191 lines
7.5 KiB
HTML
191 lines
7.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
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<HTML>
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
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<META NAME="AUTHOR" CONTENT="pme@sources.redhat.com (Phil Edwards)">
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<META NAME="KEYWORDS" CONTENT="libstdc++, libstdc++-v3, GCC, g++">
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<META NAME="DESCRIPTION" CONTENT="Configuration options for libstdc++-v3.">
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<META NAME="GENERATOR" CONTENT="vi and eight fingers">
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<TITLE>libstdc++-v3 configure options</TITLE>
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<LINK REL="home" HREF="http://sources.redhat.com/libstdc++/">
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<!-- $Id: configopts.html,v 1.15 2000/10/26 14:56:04 bkoz Exp $ -->
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<BODY>
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<H1 CLASS="centered"><A NAME="top">Interesting <TT>configure</TT>
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options</A></H1>
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<P>The latest version of this document is always available at
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<A HREF="http://sources.redhat.com/libstdc++/configopts.html">
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http://sources.redhat.com/libstdc++/configopts.html</A>.
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</P>
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<P>To the <A HREF="index.html">libstdc++-v3 homepage</A>.
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<!-- ####################################################### -->
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<HR>
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<P>Here are some of the non-obvious options to libstdc++'s configure.
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Keep in mind that
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<!-- This SECnn should be the "Choosing Package Options" section. -->
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<A HREF="http://sources.redhat.com/autoconf/autoconf.html#SEC74">they
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all have opposite forms as well</A>
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(enable/disable and with/without). The defaults are for the latest
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snapshot, 2.90.8.
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</P>
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<P>The canonical way to find out the configure options that are
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available for a given set of libstdc++ sources is to go to the
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source directory and then type:<TT> ./configure --help</TT>
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<DL>
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<DT><TT>--enable-multilib </TT>[default]
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<DD><P>This is part of the generic multilib support for building cross
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compilers. As such, targets like "powerpc-elf" will have
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libstdc++ built many different ways: "-msoft-float"
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and not, etc. A different libstdc++ will be built for each of
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the different multilib versions. This option is on by default.
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</P>
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<DT><TT>--enable-debug </TT>
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<DD><P>The configure script will automatically detect the highest level
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of optimization that the compiler in use can use (certain
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versions of g++ will ICE if given the <TT>-O2</TT> option, but
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this is fixed in later versions of the compiler). This --enable
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flag will disable all optimizations and instruct the compiler to
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emit as much extra debugging information as it can, for use
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inside GDB.
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</P>
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<DT><TT>--enable-cstdio </TT>[default]
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<DD><P>This is an abbreviated form of <TT>'--enable-cstdio=libio'</TT>
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(described next).
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</P>
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<DT><TT>--enable-cstdio=LIB </TT>
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<DD><P>Select a target-specific I/O package. As of libstdc++-v3
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snapshot 2.90.8, the choices are 'libio' to specify the GNU
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I/O package (from
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<A HREF="http://sources.redhat.com/glibc/">glibc</A>, the
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GNU C library), or 'stdio' to use a generic "C" abstraction.
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</P>
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<DT><TT>--enable-long-long </TT>
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<DD><P>The "long long" type was introduced in C99. It is
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provided as a GNU extension to C++98 in g++. This flag builds
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support for "long long" into the library (specialized
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templates and the like).
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</P>
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<DT><TT>--enable-namespaces </TT>[default]
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<DD><P>By default, g++ currently ignores namespace <TT>std</TT> for
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backwards compatibility. It can be turned on with the
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<TT> -fhonor-std </TT> flag to the compiler. As of libstdc++-v3
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snapshot 2.90.8, that flag is passed to g++ when building the
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library. (In g++ 2.96 and later, this flag is on by default if
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libstdc++-v3 is used.) The --disable variant will put all std::
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symbols into the global namespace.
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</P>
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<P>This option has been removed in current sources; disabling
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namespaces is just not possible.
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</P>
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<DT><TT>--enable-cshadow-headers </TT>
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<DD><P>This turns on the code to construct shadowed C headers, and to
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use c headers in the std:: namespace. Very experimental as of
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this writing.
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</P>
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<DT><TT>--enable-threads </TT>
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<DD><P>This is an abbreviated form of <TT>'--enable-threads=yes'</TT>
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(described next).
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</P>
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<DT><TT>--enable-threads=LIB </TT>
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<DD><P>Select a threading library. As of libstdc++-v3 snapshot 2.90.8,
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the choices are:
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'yes' for some kind of default (hmmmmm);
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'decosf1', 'irix', 'mach', 'os2', 'posix'/'pthreads'
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(same thing),
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'solaris', 'win32', 'dce', or 'vxworks' to select the
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corresponding interface;
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and 'single', 'no', or 'none' for the null-case,
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single-threaded library.
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</P>
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<P>All of this is currently undergoing a lot of changes. As of
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2.90.8, 'single' and 'posix' are the only implemented models.
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</P>
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<DT><TT>--enable-version-specific-runtime-libs </TT>
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<DD><P>Specify that run-time libraries should be installed in the
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compiler-specific subdirectory (i.e.,
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<TT>$(libdir)/gcc-lib/$(target_alias)/$(gcc_version)</TT>)
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instead of <TT>$(libdir)</TT>. This option is useful if you
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intend to use several versions of gcc in parallel. In addition,
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libstdc++'s include files will be installed in
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<TT>$(libdir)/gcc-lib/$(target_alias)/$(gcc_version)/include/g++</TT>,
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unless you also specify
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<TT>--with-gxx-include-dir=_dirname_</TT> during configuration.
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</P>
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<DT><TT>--with-gxx-include-dir=<include-files dir></TT>
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<DD><P>Adds support for named libstdc++ include directory. For instance,
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the following puts all the libstdc++ headers into a directory
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called "2.97-20001008" instead of the usual
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"g++-v3".
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<PRE>
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--with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</PRE>
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</P>
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<DT><TT>--enable-cxx-flags=FLAGS</TT>
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<DD><P>With this option, you can pass a string of -f (functionality)
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flags to the compiler to use when building libstdc++. FLAGS
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is a quoted string of options, like
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<PRE>
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--enable-cxx-flags='-fsquangle -fvtable-gc -ansi'</PRE>
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Note that the flags don't necessarily have to all be -f flags,
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as shown, but usually those are the ones that will make sense
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for experimentation and configure-time overriding.
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</P>
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<P>The advantage of --enable-cxx-flags over setting CXXFLAGS in
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the 'make' environment is that, if libgcc is automatically
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rebuilt, the same flags will be used when compiling those files
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as well, so that everything matches.
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</P>
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<P>Fun flags to try might include combinations of
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<PRE>
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-fstrict-aliasing
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-fnew-abi
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-fnew-exceptions
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-ffunction-sections
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-fvtable-gc</PRE>
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and -fno- forms of the same. Tell us (the mailing list) if
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you discover more!
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</P>
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<DT><TT>--enable-wchar </TT>[default]
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<DD><P>Certain template specializations are required for wide character
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conversion support. This is tricky and currently changing rapidly,
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and can cause problems on new platforms. Disabling wide character
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specializations is useful for initial porting steps, but builds
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only a subset of what is required by ISO.
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</P>
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</DL>
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</P>
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<P>Return <A HREF="#top">to the top of the page</A> or
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<A HREF="index.html">to the homepage</A>.
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</P>
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<!-- ####################################################### -->
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<HR>
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<P CLASS="fineprint"><EM>
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$Id: configopts.html,v 1.15 2000/10/26 14:56:04 bkoz Exp $
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</EM></P>
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</HTML>
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