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| <!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> | |
| When configuring libstdc++, you'll have to configure the entire | |
| <span class="emphasis"><em>gccsrcdir</em></span> directory. Consider using the | |
| toplevel gcc configuration option | |
| <code class="literal">--enable-languages=c++</code>, which saves time by only | |
| building the C++ toolchain. | |
| </p><p> | |
| Here are all of the configure options specific to libstdc++. Keep | |
| in mind that | |
| <a class="link" href="https://sourceware.org/autobook/autobook/autobook_14.html" target="_top">they | |
| all have opposite forms as well</a> (enable/disable and | |
| with/without). The defaults are for the <span class="emphasis"><em>current | |
| development sources</em></span>, which may be different than those | |
| for released versions. | |
| </p><p>The canonical way to find out the configure options that are | |
| available for a given set of libstdc++ sources is to go to the | |
| source directory and then type: <span class="command"><strong>./configure --help</strong></span>. | |
| </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 | |
| compilers. As such, targets like "powerpc-elf" will have | |
| libstdc++ built many different ways: "-msoft-float" | |
| and not, etc. A different libstdc++ will be built for each of | |
| the different multilib versions. This option is on by default. | |
| </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 | |
| compiler-specific subdirectory (i.e., | |
| <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>) | |
| instead of <code class="code">${libdir}</code>. This option is useful if you | |
| intend to use several versions of gcc in parallel. In addition, | |
| libstdc++'s include files will be installed in | |
| <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>, | |
| unless you also specify | |
| <code class="literal">--with-gxx-include-dir=</code><code class="filename">dirname</code> during configuration. | |
| </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, | |
| the following puts all the libstdc++ headers into a directory | |
| called "4.4-20090404" instead of the usual | |
| "c++/(version)". | |
| </p><pre class="programlisting"> | |
| --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> | |
| (described next). | |
| </p></dd><dt><span class="term"><code class="code">--enable-cstdio=OPTION</code></span></dt><dd><p>Select a target-specific I/O package. The choices are 'stdio' | |
| which is a generic abstraction using POSIX file I/O APIs | |
| (<code class="function">read</code>, <code class="function">write</code>, | |
| <code class="function">lseek</code>, etc.), and 'stdio_pure' which is similar | |
| but only uses standard C file I/O APIs (<code class="function">fread</code>, | |
| <code class="function">fwrite</code>, <code class="function">fseek</code>, etc.). | |
| The 'stdio_posix' choice is a synonym for 'stdio'. | |
| The default is 'stdio'. This option can change the library ABI. | |
| </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> | |
| (described next). | |
| </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 | |
| choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix | |
| (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets, | |
| 'gnu' to specify a model based on functionality from the GNU C | |
| library (langinfo/iconv/gettext) (from <a class="link" href="https://www.gnu.org/software/libc/" target="_top">glibc</a>, the GNU C | |
| library), 'generic' to use a generic "C" abstraction which consists | |
| of "C" locale info, 'newlib' to specify the Newlib C library model | |
| which only differs from the 'generic' model in the handling of | |
| ctype, or 'darwin' which omits the <span class="type">wchar_t</span> specializations | |
| needed by the 'generic' model. | |
| </p><p>If not explicitly specified, the configure process tries | |
| to guess the most suitable package from the choices above. The | |
| default is 'generic'. On glibc-based systems of sufficient | |
| vintage (2.3 and newer), 'gnu' is automatically selected. On newlib-based | |
| systems (<code class="code">'--with_newlib=yes'</code>) and OpenBSD, 'newlib' is | |
| automatically selected. On Mac OS X 'darwin' is automatically selected. | |
| This option can change the library ABI. | |
| </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator</code></span></dt><dd><p>This is an abbreviated form of | |
| <code class="code">'--enable-libstdcxx-allocator=auto'</code> (described | |
| next). | |
| </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 | |
| choices are 'new' to specify a wrapper for new, and 'malloc' to | |
| specify a wrapper for malloc. | |
| See <a class="xref" href="memory.html#allocator.ext" title="Extension Allocators">the section called “Extension Allocators”</a> for more information. | |
| This option can change the library ABI. | |
| </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 | |
| compatibility with C++. Options are c, c_std, and c_global. | |
| These correspond to the source directory's include/c, | |
| include/c_std, and include/c_global, and may also include | |
| include/c_compatibility. The default is 'c_global'. | |
