1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html 3 PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 4 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 5 6<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 7<head> 8 <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" /> 9 <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++" /> 10 <meta name="DESCRIPTION" content="Configuration options for libstdc++-v3." /> 11 <meta name="GENERATOR" content="vi and eight fingers" /> 12 <title>libstdc++-v3 configure options</title> 13<link rel="StyleSheet" href="lib3styles.css" type="text/css" /> 14<link rel="Copyright" href="17_intro/license.html" type="text/html" /> 15</head> 16<body> 17 18<h1 class="centered"><a name="top">Interesting <code>configure</code> 19options</a></h1> 20 21<p class="fineprint"><em> 22 The latest version of this document is always available at 23 <a href="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html"> 24 http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</a>. 25</em></p> 26 27<p><em> 28 To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>. 29</em></p> 30 31<!-- ####################################################### --> 32<hr /> 33<p>Here are some of the non-obvious options to libstdc++'s configure. 34 Keep in mind that 35 <!-- This SECnn should be the "Choosing Package Options" section. --> 36 <a href="http://www.gnu.org/software/autoconf/manual/autoconf-2.57/html_node/autoconf_131.html#SEC131">they 37 all have opposite forms as well</a> 38 (enable/disable and with/without). The defaults are for <strong>current 39 development sources</strong>, which may be different than those for 40 released versions. 41</p> 42<p>The canonical way to find out the configure options that are 43 available for a given set of libstdc++ sources is to go to the 44 source directory and then type:<code> ./configure --help</code> 45</p> 46 47<dl> 48 <dt><code>--enable-multilib </code>[default]</dt> 49 <dd><p>This is part of the generic multilib support for building cross 50 compilers. As such, targets like "powerpc-elf" will have 51 libstdc++ built many different ways: "-msoft-float" 52 and not, etc. A different libstdc++ will be built for each of 53 the different multilib versions. This option is on by default. 54 </p> 55 </dd> 56 57 <dt><code>--enable-sjlj-exceptions </code></dt> 58 <dd><p>Forces old, set-jump/long-jump exception handling model. If 59 at all possible, the new, frame unwinding exception handling routines 60 should be used instead, as they significantly reduce both 61 runtime memory usage and executable size. This option can 62 change the library ABI. 63 </p> 64 </dd> 65 66 <dt><code>--enable-version-specific-runtime-libs </code></dt> 67 <dd><p>Specify that run-time libraries should be installed in the 68 compiler-specific subdirectory (i.e., 69 <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>) 70 instead of <code>${libdir}</code>. This option is useful if you 71 intend to use several versions of gcc in parallel. In addition, 72 libstdc++'s include files will be installed in 73 <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>, 74 unless you also specify 75 <code>--with-gxx-include-dir=<em>dirname</em></code> during configuration. 76 </p> 77 </dd> 78 79 <dt><code>--with-gxx-include-dir=<include-files dir></code></dt> 80 <dd><p>Adds support for named libstdc++ include directory. For instance, 81 the following puts all the libstdc++ headers into a directory 82 called "2.97-20001008" instead of the usual 83 "c++/(version)". 84 </p> 85 <pre> 86 --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre> </dd> 87 88 <dt><code>--enable-cstdio </code></dt> 89 <dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code> 90 (described next). This option can change the library ABI. 91 </p> 92 </dd> 93 94 <dt><code>--enable-cstdio=OPTION </code></dt> 95 <dd><p>Select a target-specific I/O package. At the moment, the only 96 choice is to use 'stdio', a generic "C" abstraction. 97 The default is 'stdio'. A longer explanation is <a 98 href="explanations.html#cstdio">here</a>. 99 </p> 100 </dd> 101 102 <dt><code>--enable-clocale </code></dt> 103 <dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code> 104 (described next). This option can change the library ABI. 105 </p> 106 </dd> 107 108 <dt><code>--enable-clocale=OPTION </code></dt> 109 <dd><p>Select a target-specific underlying locale package. The 110 choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix 111 (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets, 112 'gnu' to specify a model based on functionality from the GNU C 113 library (langinfo/iconv/gettext) (from <a 114 href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C 115 library), or 'generic' to use a generic "C" 116 abstraction which consists of "C" locale info. 117 </p> 118 119 <p>As part of the configuration process, the "C" library is 120 probed both for sufficient vintage, and installed locale 121 data. If either of these elements are not present, the C++ 122 locale model default to 'generic.' On glibc-based systems of 123 version 2.2.5 and above with installed locale files, 'gnu' is 124 automatically selected. 