1<section xmlns="http://docbook.org/ns/docbook" version="5.0" 2 xml:id="manual.intro.setup.configure" xreflabel="Configuring"> 3<?dbhtml filename="configure.html"?> 4 5<info><title>Configure</title> 6 <keywordset> 7 <keyword>ISO C++</keyword> 8 <keyword>configure</keyword> 9 <keyword>options</keyword> 10 </keywordset> 11</info> 12 13 14 15<para> 16 When configuring libstdc++, you'll have to configure the entire 17 <emphasis>gccsrcdir</emphasis> directory. Consider using the 18 toplevel gcc configuration option 19 <literal>--enable-languages=c++</literal>, which saves time by only 20 building the C++ toolchain. 21</para> 22 23<para> 24 Here are all of the configure options specific to libstdc++. Keep 25 in mind that 26 <!-- This SECnn should be the "Choosing Package Options" section. --> 27 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://sourceware.org/autobook/autobook/autobook_14.html">they 28 all have opposite forms as well</link> (enable/disable and 29 with/without). The defaults are for the <emphasis>current 30 development sources</emphasis>, which may be different than those 31 for released versions. 32</para> 33<para>The canonical way to find out the configure options that are 34 available for a given set of libstdc++ sources is to go to the 35 source directory and then type: <command>./configure --help</command>. 36</para> 37 38<variablelist> 39 <varlistentry><term><code>--enable-multilib</code>[default]</term> 40 <listitem><para>This is part of the generic multilib support for building cross 41 compilers. As such, targets like "powerpc-elf" will have 42 libstdc++ built many different ways: "-msoft-float" 43 and not, etc. A different libstdc++ will be built for each of 44 the different multilib versions. This option is on by default. 45 </para> 46 </listitem></varlistentry> 47 48 <varlistentry><term><code>--enable-version-specific-runtime-libs</code></term> 49 <listitem><para>Specify that run-time libraries should be installed in the 50 compiler-specific subdirectory (i.e., 51 <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>) 52 instead of <code>${libdir}</code>. This option is useful if you 53 intend to use several versions of gcc in parallel. In addition, 54 libstdc++'s include files will be installed in 55 <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>, 56 unless you also specify 57 <literal>--with-gxx-include-dir=</literal><filename class="directory">dirname</filename> during configuration. 58 </para> 59 </listitem></varlistentry> 60 61 <varlistentry><term><code>--with-gxx-include-dir=<include-files dir></code></term> 62 <listitem><para>Adds support for named libstdc++ include directory. For instance, 63 the following puts all the libstdc++ headers into a directory 64 called "4.4-20090404" instead of the usual 65 "c++/(version)". 66 </para> 67 <programlisting> 68 --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/4.4-20090404</programlisting> </listitem></varlistentry> 69 70 <varlistentry><term><code>--enable-cstdio</code></term> 71 <listitem><para>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code> 72 (described next). 73 </para> 74 </listitem></varlistentry> 75 76 <varlistentry><term><code>--enable-cstdio=OPTION</code></term> 77 <listitem><para>Select a target-specific I/O package. At the moment, the only 78 choice is to use 'stdio', a generic "C" abstraction. 79 The default is 'stdio'. This option can change the library ABI. 80 </para> 81 </listitem></varlistentry> 82 83 <varlistentry><term><code>--enable-clocale</code></term> 84 <listitem><para>This is an abbreviated form of <code>'--enable-clocale=generic'</code> 85 (described next). 86 </para> 87 </listitem></varlistentry> 88 89 <varlistentry><term><code>--enable-clocale=OPTION</code></term> 90 <listitem><para>Select a target-specific underlying locale package. The 91 choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix 92 (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets, 93 'gnu' to specify a model based on functionality from the GNU C 94 library (langinfo/iconv/gettext) (from <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.gnu.org/software/libc/">glibc</link>, the GNU C 95 library), 'generic' to use a generic "C" abstraction which consists 96 of "C" locale info, 'newlib' to specify the Newlib C library model 97 which only differs from the 'generic' model in the handling of 98 ctype, or 'darwin' which omits the <type>wchar_t</type> specializations 99 needed by the 'generic' model. 