| </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> | |
| (described next). | |
| </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 | |
| given in the | |
| general <a class="link" href="https://gcc.gnu.org/install/configure.html" target="_top">compiler | |
| configuration instructions</a>. This option can change the | |
| library ABI. | |
| </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, | |
| the configure process enables it if possible. This | |
| option can change the library ABI. | |
| </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time</code></span></dt><dd><p>This is an abbreviated form of | |
| <code class="code">'--enable-libstdcxx-time=yes'</code>(described next). | |
| </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 | |
| <code class="function">clock_gettime</code> clocks, used in the implementation | |
| of [time.clock], and of the <code class="function">nanosleep</code> and | |
| <code class="function">sched_yield</code> functions, used in the | |
| implementation of [thread.thread.this] of the 2011 ISO C++ standard. | |
| The choice OPTION=yes checks for the availability of the facilities | |
| in libc. OPTION=rt also checks in | |
| librt (and, if it's needed, links to it). Note that linking to librt | |
| is not always desirable because for glibc it requires linking to | |
| libpthread too, which causes all reference counting to use atomic | |
| operations, resulting in a potentially large overhead for | |
| single-threaded programs. OPTION=no skips the tests completely. | |
| The default is OPTION=auto, which skips the checks and enables the | |
| features only for targets known to support them. | |
| For Linux targets, if <code class="function">clock_gettime</code> is not used | |
| then the [time.clock] implementation will use a system call to access | |
| the realtime and monotonic clocks, which is significantly slower than | |
| the C library's <code class="function">clock_gettime</code> function. | |
| </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. | |
| By default, the debug libraries are compiled with | |
| <code class="code"> CXXFLAGS='-g3 -O0 -fno-inline'</code> | |
| , are installed in <code class="code">${libdir}/debug</code>, and have the | |
| same names and versioning information as the non-debug | |
| libraries. This option is off by default. | |
| </p><p>Note this make command, executed in | |
| the build directory, will do much the same thing, without the | |
| configuration difference and without building everything twice: | |
| <code class="code">make CXXFLAGS='-g3 -O0 -fno-inline' all</code> | |
| </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-libstdcxx-debug</code> | |
| is also specified, and applies to the debug builds only. With | |
| this option, you can pass a specific string of flags to the | |
| compiler to use when building the debug versions of libstdc++. | |
| FLAGS is a quoted string of options, like | |
| </p><pre class="programlisting"> | |
| --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) | |
| flags to the compiler to use when building libstdc++. This | |
| option can change the library ABI. FLAGS is a quoted string of | |
| options, like | |
| </p><pre class="programlisting"> | |
| --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre><p> | |
| Note that the flags don't necessarily have to all be -f flags, | |
| as shown, but usually those are the ones that will make sense | |
| for experimentation and configure-time overriding. | |
| </p><p>The advantage of --enable-cxx-flags over setting CXXFLAGS in | |
| the 'make' environment is that, if files are automatically | |
| rebuilt, the same flags will be used when compiling those files | |
| as well, so that everything matches. | |
| </p><p>Fun flags to try might include combinations of | |
| </p><pre class="programlisting"> | |
| -fstrict-aliasing | |
| -fno-exceptions | |
| -ffunction-sections | |
| -fvtable-gc</pre><p>and opposite forms (-fno-) of the same. Tell us (the libstdc++ | |
| mailing list) if you discover more! | |
| </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 | |
| with many other functions for wide characters, and math | |
| classification macros, etc. If enabled, all C99 functions not | |
| specified by the C++ standard will be put into <code class="code">namespace | |
| __gnu_cxx</code>, and then all these names will | |
| be injected into namespace std, so that C99 functions can be | |
| used "as if" they were in the C++ standard (as they | |
| will eventually be in some future revision of the standard, | |
| without a doubt). By default, C99 support is on, assuming the | |
| configure probes find all the necessary functions and bits | |
| necessary. This option can change the library ABI. | |
| </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 | |
| required for wide character conversion support. Disabling | |
| wide character specializations may be expedient for initial | |
| porting efforts, but builds only a subset of what is required by | |
| ISO, and is not recommended. By default, this option is on. | |
| This option can change the library ABI. | |
| </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 | |
| provided as a GNU extension to C++98 in g++. This flag builds | |
