-<html>
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!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" xml:lang="en" lang="en">
<head>
- <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
- <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++, libg++, STL">
- <meta name="DESCRIPTION" content="FAQ for the GNU libstdc++ effort.">
+ <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
+ <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++, libg++, STL" />
+ <meta name="DESCRIPTION" content="FAQ for the GNU libstdc++ effort." />
<title>libstdc++-v3 FAQ</title>
-<link rel="StyleSheet" href="../lib3styles.css">
+<link rel="StyleSheet" href="../lib3styles.css" />
<!--
** Locations of "the most recent snapshot is the Nth" text are
** answers 1_1, 1_4, 4_1.
<h1 class="centered">libstdc++ Frequently Asked Questions</h1>
-<p>The latest version of this document is always available at
+<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>.
-</p>
+</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>
+<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>
- <li><a href="#1_9">What are the license terms for libstdc++-v3?</a>
+ <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><a href="#2_2">[removed]</a>
+ <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><a href="#2_4">How do I know if it works?</a>
- <li><a href="#2_5">This library is HUGE! And what's libsupc++?</a>
+ 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><a href="#3_2">[removed]</a>
- <li><a href="#3_3">[removed]</a>
- <li><a href="#3_4">I can't use 'long long' on Solaris</a>
+ 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><a href="#3_6">OS X ctype.h is broken! How can I hack it?</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><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_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><a href="#4_4_Weff">-Weffc++ complains too much</a>
+ <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>
+ 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><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>
+ <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>
+ in a dynamically-loaded library</a> </li>
+ <li><a href="#4_4_leak">"memory leaks" in containers</a> </li>
</ul>
- <li><a href="#4_5">Aw, that's easy to fix!</a>
+ </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><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>
- <li><a href="#5_8">What's an ABI and why is it so messy?</a>
+ 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>
+<hr />
<!-- ####################################################### -->
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="http://gcc.gnu.org/libstdc++/download.html">the
- fourteenth 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).
+ 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.
official <a href="../17_intro/DESIGN">design document</a>.
</p>
-<hr>
+<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
nor be worried about platform-specific incompatibilities.
</p>
-<hr>
+<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.
+ 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
If you have questions, ideas, code, or are just curious, sign up!
</p>
-<hr>
+<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++/download.html">available via
- ftp</a>.
+ <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
of the SGI STL.
</p>
-<hr>
+<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
+<!-- <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...-->
Usenet article asking this question: <em>Sooner, if you help.</em>
</p>
-<hr>
+<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
we all thought was working, is more than welcome!
</p>
-<hr>
+<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
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>
+ <a href="http://gcc.gnu.org/extensions.html">GCC extensions page</a>
describes where to find the last libg++ source.
</p>
-<hr>
+<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.
or <a href="mailto:gdr@gcc.gnu.org">Gabriel Dos Reis</a>.
</p>
-<hr>
+<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>
+<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
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>
<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.
+ </li>
</ul>
<p>The file <a href="../documentation.html">documentation.html</a>
provides a good overview of the steps necessary to build, install,
".../docs/17_intro/" directory of the distribution.
</p>
-<hr>
+<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>
-<hr>
+<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
+ 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
<!-- wonder how long that'll live -->
</p>
-<hr>
+<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
<strong>please</strong> write up your idea and send it to the list!
</p>
-<hr>
+<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
when building the library.
</p>
-<hr>
+<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>
GCC/g++, however.
</p>
-<hr>
+<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>
+<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>
+<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>This has been fixed for 3.0.3 and onwards.
</p>
-<hr>
+<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
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>.
+ <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>
+<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.
link to the solution.</a>
</p>
-<hr>
+<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
<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.
- </p>
- <p>Please read
+ 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,
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
<!-- Yeah, I meant that "verbatim clip" thing literally... :-) -->
<pre>
-New in 3.0.97:
+New:
---
+(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>
+<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
experiences. :-)</li>
</ul>
-<hr>
+<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
Some of these have resulted in <a href="#5_2">code changes</a>.
</p>
-<hr>
+<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 <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>
- </a>
- <a name="4_4_iostreamclear">
- <p><strong>reopening a stream fails</strong>
- 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
- <pre>
+ <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");
// .
fs.close();
fs.open("a_new_file");</pre>
- 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>
- </a>
- <a name="4_4_rel_ops">
- <p><strong>rel_ops</strong>
- 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>
- </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
+ <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>${prefix}/include/g++-3</code>, or if
- the installed library's name looks like <code>libstdc++-2.10.a</code>
- or <code>libstdc++-libc6-2.10.so</code>,
- then you are using the old libstdc++-v2 library, which is nonstandard
- and unmaintained. Do not report problems with -v2 to the -v3
- mailing list.
- </p>
- <p>Currently our header files are installed in
- <code>${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>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
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
- <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>
- </a>
- <a name="4_4_dlsym">
- <p><strong>dlopen/dlsym</strong>
- If you are using the C++ library across dynamically-loaded
- objects, make certain that you are passing the correct options
- when compiling and linking:
- <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 -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>
+ 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>
+<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
<a href="#2_4">testsuite</a> -- but only if such a test exists.
</p>
-<hr>
+<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>
vector<> (but not for basic_string<>).
</p>
-<hr>
+<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 add code to the library based on what the current proposed
resolution specifies. Those additions are listed in
<a href="../ext/howto.html#5">the extensions page</a>.
- </p>
+ </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>
+ </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>
+ </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
(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></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
<a href="http://gcc.gnu.org/ml/libstdc++/1999/msg00084.html">speculation</a>.
</p>
-<hr>
+<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
recommended reading.
</p>
-<hr>
+<hr />
<h2><a name="5_4">5.4 Extensions and Backward Compatibility</a></h2>
- <p>Although you can specify <code>-I</code> 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:
+ <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>
+ <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>
+<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>
+<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
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:
- <pre>
+ </p>
+ <pre>
library_class_a shared_object_a;
thread_main () {
}
// Multiple copies of thread_main() are started in independent threads.</pre>
- </p>
<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:
- <pre>
+ </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>
<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,
more information.
</p>
-<hr>
+<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
<a href="http://www.iso.ch/">ISO homepage</a> and find out!
</p>
-<hr>
+<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
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-<hr>
+<hr />
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