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<!--
** Locations of "the most recent snapshot is the Nth" text are
- ** answers 1_1, 1_4, 4_1, 5_6.
+ ** answers 1_1, 1_4, 4_1.
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-</HEAD>
-<BODY>
+</head>
+<body>
-<H1 CLASS="centered">libstdc++ Frequently Asked Questions</H1>
+<h1 class="centered">libstdc++ Frequently Asked Questions</h1>
-<P>The latest version of this document is always available at
-<A HREF="http://gcc.gnu.org/onlinedocs/libstdc++/faq/">
-http://gcc.gnu.org/onlinedocs/libstdc++/faq/</A>.</P>
+<p class="fineprint"><em>
+ The latest version of this document is always available at
+ <a href="http://gcc.gnu.org/onlinedocs/libstdc++/faq/">
+ http://gcc.gnu.org/onlinedocs/libstdc++/faq/</a>. The main documentation
+ page is at
+ <a href="http://gcc.gnu.org/onlinedocs/libstdc++/documentation.html">
+ http://gcc.gnu.org/onlinedocs/libstdc++/documentation.html</a>.
+</em></p>
-<P>To the <A HREF="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</A>.
+<p><em>
+ To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
+</em></p>
<!-- ####################################################### -->
-<HR>
-<H1>Questions</H1>
-<OL>
- <LI><A HREF="#1_0">General Information</A>
+<hr />
+<h1>Questions</h1>
+<ol>
+ <li><a href="#1_0">General Information</a>
<!-- I suspect these will mostly be links to/into existing documents. -->
- <OL>
- <LI><A HREF="#1_1">What is libstdc++-v3?</A>
- <LI><A HREF="#1_2">Why should I use libstdc++?</A>
- <LI><A HREF="#1_3">Who's in charge of it?</A>
- <LI><A HREF="#1_4">How do I get libstdc++?</A>
- <LI><A HREF="#1_5">When is libstdc++ going to be finished?</A>
- <LI><A HREF="#1_6">How do I contribute to the effort?</A>
- <LI><A HREF="#1_7">What happened to libg++? I need that!</A>
- <LI><A HREF="#1_8">What if I have more questions?</A>
- </OL>
-
- <LI><A HREF="#2_0">Installation</A>
- <OL>
- <LI><A HREF="#2_1">How do I install libstdc++-v3?</A>
- <LI><A HREF="#2_2">[removed]</A>
- <LI><A HREF="#2_3">What is this CVS thing that you keep
- mentioning?</A>
- <LI><A HREF="#2_4">How do I know if it works?</A>
- </OL>
-
- <LI><A HREF="#3_0">Platform-Specific Issues</A>
- <OL>
- <LI><A HREF="#3_1">Can libstdc++-v3 be used with <my
- favorite compiler>?</A>
- <LI><A HREF="#3_2">[removed]</A>
- <LI><A HREF="#3_3">Building under DEC OSF kills the assembler</A>
- </OL>
-
- <LI><A HREF="#4_0">Known Bugs and Non-Bugs</A>
- <OL>
- <LI><A HREF="#4_1">What works already?</A>
- <LI><A HREF="#4_2">Bugs in gcc/g++ (not libstdc++-v3)</A>
- <LI><A HREF="#4_3">Bugs in the C++ language/lib specification</A>
- <LI><A HREF="#4_4">Things in libstdc++ that look like bugs</A>
- <UL>
- <LI><A HREF="#4_4_Weff">-Weffc++ complains too much</A>
- <LI><A HREF="#4_4_rel_ops">"ambiguous overloads"
- after including an old-style header</A>
- <LI><A HREF="#4_4_interface">The g++-3 headers are
- <STRONG>not ours</STRONG></A>
- <LI><A HREF="#4_4_glibc">compilation errors from streambuf.h</A>
- <LI><A HREF="#4_4_checks">errors about <EM>*Cconcept</EM> and
- <EM>constraints</EM> in the STL...</A>
- </UL>
- <LI><A HREF="#4_5">Aw, that's easy to fix!</A>
- </OL>
-
- <LI><A HREF="#5_0">Miscellaneous</A>
- <OL>
- <LI><A HREF="#5_1">string::iterator is not char*;
- vector<T>::iterator is not T*</A>
- <LI><A HREF="#5_2">What's next after libstdc++-v3?</A>
- <LI><A HREF="#5_3">What about the STL from SGI?</A>
- <LI><A HREF="#5_4">Extensions and Backward Compatibility</A>
- <LI><A HREF="#5_5">[removed]</A>
- <LI><A HREF="#5_6">Is libstdc++-v3 thread-safe?</A>
- <LI><A HREF="#5_7">How do I get a copy of the ISO C++ Standard?</A>
- </OL>
-
-</OL>
-
-<HR>
+ <ol>
+ <li><a href="#1_1">What is libstdc++-v3?</a> </li>
+ <li><a href="#1_2">Why should I use libstdc++?</a> </li>
+ <li><a href="#1_3">Who's in charge of it?</a> </li>
+ <li><a href="#1_4">How do I get libstdc++?</a> </li>
+ <li><a href="#1_5">When is libstdc++ going to be finished?</a> </li>
+ <li><a href="#1_6">How do I contribute to the effort?</a> </li>
+ <li><a href="#1_7">What happened to libg++? I need that!</a> </li>
+ <li><a href="#1_8">What if I have more questions?</a> </li>
+ <li><a href="#1_9">What are the license terms for libstdc++-v3?</a> </li>
+ </ol>
+ </li>
+
+ <li><a href="#2_0">Installation</a>
+ <ol>
+ <li><a href="#2_1">How do I install libstdc++-v3?</a> </li>
+ <li><a href="#2_2">[removed]</a> </li>
+ <li><a href="#2_3">What is this CVS thing that you keep
+ mentioning?</a> </li>
+ <li><a href="#2_4">How do I know if it works?</a> </li>
+ <li><a href="#2_5">This library is HUGE! And what's libsupc++?</a> </li>
+ </ol>
+ </li>
+
+ <li><a href="#3_0">Platform-Specific Issues</a>
+ <ol>
+ <li><a href="#3_1">Can libstdc++-v3 be used with <my
+ favorite compiler>?</a> </li>
+ <li><a href="#3_2">[removed]</a> </li>
+ <li><a href="#3_3">[removed]</a> </li>
+ <li><a href="#3_4">I can't use 'long long' on Solaris</a> </li>
+ <li><a href="#3_5"><code>_XOPEN_SOURCE</code> /
+ <code>_GNU_SOURCE</code> / etc is always defined</a>
+ </li>
+ <li><a href="#3_6">OS X ctype.h is broken! How can I hack it?</a></li>
+ <li><a href="#3_7">Threading is broken on i386</a></li>
+ <li><a href="#3_8">Recent GNU/Linux glibc required?</a></li>
+ <li><a href="#3_9">Can't use wchar_t/wstring on FreeBSD</a></li>
+ </ol>
+ </li>
+
+ <li><a href="#4_0">Known Bugs and Non-Bugs</a>
+ <ol>
+ <li><a href="#4_1">What works already?</a> </li>
+ <li><a href="#4_2">Bugs in gcc/g++ (not libstdc++-v3)</a> </li>
+ <li><a href="#4_3">Bugs in the C++ language/lib specification</a> </li>
+ <li><a href="#4_4">Things in libstdc++ that only look like bugs</a><ul>
+ <li><a href="#4_4_iostreamclear">reopening a stream fails</a> </li>
+ <li><a href="#4_4_Weff">-Weffc++ complains too much</a> </li>
+ <li><a href="#4_4_rel_ops">"ambiguous overloads"
+ after including an old-style header</a> </li>
+ <li><a href="#4_4_interface">The g++-3 headers are
+ <strong>not ours</strong></a> </li>
+ <li><a href="#4_4_glibc">compilation errors from streambuf.h</a> </li>
+ <li><a href="#4_4_checks">errors about <em>*Concept</em> and
+ <em>constraints</em> in the STL...</a> </li>
+ <li><a href="#4_4_dlsym">program crashes when using library code
+ in a dynamically-loaded library</a> </li>
+ <li><a href="#4_4_leak">"memory leaks" in containers</a> </li>
+ </ul>
+ </li>
+ <li><a href="#4_5">Aw, that's easy to fix!</a> </li>
+ </ol>
+ </li>
+
+ <li><a href="#5_0">Miscellaneous</a>
+ <ol>
+ <li><a href="#5_1">string::iterator is not char*;
+ vector<T>::iterator is not T*</a> </li>
+ <li><a href="#5_2">What's next after libstdc++-v3?</a> </li>
+ <li><a href="#5_3">What about the STL from SGI?</a> </li>
+ <li><a href="#5_4">Extensions and Backward Compatibility</a> </li>
+ <li><a href="#5_5">[removed]</a> </li>
+ <li><a href="#5_6">Is libstdc++-v3 thread-safe?</a> </li>
+ <li><a href="#5_7">How do I get a copy of the ISO C++ Standard?</a> </li>
+ <li><a href="#5_8">What's an ABI and why is it so messy?</a> </li>
+ </ol>
+ </li>
+
+</ol>
+
+<hr />
<!-- ####################################################### -->
-<H1><A NAME="1_0">1.0 General Information</A></H1>
+<h1><a name="1_0">1.0 General Information</a></h1>
<!-- I suspect these will mostly be links to/into existing documents. -->
- <H2><A NAME="1_1">1.1 What is libstdc++-v3?</A></H2>
- <P>The GNU Standard C++ Library v3, or libstdc++-2.9x, is an
+ <h2><a name="1_1">1.1 What is libstdc++-v3?</a></h2>
+ <p>The GNU Standard C++ Library v3 is an
ongoing project to implement the ISO 14882 Standard C++ library
as described in chapters 17 through 27 and annex D. As the
library reaches stable plateaus, it is captured in a snapshot
- and released. The current release is <A
-HREF="ftp://gcc.gnu.org/pub/libstdc++/libstdc++-2.92.tar.gz">the
- eleventh snapshot</A>. For those who want to see exactly how
+ and released. The latest release is
+ <a href="http://gcc.gnu.org/libstdc++/index.html#download">the
+ fourteenth snapshot</a> but newer versions have been included
+ in recent GCC releases. For those who want to see exactly how
far the project has come, or just want the latest
bleeding-edge code, the up-to-date source is available over
- anonymous CVS, and can even be browsed over the Web (see below).