100 </para> 101 102 <para>If not explicitly specified, the configure process tries 103 to guess the most suitable package from the choices above. The 104 default is 'generic'. On glibc-based systems of sufficient 105 vintage (2.3 and newer), 'gnu' is automatically selected. On newlib-based 106 systems (<code>'--with_newlib=yes'</code>) and OpenBSD, 'newlib' is 107 automatically selected. On Mac OS X 'darwin' is automatically selected. 108 This option can change the library ABI. 109 </para> 110 </listitem></varlistentry> 111 112 <varlistentry><term><code>--enable-libstdcxx-allocator</code></term> 113 <listitem><para>This is an abbreviated form of 114 <code>'--enable-libstdcxx-allocator=auto'</code> (described 115 next). 116 </para> 117 </listitem></varlistentry> 118 119 <varlistentry><term><code>--enable-libstdcxx-allocator=OPTION </code></term> 120 <listitem><para>Select a target-specific underlying std::allocator. The 121 choices are 'new' to specify a wrapper for new, 'malloc' to 122 specify a wrapper for malloc, 'mt' for a fixed power of two allocator, 123 'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator. 124 See this page for more information on allocator 125 <link linkend="allocator.ext">extensions</link>. This option 126 can change the library ABI. 127 </para> 128 </listitem></varlistentry> 129 130 <varlistentry><term><code>--enable-cheaders=OPTION</code></term> 131 <listitem><para>This allows the user to define the approach taken for C header 132 compatibility with C++. Options are c, c_std, and c_global. 133 These correspond to the source directory's include/c, 134 include/c_std, and include/c_global, and may also include 135 include/c_compatibility. The default is 'c_global'. 136 </para> 137 </listitem></varlistentry> 138 139 <varlistentry><term><code>--enable-threads</code></term> 140 <listitem><para>This is an abbreviated form of <code>'--enable-threads=yes'</code> 141 (described next). 142 </para> 143 </listitem></varlistentry> 144 145 <varlistentry><term><code>--enable-threads=OPTION</code></term> 146 <listitem><para>Select a threading library. A full description is 147 given in the 148 general <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://gcc.gnu.org/install/configure.html">compiler 149 configuration instructions</link>. This option can change the 150 library ABI. 151 </para> 152 </listitem></varlistentry> 153 154 <varlistentry><term><code>--enable-libstdcxx-threads</code></term> 155 <listitem><para>Enable C++11 threads support. If not explicitly specified, 156 the configure process enables it if possible. This 157 option can change the library ABI. 158 </para> 159 </listitem></varlistentry> 160 161 <varlistentry><term><code>--enable-libstdcxx-time</code></term> 162 <listitem><para>This is an abbreviated form of 163 <code>'--enable-libstdcxx-time=yes'</code>(described next). 164 </para> 165 </listitem></varlistentry> 166 167 <varlistentry><term><code>--enable-libstdcxx-time=OPTION</code></term> 168 <listitem><para>Enables link-type checks for the availability of the 169 <function>clock_gettime</function> clocks, used in the implementation 170 of [time.clock], and of the <function>nanosleep</function> and 171 <function>sched_yield</function> functions, used in the 172 implementation of [thread.thread.this] of the 2011 ISO C++ standard. 173 The choice OPTION=yes checks for the availability of the facilities 174 in libc and libposix4. In case it's needed the latter is also linked 175 to libstdc++ as part of the build process. OPTION=rt also checks in 176 librt (and, if it's needed, links to it). Note that linking to librt 177 is not always desirable because for glibc it requires linking to 178 libpthread too, which causes all reference counting to use atomic 179 operations, resulting in a potentially large overhead for 180 single-threaded programs. OPTION=no skips the tests completely. 