="internals.html#internals.os">Operating System</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.cpu">CPU</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.char_types">Character Types</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.thread_safety">Thread Safety</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.numeric_limits">Numeric Limits</a></span></dt><dt><span class="sect2"><a href="internals.html#internals.libtool">Libtool</a></span></dt></dl></dd><dt><span class="sect1"><a href="test.html">Test</a></span></dt><dd><dl><dt><span class="sect2"><a href="test.html#test.organization">Organization</a></span></dt><dt><span class="sect2"><a href="test.html#test.run">Running the Testsuite</a></span></dt><dt><span class="sect2"><a href="test.html#test.new_tests">Writing a new test case</a></span></dt><dt><span class="sect2"><a href="test.html#test.harness">Test Harness and Utilities</a></span></dt><dt><span class="sect2"><a href="test.html#test.special">Special Topics</a></span></dt></dl></dd><dt><span class="sect1"><a href="abi.html">ABI Policy and Guidelines</a></span></dt><dd><dl><dt><span class="sect2"><a href="abi.html#abi.cxx_interface">The C++ Interface</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.versioning">Versioning</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.changes_allowed">Allowed Changes</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.changes_no">Prohibited Changes</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.impl">Implementation</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.testing">Testing</a></span></dt><dt><span class="sect2"><a href="abi.html#abi.issues">Outstanding Issues</a></span></dt></dl></dd><dt><span class="sect1"><a href="api.html">API Evolution and Deprecation History</a></span></dt><dd><dl><dt><span class="sect2"><a href="api.html#api.rel_300"><code class="constant">3.0</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_310"><code class="constant">3.1</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_320"><code class="constant">3.2</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_330"><code class="constant">3.3</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_340"><code class="constant">3.4</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_400"><code class="constant">4.0</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_410"><code class="constant">4.1</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_420"><code class="constant">4.2</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_430"><code class="constant">4.3</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_440"><code class="constant">4.4</code></a></span></dt><dt><span class="sect2"><a href="api.html#api.rel_450"><code class="constant">4.5</code></a></span></dt></dl></dd><dt><span class="sect1"><a href="backwards.html">Backwards Compatibility</a></span></dt><dd><dl><dt><span class="sect2"><a href="backwards.html#backwards.first">First</a></span></dt><dt><span class="sect2"><a href="backwards.html#backwards.second">Second</a></span></dt><dt><span class="sect2"><a href="backwards.html#backwards.third">Third</a></span></dt></dl></dd></dl></div><div class="sect1" 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="sect2" title="Prerequisites"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.prereq"></a>Prerequisites</h3></div></div></div><p>
12 As noted <a class="ulink" href="http://gcc.gnu.org/install/prerequisites.html" target="_top">previously</a>,
13 certain other tools are necessary for hacking on files that
14 control configure (<code class="code">configure.ac</code>,
15 <code class="code">acinclude.m4</code>) and make
16 (<code class="code">Makefile.am</code>). These additional tools
17 (<code class="code">automake</code>, and <code class="code">autoconf</code>) are further
18 described in detail in their respective manuals. All the libraries
19 in GCC try to stay in sync with each other in terms of versions of
20 the auto-tools used, so please try to play nicely with the
22 </p></div><div class="sect2" title="Overview: What Comes from Where"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.map"></a>Overview: What Comes from Where</h3></div></div></div><pre class="screen">
23 <img src="../images/confdeps.png" alt="Dependency Graph Configure to Build Files" />
25 Regenerate all generated files by using the command sequence
26 <code class="code">"autoreconf"</code> at the top level of the libstdc++ source
27 directory. The following will also work, but is much more complex:
28 <code class="code">"aclocal-1.11 && autoconf-2.64 &&
29 autoheader-2.64 && automake-1.11"</code> The version
30 numbers may be absent entirely or otherwise vary depending on
31 <a class="ulink" href="http://gcc.gnu.org/install/prerequisites.html" target="_top">the
32 current requirements</a> and your vendor's choice of
34 </p></div><div class="sect2" title="Storing Information in non-AC files (like configure.host)"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.scripts"></a>Storing Information in non-AC files (like configure.host)</h3></div></div></div><p>
35 Until that glorious day when we can use AC_TRY_LINK with a
36 cross-compiler, we have to hardcode the results of what the tests
37 would have shown if they could be run. So we have an inflexible
38 mess like crossconfig.m4.
40 Wouldn't it be nice if we could store that information in files
41 like configure.host, which can be modified without needing to
42 regenerate anything, and can even be tweaked without really
43 knowing how the configury all works? Perhaps break the pieces of
44 crossconfig.m4 out and place them in their appropriate
45 config/{cpu,os} directory.
