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, and 'malloc' to 68 specify a wrapper for malloc. 69 See <a class="xref" href="memory.html#allocator.ext" title="Extension Allocators">the section called “Extension Allocators”</a> for more information. 70 This option can change the library ABI. 71 </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 72 compatibility with C++. Options are c, c_std, and c_global. 73 These correspond to the source directory's include/c, 74 include/c_std, and include/c_global, and may also include 75 include/c_compatibility. The default is 'c_global'. 76 </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> 77 (described next). 78 </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 79 given in the 80 general <a class="link" href="http://gcc.gnu.org/install/configure.html" target="_top">compiler 81 configuration instructions</a>. This option can change the 82 library ABI. 83 </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, 84 the configure process enables it if possible. This 85 option can change the library ABI. 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 <code class="function">clock_gettime</code> clocks, used in the implementation 90 of [time.clock], and of the <code class="function">nanosleep</code> and 91 <code class="function">sched_yield</code> functions, used in the 92 implementation of [thread.thread.this] of the 2011 ISO C++ standard. 93 The choice OPTION=yes checks for the availability of the facilities 94 in libc. OPTION=rt also checks in 95 librt (and, if it's needed, links to it). Note that linking to librt 96 is not always desirable because for glibc it requires linking to 97 libpthread too, which causes all reference counting to use atomic 98 operations, resulting in a potentially large overhead for 99 single-threaded programs. OPTION=no skips the tests completely. 100 The default is OPTION=auto, which skips the checks and enables the 101 features only for targets known to support them. 102 For Linux targets, if <code class="function">clock_gettime</code> is not used 103 then the [time.clock] implementation will use a system call to access 104 the realtime and monotonic clocks, which is significantly slower than 105 the C library's <code class="function">clock_gettime</code> function. 106 </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. 107 By default, the debug libraries are compiled with 108 <code class="code"> CXXFLAGS='-g3 -O0 -fno-inline'</code> 109 , are installed in <code class="code">${libdir}/debug</code>, and have the 110 same names and versioning information as the non-debug 111 libraries. This option is off by default. 112 </p><p>Note this make command, executed in 113 the build directory, will do much the same thing, without the 114 configuration difference and without building everything twice: 115 <code class="code">make CXXFLAGS='-g3 -O0 -fno-inline' all</code> 116 </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 117 <code class="code">--enable-libstdcxx-debug</code> 118 is also specified, and applies to the debug builds only. With 119 this option, you can pass a specific string of flags to the 120 compiler to use when building the debug versions of libstdc++. 121 FLAGS is a quoted string of options, like 122 </p><pre class="programlisting"> 123 --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) 124 flags to the compiler to use when building libstdc++. This 125 option can change the library ABI. FLAGS is a quoted string of 126 options, like 127 </p><pre class="programlisting"> 128 --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre><p> 129 Note that the flags don't necessarily have to all be -f flags, 130 as shown, but usually those are the ones that will make sense 131 for experimentation and configure-time overriding. 132 </p><p>The advantage of --enable-cxx-flags over setting CXXFLAGS in 133 the 'make' environment is that, if files are automatically 134 rebuilt, the same flags will be used when compiling those files 135 as well, so that everything matches. 136 </p><p>Fun flags to try might include combinations of 137 </p><pre class="programlisting"> 138 -fstrict-aliasing 139 -fno-exceptions 140 -ffunction-sections 141 -fvtable-gc</pre><p>and opposite forms (-fno-) of the same. Tell us (the libstdc++ 142 mailing list) if you discover more! 143 </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 144 with many other functions for wide characters, and math 145 classification macros, etc. If enabled, all C99 functions not 146 specified by the C++ standard will be put into <code class="code">namespace 147 __gnu_cxx</code>, and then all these names will 148 be injected into namespace std, so that C99 functions can be 149 used "as if" they were in the C++ standard (as they 150 will eventually be in some future revision of the standard, 151 without a doubt). By default, C99 support is on, assuming the 152 configure probes find all the necessary functions and bits 153 necessary. This option can change the library ABI. 154 </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 155 required for wide character conversion support. Disabling 156 wide character specializations may be expedient for initial 157 porting efforts, but builds only a subset of what is required by 158 ISO, and is not recommended. By default, this option is on. 159 This option can change the library ABI. 160 </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 161 provided as a GNU extension to C++98 in g++. This flag builds 162 support for "long long" into the library (specialized 163 templates and the like for iostreams). This option is on by default: 164 if enabled, users will have to either use the new-style "C" 165 headers by default (i.e., <cmath> not <math.h>) 166 or add appropriate compile-time flags to all compile lines to 167 allow "C" visibility of this feature (on GNU/Linux, 168 the flag is -D_ISOC99_SOURCE, which is added automatically via 169 CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE). 170 This option can change the library ABI. 171 </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 172 the optimization that allocates empty objects in static memory. 173 Mostly useful together with shared memory allocators, see PR 174 libstdc++/16612 for details. 