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"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Configure</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><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 width="20%" align="left"><a accesskey="p" href="setup.html">Prev</a>��</td><th width="60%" align="center">Chapter��2.��Setup</th><td width="20%" align="right">��<a accesskey="n" href="make.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.setup.configure"></a>Configure</h2></div></div></div><p> 3 When configuring libstdc++, you'll have to configure the entire 4 <span class="emphasis"><em>gccsrcdir</em></span> directory. Consider using the 5 toplevel gcc configuration option 6 <code class="literal">--enable-languages=c++</code>, which saves time by only 7 building the C++ toolchain. 8</p><p> 9 Here are all of the configure options specific to libstdc++. Keep 10 in mind that 11 12 <a class="link" href="http://sourceware.org/autobook/autobook/autobook_14.html" target="_top">they 13 all have opposite forms as well</a> (enable/disable and 14 with/without). The defaults are for the <span class="emphasis"><em>current 15 development sources</em></span>, which may be different than those 16 for released versions. 17</p><p>The canonical way to find out the configure options that are 18 available for a given set of libstdc++ sources is to go to the 19 source directory and then type: <span class="command"><strong>./configure --help</strong></span>. 20</p><div class="variablelist"><dl class="variablelist"><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 21 compilers. As such, targets like "powerpc-elf" will have 22 libstdc++ built many different ways: "-msoft-float" 23 and not, etc. A different libstdc++ will be built for each of 24 the different multilib versions. This option is on by default. 25 </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 26 compiler-specific subdirectory (i.e., 27 <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>) 28 instead of <code class="code">${libdir}</code>. This option is useful if you 29 intend to use several versions of gcc in parallel. In addition, 30 libstdc++'s include files will be installed in 31 <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>, 32 unless you also specify 33 <code class="literal">--with-gxx-include-dir=</code><code class="filename">dirname</code> during configuration. 34 </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, 35 the following puts all the libstdc++ headers into a directory 36 called "4.4-20090404" instead of the usual 37 "c++/(version)". 38 </p><pre class="programlisting"> 39 --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> 40 (described next). 41 </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 42 choice is to use 'stdio', a generic "C" abstraction. 43 The default is 'stdio'. This option can change the library ABI. 44 </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> 45 (described next). 46 </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 47 choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix 48 (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets, 49 'gnu' to specify a model based on functionality from the GNU C 50 library (langinfo/iconv/gettext) (from <a class="link" href="https://www.gnu.org/software/libc/" target="_top">glibc</a>, the GNU C 51 library), 'generic' to use a generic "C" abstraction which consists 52 of "C" locale info, 'newlib' to specify the Newlib C library model 53 which only differs from the 'generic' model in the handling of 54 ctype, or 'darwin' which omits the <span class="type">wchar_t</span> specializations 55 needed by the 'generic' model. 56 </p><p>If not explicitly specified, the configure process tries 57 to guess the most suitable package from the choices above. The 58 default is 'generic'. On glibc-based systems of sufficient 59 vintage (2.3 and newer), 'gnu' is automatically selected. On newlib-based 60 systems (<code class="code">'--with_newlib=yes'</code>) and OpenBSD, 'newlib' is 61 automatically selected. On Mac OS X 'darwin' is automatically selected. 62 This option can change the library ABI. 63 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator</code></span></dt><dd><p>This is an abbreviated form of 64 <code class="code">'--enable-libstdcxx-allocator=auto'</code> (described 65 next). 66 </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 67 choices are 'new' to specify a wrapper for new, 'malloc' to 68 specify a wrapper for malloc, 'mt' for a fixed power of two allocator, 69 'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator. 70 See this page for more information on allocator 71 <a class="link" href="memory.html#allocator.ext" title="Extension Allocators">extensions</a>. This option 72 can change the library ABI. 73 </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 74 compatibility with C++. Options are c, c_std, and c_global. 75 These correspond to the source directory's include/c, 76 include/c_std, and include/c_global, and may also include 77 include/c_compatibility. The default is 'c_global'. 78 </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> 79 (described next). 80 </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 81 given in the 82 general <a class="link" href="http://gcc.gnu.org/install/configure.html" target="_top">compiler 83 configuration instructions</a>. This option can change the 84 library ABI. 85 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-threads</code></span></dt><dd><p>Enable C++11 threads support. If not explicitly specified, 86 the configure process enables it if possible. This 87 option can change the library ABI. 88 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time</code></span></dt><dd><p>This is an abbreviated form of 89 <code class="code">'--enable-libstdcxx-time=yes'</code>(described next). 90 </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 91 <code class="function">clock_gettime</code> clocks, used in the implementation 92 of [time.clock], and of the <code class="function">nanosleep</code> and 93 <code class="function">sched_yield</code> functions, used in the 94 implementation of [thread.thread.this] of the 2011 ISO C++ standard. 