| support for "long long" into the library (specialized | |
| templates and the like for iostreams). This option is on by default: | |
| if enabled, users will have to either use the new-style "C" | |
| headers by default (i.e., <cmath> not <math.h>) | |
| or add appropriate compile-time flags to all compile lines to | |
| allow "C" visibility of this feature (on GNU/Linux, | |
| the flag is -D_ISOC99_SOURCE, which is added automatically via | |
| CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE). | |
| This option can change the library ABI. | |
| </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 | |
| the optimization that allocates empty objects in static memory. | |
| Mostly useful together with shared memory allocators, see PR | |
| libstdc++/16612 for details. | |
| </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 | |
| library templates, in the form of specialized templates described in | |
| the <a class="link" href="concept_checking.html" title="Concept Checking">Concept | |
| Checking</a> section. They | |
| can help users discover when they break the rules of the STL, before | |
| their programs run. These checks are based on C++03 rules and some of | |
| them are not compatible with correct C++11 code. | |
| </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 | |
| shared library (if a shared library has been | |
| requested). Values for 'style' that are currently supported | |
| are 'gnu', 'gnu-versioned-namespace', 'darwin', | |
| 'darwin-export', and 'sun'. Both gnu- options require that a recent | |
| version of the GNU linker be in use. Both darwin options are | |
| equivalent. With no style given, the configure script will try | |
| to guess correct defaults for the host system, probe to see if | |
| additional requirements are necessary and present for | |
| activation, and if so, will turn symbol versioning on. This | |
| option can change the library ABI. | |
| </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 | |
| attributes. If enabled (as by default), and the compiler seems | |
| capable of passing the simple sanity checks thrown at it, adjusts | |
| items in namespace std, namespace std::tr1, namespace std::tr2, | |
| and namespace __gnu_cxx to have <code class="code">visibility ("default")</code> | |
| so that -fvisibility options can be used without affecting the | |
| normal external-visibility of namespace std entities. | |
| Prior to 4.7 this option was spelled <code class="code">--enable-visibility</code>. | |
| </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 | |
| stdc++.h.gch, a pre-compiled file including all the standard | |
| C++ includes. If enabled (as by default), and the compiler | |
| seems capable of passing the simple sanity checks thrown at | |
| it, try to build stdc++.h.gch as part of the make process. | |
| In addition, this generated file is used later on (by appending | |
| <code class="code">-include bits/stdc++.h</code> to CXXFLAGS) when running the | |
| testsuite. | |
| </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 | |
| specializations for certain types defined in the standard libraries. | |
| These types include <code class="classname">string</code> and dependents like | |
| <code class="classname">char_traits</code>, the templatized IO classes, | |
| <code class="classname">allocator</code>, and others. | |
| Disabling means that implicit | |
| template generation will be used when compiling these types. By | |
| default, this option is on. This option can change the library ABI. | |
| </p></dd><dt><span class="term"><code class="code">--disable-hosted-libstdcxx</code></span></dt><dd><p> | |
| By default, a complete <span class="emphasis"><em>hosted</em></span> C++ library is | |
| built. The C++ Standard also describes a | |
| <span class="emphasis"><em>freestanding</em></span> environment, in which only a | |
| minimal set of headers are provided. This option builds such an | |
| environment. Note that a hosted library installs headers that still can | |
| be used in non hosted environments, as the library checks for | |
| <code class="code">__STDC_HOSTED__</code>, however, a library configured with | |
| <code class="code">--disable-hosted-libstdcxx</code> will not install unusable headers. | |
| </p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-hosted</code></span></dt><dd><p>This is an alias for <code class="code">--disable-hosted-libstdcxx</code>.</p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-verbose</code></span></dt><dd><p> | |
| By default, the library is configured to write descriptive messages | |
| to standard error for certain events such as calling a pure virtual | |
| function or the invocation of the standard terminate handler. Those | |
| messages cause the library to depend on the demangler and standard I/O | |
| facilities, which might be undesirable in a low-memory environment or | |
| when standard error is not available. This option disables those | |
| messages. This option does not change the library ABI. | |
| </p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-dual-abi</code></span></dt><dd><p> | |
| Disable support for the new, C++11-conforming implementations of | |
