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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> |