47 Alas, writing macros like
48 "<code class="code">AC_DEFINE(HAVE_A_NICE_DAY)</code>" can only be done inside
49 files which are passed through autoconf. Files which are pure
50 shell script can be source'd at configure time. Files which
51 contain autoconf macros must be processed with autoconf. We could
52 still try breaking the pieces out into "config/*/cross.m4" bits,
53 for instance, but then we would need arguments to aclocal/autoconf
54 to properly find them all when generating configure. I would
56 </p></div><div class="sect2" title="Coding and Commenting Conventions"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.conventions"></a>Coding and Commenting Conventions</h3></div></div></div><p>
57 Most comments should use {octothorpes, shibboleths, hash marks,
58 pound signs, whatever} rather than "dnl". Nearly all comments in
59 configure.ac should. Comments inside macros written in ancilliary
60 .m4 files should. About the only comments which should
61 <span class="emphasis"><em>not</em></span> use #, but use dnl instead, are comments
62 <span class="emphasis"><em>outside</em></span> our own macros in the ancilliary
63 files. The difference is that # comments show up in
64 <code class="code">configure</code> (which is most helpful for debugging),
65 while dnl'd lines just vanish. Since the macros in ancilliary
66 files generate code which appears in odd places, their "outside"
67 comments tend to not be useful while reading
68 <code class="code">configure</code>.
70 Do not use any <code class="code">$target*</code> variables, such as
71 <code class="code">$target_alias</code>. The single exception is in
72 configure.ac, for automake+dejagnu's sake.
73 </p></div><div class="sect2" title="The acinclude.m4 layout"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.acinclude"></a>The acinclude.m4 layout</h3></div></div></div><p>
74 The nice thing about acinclude.m4/aclocal.m4 is that macros aren't
75 actually performed/called/expanded/whatever here, just loaded. So
76 we can arrange the contents however we like. As of this writing,
77 acinclude.m4 is arranged as follows:
78 </p><pre class="programlisting">
80 GLIBCXX_TOPREL_CONFIGURE
83 All the major variable "discovery" is done here. CXX, multilibs,
85 </p><pre class="programlisting">
86 fragments included from elsewhere
88 Right now, "fragments" == "the math/linkage bits".
89 </p><pre class="programlisting">
90 GLIBCXX_CHECK_COMPILER_FEATURES
91 GLIBCXX_CHECK_LINKER_FEATURES
92 GLIBCXX_CHECK_WCHAR_T_SUPPORT
94 Next come extra compiler/linker feature tests. Wide character
95 support was placed here because I couldn't think of another place
96 for it. It will probably get broken apart like the math tests,
97 because we're still disabling wchars on systems which could actually
99 </p><pre class="programlisting">
100 GLIBCXX_CHECK_SETRLIMIT_ancilliary
101 GLIBCXX_CHECK_SETRLIMIT
102 GLIBCXX_CHECK_S_ISREG_OR_S_IFREG
106 GLIBCXX_CONFIGURE_TESTSUITE
108 Feature tests which only get used in one place. Here, things used
109 only in the testsuite, plus a couple bits used in the guts of I/O.
110 </p><pre class="programlisting">
111 GLIBCXX_EXPORT_INCLUDES
113 GLIBCXX_EXPORT_INSTALL_INFO
115 Installation variables, multilibs, working with the rest of the
116 compiler. Many of the critical variables used in the makefiles are
118 </p><pre class="programlisting">
121 GLIBCXX_ENABLE_CHEADERS
122 GLIBCXX_ENABLE_CLOCALE
123 GLIBCXX_ENABLE_CONCEPT_CHECKS
124 GLIBCXX_ENABLE_CSTDIO
125 GLIBCXX_ENABLE_CXX_FLAGS
126 GLIBCXX_ENABLE_C_MBCHAR
128 GLIBCXX_ENABLE_DEBUG_FLAGS
129 GLIBCXX_ENABLE_LONG_LONG
131 GLIBCXX_ENABLE_SJLJ_EXCEPTIONS
132 GLIBCXX_ENABLE_SYMVERS
133 GLIBCXX_ENABLE_THREADS
135 All the features which can be controlled with enable/disable
136 configure options. Note how they're alphabetized now? Keep them
138 </p><pre class="programlisting">
142 Things which we don't seem to use directly, but just has to be
143 present otherwise stuff magically goes wonky.
144 </p></div><div class="sect2" title="GLIBCXX_ENABLE, the --enable maker"><div class="titlepage"><div><div><h3 class="title"><a id="build_hacking.enable"></a><code class="constant">GLIBCXX_ENABLE</code>, the <code class="literal">--enable</code> maker</h3></div></div></div><p>
145 All the GLIBCXX_ENABLE_FOO macros use a common helper,
146 GLIBCXX_ENABLE. (You don't have to use it, but it's easy.) The
147 helper does two things for us:
148 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
149 Builds the call to the AC_ARG_ENABLE macro, with --help text
150 properly quoted and aligned. (Death to changequote!)
