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3 <html xmlns="http://www.w3.org/1999/xhtml"><head><title>Configure</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , configure , options "/><meta name="keywords" content=" ISO C++ , library "/><meta name="keywords" content=" ISO C++ , runtime , library "/><link rel="home" href="../index.html" title="The GNU C++ Library"/><link rel="up" href="setup.html" title="Chapter 2. Setup"/><link rel="prev" href="setup.html" title="Chapter 2. Setup"/><link rel="next" href="make.html" title="Make"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Configure</th></tr><tr><td align="left"><a accesskey="p" href="setup.html">Prev</a> </td><th width="60%" align="center">Chapter 2. Setup</th><td align="right"> <a accesskey="n" href="make.html">Next</a></td></tr></table><hr/></div><div class="section" title="Configure"><div class="titlepage"><div><div><h2 class="title"><a id="manual.intro.setup.configure"/>Configure</h2></div></div></div><p>
4 When configuring libstdc++, you'll have to configure the entire
5 <span class="emphasis"><em>gccsrcdir</em></span> directory. Consider using the
6 toplevel gcc configuration option
7 <code class="literal">--enable-languages=c++</code>, which saves time by only
8 building the C++ toolchain.
10 Here are all of the configure options specific to libstdc++. Keep
13 <a class="link" href="http://sourceware.org/autobook/autobook/autobook_14.html">they
14 all have opposite forms as well</a> (enable/disable and
15 with/without). The defaults are for the <span class="emphasis"><em>current
16 development sources</em></span>, which may be different than those
17 for released versions.
18 </p><p>The canonical way to find out the configure options that are
19 available for a given set of libstdc++ sources is to go to the
20 source directory and then type:<span class="command"><strong>./configure --help</strong></span>.
21 </p><div class="variablelist"><dl><dt><span class="term"><code class="code">--enable-multilib</code>[default]</span></dt><dd><p>This is part of the generic multilib support for building cross
22 compilers. As such, targets like "powerpc-elf" will have
23 libstdc++ built many different ways: "-msoft-float"
24 and not, etc. A different libstdc++ will be built for each of
25 the different multilib versions. This option is on by default.
26 </p></dd><dt><span class="term"><code class="code">--enable-sjlj-exceptions</code></span></dt><dd><p>Forces old, set-jump/long-jump exception handling model. If
27 at all possible, the new, frame unwinding exception handling routines
28 should be used instead, as they significantly reduce both
29 runtime memory usage and executable size. This option can
30 change the library ABI.
31 </p></dd><dt><span class="term"><code class="code">--enable-version-specific-runtime-libs</code></span></dt><dd><p>Specify that run-time libraries should be installed in the
32 compiler-specific subdirectory (i.e.,
33 <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
34 instead of <code class="code">${libdir}</code>. This option is useful if you
35 intend to use several versions of gcc in parallel. In addition,
36 libstdc++'s include files will be installed in
37 <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
38 unless you also specify
39 <code class="literal">--with-gxx-include-dir=</code><code class="filename">dirname</code> during configuration.
40 </p></dd><dt><span class="term"><code class="code">--with-gxx-include-dir=<include-files dir></code></span></dt><dd><p>Adds support for named libstdc++ include directory. For instance,
41 the following puts all the libstdc++ headers into a directory
42 called "4.4-20090404" instead of the usual
44 </p><pre class="programlisting">
45 --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/4.4-20090404</pre></dd><dt><span class="term"><code class="code">--enable-cstdio</code></span></dt><dd><p>This is an abbreviated form of <code class="code">'--enable-cstdio=stdio'</code>
47 </p></dd><dt><span class="term"><code class="code">--enable-cstdio=OPTION</code></span></dt><dd><p>Select a target-specific I/O package. At the moment, the only
48 choice is to use 'stdio', a generic "C" abstraction.
49 The default is 'stdio'. This option can change the library ABI.
50 </p></dd><dt><span class="term"><code class="code">--enable-clocale</code></span></dt><dd><p>This is an abbreviated form of <code class="code">'--enable-clocale=generic'</code>
52 </p></dd><dt><span class="term"><code class="code">--enable-clocale=OPTION</code></span></dt><dd><p>Select a target-specific underlying locale package. The
53 choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
54 (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
55 'gnu' to specify a model based on functionality from the GNU C
56 library (langinfo/iconv/gettext) (from <a class="link" href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C
57 library), or 'generic' to use a generic "C"
58 abstraction which consists of "C" locale info.
59 </p><p>If not explicitly specified, the configure proccess tries
60 to guess the most suitable package from the choices above. The
61 default is 'generic'. On glibc-based systems of sufficient
62 vintage (2.3 and newer), 'gnu' is automatically selected. This option
63 can change the library ABI.