181 The default is OPTION=auto, which skips the checks and enables the 182 features only for targets known to support them. 183 For Linux targets, if <function>clock_gettime</function> is not used 184 then the [time.clock] implementation will use a system call to access 185 the realtime and monotonic clocks, which is significantly slower than 186 the C library's <function>clock_gettime</function> function. 187 </para> 188 </listitem></varlistentry> 189 190 <varlistentry><term><code>--enable-libstdcxx-debug</code></term> 191 <listitem><para>Build separate debug libraries in addition to what is normally built. 192 By default, the debug libraries are compiled with 193 <code> CXXFLAGS='-g3 -O0 -fno-inline'</code> 194 , are installed in <code>${libdir}/debug</code>, and have the 195 same names and versioning information as the non-debug 196 libraries. This option is off by default. 197 </para> 198 <para>Note this make command, executed in 199 the build directory, will do much the same thing, without the 200 configuration difference and without building everything twice: 201 <code>make CXXFLAGS='-g3 -O0 -fno-inline' all</code> 202 </para> 203 </listitem></varlistentry> 204 205 <varlistentry><term><code>--enable-libstdcxx-debug-flags=FLAGS</code></term> 206 207 <listitem><para>This option is only valid when 208 <code>--enable-libstdcxx-debug</code> 209 is also specified, and applies to the debug builds only. With 210 this option, you can pass a specific string of flags to the 211 compiler to use when building the debug versions of libstdc++. 212 FLAGS is a quoted string of options, like 213 </para> 214 <programlisting> 215 --enable-libstdcxx-debug-flags='-g3 -O1 -fno-inline'</programlisting> 216 </listitem></varlistentry> 217 218 <varlistentry><term><code>--enable-cxx-flags=FLAGS</code></term> 219 <listitem><para>With this option, you can pass a string of -f (functionality) 220 flags to the compiler to use when building libstdc++. This 221 option can change the library ABI. FLAGS is a quoted string of 222 options, like 223 </para> 224 <programlisting> 225 --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</programlisting> 226 <para> 227 Note that the flags don't necessarily have to all be -f flags, 228 as shown, but usually those are the ones that will make sense 229 for experimentation and configure-time overriding. 230 </para> 231 <para>The advantage of --enable-cxx-flags over setting CXXFLAGS in 232 the 'make' environment is that, if files are automatically 233 rebuilt, the same flags will be used when compiling those files 234 as well, so that everything matches. 235 </para> 236 <para>Fun flags to try might include combinations of 237 </para> 238 <programlisting> 239 -fstrict-aliasing 240 -fno-exceptions 241 -ffunction-sections 242 -fvtable-gc</programlisting> 243 <para>and opposite forms (-fno-) of the same. Tell us (the libstdc++ 244 mailing list) if you discover more! 245 </para> 246 </listitem></varlistentry> 247 248 <varlistentry><term><code>--enable-c99</code></term> 249 <listitem><para>The <type>long long</type> type was introduced in C99, along 250 with many other functions for wide characters, and math 251 classification macros, etc. If enabled, all C99 functions not 252 specified by the C++ standard will be put into <code>namespace 253 __gnu_cxx</code>, and then all these names will 254 be injected into namespace std, so that C99 functions can be 255 used "as if" they were in the C++ standard (as they 256 will eventually be in some future revision of the standard, 257 without a doubt). By default, C99 support is on, assuming the 258 configure probes find all the necessary functions and bits 259 necessary. This option can change the library ABI. 260 </para> 261 </listitem></varlistentry> 262 263 <varlistentry><term><code>--enable-wchar_t</code>[default]</term> 264 <listitem><para>Template specializations for the <type>wchar_t</type> type are 265 required for wide character conversion support. Disabling 266 wide character specializations may be expedient for initial 267 porting efforts, but builds only a subset of what is required by 268 ISO, and is not recommended. By default, this option is on. 269 This option can change the library ABI. 270 </para> 271 </listitem></varlistentry> 272 273 <varlistentry><term><code>--enable-long-long </code></term> 274 <listitem><para>The <type>long long</type> type was introduced in C99. It is 275 provided as a GNU extension to C++98 in g++. This flag builds 276 support for "long long" into the library (specialized 277 templates and the like for iostreams). This option is on by default: 278 if enabled, users will have to either use the new-style "C" 279 headers by default (i.e., <cmath> not <math.h>) 280 or add appropriate compile-time flags to all compile lines to 281 allow "C" visibility of this feature (on GNU/Linux, 282 the flag is -D_ISOC99_SOURCE, which is added automatically via 283 CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE). 