- </P>
- <P>A more formal description of the V3 goals can be found in the
- official <A HREF="../17_intro/DESIGN">design document</A>.
- </P>
-
-<HR>
- <H2><A NAME="1_2">1.2 Why should I use libstdc++?</A></H2>
- <P>The completion of the ISO C++ standardization gave the
+ anonymous CVS, and can even be browsed over the Web (see
+ <a href="#1_4">1.4</a> below).
+ </p>
+ <p>The older libstdc++-v2 project is no longer maintained; the code
+ has been completely replaced and rewritten.
+ <a href="#4_4_interface">If you are using V2</a>, then you need to
+ report bugs to your system vendor, not to the V3 list.
+ </p>
+ <p>A more formal description of the V3 goals can be found in the
+ official <a href="../17_intro/DESIGN">design document</a>.
+ </p>
+
+<hr />
+ <h2><a name="1_2">1.2 Why should I use libstdc++?</a></h2>
+ <p>The completion of the ISO C++ standardization gave the
C++ community a powerful set of reuseable tools in the form
of the C++ Standard Library. However, all existing C++
implementations are (as the Draft Standard used to say)
"incomplet and incorrekt," and many suffer from
limitations of the compilers that use them.
- </P>
- <P>The GNU C/C++/FORTRAN/<pick-a-language> compiler
- (<TT>gcc</TT>, <TT>g++</TT>, etc) is widely considered to be
+ </p>
+ <p>The GNU C/C++/FORTRAN/<pick-a-language> compiler
+ (<code>gcc</code>, <code>g++</code>, etc) is widely considered to be
one of the leading compilers in the world. Its development
has recently been taken over by the
- <A HREF="http://gcc.gnu.org/">GCC team</A>. All of
+ <a href="http://gcc.gnu.org/">GCC team</a>. All of
the rapid development and near-legendary
- <A
-HREF="http://gcc.gnu.org/gcc-2.95/buildstat.html">portability</A>
+ <a href="http://gcc.gnu.org/gcc-3.0/buildstat.html">portability</a>
that are the hallmarks of an open-source project are being
applied to libstdc++.
- </P>
- <P>That means that all of the Standard classes and functions
- (such as <TT>string</TT>, <TT>vector<></TT>, iostreams,
+ </p>
+ <p>That means that all of the Standard classes and functions
+ (such as <code>string</code>, <code>vector<></code>, iostreams,
and algorithms) will be freely available and fully compliant.
Programmers will no longer need to "roll their own"
- nor be worried about platform-specific incompatabilities.
- </P>
+ nor be worried about platform-specific incompatibilities.
+ </p>
-<HR>
- <H2><A NAME="1_3">1.3 Who's in charge of it?</A></H2>
- <P>The libstdc++ project is contributed to by several developers
+<hr />
+ <h2><a name="1_3">1.3 Who's in charge of it?</a></h2>
+ <p>The libstdc++ project is contributed to by several developers
all over the world, in the same way as GCC or Linux.
- Benjamin Kosnik, Gabriel Dos Reis, Phil Edwards, and Ulrich
- Drepper are the lead maintainers of the CVS archive.
- </P>
- <P>Development and discussion is held on the libstdc++ mailing
+ Benjamin Kosnik, Gabriel Dos Reis, Phil Edwards, Ulrich Drepper,
+ Loren James Rittle, and Paolo Carlini are the lead maintainers of
+ the CVS archive.
+ </p>
+ <p>Development and discussion is held on the libstdc++ mailing
list. Subscribing to the list, or searching the list
archives, is open to everyone. You can read instructions for
- doing so on the <A HREF="http://gcc.gnu.org/libstdc++/">homepage</A>.
+ doing so on the <a href="http://gcc.gnu.org/libstdc++/">homepage</a>.
If you have questions, ideas, code, or are just curious, sign up!
- </P>
-
-<HR>
- <H2><A NAME="1_4">1.4 How do I get libstdc++?</A></H2>
- <P>The eleventh (and latest) snapshot of libstdc++-v3 is <A
-HREF="ftp://gcc.gnu.org/pub/libstdc++/libstdc++-2.92.tar.gz">
- available via ftp</A>.
- </P>
- <P>The <A HREF="http://gcc.gnu.org/libstdc++/">homepage</A>
+ </p>
+
+<hr />
+ <h2><a name="1_4">1.4 How do I get libstdc++?</a></h2>
+ <p>The fourteenth (and latest) snapshot of libstdc++-v3 is
+ <a href="http://gcc.gnu.org/libstdc++/index.html#download">available
+ via ftp</a>.
+ </p>
+ <p>The <a href="http://gcc.gnu.org/libstdc++/">homepage</a>
has instructions for retrieving the latest CVS sources, and for
browsing the CVS sources over the web.
- </P>
- <P>The subset commonly known as the Standard Template Library
- (chapters 23 through 25, mostly) is adapted from the SGI STL,
- which is also an ongoing work.<!-- Possibly a link to SGI's
- STL here. -->
- </P>
-
-<HR>
- <H2><A NAME="1_5">1.5 When is libstdc++ going to be finished?</A></H2>
-<!-- <P>Nathan Myers gave the best of all possible answers in <A
- HREF="http://www.deja.com/getdoc.xp?AN=469581698&fmt=text">a
- Usenet article</A>.</P>
-which is no longer available, thanks deja...-->
- <P>Nathan Myers gave the best of all possible answers, responding to a
- Usenet article asking this question: <EM>Sooner, if you help.</EM>
- </P>
+ </p>
+ <p>The subset commonly known as the Standard Template Library
+ (chapters 23 through 25, mostly) is adapted from the final release
+ of the SGI STL.
+ </p>
+<hr />
+ <h2><a name="1_5">1.5 When is libstdc++ going to be finished?</a></h2>
+<!-- <p>Nathan Myers gave the best of all possible answers in <a
+ href="http://www.deja.com/getdoc.xp?AN=469581698&fmt=text">a
+ Usenet article</a>.</p>
+which is no longer available, thanks deja...-->
+ <p>Nathan Myers gave the best of all possible answers, responding to a
+ Usenet article asking this question: <em>Sooner, if you help.</em>
+ </p>
-<HR>
- <H2><A NAME="1_6">1.6 How do I contribute to the effort?</A></H2>
- <P>Here is <A HREF="../17_intro/contribute.html">a
- page devoted to this topic</A>. Subscribing to the mailing
+<hr />
+ <h2><a name="1_6">1.6 How do I contribute to the effort?</a></h2>
+ <p>Here is <a href="../17_intro/contribute.html">a
+ page devoted to this topic</a>. Subscribing to the mailing
list (see above, or the homepage) is a very good idea if you
have something to contribute, or if you have spare time and
want to help. Contributions don't have to be in the form of
source code; anybody who is willing to help write
documentation, for example, or has found a bug in code that
we all thought was working, is more than welcome!
- </P>
+ </p>
-<HR>
- <H2><A NAME="1_7">1.7 What happened to libg++? I need that!</A></H2>
- <P>The most recent libg++ README states that libg++ is no longer
+<hr />
+ <h2><a name="1_7">1.7 What happened to libg++? I need that!</a></h2>
+ <p>The most recent libg++ README states that libg++ is no longer
being actively maintained. It should not be used for new
projects, and is only being kicked along to support older code.
