libstdc++-v3/docs/html/faq/index.html

   1 <html>
   2 <head>
   3    <meta HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
   4    <meta NAME="KEYWORDS" CONTENT="libstdc++, libstdc++-v3, GCC, g++, libg++, STL">
   5    <meta NAME="DESCRIPTION" CONTENT="FAQ for the GNU libstdc++ effort.">
   6    <title>libstdc++-v3 FAQ</title>
   7 <link REL=StyleSheet HREF="../lib3styles.css">
   8 <!--
   9   ** Locations of "the most recent snapshot is the Nth" text are
  10   ** answers 1_1, 1_4, 4_1, 5_6.
  11 -->
  12 </head>
  13 <body>
  14
  15 <h1 CLASS="centered">libstdc++ Frequently Asked Questions</h1>
  16
  17 <p>The latest version of this document is always available at
  18 <a href="http://gcc.gnu.org/onlinedocs/libstdc++/faq/">
  19 http://gcc.gnu.org/onlinedocs/libstdc++/faq/</a>.</p>
  20
  21 <p>To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
  22
  23 <!-- ####################################################### -->
  24 <hr>
  25 <h1>Questions</h1>
  26 <ol>
  27    <li><a href="#1_0">General Information</a>
  28    <!-- I suspect these will mostly be links to/into existing documents. -->
  29    <ol>
  30       <li><a href="#1_1">What is libstdc++-v3?</a>
  31       <li><a href="#1_2">Why should I use libstdc++?</a>
  32       <li><a href="#1_3">Who's in charge of it?</a>
  33       <li><a href="#1_4">How do I get libstdc++?</a>
  34       <li><a href="#1_5">When is libstdc++ going to be finished?</a>
  35       <li><a href="#1_6">How do I contribute to the effort?</a>
  36       <li><a href="#1_7">What happened to libg++?  I need that!</a>
  37       <li><a href="#1_8">What if I have more questions?</a>
  38       <li><a href="#1_9">What are the license terms for libstdc++-v3?</a>
  39    </ol>
  40
  41    <li><a href="#2_0">Installation</a>
  42       <ol>
  43          <li><a href="#2_1">How do I install libstdc++-v3?</a>
  44          <li><a href="#2_2">[removed]</a>
  45          <li><a href="#2_3">What is this CVS thing that you keep
  46                             mentioning?</a>
  47          <li><a href="#2_4">How do I know if it works?</a>
  48       </ol>
  49
  50    <li><a href="#3_0">Platform-Specific Issues</a>
  51       <ol>
  52          <li><a href="#3_1">Can libstdc++-v3 be used with &lt;my
  53                             favorite compiler&gt;?</a>
  54          <li><a href="#3_2">[removed]</a>
  55          <li><a href="#3_3">Building under DEC OSF kills the assembler</a>
  56       </ol>
  57
  58    <li><a href="#4_0">Known Bugs and Non-Bugs</a>
  59       <ol>
  60          <li><a href="#4_1">What works already?</a>
  61          <li><a href="#4_2">Bugs in gcc/g++ (not libstdc++-v3)</a>
  62          <li><a href="#4_3">Bugs in the C++ language/lib specification</a>
  63          <li><a href="#4_4">Things in libstdc++ that look like bugs</a>
  64            <ul>
  65              <li><a href="#4_4_Weff">-Weffc++ complains too much</a>
  66              <li><a href="#4_4_rel_ops">&quot;ambiguous overloads&quot;
  67                                  after including an old-style header</a>
  68              <li><a href="#4_4_interface">The g++-3 headers are
  69                                  <strong>not ours</strong></a>
  70              <li><a href="#4_4_glibc">compilation errors from streambuf.h</a>
  71              <li><a href="#4_4_checks">errors about <em>*Cconcept</em> and
  72                                  <em>constraints</em> in the STL...</a>
  73            </ul>
  74          <li><a href="#4_5">Aw, that's easy to fix!</a>
  75       </ol>
  76
  77    <li><a href="#5_0">Miscellaneous</a>
  78       <ol>
  79          <li><a href="#5_1">string::iterator is not char*;
  80                             vector&lt;T&gt;::iterator is not T*</a>
  81          <li><a href="#5_2">What's next after libstdc++-v3?</a>
  82          <li><a href="#5_3">What about the STL from SGI?</a>
  83          <li><a href="#5_4">Extensions and Backward Compatibility</a>