284 This option can change the library ABI. 285 </para> 286 </listitem></varlistentry> 287 288 <varlistentry><term><code>--enable-fully-dynamic-string</code></term> 289 <listitem><para>This option enables a special version of basic_string avoiding 290 the optimization that allocates empty objects in static memory. 291 Mostly useful together with shared memory allocators, see PR 292 libstdc++/16612 for details. 293 </para> 294 </listitem></varlistentry> 295 296 <varlistentry><term><code>--enable-concept-checks</code></term> 297 <listitem><para>This turns on additional compile-time checks for instantiated 298 library templates, in the form of specialized templates described in 299 the <link linkend="std.diagnostics.concept_checking">Concept 300 Checking</link> section. They 301 can help users discover when they break the rules of the STL, before 302 their programs run. These checks are based on C++03 rules and some of 303 them are not compatible with correct C++11 code. 304 </para> 305 </listitem></varlistentry> 306 307 <varlistentry><term><code>--enable-symvers[=style]</code></term> 308 309 <listitem><para>In 3.1 and later, tries to turn on symbol versioning in the 310 shared library (if a shared library has been 311 requested). Values for 'style' that are currently supported 312 are 'gnu', 'gnu-versioned-namespace', 'darwin', 313 'darwin-export', and 'sun'. Both gnu- options require that a recent 314 version of the GNU linker be in use. Both darwin options are 315 equivalent. With no style given, the configure script will try 316 to guess correct defaults for the host system, probe to see if 317 additional requirements are necessary and present for 318 activation, and if so, will turn symbol versioning on. This 319 option can change the library ABI. 320 </para> 321 322 </listitem></varlistentry> 323 324 <varlistentry><term><code>--enable-libstdcxx-visibility</code></term> 325 <listitem><para> In 4.2 and later, enables or disables visibility 326 attributes. If enabled (as by default), and the compiler seems 327 capable of passing the simple sanity checks thrown at it, adjusts 328 items in namespace std, namespace std::tr1, namespace std::tr2, 329 and namespace __gnu_cxx to have <code>visibility ("default")</code> 330 so that -fvisibility options can be used without affecting the 331 normal external-visibility of namespace std entities. 332 Prior to 4.7 this option was spelled <code>--enable-visibility</code>. 333 </para> 334 </listitem></varlistentry> 335 336 <varlistentry><term><code>--enable-libstdcxx-pch</code></term> 337 <listitem><para>In 3.4 and later, tries to turn on the generation of 338 stdc++.h.gch, a pre-compiled file including all the standard 339 C++ includes. If enabled (as by default), and the compiler 340 seems capable of passing the simple sanity checks thrown at 341 it, try to build stdc++.h.gch as part of the make process. 342 In addition, this generated file is used later on (by appending <code> 343 --include bits/stdc++.h </code> to CXXFLAGS) when running the 344 testsuite. 345 </para> 346 </listitem></varlistentry> 347 348 349 <varlistentry><term><code>--enable-extern-template</code>[default]</term> 350 <listitem><para>Use extern template to pre-instantiate all required 351 specializations for certain types defined in the standard libraries. 352 These types include <classname>string</classname> and dependents like 353 <classname>char_traits</classname>, the templatized IO classes, 354 <classname>allocator</classname>, and others. 