- </P>
- <P>The libg++ was designed and created when there was no Standard
+ </p>
+ <p>The libg++ was designed and created when there was no Standard
to provide guidance. Classes like linked lists are now provided
- for by <TT>list<T></TT> and do not need to be created by
- <TT>genclass</TT>. (For that matter, templates exist now and
+ for by <code>list<T></code> and do not need to be created by
+ <code>genclass</code>. (For that matter, templates exist now and
are well-supported, whereas genclass (mostly) predates them.)
- </P>
- <P>There are other classes in libg++ that are not specified in the
+ </p>
+ <p>There are other classes in libg++ that are not specified in the
ISO Standard (e.g., statistical analysis). While there are a
lot of really useful things that are used by a lot of people
(e.g., statistics :-), the Standards Committee couldn't include
everything, and so a lot of those "obvious" classes
didn't get included.
- </P>
- <P>Since libstdc++ is an implementation of the Standard Library, we
+ </p>
+ <p>Since libstdc++ is an implementation of the Standard Library, we
have no plans at this time to include non-Standard utilities
in the implementation, however handy they are. (The extensions
provided in the SGI STL aren't maintained by us and don't get
time.) It is entirely plausable that the "useful stuff"
from libg++ might be extracted into an updated utilities library,
but nobody has stated such a project yet.
- </P>
+ </p>
<!-- The advertisement, so to speak, might have to go. Hmmmmm. -->
- <P>(The <A HREF="http://www.boost.org/">Boost</A> site houses free
+ <p>(The <a href="http://www.boost.org/">Boost</a> site houses free
C++ libraries that do varying things, and happened to be started
by members of the Standards Committee. Certain "useful
stuff" classes will probably migrate there.)
- </P>
- <P>For the bold and/or desperate, the
- <A HREF="http://gcc.gnu.org/fom_serv/cache/33.html">GCC FAQ</A>
+ </p>
+ <p>For the bold and/or desperate, the
+ <a href="http://gcc.gnu.org/extensions.html">GCC extensions page</a>
describes where to find the last libg++ source.
- </P>
+ </p>
-<HR>
- <H2><A NAME="1_8">1.8 What if I have more questions?</A></H2>
- <P>If you have read the README and RELEASE-NOTES files, and your
+<hr />
+ <h2><a name="1_8">1.8 What if I have more questions?</a></h2>
+ <p>If you have read the README and RELEASE-NOTES files, and your
question remains unanswered, then just ask the mailing list.
At present, you do not need to be subscribed to the list to
send a message to it. More information is available on the
homepage (including how to browse the list archives); to send
- to the list, use <A HREF="mailto:libstdc++@gcc.gnu.org">
- <CODE>libstdc++@gcc.gnu.org</CODE></A>.
- </P>
- <P>If you have a question that you think should be included here,
- or if you have a question <EM>about</EM> a question/answer here,
- contact <A HREF="mailto:pme@sources.redhat.com">Phil Edwards</A>
- or <A HREF="mailto:gdr@gcc.gnu.org">Gabriel Dos Reis</A>.
- </P>
-
-<HR>
-
-<H1><A NAME="2_0">2.0 Installation</A></H1>
- <H2><A NAME="2_1">2.1 How do I install libstdc++-v3?</A></H2>
- <P>Complete instructions are not given here (this is a FAQ, not
+ to the list, use <a href="mailto:libstdc++@gcc.gnu.org">
+ <code>libstdc++@gcc.gnu.org</code></a>.
+ </p>
+ <p>If you have a question that you think should be included here,
+ or if you have a question <em>about</em> a question/answer here,
+ contact <a href="mailto:pme@gcc.gnu.org">Phil Edwards</a>
+ or <a href="mailto:gdr@gcc.gnu.org">Gabriel Dos Reis</a>.
+ </p>
+
+<hr />
+ <h2><a name="1_9">1.9 What are the license terms for libstdc++-v3?</a></h2>
+ <p>See <a href="../17_intro/license.html">our license description</a>
+ for these and related questions.
+ </p>
+
+<hr />
+<h1><a name="2_0">2.0 Installation</a></h1>
+ <h2><a name="2_1">2.1 How do I install libstdc++-v3?</a></h2>
+ <p>Complete instructions are not given here (this is a FAQ, not
an installation document), but the tools required are few:
- </P>
- <UL>
- <LI> A 3.x release of GCC. Note that building GCC is much
+ </p>
+ <ul>
+ <li> A 3.x release of GCC. Note that building GCC is much
easier and more automated than building the GCC 2.[78]
series was. If you are using GCC 2.95, you can still
build earlier snapshots of libstdc++.
- <LI> GNU Make is the only make that supports these makefiles.
- <LI> The GNU Autotools are needed if you are messing with
+ </li>
+ <li> GNU Make is recommended, but should not be required.
+ </li>
+ <li> The GNU Autotools are needed if you are messing with
the configury or makefiles.
- </UL>
- <P>The file <A HREF="../documentation.html">documentation.html</A>
+ </li>
+ </ul>
+ <p>The file <a href="../documentation.html">documentation.html</a>
provides a good overview of the steps necessary to build, install,
and use the library. Instructions for configuring the library
with new flags such as --enable-threads are there also, as well as
patches and instructions for working with GCC 2.95.
- </P>
- <P>The top-level install.html and
- <A HREF="../17_intro/RELEASE-NOTES">RELEASE-NOTES</A> files contain
+ </p>
+ <p>The top-level install.html and
+ <a href="../17_intro/RELEASE-NOTES">RELEASE-NOTES</a> files contain
the exact build and installation instructions. You may wish to
browse those files over CVSweb ahead of time to get a feel for
what's required. RELEASE-NOTES is located in the
".../docs/17_intro/" directory of the distribution.
- </P>
+ </p>
-<HR>
- <H2><A NAME="2_2">2.2 [removed]</A></H2>
- <P>This question has become moot and has been removed. The stub
+<hr />
+ <h2><a name="2_2">2.2 [removed]</a></h2>
+ <p>This question has become moot and has been removed. The stub
is here to preserve numbering (and hence links/bookmarks).
- </P>
+ </p>
-<HR>
- <H2><A NAME="2_3">2.3 What is this CVS thing that you
- keep mentioning?</A></H2>
- <P>The <EM>Concurrent Versions System</EM> is one of several revision
+<hr />
+ <h2><a name="2_3">2.3 What is this CVS thing that you
+ keep mentioning?</a></h2>
+ <p>The <em>Concurrent Versions System</em> is one of several revision
control packages. It was selected for GNU projects because it's
- free (speech), free (beer), and very high quality. The <A
- HREF="http://www.gnu.org/software/cvs/cvs.html">CVS entry in
- the GNU software catalogue</A> has a better description as
+ free (speech), free (beer), and very high quality. The <a
+ href="http://www.gnu.org/software/cvs/cvs.html">CVS entry in
+ the GNU software catalogue</a> has a better description as
well as a
- <A HREF="http://www.cvshome.org/">link to the makers of CVS</A>.
- </P>
- <P>The "anonymous client checkout" feature of CVS is
+ <a href="http://www.cvshome.org/">link to the makers of CVS</a>.
+ </p>
+ <p>The "anonymous client checkout" feature of CVS is
similar to anonymous FTP in that it allows anyone to retrieve
the latest libstdc++ sources.
- </P>
- <P>After the first of April, American users will have a
+ </p>
+ <p>After the first of April, American users will have a
"/pharmacy" command-line option...
<!-- wonder how long that'll live -->
- </P>
-
-<HR>
- <H2><A NAME="2_4">2.4 How do I know if it works?</A></H2>
- <P>libstdc++-v3 comes with its own testsuite. You do not need
- to actually install the library ("<TT>gmake
- install</TT>") to run the testsuite.
- </P>
- <P>To run the testsuite on the library after building it, use
- "gmake check" while in your build directory. To run
+ </p>
+
+<hr />
+ <h2><a name="2_4">2.4 How do I know if it works?</a></h2>
+ <p>libstdc++-v3 comes with its own testsuite. You do not need
+ to actually install the library ("<code>make
+ install</code>") to run the testsuite.
+ </p>
+ <p>To run the testsuite on the library after building it, use
+ "make check" while in your build directory. To run
the testsuite on the library after building and installing it,
- use "gmake check-install" instead.
- </P>
- <P>If you find bugs in the testsuite programs themselves, or if
- you think of a new test program that should be added to the
- suite, <B>please</B> write up your idea and send it to the list!