  84          <li><a href="#5_5">[removed]</a>
  85          <li><a href="#5_6">Is libstdc++-v3 thread-safe?</a>
  86          <li><a href="#5_7">How do I get a copy of the ISO C++ Standard?</a>
  87       </ol>
  88
  89 </ol>
  90
  91 <hr>
  92
  93 <!-- ####################################################### -->
  94
  95 <h1><a name="1_0">1.0 General Information</a></h1>
  96 <!-- I suspect these will mostly be links to/into existing documents. -->
  97    <h2><a name="1_1">1.1 What is libstdc++-v3?</a></h2>
  98       <p>The GNU Standard C++ Library v3, or libstdc++-2.9x, is an
  99          ongoing project to implement the ISO 14882 Standard C++ library
 100          as described in chapters 17 through 27 and annex D.  As the
 101          library reaches stable plateaus, it is captured in a snapshot
 102          and released.  The current release is <A
 103 HREF="ftp://gcc.gnu.org/pub/libstdc++/libstdc++-2.92.tar.gz">the
 104          eleventh snapshot</a>.  For those who want to see exactly how
 105          far the project has come, or just want the latest
 106          bleeding-edge code, the up-to-date source is available over
 107          anonymous CVS, and can even be browsed over the Web (see below).
 108       </p>
 109       <p>A more formal description of the V3 goals can be found in the
 110          official <a href="../17_intro/DESIGN">design document</a>.
 111       </p>
 112
 113 <hr>
 114    <h2><a name="1_2">1.2 Why should I use libstdc++?</a></h2>
 115       <p>The completion of the ISO C++ standardization gave the
 116          C++ community a powerful set of reuseable tools in the form
 117          of the C++ Standard Library.  However, all existing C++
 118          implementations are (as the Draft Standard used to say)
 119          &quot;incomplet and incorrekt,&quot; and many suffer from
 120          limitations of the compilers that use them.
 121       </p>
 122       <p>The GNU C/C++/FORTRAN/&lt;pick-a-language&gt; compiler
 123          (<code>gcc</code>, <code>g++</code>, etc) is widely considered to be
 124          one of the leading compilers in the world.  Its development
 125          has recently been taken over by the
 126          <a href="http://gcc.gnu.org/">GCC team</a>.  All of
 127          the rapid development and near-legendary
 128      <A
 129 HREF="http://gcc.gnu.org/gcc-2.95/buildstat.html">portability</a>
 130          that are the hallmarks of an open-source project are being
 131          applied to libstdc++.
 132       </p>
 133       <p>That means that all of the Standard classes and functions
 134          (such as <code>string</code>, <code>vector&lt;&gt;</code>, iostreams,
 135          and algorithms) will be freely available and fully compliant.
 136          Programmers will no longer need to &quot;roll their own&quot;
 137          nor be worried about platform-specific incompatabilities.
 138       </p>
 139
 140 <hr>
 141    <h2><a name="1_3">1.3 Who's in charge of it?</a></h2>
 142       <p>The libstdc++ project is contributed to by several developers
 143          all over the world, in the same way as GCC or Linux.
 144          Benjamin Kosnik, Gabriel Dos Reis, Phil Edwards, and Ulrich
 145          Drepper are the lead maintainers of the CVS archive.
 146       </p>
 147       <p>Development and discussion is held on the libstdc++ mailing
 148          list.  Subscribing to the list, or searching the list
 149          archives, is open to everyone.  You can read instructions for
 150          doing so on the <a href="http://gcc.gnu.org/libstdc++/">homepage</a>.
 151          If you have questions, ideas, code, or are just curious, sign up!
 152       </p>
 153
 154 <hr>
 155    <h2><a name="1_4">1.4 How do I get libstdc++?</a></h2>
 156       <p>The eleventh (and latest) snapshot of libstdc++-v3 is <A
 157 HREF="ftp://gcc.gnu.org/pub/libstdc++/libstdc++-2.92.tar.gz">
 158          available via ftp</a>.