64 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator</code></span></dt><dd><p>This is an abbreviated form of
65 <code class="code">'--enable-libstdcxx-allocator=auto'</code> (described
67 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator=OPTION </code></span></dt><dd><p>Select a target-specific underlying std::allocator. The
68 choices are 'new' to specify a wrapper for new, 'malloc' to
69 specify a wrapper for malloc, 'mt' for a fixed power of two allocator,
70 'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator.
71 See this page for more information on allocator
72 <a class="link" href="memory.html#allocator.ext" title="Extension Allocators">extensions</a>. This option
73 can change the library ABI.
74 </p></dd><dt><span class="term"><code class="code">--enable-cheaders=OPTION</code></span></dt><dd><p>This allows the user to define the approach taken for C header
75 compatibility with C++. Options are c, c_std, and c_global.
76 These correspond to the source directory's include/c,
77 include/c_std, and include/c_global, and may also include
78 include/c_compatibility. The default is 'c_global'.
79 </p></dd><dt><span class="term"><code class="code">--enable-threads</code></span></dt><dd><p>This is an abbreviated form of <code class="code">'--enable-threads=yes'</code>
81 </p></dd><dt><span class="term"><code class="code">--enable-threads=OPTION</code></span></dt><dd><p>Select a threading library. A full description is
83 general <a class="link" href="http://gcc.gnu.org/install/configure.html">compiler
84 configuration instructions</a>. This option can change the
86 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time</code></span></dt><dd><p>This is an abbreviated form of
87 <code class="code">'--enable-libstdcxx-time=yes'</code>(described next).
88 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time=OPTION</code></span></dt><dd><p>Enables link-type checks for the availability of the
89 clock_gettime clocks, used in the implementation of [time.clock],
90 and of the nanosleep and sched_yield functions, used in the
91 implementation of [thread.thread.this] of the 2011 ISO C++ standard.
92 The choice OPTION=yes checks for the availability of the facilities
93 in libc and libposix4. In case of need the latter is also linked
94 to libstdc++ as part of the build process. OPTION=rt also searches
95 (and, in case, links) librt. Note that the latter is not always
96 desirable because, in glibc, for example, in turn it triggers the
97 linking of libpthread too, which activates locking, a large overhead
98 for single-thread programs. OPTION=no skips the tests completely.
99 The default is OPTION=no.
100 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-debug</code></span></dt><dd><p>Build separate debug libraries in addition to what is normally built.
101 By default, the debug libraries are compiled with
102 <code class="code"> CXXFLAGS='-g3 -O0 -fno-inline'</code>
103 , are installed in <code class="code">${libdir}/debug</code>, and have the
104 same names and versioning information as the non-debug
105 libraries. This option is off by default.
106 </p><p>Note this make command, executed in
107 the build directory, will do much the same thing, without the
108 configuration difference and without building everything twice:
109 <code class="code">make CXXFLAGS='-g3 -O0 -fno-inline' all</code>
110 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-debug-flags=FLAGS</code></span></dt><dd><p>This option is only valid when <code class="code"> --enable-debug </code>
111 is also specified, and applies to the debug builds only. With
112 this option, you can pass a specific string of flags to the
113 compiler to use when building the debug versions of libstdc++.
114 FLAGS is a quoted string of options, like
115 </p><pre class="programlisting">
116 --enable-libstdcxx-debug-flags='-g3 -O1 -fno-inline'</pre></dd><dt><span class="term"><code class="code">--enable-cxx-flags=FLAGS</code></span></dt><dd><p>With this option, you can pass a string of -f (functionality)
117 flags to the compiler to use when building libstdc++. This
118 option can change the library ABI. FLAGS is a quoted string of
120 </p><pre class="programlisting">
121 --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre><p>
122 Note that the flags don't necessarily have to all be -f flags,
123 as shown, but usually those are the ones that will make sense
124 for experimentation and configure-time overriding.
125 </p><p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
126 the 'make' environment is that, if files are automatically
127 rebuilt, the same flags will be used when compiling those files
128 as well, so that everything matches.
129 </p><p>Fun flags to try might include combinations of
130 </p><pre class="programlisting">
134 -fvtable-gc</pre><p>and opposite forms (-fno-) of the same. Tell us (the libstdc++
135 mailing list) if you discover more!
136 </p></dd><dt><span class="term"><code class="code">--enable-c99</code></span></dt><dd><p>The "long long" type was introduced in C99, along
137 with many other functions for wide characters, and math
138 classification macros, etc. If enabled, all C99 functions not
139 specified by the C++ standard will be put into <code class="code">namespace
140 __gnu_cxx</code>, and then all these names will
141 be injected into namespace std, so that C99 functions can be
142 used "as if" they were in the C++ standard (as they
143 will eventually be in some future revision of the standard,
144 without a doubt). By default, C99 support is on, assuming the
145 configure probes find all the necessary functions and bits
146 necessary. This option can change the library ABI.