- </P>
-
-<HR>
-<H1><A NAME="3_0">3.0 Platform-Specific Issues</A></H1>
- <H2><A NAME="3_1">3.1 Can libstdc++-v3 be used with <my
- favorite compiler>?</A></H2>
- <P>Probably not. Yet.</P>
- <P>Because GCC advances so rapidly, development and testing of
+ use "make check-install" instead.
+ </p>
+ <p>If you find bugs in the testsuite programs themselves, or if you
+ think of a new test program that should be added to the suite,
+ <strong>please</strong> write up your idea and send it to the list!
+ </p>
+
+<hr />
+ <h2><a name="2_5">2.4 This library is HUGE! And what's libsupc++?</a></h2>
+ <p>Usually the size of libraries on disk isn't noticeable. When a
+ link editor (or simply "linker") pulls things from a
+ static archive library, only the necessary object files are copied
+ into your executable, not the entire library. Unfortunately, even
+ if you only need a single function or variable from an object file,
+ the entire object file is extracted. (There's nothing unique to C++
+ or libstdc++-v3 about this; it's just common behavior, given here
+ for background reasons.)
+ </p>
+ <p>Some of the object files which make up libstdc++.a are rather large.
+ If you create a statically-linked executable with
+ <code> -static</code>, those large object files are suddenly part
+ of your executable. Historically the best way around this was to
+ only place a very few functions (often only a single one) in each
+ source/object file; then extracting a single function is the same
+ as extracting a single .o file. For libstdc++-v3 this is only
+ possible to a certain extent; the object files in question contain
+ template classes and template functions, pre-instantiated, and
+ splitting those up causes severe maintenance headaches.
+ </p>
+ <p>It's not a bug, and it's not really a problem. Nevertheless, some
+ people don't like it, so here are two pseudo-solutions:
+ </p>
+ <p>If the only functions from libstdc++.a which you need are language
+ support functions (those listed in
+ <a href="../18_support/howto.html">clause 18</a> of the standard,
+ e.g., <code>new</code> and <code>delete</code>), then try linking
+ against <code>libsupc++.a</code> (usually specifying
+ <code>-lsupc++</code> when calling g++ for the final link step will
+ do it). This library contains only those support routines, one per
+ object file. But if you are using anything from the rest of the
+ library, such as IOStreams or vectors, then you'll still need
+ pieces from <code>libstdc++.a</code>.
+ </p>
+ <p>The second method is one we hope to incorporate into the library
+ build process. Some platforms can place each function and variable
+ into its own section in a .o file. The GNU linker can then perform
+ garbage collection on unused sections; this reduces the situation
+ to only copying needed functions into the executable, as before,
+ but all happens automatically.
+ </p>
+ <p>Unfortunately the garbage collection in GNU ld is buggy; sections
+ (corresponding to functions and variables) which <em>are</em> used
+ are mistakenly removed, leading to horrible crashes when your
+ executable starts up. For the time being, this feature is not used
+ when building the library.
+ </p>
+
+<hr />
+<h1><a name="3_0">3.0 Platform-Specific Issues</a></h1>
+ <h2><a name="3_1">3.1 Can libstdc++-v3 be used with <my
+ favorite compiler>?</a></h2>
+ <p>Probably not. Yet.</p>
+ <p>Because GCC advances so rapidly, development and testing of
libstdc++ is being done almost entirely under that compiler.
If you are curious about whether other, lesser compilers
(*grin*) support libstdc++, you are more than welcome to try.
Configuring and building the library (see above) will still
require certain tools, however. Also keep in mind that
- <EM>building</EM> libstdc++ does not imply that your compiler
- will be able to <EM>use</EM> all of the features found in the
+ <em>building</em> libstdc++ does not imply that your compiler
+ will be able to <em>use</em> all of the features found in the
C++ Standard Library.
- </P>
- <P>Since the goal of ISO Standardization is for all C++
+ </p>
+ <p>Since the goal of ISO Standardization is for all C++
implementations to be able to share code, the final libstdc++
- should, in theory, be useable under any ISO-compliant
+ should, in theory, be usable under any ISO-compliant
compiler. It will still be targeted and optimized for
GCC/g++, however.
- </P>
+ </p>
-<HR>
- <H2><A NAME="3_2">3.2 [removed]</A></H2>
- <P>This question has become moot and has been removed. The stub
+<hr />
+ <h2><a name="3_2">3.2 [removed]</a></h2>
+ <p>This question has become moot and has been removed. The stub
is here to preserve numbering (and hence links/bookmarks).
- </P>
-
-<HR>
- <H2><A NAME="3_3">3.3 Building DEC OSF kills the assembler</A></H2>
- <P>The <TT>atomicity.h</TT> header for the Alpha processor
- currently uses pseudo-operators which the DEC assembler
- doesn't understand (in particular, .subsection and .previous).
- The simple solution is to install GNU <TT>as</TT> and arrange
- for the GCC build to use it (or merge the sources and build
- it during the bootstrap).
- </P>
- <P>Anyone who
- <A HREF="http://gcc.gnu.org/ml/libstdc++/2000-12/msg00279.html">knows
- the DEC assembler well enough</A> to provide the equivalent of
- these two pseudos would win praise and accolades from many.
- </P>
-
-
-<HR>
-<H1><A NAME="4_0">4.0 Known Bugs and Non-Bugs</A></H1>
- <EM>Note that this section can get rapdily outdated -- such is the
+ </p>
+
+<hr />
+ <h2><a name="3_3">3.3 [removed]</a></h2>
+ <p>This question has become moot and has been removed. The stub
+ is here to preserve numbering (and hence links/bookmarks).
+ </p>
+
+<hr />
+ <h2><a name="3_4">3.4 I can't use 'long long' on Solaris</a></h2>
+ <p>By default we try to support the C99 <code>long long</code> type.
+ This requires that certain functions from your C library be present.
+ </p>
+ <p>Up through release 3.0.2 the tests performed were too general, and
+ this feature was disabled when it did not need to be. The most
+ commonly reported platform affected was Solaris.
+ </p>
+ <p>This has been fixed for 3.0.3 and onwards.
+ </p>
+
+<hr />
+ <h2><a name="3_5">3.5 <code>_XOPEN_SOURCE</code> / <code>_GNU_SOURCE</code>
+ / etc is always defined</a></h2>
+ <p>On Solaris, g++ (but not gcc) always defines the preprocessor
+ macro <code>_XOPEN_SOURCE</code>. On GNU/Linux, the same happens
+ with <code>_GNU_SOURCE</code>. (This is not an exhaustive list;
+ other macros and other platforms are also affected.)
+ </p>
+ <p>These macros are typically used in C library headers, guarding new
+ versions of functions from their older versions. The C++ standard
+ library includes the C standard library, but it requires the C90
+ version, which for backwards-compatability reasons is often not the
+ default for many vendors.
+ </p>
+ <p>More to the point, the C++ standard requires behavior which is only
+ available on certain platforms after certain symbols are defined.
+ Usually the issue involves I/O-related typedefs. In order to
+ ensure correctness, the compiler simply predefines those symbols.
+ </p>
+ <p>Note that it's not enough to #define them only when the library is
+ being built (during installation). Since we don't have an 'export'
+ keyword, much of the library exists as headers, which means that
+ the symbols must also be defined as your programs are parsed and
+ compiled.
+ </p>
+ <p>To see which symbols are defined, look for CPLUSPLUS_CPP_SPEC in
+ the gcc config headers for your target (and try changing them to
+ see what happens when building complicated code). You can also run
+ <code>"g++ -E -dM - < /dev/null"</code> to display
+ a list of predefined macros for any particular installation.
+ </p>
+ <p>This has been discussed on the mailing lists
+ <a href="http://gcc.gnu.org/cgi-bin/htsearch?method=and&format=builtin-long&sort=score&words=_XOPEN_SOURCE+Solaris">quite a bit</a>.
+ </p>
+ <p>This method is something of a wart. We'd like to find a cleaner
+ solution, but nobody yet has contributed the time.
+ </p>
+
+<hr />
+ <h2><a name="3_6">3.6 OS X ctype.h is broken! How can I hack it?</a></h2>
+ <p>This is a long-standing bug in the OS X support. Fortunately,
+ the patch is quite simple, and well-known.
+ <a href="http://gcc.gnu.org/ml/gcc/2002-03/msg00817.html"> Here's a
+ link to the solution.</a>
+ </p>
+
+<hr />
+ <h2><a name="3_7">3.7 Threading is broken on i386</a></h2>
+ <p>Support for atomic integer operations is/was broken on i386
+ platforms. The assembly code accidentally used opcodes that are
+ only available on the i486 and later. So if you configured GCC
+ to target, for example, i386-linux, but actually used the programs
+ on an i686, then you would encounter no problems. Only when
+ actually running the code on a i386 will the problem appear.
+ </p>
+ <p>This is fixed in 3.2.2.