175 </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 176 library templates, in the form of specialized templates described in 177 the <a class="link" href="concept_checking.html" title="Concept Checking">Concept 178 Checking</a> section. They 179 can help users discover when they break the rules of the STL, before 180 their programs run. These checks are based on C++03 rules and some of 181 them are not compatible with correct C++11 code. 182 </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 183 shared library (if a shared library has been 184 requested). Values for 'style' that are currently supported 185 are 'gnu', 'gnu-versioned-namespace', 'darwin', 186 'darwin-export', and 'sun'. Both gnu- options require that a recent 187 version of the GNU linker be in use. Both darwin options are 188 equivalent. With no style given, the configure script will try 189 to guess correct defaults for the host system, probe to see if 190 additional requirements are necessary and present for 191 activation, and if so, will turn symbol versioning on. This 192 option can change the library ABI. 193 </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 194 attributes. If enabled (as by default), and the compiler seems 195 capable of passing the simple sanity checks thrown at it, adjusts 196 items in namespace std, namespace std::tr1, namespace std::tr2, 197 and namespace __gnu_cxx to have <code class="code">visibility ("default")</code> 198 so that -fvisibility options can be used without affecting the 199 normal external-visibility of namespace std entities. 200 Prior to 4.7 this option was spelled <code class="code">--enable-visibility</code>. 201 </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 202 stdc++.h.gch, a pre-compiled file including all the standard 203 C++ includes. If enabled (as by default), and the compiler 204 seems capable of passing the simple sanity checks thrown at 205 it, try to build stdc++.h.gch as part of the make process. 206 In addition, this generated file is used later on (by appending <code class="code"> 207 --include bits/stdc++.h </code> to CXXFLAGS) when running the 208 testsuite. 209 </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 210 specializations for certain types defined in the standard libraries. 211 These types include <code class="classname">string</code> and dependents like 212 <code class="classname">char_traits</code>, the templatized IO classes, 213 <code class="classname">allocator</code>, and others. 214 Disabling means that implicit 215 template generation will be used when compiling these types. By 216 default, this option is on. This option can change the library ABI. 217 </p></dd><dt><span class="term"><code class="code">--disable-hosted-libstdcxx</code></span></dt><dd><p> 218 By default, a complete <span class="emphasis"><em>hosted</em></span> C++ library is 219 built. The C++ Standard also describes a 220 <span class="emphasis"><em>freestanding</em></span> environment, in which only a 221 minimal set of headers are provided. This option builds such an 222 environment. 223 </p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-verbose</code></span></dt><dd><p> 224 By default, the library is configured to write descriptive messages 225 to standard error for certain events such as calling a pure virtual 226 function or the invocation of the standard terminate handler. Those 227 messages cause the library to depend on the demangler and standard I/O 228 facilities, which might be undesirable in a low-memory environment or 229 when standard error is not available. This option disables those 230 messages. This option does not change the library ABI. 231 </p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-dual-abi</code></span></dt><dd><p> 232 Disable support for the new, C++11-conforming implementations of 233 <code class="code">std::string</code>, <code class="code">std::list</code> etc. so that the 234 library only provides definitions of types using the old ABI 235 (see <a class="xref" href="using_dual_abi.html" title="Dual ABI">Dual ABI</a>). 236 This option changes the library ABI. 237 </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> 238 Set the default value for the <span class="symbol">_GLIBCXX_USE_CXX11_ABI</span> 239 macro (see <a class="xref" href="using_macros.html" title="Macros">Macros</a>). 240 The default is <code class="option">OPTION=new</code> which sets the macro to 241 <code class="literal">1</code>, 242 use <code class="option">OPTION=gcc4-compatible</code> to set it to 243 <code class="literal">0</code>. 244 This option does not change the library ABI. 245 </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 246 <code class="classname">shared_ptr</code> reference counting is 247 synchronized. 248 The choice OPTION=atomic enables use of atomics for updates to 249 <code class="classname">shared_ptr</code> reference counts. 250 The choice OPTION=mutex enables use of a mutex to synchronize updates 251 to <code class="classname">shared_ptr</code> reference counts. 252 If the compiler's thread model is "single" then this option has no 253 effect, as no synchronization is used for the reference counts. 254 The default is OPTION=auto, which checks for the availability of 255 compiler built-ins for 2-byte and 4-byte atomic compare-and-swap, 256 and uses OPTION=atomic if they're available, OPTION=mutex otherwise. 257 This option can change the library ABI. 258 If the library is configured to use atomics and user programs are 259 compiled using a target that doesn't natively support the atomic 260 operations (e.g. the library is configured for armv7 and then code 261 is compiled with <code class="option">-march=armv5t</code>) then the program 262 might rely on support in libgcc to provide the atomics. 263 </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++ 264 runtime with instrumentation for vtable verification. All virtual 265 functions in the standard library will be verified at runtime. 266 Types impacted include <code class="classname">locale</code> and 267 <code class="classname">iostream</code>, and others. Disabling means that 268 the C++ runtime is compiled without support for vtable 269 verification. By default, this option is off. 270 </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 271 as the usual libstdc++ and libsupc++ libraries. This is enabled by 272 default on select POSIX targets where it is known to work and disabled 273 otherwise. 274 </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>