125 </p> 126 </dd> 127 128 <dt><code>--enable-libstdcxx-allocator </code></dt> 129 <dd><p>This is an abbreviated form of 130 <code>'--enable-libstdcxx-allocator=auto'</code> (described 131 next). This option can change the library ABI. 132 </p> 133 </dd> 134 135 <dt><code>--enable-libstdcxx-allocator=OPTION </code></dt> 136 <dd><p>Select a target-specific underlying std::allocator. The 137 choices are 'new' to specify a wrapper for new, 'malloc' to 138 specify a wrapper for malloc, 'mt' for a fixed power of two allocator 139 (<a href="ext/mt_allocator.html">documented</a> under extensions), 140 'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator. 141 This option can change the library ABI. 142 </p> 143 </dd> 144 145 <dt><code>--enable-cheaders=OPTION </code></dt> 146 <dd><p>This allows the user to define what kind of C headers are 147 used. Options are c and c_std. These correspond to the source 148 directory's include/c and include/c_std. The default is c_std. 149 </p> 150 </dd> 151 152 <dt><code>--enable-threads </code></dt> 153 <dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code> 154 (described next). This option can change the library ABI. 155 </p> 156 </dd> 157 158 <dt><code>--enable-threads=OPTION </code></dt> 159 <dd><p>Select a threading library. A full description is given in the 160 general <a href="http://gcc.gnu.org/install/configure.html">compiler 161 configuration instructions</a>. 162 </p> 163 </dd> 164 165 <dt><code>--enable-libstdcxx-debug </code></dt> 166 <dd><p>Build separate debug libraries in addition to what is normally built. 167 By default, the debug libraries are compiled with 168 <code> CXXFLAGS='-g3 -O0'</code> 169 , are installed in <code>${libdir}/debug</code>, and have the 170 same names and versioning information as the non-debug 171 libraries. This option is off by default. 172 </p> 173 <p>Note this make command, executed in 174 the build directory, will do much the same thing, without the 175 configuration difference and without building everything twice: 176 <code>make CXXFLAGS='-g3 -O0' all</code> 177 </p> 178 </dd> 179 180 <dt><code>--enable-libstdcxx-debug-flags=FLAGS</code></dt> 181 182 <dd><p>This option is only valid when <code> --enable-debug </code> 183 is also specified, and applies to the debug builds only. With 184 this option, you can pass a specific string of flags to the 185 compiler to use when building the debug versions of libstdc++. 186 FLAGS is a quoted string of options, like 187 </p> 188 <pre> 189 --enable-libstdcxx-debug-flags='-g3 -O1 -gdwarf-2'</pre> 190 </dd> 191 192 <dt><code>--enable-cxx-flags=FLAGS</code></dt> 193 <dd><p>With this option, you can pass a string of -f (functionality) 194 flags to the compiler to use when building libstdc++. This 195 option can change the library ABI. FLAGS is a quoted string of 196 options, like 197 </p> 198 <pre> 199 --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre> 200 <p> 201 Note that the flags don't necessarily have to all be -f flags, 202 as shown, but usually those are the ones that will make sense 203 for experimentation and configure-time overriding. 204 </p> 205 <p>The advantage of --enable-cxx-flags over setting CXXFLAGS in 206 the 'make' environment is that, if files are automatically 207 rebuilt, the same flags will be used when compiling those files 208 as well, so that everything matches. 209 </p> 210 <p>Fun flags to try might include combinations of 211 </p> 212 <pre> 213 -fstrict-aliasing 214 -fno-exceptions 215 -ffunction-sections 216 -fvtable-gc</pre> 217 <p>and opposite forms (-fno-) of the same. Tell us (the libstdc++ 218 mailing list) if you discover more! 219 </p> 220 </dd> 221 222 <dt><code>--enable-c99 </code></dt> 223 <dd><p>The "long long" type was introduced in C99, along 224 with many other functions for wide characters, and math 225 classification macros, etc. If enabled, all C99 functions not 226 specified by the C++ standard will be put into <code>namespace 227 __gnu_cxx</code>, and then all these names will 228 be injected into namespace std, so that C99 functions can be 229 used "as if" they were in the C++ standard (as they 230 will eventually be in some future revision of the standard, 231 without a doubt). By default, C99 support is on, assuming the 232 configure probes find all the necessary functions and bits 233 necessary. This option can change the library ABI. 234 </p> 235 </dd> 236 237 <dt><code>--enable-wchar_t </code>[default]</dt> 238 <dd><p>Template specializations for the "wchar_t" type are 239 required for wide character conversion support. Disabling 240 wide character specializations may be expedient for initial 241 porting efforts, but builds only a subset of what is required by 242 ISO, and is not recommended. By default, this option is on. 243 This option can change the library ABI. 244 </p> 245 </dd> 246 247 <dt><code>--enable-long-long </code></dt> 248 <dd><p>The "long long" type was introduced in C99. It is 249 provided as a GNU extension to C++98 in g++. This flag builds 250 support for "long long" into the library (specialized 251 templates and the like for iostreams). This option is on by default: 252 if enabled, users will have to either use the new-style "C" 253 headers by default (i.e., <cmath> not <math.h>) 254 or add appropriate compile-time flags to all compile lines to 255 allow "C" visibility of this feature (on GNU/Linux, 256 the flag is -D_ISOC99_SOURCE, which is added automatically via 257 CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE). 258 This option can change the library ABI. 259 </p> 260 </dd> 261 262 <dt><code>--enable-fully-dynamic-string </code></dt> 263 <dd><p>This option enables a special version of basic_string avoiding 264 the optimization that allocates empty objects in static memory. 265 Mostly useful together with shared memory allocators, see PR 266 libstdc++/16612 for details. 267 </p> 268 </dd> 269 270 <dt><code>--enable-concept-checks </code></dt> 271 <dd><p>This turns on additional compile-time checks for instantiated 272 library templates, in the form of specialized templates, 273 <a href="19_diagnostics/howto.html#3">described here</a>. They 274 can help users discover when they break the rules of the STL, before 275 their programs run. 276 </p> 277 </dd> 278 279 <dt><code>--enable-symvers[=style] </code></dt> 280 281 <dd><p>In 3.1 and later, tries to turn on symbol versioning in the 282 shared library (if a shared library has been 283 requested). Values for 'style' that are currently supported 284 are 'gnu', 'gnu-versioned-namespace', 'darwin', and 285 'darwin-export'. Both gnu- options require that a recent 286 version of the GNU linker be in use. Both darwin options are 287 equivalent. With no style given, the configure script will try 288 to guess correct defaults for the host system, probe to see if 289 additional requirements are necessary and present for 290 activation, and if so, will turn symbol versioning on. This 291 option can change the library ABI. 292 </p> 293 294 </dd> 295 296 <dt><code>--enable-visibility </code></dt> 297 <dd><p> In 4.2 and later, enables or disables visibility attributes. 298 If enabled (as by default), and the compiler seems capable of 299 passing the simple sanity checks thrown at it, adjusts items 300 in namespace std, namespace std::tr1, and namespace __gnu_cxx 301 so that -fvisibility options work. 302 </p> 303 </dd> 304 305 <dt><code>--enable-libstdcxx-pch </code></dt> 306 <dd><p>In 3.4 and later, tries to turn on the generation of 307 stdc++.h.gch, a pre-compiled file including all the standard 308 C++ includes. If enabled (as by default), and the compiler 309 seems capable of passing the simple sanity checks thrown at 310 it, try to build stdc++.h.gch as part of the make process. 311 In addition, this generated file is used later on (by appending <code> 312 --include bits/stdc++.h </code> to CXXFLAGS) when running the 313 testsuite. 314 </p> 315 </dd> 316 317 <dt><code>--disable-hosted-libstdcxx </code></dt> 318 <dd><p>By default, a complete <em>hosted</em> C++ library is built. The 319 C++ Standard also describes a <em>freestanding</em> environment, 320 in which only a minimal set of headers are provided. This option 321 builds such an environment. 322 </p> 323 </dd> 324</dl> 325<p>Return <a href="#top">to the top of the page</a> or 326 <a href="http://gcc.gnu.org/libstdc++/">to the libstdc++ homepage</a>. 327</p> 328 329 330<!-- ####################################################### --> 331 332<hr /> 333<p class="fineprint"><em> 334See <a href="17_intro/license.html">license.html</a> for copying conditions. 335Comments and suggestions are welcome, and may be sent to 336<a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>. 337</em></p> 338 339 340</body> 341</html> 342