+ </p>
+
+<hr />
+ <h2><a name="3_8">3.8 Recent GNU/Linux glibc required?</a></h2>
+ <p>For 3.2.1 (shared library version 5.0.1) and later, the library
+ uses localization and formatting code from the system C library
+ (glibc) version 2.2.5. That version of glibc is over a year old
+ and contains necessary bugfixes. Many GNU/Linux distros make
+ glibc version 2.3.x available now.
+ </p>
+ <p>The guideline is simple: the more recent the C++ library, the
+ more recent the C library. (This is also documented in the main
+ GCC installation instructions.)
+ </p>
+
+<hr />
+ <h2><a name="3_9">3.9 Can't use wchar_t/wstring on FreeBSD</a></h2>
+ <p>At the moment there are a few problems in FreeBSD's support for
+ wide character functions, and as a result the libstdc++ configury
+ decides that wchar_t support should be disabled. Once the underlying
+ problems are fixed in FreeBSD (soon), the library support will
+ automatically enable itself.
+ </p>
+ <p>You can fix the problems yourself, and learn more about the situation,
+ by reading
+ <a href="http://gcc.gnu.org/ml/libstdc++/2003-02/subjects.html#00286">
+ this short thread</a> ("_GLIBCPP_USE_WCHAR_T undefined in
+ FreeBSD's c++config.h?").
+ </p>
+
+<hr />
+<h1><a name="4_0">4.0 Known Bugs and Non-Bugs</a></h1>
+ <em>Note that this section can get rapdily outdated -- such is the
nature of an open-source project. For the latest information, join
the mailing list or look through recent archives. The RELEASE-
- NOTES and BUGS files are generally kept up-to-date.</EM>
+ NOTES and BUGS files are generally kept up-to-date.</em>
+
+ <p>For 3.0.1, the most common "bug" is an apparently missing
+ "<code>../</code>" in include/Makefile, resulting in files
+ like gthr.h and gthr-single.h not being found. Please read
+ <a href="http://gcc.gnu.org/install/configure.html">the configuration
+ instructions for GCC</a>,
+ specifically the part about configuring in a separate build directory,
+ and how strongly recommended it is. Building in the source directory
+ is fragile, is rarely tested, and tends to break, as in this case.
+ This was fixed for 3.0.2.
+ </p>
+
+ <p>For 3.1, the most common "bug" is a parse error when using
+ <code><fstream></code>, ending with a message,
+ "<code>bits/basic_file.h:52: parse error before `{'
+ token</code>." Please read
+ <a href="http://gcc.gnu.org/install/">the installation instructions for
+ GCC</a>, specifically the part about not installing newer versions on
+ top of older versions. If you install 3.1 over a 3.0.x release, then
+ the wrong basic_file.h header will be found (its location changed
+ between releases).
+ </p>
+
+ <p><strong>Please do not report these as bugs. We know about them.</strong>
+ Reporting this -- or any other problem that's already been fixed --
+ hinders the development of GCC, because we have to take time to
+ respond to your report. Thank you.
+ </p>
- <H2><A NAME="4_1">4.1 What works already?</A></H2>
- <P>This is a verbatim clip from the "Status" section
- of the RELEASE-NOTES for the latest snapshot.
- </P>
+ <h2><a name="4_1">4.1 What works already?</a></h2>
+ <p>This is a verbatim clip from the "Status" section
+ of the RELEASE-NOTES for the latest snapshot. For a list of
+ fixed bugs, see that file.
+ </p>
<!-- Yeah, I meant that "verbatim clip" thing literally... :-) -->
<pre>
New:
---
-- preliminary doxygen documentation has been added. Running "make
- doxygen" in the libstdc++-v3 build directory will generate HTML
- documentation that can be used to cross-reference names and files in
- the library.
-- a dejagnu based testing framework has been added
-- a new implementation of the concept checking code has been ported
- from the boost libraries.
-- support for -fno-exceptions has been added
-- stdexcept was re-written
-- using deprecated or antiquated headers now gives a warning
-- the stdio interface to iostreams has been tweaked, and now works
- with synchronized c/c++ io
-- new libsupc++ routines implementing the IA-64 C++ ABI.
-- HPUX configuration files
-- support for AIX added
-- a lot of bugs were fixed.
-- preliminary named locales implemented
-- portability improvements made to generation of <limits>
-- speedups to improve configuration time.
-- DJGPP support added.
-- support for dlopening shared libstdc++
+(post 3.0.97)
+- more doxygen documentation
+- more named locale fixups
+- stdio_filebuf that takes fd, FILE
+- io performance tuning
+- allocation tuning, valgrind fixups
+- __cxa_demangle now supported
+(3.0.97)
+- more doxygen documentation.
+- more named locale bug fixes
+- support for symbol versioning when using GNU ld >= 2.12
+- wide-io
+- tuning for executable size
+(3.0.96)
+- more doxygen documentation.
+- extensions moved out of namespace std
+- HPUX long long support
+- more string optimizations
+- support for NetBSD cross compiles
+- concept_check merge from boost
+- header simplification
+- named locale bug shakeout
+- thread testsuite
+(3.0.95)
+- add S390, m68k, x86-64 support.
+- doxygen documentation has been extended, including man pages.
+- verbose terminate handling has been added.
+- some libsupc++ tweaks
+- warnings for deprecated headers now active.
+- dejagnu testsuite preliminary documentation.
+- dejagnu testsuite default.
+- dejagnu testsuite cross compiler, multilib safe.
+- long long iostreams on by default, rework of ISO C99 support.
+- iterator re-write and testsuites.
+- container testsuites.
+- allocator revamp and testsuites.
+- more concept-checking work.
+- basic_string optimization and MT fixes.
+- new limits implementation.
+- update -fno-exceptions code, verify it works.
+- full named locale support fpr all facets, choice of gnu,
+ ieee_1003.1-200x (POSIX 2), or generic models. Full support depends
+ on target OS and underlying "C" library support.
</pre>
-<HR>
- <H2><A NAME="4_2">4.2 Bugs in gcc/g++ (not libstdc++-v3)</A></H2>
- <P>This is by no means meant to be complete nor exhaustive, but
+<hr />
+ <h2><a name="4_2">4.2 Bugs in gcc/g++ (not libstdc++-v3)</a></h2>
+ <p>This is by no means meant to be complete nor exhaustive, but
mentions some problems that users may encounter when building
or using libstdc++. If you are experiencing one of these
problems, you can find more information on the libstdc++ and
the GCC mailing lists.
- </P>
- <UL>
- <LI>As of 2.91, these bugs have all been fixed. We look forward
- to new ones, well, not exactly...
- </UL>
-
-<HR>
- <H2><A NAME="4_3">4.3 Bugs in the C++ language/lib specification</A></H2>
- <P>Yes, unfortunately, there are some. In a <A
-HREF="http://gcc.gnu.org/ml/libstdc++/1998/msg00006.html">message
-to the list</A>, Nathan Myers announced that he has started a list of
+ </p>
+ <p>Before reporting a bug, examine the
+ <a href="http://gcc.gnu.org/bugs.html">bugs database</a> with the
+ category set to "libstdc++". The BUGS file in the source
+ tree also tracks known serious problems.
+ </p>
+ <ul>
+ <li>Debugging is problematic, due to bugs in line-number generation
+ (mostly fixed in the compiler) and gdb lagging behind the
+ compiler (lack of personnel). We recommend configuring the
+ compiler using <code>--with-dwarf2</code> if the DWARF2
+ debugging format is not already the default on your platform.
+ Also,
+<a href="http://gcc.gnu.org/ml/libstdc++/2002-02/msg00034.html">changing your
+ GDB settings</a> can have a profound effect on your C++ debugging
+ experiences. :-)</li>
+ </ul>
+
+<hr />
+ <h2><a name="4_3">4.3 Bugs in the C++ language/lib specification</a></h2>
+ <p>Yes, unfortunately, there are some. In a
+ <a href="http://gcc.gnu.org/ml/libstdc++/1998/msg00006.html">message
+ to the list</a>, Nathan Myers announced that he has started a list of
problems in the ISO C++ Standard itself, especially with
regard to the chapters that concern the library. The list
- itself is <A
- HREF="http://www.cantrip.org/draft-bugs.txt">posted on his
- website</A>. Developers who are having problems interpreting
+ itself is
+ <a href="http://www.cantrip.org/draft-bugs.txt">posted on his
+ website</a>. Developers who are having problems interpreting
the Standard may wish to consult his notes.
- </P>
- <P>For those people who are not part of the ISO Library Group
+ </p>
+ <p>For those people who are not part of the ISO Library Group
(i.e., nearly all of us needing to read this page in the first
place :-), a public list of the library defects is occasionally
- published <A HREF="http://anubis.dkuug.dk/jtc1/sc22/wg21/">here</A>.