| <code class="code">std::string</code>, <code class="code">std::list</code> etc. so that the | |
| library only provides definitions of types using the old ABI | |
| (see <a class="xref" href="using_dual_abi.html" title="Dual ABI">Dual ABI</a>). | |
| This option changes the library ABI. | |
| </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> | |
| Set the default value for the <span class="symbol">_GLIBCXX_USE_CXX11_ABI</span> | |
| macro (see <a class="xref" href="using_macros.html" title="Macros">Macros</a>). | |
| The default is <code class="option">OPTION=new</code> which sets the macro to | |
| <code class="literal">1</code>, | |
| use <code class="option">OPTION=gcc4-compatible</code> to set it to | |
| <code class="literal">0</code>. | |
| This option does not change the library ABI. | |
| </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 | |
| <code class="classname">shared_ptr</code> reference counting is | |
| synchronized. | |
| The choice OPTION=atomic enables use of atomics for updates to | |
| <code class="classname">shared_ptr</code> reference counts. | |
| The choice OPTION=mutex enables use of a mutex to synchronize updates | |
| to <code class="classname">shared_ptr</code> reference counts. | |
| If the compiler's thread model is "single" then this option has no | |
| effect, as no synchronization is used for the reference counts. | |
| The default is OPTION=auto, which checks for the availability of | |
| compiler built-ins for 2-byte and 4-byte atomic compare-and-swap, | |
| and uses OPTION=atomic if they're available, OPTION=mutex otherwise. | |
| This option can change the library ABI. | |
| If the library is configured to use atomics and user programs are | |
| compiled using a target that doesn't natively support the atomic | |
| operations (e.g. the library is configured for armv7 and then code | |
| is compiled with <code class="option">-march=armv5t</code>) then the program | |
| might rely on support in libgcc to provide the atomics. | |
| </p></dd><dt><span class="term"><code class="code">--enable-vtable-verify</code></span></dt><dd><p>Use <code class="code">-fvtable-verify=std</code> to compile the C++ | |
| runtime with instrumentation for vtable verification. All virtual | |
| functions in the standard library will be verified at runtime. | |
| Types impacted include <code class="classname">locale</code> and | |
| <code class="classname">iostream</code>, and others. Disabling means that | |
| the C++ runtime is compiled without support for vtable | |
| verification. By default, this option is off. | |
| </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 | |
| as the usual libstdc++ and libsupc++ libraries. This is enabled by | |
| default on select POSIX targets where it is known to work and disabled | |
| otherwise. | |
| </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-static-eh-pool</code></span></dt><dd><p>Use a fixed-size static buffer for the emergency exception handling | |
| pool (see <a class="xref" href="using_exceptions.html#intro.using.exception.alloc" title="Memory allocation">Memory allocation for exceptions</a>). The default | |
| is to allocate the pool on program startup using <code class="code">malloc</code>. | |
| With this option, a static buffer will be provided by libstdc++ instead. | |
| This does not change the library ABI. | |
| </p></dd><dt><span class="term"><code class="code">--with-libstdcxx-eh-pool-obj-count=NUM</code></span></dt><dd><p>Set the size of the emergency exception handling pool. NUM is the | |
| number of simultaneous allocated exceptions to support. | |
| This does not change the library ABI. | |
| </p></dd><dt><span class="term"><code class="code">--with-libstdcxx-zoneinfo=OPTION</code></span></dt><dd><p>Choose how <code class="classname">std::chrono::tzdb</code> will obtain | |
| the time zone info. The library requires a copy of the | |
| <code class="filename">tzdata.zi</code> and <code class="filename">leapseconds</code> | |
| files from the <a class="link" href="https://www.iana.org/time-zones" target="_top">IANA Time Zone | |
| Database</a>. The choice OPTION=static will embed a copy of the files | |
| into the library, and use that static data when time zone information | |
| is required. The choice OPTION=dir will use the files | |
| <code class="filename">dir/tzdata.zi</code> and | |
| <code class="filename">dir/leapseconds</code> (which must exist when a program | |
| tries to access time zone information). The choice OPTION=dir,static | |
| will try to use files in <code class="filename">dir</code> but if they are | |
| not available the embedded static data will be used instead. | |
| The default choice is OPTION=yes. This is equivalent to OPTION=dir,static | |
| with a system-specific default directory (if a suitable default for | |
| the target is known). | |
| The choice OPTION=no will disable all code for loading time zone info | |
| from file or from the embedded static data, which means that only the | |
| "UTC" and "GMT" time zones are defined. Using OPTION=no results in a | |
| smaller library, so is suitable for systems that will never need to | |
| query the time zone database. | |
| This does not change the library ABI. | |
| </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> |