95 The choice OPTION=yes checks for the availability of the facilities 96 in libc and libposix4. In case it's needed the latter is also linked 97 to libstdc++ as part of the build process. OPTION=rt also checks in 98 librt (and, if it's needed, links to it). Note that linking to librt 99 is not always desirable because for glibc it requires linking to 100 libpthread too, which causes all reference counting to use atomic 101 operations, resulting in a potentially large overhead for 102 single-threaded programs. OPTION=no skips the tests completely. 103 The default is OPTION=auto, which skips the checks and enables the 104 features only for targets known to support them. 105 For Linux targets, if <code class="function">clock_gettime</code> is not used 106 then the [time.clock] implementation will use a system call to access 107 the realtime and monotonic clocks, which is significantly slower than 108 the C library's <code class="function">clock_gettime</code> function. 109 </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. 110 By default, the debug libraries are compiled with 111 <code class="code"> CXXFLAGS='-g3 -O0 -fno-inline'</code> 112 , are installed in <code class="code">${libdir}/debug</code>, and have the 113 same names and versioning information as the non-debug 114 libraries. This option is off by default. 115 </p><p>Note this make command, executed in 116 the build directory, will do much the same thing, without the 117 configuration difference and without building everything twice: 118 <code class="code">make CXXFLAGS='-g3 -O0 -fno-inline' all</code> 119 </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 120 <code class="code">--enable-libstdcxx-debug</code> 121 is also specified, and applies to the debug builds only. With 122 this option, you can pass a specific string of flags to the 123 compiler to use when building the debug versions of libstdc++. 124 FLAGS is a quoted string of options, like 125 </p><pre class="programlisting"> 126 --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) 127 flags to the compiler to use when building libstdc++. This 128 option can change the library ABI. FLAGS is a quoted string of 129 options, like 130 </p><pre class="programlisting"> 131 --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre><p> 132 Note that the flags don't necessarily have to all be -f flags, 133 as shown, but usually those are the ones that will make sense 134 for experimentation and configure-time overriding. 135 </p><p>The advantage of --enable-cxx-flags over setting CXXFLAGS in 136 the 'make' environment is that, if files are automatically 137 rebuilt, the same flags will be used when compiling those files 138 as well, so that everything matches. 139 </p><p>Fun flags to try might include combinations of 140 </p><pre class="programlisting"> 141 -fstrict-aliasing 142 -fno-exceptions 143 -ffunction-sections 144 -fvtable-gc</pre><p>and opposite forms (-fno-) of the same. Tell us (the libstdc++ 145 mailing list) if you discover more! 146 </p></dd><dt><span class="term"><code class="code">--enable-c99</code></span></dt><dd><p>The <span class="type">long long</span> type was introduced in C99, along 147 with many other functions for wide characters, and math 148 classification macros, etc. If enabled, all C99 functions not 149 specified by the C++ standard will be put into <code class="code">namespace 150 __gnu_cxx</code>, and then all these names will 151 be injected into namespace std, so that C99 functions can be 152 used "as if" they were in the C++ standard (as they 153 will eventually be in some future revision of the standard, 154 without a doubt). By default, C99 support is on, assuming the 155 configure probes find all the necessary functions and bits 156 necessary. This option can change the library ABI. 157 </p></dd><dt><span class="term"><code class="code">--enable-wchar_t</code>[default]</span></dt><dd><p>Template specializations for the <span class="type">wchar_t</span> type are 158 required for wide character conversion support. Disabling 159 wide character specializations may be expedient for initial 160 porting efforts, but builds only a subset of what is required by 161 ISO, and is not recommended. By default, this option is on. 162 This option can change the library ABI. 163 </p></dd><dt><span class="term"><code class="code">--enable-long-long </code></span></dt><dd><p>The <span class="type">long long</span> type was introduced in C99. It is 164 provided as a GNU extension to C++98 in g++. This flag builds 165 support for "long long" into the library (specialized 166 templates and the like for iostreams). This option is on by default: 167 if enabled, users will have to either use the new-style "C" 168 headers by default (i.e., <cmath> not <math.h>) 169 or add appropriate compile-time flags to all compile lines to 170 allow "C" visibility of this feature (on GNU/Linux, 171 the flag is -D_ISOC99_SOURCE, which is added automatically via 172 CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE). 173 This option can change the library ABI. 174 </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 175 the optimization that allocates empty objects in static memory. 176 Mostly useful together with shared memory allocators, see PR 177 libstdc++/16612 for details. 178 </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 179 library templates, in the form of specialized templates described in 180 the <a class="link" href="concept_checking.html" title="Concept Checking">Concept 181 Checking</a> section. They 182 can help users discover when they break the rules of the STL, before 183 their programs run. These checks are based on C++03 rules and some of 184 them are not compatible with correct C++11 code. 185 </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 186 shared library (if a shared library has been 187 requested). Values for 'style' that are currently supported 188 are 'gnu', 'gnu-versioned-namespace', 'darwin', 189 'darwin-export', and 'sun'. Both gnu- options require that a recent 190 version of the GNU linker be in use. Both darwin options are 191 equivalent. With no style given, the configure script will try 192 to guess correct defaults for the host system, probe to see if 193 additional requirements are necessary and present for 194 activation, and if so, will turn symbol versioning on. This 195 option can change the library ABI. 196 </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 197 attributes. If enabled (as by default), and the compiler seems 198 capable of passing the simple sanity checks thrown at it, adjusts 199 items in namespace std, namespace std::tr1, namespace std::tr2, 200 and namespace __gnu_cxx to have <code class="code">visibility ("default")</code> 201 so that -fvisibility options can be used without affecting the 202 normal external-visibility of namespace std entities. 