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4 <META NAME="AUTHOR" CONTENT="pme@sources.redhat.com (Phil Edwards)">
5 <META NAME="KEYWORDS" CONTENT="libstdc++, libstdc++-v3, GCC, g++">
6 <META NAME="DESCRIPTION" CONTENT="Configuration options for libstdc++-v3.">
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8 <TITLE>libstdc++-v3 configure options</TITLE>
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10 <!-- $Id: configopts.html,v 1.6 2001/02/07 00:03:20 pme Exp $ -->
14 <H1 CLASS="centered"><A NAME="top">Interesting <TT>configure</TT>
17 <P>The latest version of this document is always available at
18 <A HREF="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html">
19 http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</A>.
22 <P>To the <A HREF="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</A>.
25 <!-- ####################################################### -->
27 <P>Here are some of the non-obvious options to libstdc++'s configure.
29 <!-- This SECnn should be the "Choosing Package Options" section. -->
30 <A HREF="http://sources.redhat.com/autoconf/autoconf.html#SEC74">they
31 all have opposite forms as well</A>
32 (enable/disable and with/without). The defaults are for current
35 <P>The canonical way to find out the configure options that are
36 available for a given set of libstdc++ sources is to go to the
37 source directory and then type:<TT> ./configure --help</TT>
40 <DT><TT>--enable-multilib </TT>[default]
41 <DD><P>This is part of the generic multilib support for building cross
42 compilers. As such, targets like "powerpc-elf" will have
43 libstdc++ built many different ways: "-msoft-float"
44 and not, etc. A different libstdc++ will be built for each of
45 the different multilib versions. This option is on by default.
48 <DT><TT>--enable-debug </TT>
49 <DD><P>The configure script will automatically detect the highest level
50 of optimization that the compiler in use can use (certain
51 versions of g++ will ICE if given the <TT>-O2</TT> option, but
52 this is fixed in later versions of the compiler). This --enable
53 flag will disable all optimizations and instruct the compiler to
54 emit as much extra debugging information as it can, for use
58 <DT><TT>--enable-cstdio </TT>
59 <DD><P>This is an abbreviated form of <TT>'--enable-cstdio=stdio'</TT>
63 <DT><TT>--enable-cstdio=LIB </TT>
64 <DD><P>Select a target-specific I/O package. As of libstdc++-v3
65 snapshot 2.91, the choices are 'libio' to specify the GNU
67 <A HREF="http://sources.redhat.com/glibc/">glibc</A>, the
68 GNU C library), or 'stdio' to use a generic "C"
69 abstraction. The default is 'stdio'.
72 <DT><TT>--enable-clocale </TT>
73 <DD><P>This is an abbreviated form of <TT>'--enable-clocale=generic'</TT>
77 <DT><TT>--enable-clocale=MODEL </TT>
78 <DD><P>Select a target-specific underlying locale package. The
79 choices are 'gnu' to specify an X/Open (IEEE Std. 1003.1-200x)
80 model based on langinfo/iconv (from <A
81 HREF="http://sources.redhat.com/glibc/">glibc</A>, the GNU C
82 library), or 'generic' to use a generic "C"
83 abstraction which consists of "C" locale info.
84 The default is 'generic'.
87 <DT><TT>--enable-long-long </TT>
88 <DD><P>The "long long" type was introduced in C99. It is
89 provided as a GNU extension to C++98 in g++. This flag builds
90 support for "long long" into the library
91 (specialized templates and the like). This option is off by
92 default: if enabled, users will have to either use the
93 new-style "C" headers by default (ie cmath not math.h)
94 or add appropriate compile-time flags to all compile lines to
95 allow "C" visibility of this feature (on GNU/Linux,
96 the flag is -D_ISOC99_SOURCE).
99 <DT><TT>--enable-cheaders=OPTION </TT>
100 <DD><P>This allows the user to define what kind of C headers are
101 used. Options are: c, c_std, and c_shadow. These correspond
102 to the source directory's include/c, include/c_std, and
103 include/c_shadow directories. The default is c_std.
106 <DT><TT>--enable-threads </TT>
107 <DD><P>This is an abbreviated form of <TT>'--enable-threads=yes'</TT>
111 <DT><TT>--enable-threads=LIB </TT>
112 <DD><P>Select a threading library. As of libstdc++-v3 snapshot 2.91,
114 'yes' for some kind of default (hmmmmm);
115 'decosf1', 'irix', 'mach', 'os2', 'posix'/'pthreads'
117 'solaris', 'win32', 'dce', or 'vxworks' to select the
118 corresponding interface;
119 and 'single', 'no', or 'none' for the null-case,
120 single-threaded library.
122 <P>All of this is currently undergoing a lot of changes. As of
123 2.91, 'single' and 'posix' are the only implemented
124 models. Default is single.
127 <DT><TT>--enable-version-specific-runtime-libs </TT>
128 <DD><P>Specify that run-time libraries should be installed in the
129 compiler-specific subdirectory (i.e.,
130 <TT>$(libdir)/gcc-lib/$(target_alias)/$(gcc_version)</TT>)
131 instead of <TT>$(libdir)</TT>. This option is useful if you
132 intend to use several versions of gcc in parallel. In addition,
133 libstdc++'s include files will be installed in
134 <TT>$(libdir)/gcc-lib/$(target_alias)/$(gcc_version)/include/g++</TT>,
135 unless you also specify
136 <TT>--with-gxx-include-dir=_dirname_</TT> during configuration.
139 <DT><TT>--with-gxx-include-dir=<include-files dir></TT>
140 <DD><P>Adds support for named libstdc++ include directory. For instance,
141 the following puts all the libstdc++ headers into a directory
142 called "2.97-20001008" instead of the usual
145 --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</PRE>
148 <DT><TT>--enable-cxx-flags=FLAGS</TT>
149 <DD><P>With this option, you can pass a string of -f (functionality)
150 flags to the compiler to use when building libstdc++. FLAGS
151 is a quoted string of options, like
153 --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</PRE>
154 Note that the flags don't necessarily have to all be -f flags,
155 as shown, but usually those are the ones that will make sense
156 for experimentation and configure-time overriding.
158 <P>The advantage of --enable-cxx-flags over setting CXXFLAGS in
159 the 'make' environment is that, if files are automatically
160 rebuilt, the same flags will be used when compiling those files
161 as well, so that everything matches.
163 <P>Fun flags to try might include combinations of
169 and opposite forms (-fno-) of the same. Tell us (the mailing
170 list) if you discover more!
173 <DT><TT>--enable-c-mbchar </TT>[default]
174 <DD><P>Certain template specializations are required for wide
175 character conversion support. This is tricky and currently
176 changing rapidly, and can cause problems on new platforms.
177 Disabling wide character specializations is useful for initial
178 porting steps, but builds only a subset of what is required by
179 ISO. Default is on, but the <TT>--enable-cstdio=stdio </TT>
180 option currently turns it off.
184 <P>Return <A HREF="#top">to the top of the page</A> or
185 <A HREF="http://gcc.gnu.org/libstdc++/">to the homepage</A>.
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193 $Id: configopts.html,v 1.6 2001/02/07 00:03:20 pme Exp $