- </P>
+ published <a href="http://anubis.dkuug.dk/jtc1/sc22/wg21/">here</a>.
+ Some of these have resulted in <a href="#5_2">code changes</a>.
+ </p>
-<HR>
- <H2><A NAME="4_4">4.4 Things in libstdc++ that look like bugs</A></H2>
- <P>There are things which are not bugs in the compiler (4.2) nor
+<hr />
+ <h2><a name="4_4">4.4 Things in libstdc++ that only look like bugs</a></h2>
+ <p>There are things which are not bugs in the compiler (4.2) nor
the language specification (4.3), but aren't really bugs in
libstdc++, either. Really! Please do not report these as bugs.
- </P>
- <A NAME="4_4_Weff">
- <P><STRONG>-Weffc++</STRONG>
- The biggest of these is the quadzillions of warnings about the
- library headers emitted when <TT>-Weffc++</TT> is used. Making
- libstdc++ "-Weffc++-clean" is not a goal of the project,
- for a few reasons. Mainly, that option tries to enforce
- object-oriented programming, while the Standard Library isn't
- necessarily trying to be OO. There are multiple solutions
- under discussion.
- </P>
- </A>
- <A NAME="4_4_rel_ops">
- <P><STRONG>rel_ops</STRONG>
- Another is the <TT>rel_ops</TT> namespace and the template
- comparison operator functions contained therein. If they become
- visible in the same namespace as other comparison functions
- (e.g., '<TT>using</TT>' them and the <iterator> header),
- then you will suddenly be faced with huge numbers of ambiguity
- errors. This was discussed on the -v3 list; Nathan Myers
- <A HREF="http://gcc.gnu.org/ml/libstdc++/2001-01/msg00247.html">sums
- things up here</A>.
- </P>
- </A>
- <A NAME="4_4_interface"><H3>The g++-3 headers are
- <EM>not ours</EM></H3>
- <P>If you have found an extremely broken header file which is
- causing problems for you, look carefully before submitting a
- "high" priority bug report (which you probably shouldn't
- do anyhow; see the last paragraph of the page describing
- <A HREF="http://gcc.gnu.org/gnatswrite.html">the GCC bug database</A>).
- </P>
- <P>If the headers are in <CODE>${prefix}/include/g++-3</CODE>, then
- you are using the old libstdc++-v2 library, which is nonstandard
- and unmaintained. Do not report problems with -v2 to the -v3
- mailing list.
- </P>
- <P>Currently our header files are installed in
- <CODE>${prefix}/include/g++-v3</CODE> (see the 'v'?). This may
- change with the next release of GCC, as it may be too confusing,
- but <A HREF="http://gcc.gnu.org/ml/gcc/2000-10/msg00732.html">the
- question has not yet been decided</A>.
- </P>
- </A>
- <A NAME="4_4_glibc">
- <P><STRONG>glibc</STRONG>
- If you're on a GNU/Linux system and have just upgraded to
- glibc 2.2, but are still using gcc 2.95.2, then you should have
- read the glibc FAQ, specifically 2.34:
- <PRE>
+ </p>
+ <p><a name="4_4_Weff"><strong>-Weffc++</strong></a>
+ The biggest of these is the quadzillions of warnings about the
+ library headers emitted when <code>-Weffc++</code> is used. Making
+ libstdc++ "-Weffc++-clean" is not a goal of the project,
+ for a few reasons. Mainly, that option tries to enforce
+ object-oriented programming, while the Standard Library isn't
+ necessarily trying to be OO.
+ </p>
+ <p><a name="4_4_iostreamclear"><strong>reopening a stream fails</strong>
+ </a> Did I just say that -Weffc++ was our biggest false-bug report?
+ I lied. (It used to be.) Today it seems to be reports that after
+ executing a sequence like
+ </p>
+ <pre>
+ #include <fstream>
+ ...
+ std::fstream fs("a_file");
+ // .
+ // . do things with fs...
+ // .
+ fs.close();
+ fs.open("a_new_file");</pre>
+ <p>all operations on the re-opened <code>fs</code> will fail, or at
+ least act very strangely. Yes, they often will, especially if
+ <code>fs</code> reached the EOF state on the previous file. The
+ reason is that the state flags are <strong>not</strong> cleared
+ on a successful call to open(). The standard unfortunately did
+ not specify behavior in this case, and to everybody's great sorrow,
+ the <a href="../ext/howto.html#5">proposed LWG resolution</a> (see
+ DR #22) is to leave the flags unchanged. You must insert a call
+ to <code>fs.clear()</code> between the calls to close() and open(),
+ and then everything will work like we all expect it to work.
+ </p>
+ <p><a name="4_4_rel_ops"><strong>rel_ops</strong></a>
+ Another is the <code>rel_ops</code> namespace and the template
+ comparison operator functions contained therein. If they become
+ visible in the same namespace as other comparison functions
+ (e.g., '<code>using</code>' them and the <iterator> header),
+ then you will suddenly be faced with huge numbers of ambiguity
+ errors. This was discussed on the -v3 list; Nathan Myers
+ <a href="http://gcc.gnu.org/ml/libstdc++/2001-01/msg00247.html">sums
+ things up here</a>. The collisions with vector/string iterator
+ types have been fixed for 3.1. <!-- more links to email here -->
+ </p>
+ <h3><a name="4_4_interface">The g++-3 headers are <em>not ours</em></a></h3>
+ <p>If you have found an extremely broken header file which is
+ causing problems for you, look carefully before submitting a
+ "high" priority bug report (which you probably shouldn't
+ do anyhow; see the last paragraph of the page describing
+ <a href="http://gcc.gnu.org/gnatswrite.html">the GCC bug database</a>).
+ </p>
+ <p>If the headers are in <code>${prefix}/include/g++-3</code>, or if
+ the installed library's name looks like <code>libstdc++-2.10.a</code>
+ or <code>libstdc++-libc6-2.10.so</code>,
+ then you are using the old libstdc++-v2 library, which is nonstandard
+ and unmaintained. Do not report problems with -v2 to the -v3
+ mailing list.
+ </p>
+ <p>For GCC versions 3.0 and 3.1 the libstdc++-v3 header files are
+ installed in <code>${prefix}/include/g++-v3</code> (see the 'v'?).
+ Starting with version 3.2 the headers are installed in
+ <code>${prefix}/include/c++/${version}</code> as this prevents
+ headers from previous versions being found by mistake.
+ </p>
+ <p><a name="4_4_glibc"><strong>glibc</strong></a>
+ If you're on a GNU/Linux system and have just upgraded to
+ glibc 2.2, but are still using gcc 2.95.2, then you should have
+ read the glibc FAQ, specifically 2.34:
+ </p>
+ <pre>
2.34. When compiling C++ programs, I get a compilation error in streambuf.h.
{BH} You are using g++ 2.95.2? After upgrading to glibc 2.2, you need to
apply a patch to the include files in /usr/include/g++, because the fpos_t
type has changed in glibc 2.2. The patch is at
http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
- </PRE>
- Note that 2.95.x shipped with the
- <A HREF="#4_4_interface">old v2 library</A> which is no longer
- maintained. Also note that gcc 2.95.3 fixes this problem, but
- requires a separate patch for libstdc++-v3.
- </P>
- </A>
- <A NAME="4_4_checks">
- <P><STRONG>concept checks</STRONG>
- If you see compilation errors containing messages about
- <TT> <EM>foo</EM>Concept </TT>and a<TT> constraints </TT>
- member function, then most likely you have violated one of the
- requirements for types used during instantiation of template
- containers and functions. For example, EqualityComparableConcept
- appears if your types must be comparable with == and you have not
- provided this capability (a typo, or wrong visibility, or you
- just plain forgot, etc).
- </P>
- <P>More information, including how to optionally enable/disable the
- checks, is available
- <A HREF="../19_diagnostics/howto.html#3">here</A>.
- </P>
- </A>
-
-<HR>
- <H2><A NAME="4_5">4.5 Aw, that's easy to fix!</A></H2>
- <P>If you have found a bug in the library and you think you have
+ </pre>
+ <p>Note that 2.95.x shipped with the
+ <a href="#4_4_interface">old v2 library</a> which is no longer
+ maintained. Also note that gcc 2.95.3 fixes this problem, but
+ requires a separate patch for libstdc++-v3.
+ </p>
+ <p><a name="4_4_checks"><strong>concept checks</strong></a>
+ If you see compilation errors containing messages about
+ <code> <em>foo</em>Concept </code>and a<code> constraints </code>
+ member function, then most likely you have violated one of the
+ requirements for types used during instantiation of template
+ containers and functions. For example, EqualityComparableConcept
+ appears if your types must be comparable with == and you have not
+ provided this capability (a typo, or wrong visibility, or you
+ just plain forgot, etc).