355 Disabling means that implicit 356 template generation will be used when compiling these types. By 357 default, this option is on. This option can change the library ABI. 358 </para> 359 </listitem></varlistentry> 360 361 <varlistentry><term><code>--disable-hosted-libstdcxx</code></term> 362 <listitem> 363 <para> 364 By default, a complete <emphasis>hosted</emphasis> C++ library is 365 built. The C++ Standard also describes a 366 <emphasis>freestanding</emphasis> environment, in which only a 367 minimal set of headers are provided. This option builds such an 368 environment. 369 </para> 370 </listitem></varlistentry> 371 372<varlistentry><term><code>--disable-libstdcxx-verbose</code></term> 373 <listitem> 374 <para> 375 By default, the library is configured to write descriptive messages 376 to standard error for certain events such as calling a pure virtual 377 function or the invocation of the standard terminate handler. Those 378 messages cause the library to depend on the demangler and standard I/O 379 facilities, which might be undesirable in a low-memory environment or 380 when standard error is not available. This option disables those 381 messages. This option does not change the library ABI. 382 </para> 383 </listitem></varlistentry> 384 385<varlistentry><term><code>--disable-libstdcxx-dual-abi</code></term> 386 <listitem> 387 <para> 388 Disable support for the new, C++11-conforming implementations of 389 <code>std::string</code>, <code>std::list</code> etc. so that the 390 library only provides definitions of types using the old ABI 391 (see <xref linkend="manual.intro.using.abi"/>). 392 This option changes the library ABI. 393 </para> 394 </listitem></varlistentry> 395 396<varlistentry><term><code>--with-default-libstdcxx-abi=</code><replaceable>OPTION</replaceable></term> 397 <listitem> 398 <para> 399 Set the default value for the <symbol>_GLIBCXX_USE_CXX11_ABI</symbol> 400 macro (see <xref linkend="manual.intro.using.macros"/>). 401 The default is <option>OPTION=new</option> which sets the macro to 402 <literal>1</literal>, 403 use <option>OPTION=gcc4-compatible</option> to set it to 404 <literal>0</literal>. 405 This option does not change the library ABI. 406 </para> 407 </listitem></varlistentry> 408 409 <varlistentry><term><code>--with-libstdcxx-lock-policy=OPTION</code></term> 410 <listitem><para>Sets the lock policy that controls how 411 <classname>shared_ptr</classname> reference counting is 412 synchronized. 413 The choice OPTION=atomic enables use of atomics for updates to 414 <classname>shared_ptr</classname> reference counts. 415 The choice OPTION=mutex enables use of a mutex to synchronize updates 416 to <classname>shared_ptr</classname> reference counts. 417 If the compiler's thread model is "single" then this option has no 418 effect, as no synchronization is used for the reference counts. 419 The default is OPTION=auto, which checks for the availability of 420 compiler built-ins for 2-byte and 4-byte atomic compare-and-swap, 421 and uses OPTION=atomic if they're available, OPTION=mutex otherwise. 422 This option can change the library ABI. 423 If the library is configured to use atomics and user programs are 424 compiled using a target that doesn't natively support the atomic 425 operations (e.g. the library is configured for armv7 and then code 426 is compiled with <option>-march=armv5t</option>) then the program 427 might rely on support in libgcc to provide the atomics. 428 </para> 429 </listitem></varlistentry> 430 431 <varlistentry><term><code>--enable-vtable-verify</code>[default]</term> 432 <listitem> 433 <para>Use <code>-fvtable-verify=std</code> to compile the C++ 434 runtime with instrumentation for vtable verification. All virtual 435 functions in the standard library will be verified at runtime. 436 Types impacted include <classname>locale</classname> and 437 <classname>iostream</classname>, and others. Disabling means that 438 the C++ runtime is compiled without support for vtable 439 verification. By default, this option is off. 440 </para> 441 </listitem></varlistentry> 442 443 <varlistentry><term><code>--enable-libstdcxx-filesystem-ts</code>[default]</term> 444 <listitem> 445 <para>Build <filename class="libraryfile">libstdc++fs.a</filename> as well 446 as the usual libstdc++ and libsupc++ libraries. This is enabled by 447 default on select POSIX targets where it is known to work and disabled 448 otherwise. 449 </para> 450 </listitem></varlistentry> 451 452</variablelist> 453 454</section> 455