203 Prior to 4.7 this option was spelled <code class="code">--enable-visibility</code>. 204 </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 205 stdc++.h.gch, a pre-compiled file including all the standard 206 C++ includes. If enabled (as by default), and the compiler 207 seems capable of passing the simple sanity checks thrown at 208 it, try to build stdc++.h.gch as part of the make process. 209 In addition, this generated file is used later on (by appending <code class="code"> 210 --include bits/stdc++.h </code> to CXXFLAGS) when running the 211 testsuite. 212 </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 213 specializations for certain types defined in the standard libraries. 214 These types include <code class="classname">string</code> and dependents like 215 <code class="classname">char_traits</code>, the templatized IO classes, 216 <code class="classname">allocator</code>, and others. 217 Disabling means that implicit 218 template generation will be used when compiling these types. By 219 default, this option is on. This option can change the library ABI. 220 </p></dd><dt><span class="term"><code class="code">--disable-hosted-libstdcxx</code></span></dt><dd><p> 221 By default, a complete <span class="emphasis"><em>hosted</em></span> C++ library is 222 built. The C++ Standard also describes a 223 <span class="emphasis"><em>freestanding</em></span> environment, in which only a 224 minimal set of headers are provided. This option builds such an 225 environment. 226 </p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-verbose</code></span></dt><dd><p> 227 By default, the library is configured to write descriptive messages 228 to standard error for certain events such as calling a pure virtual 229 function or the invocation of the standard terminate handler. Those 230 messages cause the library to depend on the demangler and standard I/O 231 facilities, which might be undesirable in a low-memory environment or 232 when standard error is not available. This option disables those 233 messages. This option does not change the library ABI. 234 </p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-dual-abi</code></span></dt><dd><p> 235 Disable support for the new, C++11-conforming implementations of 236 <code class="code">std::string</code>, <code class="code">std::list</code> etc. so that the 237 library only provides definitions of types using the old ABI 238 (see <a class="xref" href="using_dual_abi.html" title="Dual ABI">Dual ABI</a>). 239 This option changes the library ABI. 240 </p></dd><dt><span class="term"><code class="code">--with-default-libstdcxx-abi=</code><em class="replaceable"><code>OPTION</code></em></span></dt><dd><p> 241 Set the default value for the <span class="symbol">_GLIBCXX_USE_CXX11_ABI</span> 242 macro (see <a class="xref" href="using_macros.html" title="Macros">Macros</a>). 243 The default is <code class="option">OPTION=new</code> which sets the macro to 244 <code class="literal">1</code>, 245 use <code class="option">OPTION=gcc4-compatible</code> to set it to 246 <code class="literal">0</code>. 247 This option does not change the library ABI. 248 </p></dd><dt><span class="term"><code class="code">--with-libstdcxx-lock-policy=OPTION</code></span></dt><dd><p>Sets the lock policy that controls how 249 <code class="classname">shared_ptr</code> reference counting is 250 synchronized. 251 The choice OPTION=atomic enables use of atomics for updates to 252 <code class="classname">shared_ptr</code> reference counts. 253 The choice OPTION=mutex enables use of a mutex to synchronize updates 254 to <code class="classname">shared_ptr</code> reference counts. 255 If the compiler's thread model is "single" then this option has no 256 effect, as no synchronization is used for the reference counts. 257 The default is OPTION=auto, which checks for the availability of 258 compiler built-ins for 2-byte and 4-byte atomic compare-and-swap, 259 and uses OPTION=atomic if they're available, OPTION=mutex otherwise. 260 This option can change the library ABI. 261 If the library is configured to use atomics and user programs are 262 compiled using a target that doesn't natively support the atomic 263 operations (e.g. the library is configured for armv7 and then code 264 is compiled with <code class="option">-march=armv5t</code>) then the program 265 might rely on support in libgcc to provide the atomics. 266 </p></dd><dt><span class="term"><code class="code">--enable-vtable-verify</code>[default]</span></dt><dd><p>Use <code class="code">-fvtable-verify=std</code> to compile the C++ 267 runtime with instrumentation for vtable verification. All virtual 268 functions in the standard library will be verified at runtime. 269 Types impacted include <code class="classname">locale</code> and 270 <code class="classname">iostream</code>, and others. Disabling means that 271 the C++ runtime is compiled without support for vtable 272 verification. By default, this option is off. 273 </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-filesystem-ts</code>[default]</span></dt><dd><p>Build <code class="filename">libstdc++fs.a</code> as well 274 as the usual libstdc++ and libsupc++ libraries. This is enabled by 275 default on select POSIX targets where it is known to work and disabled 276 otherwise. 277 </p></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="setup.html">Prev</a>��</td><td width="20%" align="center"><a accesskey="u" href="setup.html">Up</a></td><td width="40%" align="right">��<a accesskey="n" href="make.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter��2.��Setup��</td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top">��Make</td></tr></table></div></body></html>