+ </p>
+ <p>More information, including how to optionally enable/disable the
+ checks, is available
+ <a href="../19_diagnostics/howto.html#3">here</a>.
+ </p>
+ <p><a name="4_4_dlsym"><strong>dlopen/dlsym</strong></a>
+ If you are using the C++ library across dynamically-loaded
+ objects, make certain that you are passing the correct options
+ when compiling and linking:
+ </p>
+ <pre>
+ // compile the library components
+ g++ -fPIC -c a.cc
+ g++ -fPIC -c b.cc
+ ...
+ g++ -fPIC -c z.cc
+
+ // create the library
+ g++ -fPIC -shared -rdynamic -o libfoo.so a.o b.o ... z.o
+
+ // link the executable
+ g++ -fPIC -rdynamic -o foo ... -L. -lfoo -ldl</pre>
+ <p><a name="4_4_leak"><strong>"memory leaks" in containers</strong></a>
+ A few people have reported that the standard containers appear
+ to leak memory when tested with memory checkers such as
+ <a href="http://developer.kde.org/~sewardj/">valgrind</a>.
+ The library's default allocators keep free memory in a pool
+ for later reuse, rather than returning it to the OS. Although
+ this memory is always reachable by the library and is never
+ lost, memory debugging tools can report it as a leak. If you
+ want to test the library for memory leaks please read
+ <a href="../debug.html#mem">Tips for memory leak hunting</a>
+ first.
+ </p>
+
+<hr />
+ <h2><a name="4_5">4.5 Aw, that's easy to fix!</a></h2>
+ <p>If you have found a bug in the library and you think you have
a working fix, then send it in! The main GCC site has a page
- on <A HREF="http://gcc.gnu.org/contribute.html">submitting
- patches</A> that covers the procedure, but for libstdc++ you
+ on <a href="http://gcc.gnu.org/contribute.html">submitting
+ patches</a> that covers the procedure, but for libstdc++ you
should also send the patch to our mailing list in addition to
the GCC patches mailing list. The libstdc++
- <A HREF="../17_intro/contribute.html">contributors' page</A>
+ <a href="../17_intro/contribute.html">contributors' page</a>
also talks about how to submit patches.
- </P>
- <P>In addition to the description, the patch, and the ChangeLog
+ </p>
+ <p>In addition to the description, the patch, and the ChangeLog
entry, it is a Good Thing if you can additionally create a small
test program to test for the presence of the bug that your
patch fixes. Bugs have a way of being reintroduced; if an old
bug creeps back in, it will be caught immediately by the
- <A HREF="#2_4">testsuite</A> -- but only if such a test exists.
- </P>
-
-<HR>
-<H1><A NAME="5_0">5.0 Miscellaneous</A></H1>
- <H2><A NAME="5_1">5.1 string::iterator is not char*;
- vector<T>::iterator is not T*</A></H2>
- <P>If you have code that depends on container<T> iterators
+ <a href="#2_4">testsuite</a> -- but only if such a test exists.
+ </p>
+
+<hr />
+<h1><a name="5_0">5.0 Miscellaneous</a></h1>
+ <h2><a name="5_1">5.1 string::iterator is not char*;
+ vector<T>::iterator is not T*</a></h2>
+ <p>If you have code that depends on container<T> iterators
being implemented as pointer-to-T, your code is broken.
- </P>
- <P>While there are arguments for iterators to be implemented in
+ </p>
+ <p>While there are arguments for iterators to be implemented in
that manner, A) they aren't very good ones in the long term,
and B) they were never guaranteed by the Standard anyway. The
type-safety achieved by making iterators a real class rather
- than a typedef for <TT>T*</TT> outweighs nearly all opposing
+ than a typedef for <code>T*</code> outweighs nearly all opposing
arguments.
- </P>
+ </p>
+ <p>Code which does assume that a vector iterator <code> i </code>
+ is a pointer can often be fixed by changing <code> i </code> in
+ certain expressions to <code> &*i </code>. Future revisions
+ of the Standard are expected to bless this usage for
+ vector<> (but not for basic_string<>).
+ </p>
-<HR>
- <H2><A NAME="5_2">5.2 What's next after libstdc++-v3?</A></H2>
- <P>Hopefully, not much. The goal of libstdc++-v3 is to produce
+<hr />
+ <h2><a name="5_2">5.2 What's next after libstdc++-v3?</a></h2>
+ <p>Hopefully, not much. The goal of libstdc++-v3 is to produce
a fully-compliant, fully-portable Standard Library. After that,
- we're mostly done: there won't <EM>be</EM> any more compliance
- work to do.
- </P>
- <P>The ISO Committee will meet periodically to review Defect Reports
+ we're mostly done: there won't <em>be</em> any more compliance
+ work to do. However:
+ </p>
+ <ol>
+ <li><p>The ISO Committee will meet periodically to review Defect Reports
in the C++ Standard. Undoubtedly some of these will result in
changes to the Standard, which will be reflected in patches to
libstdc++. Some of that is already happening, see 4.2. Some of
those changes are being predicted by the library maintainers, and
we add code to the library based on what the current proposed
- resolution specifies.
- </P>
- <P>The current libstdc++ contains extensions to the Library which
+ resolution specifies. Those additions are listed in
+ <a href="../ext/howto.html#5">the extensions page</a>.
+ </p></li>
+ <li><p>Performance tuning. Lots of performance tuning. This too is
+ already underway for post-3.0 releases, starting with memory
+ expansion in container classes and buffer usage in synchronized
+ stream objects.
+ </p></li>
+ <li><p>An ABI for libstdc++ is being developed, so that
+ multiple binary-incompatible copies of the library can be replaced
+ with a single backwards-compatible library, like libgcc_s.so is.
+ </p></li>
+ <li><p>The current libstdc++ contains extensions to the Library which
must be explicitly requested by client code (for example, the
hash tables from SGI). Other extensions may be added to
libstdc++-v3 if they seem to be "standard" enough.
(For example, the "long long" type from C99.)
Bugfixes and rewrites (to improve or fix thread safety, for
instance) will of course be a continuing task.
- </P>
- <P><A
-HREF="http://gcc.gnu.org/ml/libstdc++/1999/msg00080.html">This
- question</A> about the next libstdc++ prompted some brief but
- interesting <A
-HREF="http://gcc.gnu.org/ml/libstdc++/1999/msg00084.html">speculation</A>.
- </P>
-
-<HR>
- <H2><A NAME="5_3">5.3 What about the STL from SGI?</A></H2>
- <P>The <A HREF="http://www.sgi.com/Technology/STL/">STL from SGI</A>
- is merged into libstdc++-v3 with changes as necessary.
- Currently release 3.3 is being used as an initial codebase, plus
- changes, fixes, and extensions.
- </P>
- <P>In particular, <TT>string</TT> is not from SGI and makes no
+ </p></li>
+ </ol>
+ <p><a href="http://gcc.gnu.org/ml/libstdc++/1999/msg00080.html">This
+ question</a> about the next libstdc++ prompted some brief but
+ interesting
+ <a href="http://gcc.gnu.org/ml/libstdc++/1999/msg00084.html">speculation</a>.
+ </p>
+
+<hr />
+ <h2><a name="5_3">5.3 What about the STL from SGI?</a></h2>
+ <p>The <a href="http://www.sgi.com/Technology/STL/">STL from SGI</a>,
+ version 3.3, was the most recent merge of the STL codebase. The
+ code in libstdc++ contains many fixes and changes, and it is
+ very likely that the SGI code is no longer under active
+ development. We expect that no future merges will take place.
+ </p>
+ <p>In particular, <code>string</code> is not from SGI and makes no
use of their "rope" class (which is included as an
- optional extension), nor is <TT>valarray</TT> and some others.
- Classes like <TT>vector<></TT> are, however.
- </P>
- <P>The FAQ for SGI's STL (one jump off of their main page) is
+ optional extension), nor is <code>valarray</code> and some others.
+ Classes like <code>vector<></code> are, however.
+ </p>
+ <p>The FAQ for SGI's STL (one jump off of their main page) is
recommended reading.
- </P>
+ </p>
-<HR>
- <H2><A NAME="5_4">5.4 Extensions and Backward Compatibility</A></H2>
- <P>Although you can specify <TT>-I</TT> options to make the
- preprocessor search the g++-v3/ext and /backward directories,
- it is better to refer to files there by their path, as in:
+<hr />
+ <h2><a name="5_4">5.4 Extensions and Backward Compatibility</a></h2>
+ <p>Headers in the <code>ext</code> and <code>backward</code>
+ subdirectories should be referred to by their relative paths:
<!-- Careful, the leading spaces in PRE show up directly. -->
- </P>
- <PRE>
- #include <ext/hash_map>
- </PRE>
- <P>Extensions to the library have
- <A HREF="../ext/howto.html">their own page</A>.