147 </p></dd><dt><span class="term"><code class="code">--enable-wchar_t</code>[default]</span></dt><dd><p>Template specializations for the "wchar_t" type are
148 required for wide character conversion support. Disabling
149 wide character specializations may be expedient for initial
150 porting efforts, but builds only a subset of what is required by
151 ISO, and is not recommended. By default, this option is on.
152 This option can change the library ABI.
153 </p></dd><dt><span class="term"><code class="code">--enable-long-long </code></span></dt><dd><p>The "long long" type was introduced in C99. It is
154 provided as a GNU extension to C++98 in g++. This flag builds
155 support for "long long" into the library (specialized
156 templates and the like for iostreams). This option is on by default:
157 if enabled, users will have to either use the new-style "C"
158 headers by default (i.e., <cmath> not <math.h>)
159 or add appropriate compile-time flags to all compile lines to
160 allow "C" visibility of this feature (on GNU/Linux,
161 the flag is -D_ISOC99_SOURCE, which is added automatically via
162 CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
163 This option can change the library ABI.
164 </p></dd><dt><span class="term"><code class="code">--enable-fully-dynamic-string</code></span></dt><dd><p>This option enables a special version of basic_string avoiding
165 the optimization that allocates empty objects in static memory.
166 Mostly useful together with shared memory allocators, see PR
167 libstdc++/16612 for details.
168 </p></dd><dt><span class="term"><code class="code">--enable-concept-checks</code></span></dt><dd><p>This turns on additional compile-time checks for instantiated
169 library templates, in the form of specialized templates,
170 <a class="link" href="bk01pt02ch05s02.html" title="Concept Checking">described here</a>. They
171 can help users discover when they break the rules of the STL, before
173 </p></dd><dt><span class="term"><code class="code">--enable-symvers[=style]</code></span></dt><dd><p>In 3.1 and later, tries to turn on symbol versioning in the
174 shared library (if a shared library has been
175 requested). Values for 'style' that are currently supported
176 are 'gnu', 'gnu-versioned-namespace', 'darwin',
177 'darwin-export', and 'sun'. Both gnu- options require that a recent
178 version of the GNU linker be in use. Both darwin options are
179 equivalent. With no style given, the configure script will try
180 to guess correct defaults for the host system, probe to see if
181 additional requirements are necessary and present for
182 activation, and if so, will turn symbol versioning on. This
183 option can change the library ABI.
184 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-visibility</code></span></dt><dd><p> In 4.2 and later, enables or disables visibility
185 attributes. If enabled (as by default), and the compiler seems
186 capable of passing the simple sanity checks thrown at it, adjusts
187 items in namespace std, namespace std::tr1, namespace std::tr2,
188 and namespace __gnu_cxx to have <code class="code">visibility ("default")</code>
189 so that -fvisibility options can be used without affecting the
190 normal external-visibility of namespace std entities.
191 Prior to 4.7 this option was spelled <code class="code">--enable-visibility</code>.
192 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-pch</code></span></dt><dd><p>In 3.4 and later, tries to turn on the generation of
193 stdc++.h.gch, a pre-compiled file including all the standard
194 C++ includes. If enabled (as by default), and the compiler
195 seems capable of passing the simple sanity checks thrown at
196 it, try to build stdc++.h.gch as part of the make process.
197 In addition, this generated file is used later on (by appending <code class="code">
198 --include bits/stdc++.h </code> to CXXFLAGS) when running the
200 </p></dd><dt><span class="term"><code class="code">--enable-extern-template</code>[default]</span></dt><dd><p>Use extern template to pre-instantiate all required
201 specializations for certain types defined in the standard libraries.
202 These types include <code class="classname">string</code> and dependents like
203 <code class="classname">char_traits</code>, the templateized io classes,
204 <code class="classname">allocator</code>, and others.
205 Disabling means that implicit
206 template generation will be used when compiling these types. By
207 default, this option is on. This option can change the library ABI.
208 </p></dd><dt><span class="term"><code class="code">--disable-hosted-libstdcxx</code></span></dt><dd><p>
209 By default, a complete <span class="emphasis"><em>hosted</em></span> C++ library is
210 built. The C++ Standard also describes a
211 <span class="emphasis"><em>freestanding</em></span> environment, in which only a
212 minimal set of headers are provided. This option builds such an
214 </p></dd></dl></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="setup.html">Prev</a> </td><td align="center"><a accesskey="u" href="setup.html">Up</a></td><td align="right"> <a accesskey="n" href="make.html">Next</a></td></tr><tr><td align="left" valign="top">Chapter 2. Setup </td><td align="center"><a accesskey="h" href="../index.html">Home</a></td><td align="right" valign="top"> Make</td></tr></table></div></body></html>