151 </p></li><li class="listitem"><p>
152 Checks the result against a list of allowed possibilities, and
153 signals a fatal error if there's no match. This means that the
154 rest of the GLIBCXX_ENABLE_FOO macro doesn't need to test for
155 strange arguments, nor do we need to protect against
156 empty/whitespace strings with the <code class="code">"x$foo" = "xbar"</code>
158 </p></li></ol></div><p>Doing these things correctly takes some extra autoconf/autom4te code,
159 which made our macros nearly illegible. So all the ugliness is factored
160 out into this one helper macro.
161 </p><p>Many of the macros take an argument, passed from when they are expanded
162 in configure.ac. The argument controls the default value of the
163 enable/disable switch. Previously, the arguments themselves had defaults.
164 Now they don't, because that's extra complexity with zero gain for us.
165 </p><p>There are three "overloaded signatures". When reading the descriptions
166 below, keep in mind that the brackets are autoconf's quotation characters,
167 and that they will be stripped. Examples of just about everything occur
168 in acinclude.m4, if you want to look.
169 </p><pre class="programlisting">
170 GLIBCXX_ENABLE (FEATURE, DEFAULT, HELP-ARG, HELP-STRING)
171 GLIBCXX_ENABLE (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, permit a|b|c)
172 GLIBCXX_ENABLE (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, SHELL-CODE-HANDLER)
173 </pre><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
174 FEATURE is the string that follows --enable. The results of the
175 test (such as it is) will be in the variable $enable_FEATURE,
176 where FEATURE has been squashed. Example:
177 <code class="code">[extra-foo]</code>, controlled by the --enable-extra-foo
178 option and stored in $enable_extra_foo.
179 </p></li><li class="listitem"><p>
180 DEFAULT is the value to store in $enable_FEATURE if the user does
181 not pass --enable/--disable. It should be one of the permitted
182 values passed later. Examples: <code class="code">[yes]</code>, or
183 <code class="code">[bar]</code>, or <code class="code">[$1]</code> (which passes the
184 argument given to the GLIBCXX_ENABLE_FOO macro as the
187 For cases where we need to probe for particular models of things,
188 it is useful to have an undocumented "auto" value here (see
189 GLIBCXX_ENABLE_CLOCALE for an example).
190 </p></li><li class="listitem"><p>
191 HELP-ARG is any text to append to the option string itself in the
192 --help output. Examples: <code class="code">[]</code> (i.e., an empty string,
193 which appends nothing), <code class="code">[=BAR]</code>, which produces
194 <code class="code">--enable-extra-foo=BAR</code>, and
195 <code class="code">[@<:@=BAR@:>@]</code>, which produces
196 <code class="code">--enable-extra-foo[=BAR]</code>. See the difference? See
197 what it implies to the user?
199 If you're wondering what that line noise in the last example was,
200 that's how you embed autoconf special characters in output text.
201 They're called <a class="ulink" href="http://www.gnu.org/software/autoconf/manual/autoconf.html#Quadrigraphs" target="_top"><span class="emphasis"><em>quadrigraphs</em></span></a>
202 and you should use them whenever necessary.
203 </p></li><li class="listitem"><p>HELP-STRING is what you think it is. Do not include the
204 "default" text like we used to do; it will be done for you by
205 GLIBCXX_ENABLE. By convention, these are not full English
206 sentences. Example: [turn on extra foo]
207 </p></li></ul></div><p>
208 With no other arguments, only the standard autoconf patterns are
209 allowed: "<code class="code">--{enable,disable}-foo[={yes,no}]</code>" The
210 $enable_FEATURE variable is guaranteed to equal either "yes" or "no"
211 after the macro. If the user tries to pass something else, an
212 explanatory error message will be given, and configure will halt.
214 The second signature takes a fifth argument, "<code class="code">[permit
215 a | b | c | ...]</code>"
216 This allows <span class="emphasis"><em>a</em></span> or <span class="emphasis"><em>b</em></span> or
217 ... after the equals sign in the option, and $enable_FEATURE is
218 guaranteed to equal one of them after the macro. Note that if you
219 want to allow plain --enable/--disable with no "=whatever", you must
220 include "yes" and "no" in the list of permitted values. Also note
221 that whatever you passed as DEFAULT must be in the list. If the
222 user tries to pass something not on the list, a semi-explanatory
223 error message will be given, and configure will halt. Example:
224 <code class="code">[permit generic|gnu|ieee_1003.1-2001|yes|no|auto]</code>
226 The third signature takes a fifth argument. It is arbitrary shell
227 code to execute if the user actually passes the enable/disable
228 option. (If the user does not, the default is used. Duh.) No
229 argument checking at all is done in this signature. See
230 GLIBCXX_ENABLE_CXX_FLAGS for an example of handling, and an error
232 </p></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="internals.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="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Porting to New Hardware or Operating Systems</td></tr></table></div></body></html>
OSDN Git Service