- </P>
-
-<HR>
- <H2><A NAME="5_5">5.5 [removed]</A></H2>
- <P>This question has become moot and has been removed. The stub
+ </p>
+ <pre>
+ #include <ext/hash_map> </pre>
+ <p>rather than using <code>-I</code> or other options. This is more
+ portable and forward-compatible. (The situation is the same as
+ that of other headers whose directories are not searched directly,
+ e.g., <code><sys/stat.h></code>, <code><X11/Xlib.h></code>.
+ </p>
+
+ <p>The extensions are no longer in the global or <code>std</code>
+ namespaces, instead they are declared in the <code>__gnu_cxx</code>
+ namespace. For maximum portability, consider defining a namespace
+ alias to use to talk about extensions, e.g.:
+ </p>
+ <pre>
+ #ifdef __GNUC__
+ #if __GNUC__ < 3
+ #include <hash_map.h>
+ namespace Sgi { using ::hash_map; }; // inherit globals
+ #else
+ #include <ext/hash_map>
+ #if __GNUC_MINOR__ == 0
+ namespace Sgi = std; // GCC 3.0
+ #else
+ namespace Sgi = ::__gnu_cxx; // GCC 3.1 and later
+ #endif
+ #endif
+ #else // ... there are other compilers, right?
+ namespace Sgi = std;
+ #endif
+
+ Sgi::hash_map<int,int> my_map; </pre>
+ <p>This is a bit cleaner than defining typedefs for all the
+ instantiations you might need.
+ </p>
+
+ <p>Extensions to the library have
+ <a href="../ext/howto.html">their own page</a>.
+ </p>
+
+<hr />
+ <h2><a name="5_5">5.5 [removed]</a></h2>
+ <p>This question has become moot and has been removed. The stub
is here to preserve numbering (and hence links/bookmarks).
- </P>
-
-<HR>
- <H2><A NAME="5_6">5.6 Is libstdc++-v3 thread-safe?</A></H2>
- <P>Quick answer: no, as of 2.92 (eleventh snapshot), the
- library is not appropriate for multithreaded access. The
- string class is MT-safe.
- </P>
- <P>This is assuming that your idea of "multithreaded"
- is the same as ours... The general question of multithreading
- and libstdc++-v3 is addressed in the chapter-specific advice for
-<A HREF="http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/howto.html#3">Library
- Introduction</A>. Threadsafe containers are covered in
- more detail in
-<A HREF="http://gcc.gnu.org/onlinedocs/libstdc++/23_containers/howto.html">the
- Received Wisdom section on containers</A>.
- <!-- I have successfully evaded the topic; my work here is
- done- no, wait, I have to write those other sections... -->
- </P>
-
-<HR>
- <H2><A NAME="5_7">5.7 How do I get a copy of the ISO C++ Standard?</A></H2>
- <P>Copies of the full ISO 14882 standard are available on line via the
+ </p>
+
+<hr />
+ <h2><a name="5_6">5.6 Is libstdc++-v3 thread-safe?</a></h2>
+ <p>When the system's libc is itself thread-safe, a non-generic
+ implementation of atomicity.h exists for the architecture, and gcc
+ itself reports a thread model other than single; libstdc++-v3
+ strives to be thread-safe. The user-code must guard against
+ concurrent method calls which may access any particular library
+ object's state. Typically, the application programmer may infer
+ what object locks must be held based on the objects referenced in
+ a method call. Without getting into great detail, here is an
+ example which requires user-level locks:
+ </p>
+ <pre>
+ library_class_a shared_object_a;
+
+ thread_main () {
+ library_class_b *object_b = new library_class_b;
+ shared_object_a.add_b (object_b); // must hold lock for shared_object_a
+ shared_object_a.mutate (); // must hold lock for shared_object_a
+ }
+
+ // Multiple copies of thread_main() are started in independent threads.</pre>
+ <p>Under the assumption that object_a and object_b are never exposed to
+ another thread, here is an example that should not require any
+ user-level locks:
+ </p>
+ <pre>
+ thread_main () {
+ library_class_a object_a;
+ library_class_b *object_b = new library_class_b;
+ object_a.add_b (object_b);
+ object_a.mutate ();
+ } </pre>
+ <p>All library objects are safe to use in a multithreaded program as
+ long as each thread carefully locks out access by any other thread
+ while it uses any object visible to another thread. In general,
+ this requirement includes both read and write access to objects;
+ unless otherwise documented as safe, do not assume that two
+ threads may access a shared standard library object at the
+ same time.
+ </p>
+ <p>See chapters <a href="../17_intro/howto.html#3">17</a> (library
+ introduction), <a href="../23_containers/howto.html#3">23</a>
+ (containers), and <a href="../27_io/howto.html#9">27</a> (I/O) for
+ more information.
+ </p>
+
+<hr />
+ <h2><a name="5_7">5.7 How do I get a copy of the ISO C++ Standard?</a></h2>
+ <p>Copies of the full ISO 14882 standard are available on line via the
ISO mirror site for committee members. Non-members, or those who
have not paid for the privilege of sitting on the committee and
sustained their two-meeting commitment for voting rights, may get a
copy of the standard from their respective national standards
organization. In the USA, this national standards organization is
- ANSI and their website is right <A HREF="http://www.ansi.org">here</A>.
+ ANSI and their website is right <a href="http://www.ansi.org">here</a>.
(And if you've already registered with them, clicking this link will
take you to directly to the place where you can
-<A HREF="http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO%2FIEC+14882%2D1998">buy
- the standard on-line</A>.
- </P>
- <P>Who is your country's member body? Visit the
- <A HREF="http://www.iso.ch/">ISO homepage</A> and find out!
- </P>
+<a href="http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO%2FIEC+14882%2D1998">buy
+ the standard on-line</a>.
+ </p>
+ <p>Who is your country's member body? Visit the
+ <a href="http://www.iso.ch/">ISO homepage</a> and find out!
+ </p>
+
+<hr />
+ <h2><a name="5_8">5.8 What's an ABI and why is it so messy?</a></h2>
+ <p>"ABI" stands for "Application Binary Interface."
+ Conventionally, it refers to a great mass of details about how
+ arguments are arranged on the call stack and/or in registers, and
+ how various types are arranged and padded in structs. A single CPU
+ design may suffer multiple ABIs designed by different development
+ tool vendors who made different choices, or even by the same vendor
+ for different target applications or compiler versions. In ideal
+ circumstances the CPU designer presents one ABI and all the OSes and
+ compilers use it. In practice every ABI omits details that compiler
+ implementers (consciously or accidentally) must choose for themselves.
+ </p>
+ <p>That ABI definition suffices for compilers to generate code so a
+ program can interact safely with an OS and its lowest-level libraries.
+ Users usually want an ABI to encompass more detail, allowing libraries
+ built with different compilers (or different releases of the same
+ compiler!) to be linked together. For C++, this includes many more
+ details than for C, and CPU designers (for good reasons elaborated
+ below) have not stepped up to publish C++ ABIs. The details include
+ virtual function implementation, struct inheritance layout, name
+ mangling, and exception handling. Such an ABI has been defined for
+ GNU C++, and is immediately useful for embedded work relying only on
+ a "free-standing implementation" that doesn't include (much
+ of) the standard library. It is a good basis for the work to come.
+ </p>
+ <p>A useful C++ ABI must also incorporate many details of the standard
+ library implementation. For a C ABI, the layouts of a few structs
+ (such as FILE, stat, jmpbuf, and the like) and a few macros suffice.
+ For C++, the details include the complete set of names of functions
+ and types used, the offsets of class members and virtual functions,
+ and the actual definitions of all inlines. C++ exposes many more
+ library details to the caller than C does. It makes defining
+ a complete ABI a much bigger undertaking, and requires not just
+ documenting library implementation details, but carefully designing
+ those details so that future bug fixes and optimizations don't
+ force breaking the ABI.
+ </p>
+ <p>There are ways to help isolate library implementation details from the
+ ABI, but they trade off against speed. Library details used in
+ inner loops (e.g., getchar) must be exposed and frozen for all
+ time, but many others may reasonably be kept hidden from user code,
+ so they may later be changed. Deciding which, and implementing
+ the decisions, must happen before you can reasonably document a
+ candidate C++ ABI that encompasses the standard library.
+ </p>
<!-- ####################################################### -->
-<HR>
-<P CLASS="fineprint"><EM>
+<hr />
+<p class="fineprint"><em>
+See <a href="../17_intro/license.html">license.html</a> for copying conditions.
Comments and suggestions are welcome, and may be sent to
-<A HREF="mailto:libstdc++@gcc.gnu.org">the mailing list</A>.
-<BR> $Id: index.html,v 1.8 2001/05/10 18:42:11 pme Exp $
-</EM></P>
+<a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.
+</em></p>
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