 159       </p>
 160       <p>The <a href="http://gcc.gnu.org/libstdc++/">homepage</a>
 161          has instructions for retrieving the latest CVS sources, and for
 162          browsing the CVS sources over the web.
 163       </p>
 164       <p>The subset commonly known as the Standard Template Library
 165          (chapters 23 through 25, mostly) is adapted from the SGI STL,
 166          which is also an ongoing work.<!-- Possibly a link to SGI's
 167          STL here. -->
 168       </p>
 169
 170 <hr>
 171    <h2><a name="1_5">1.5 When is libstdc++ going to be finished?</a></h2>
 172 <!--      <p>Nathan Myers gave the best of all possible answers in <A
 173          HREF="http://www.deja.com/getdoc.xp?AN=469581698&fmt=text">a
 174          Usenet article</a>.</p>
 175 which is no longer available, thanks deja...-->
 176       <p>Nathan Myers gave the best of all possible answers, responding to a
 177          Usenet article asking this question:  <em>Sooner, if you help.</em>
 178       </p>
 179
 180
 181 <hr>
 182    <h2><a name="1_6">1.6 How do I contribute to the effort?</a></h2>
 183       <p>Here is <a href="../17_intro/contribute.html">a
 184          page devoted to this topic</a>.  Subscribing to the mailing
 185          list (see above, or the homepage) is a very good idea if you
 186          have something to contribute, or if you have spare time and
 187          want to help.  Contributions don't have to be in the form of
 188          source code; anybody who is willing to help write
 189          documentation, for example, or has found a bug in code that
 190          we all thought was working, is more than welcome!
 191       </p>
 192
 193 <hr>
 194    <h2><a name="1_7">1.7 What happened to libg++?  I need that!</a></h2>
 195       <p>The most recent libg++ README states that libg++ is no longer
 196          being actively maintained.  It should not be used for new
 197          projects, and is only being kicked along to support older code.
 198       </p>
 199       <p>The libg++ was designed and created when there was no Standard
 200          to provide guidance.  Classes like linked lists are now provided
 201          for by <code>list&lt;T&gt;</code> and do not need to be created by
 202          <code>genclass</code>.  (For that matter, templates exist now and
 203          are well-supported, whereas genclass (mostly) predates them.)
 204       </p>
 205       <p>There are other classes in libg++ that are not specified in the
 206          ISO Standard (e.g., statistical analysis).  While there are a
 207          lot of really useful things that are used by a lot of people
 208          (e.g., statistics :-), the Standards Committee couldn't include
 209          everything, and so a lot of those &quot;obvious&quot; classes
 210          didn't get included.
 211       </p>
 212       <p>Since libstdc++ is an implementation of the Standard Library, we
 213          have no plans at this time to include non-Standard utilities
 214          in the implementation, however handy they are.  (The extensions
 215          provided in the SGI STL aren't maintained by us and don't get
 216          a lot of our attention, because they don't require a lot of our
 217          time.)  It is entirely plausable that the &quot;useful stuff&quot;
 218          from libg++ might be extracted into an updated utilities library,
 219          but nobody has stated such a project yet.
 220       </p>
 221       <!-- The advertisement, so to speak, might have to go.  Hmmmmm.  -->
 222       <p>(The <a href="http://www.boost.org/">Boost</a> site houses free
 223          C++ libraries that do varying things, and happened to be started
 224          by members of the Standards Committee.  Certain &quot;useful
 225          stuff&quot; classes will probably migrate there.)
 226       </p>
 227       <p>For the bold and/or desperate, the
 228          <a href="http://gcc.gnu.org/fom_serv/cache/33.html">GCC FAQ</a>
 229          describes where to find the last libg++ source.
 230       </p>
 231
 232 <hr>
 233    <h2><a name="1_8">1.8 What if I have more questions?</a></h2>
 234       <p>If you have read the README and RELEASE-NOTES files, and your
 235          question remains unanswered, then just ask the mailing list.
 236          At present, you do not need to be subscribed to the list to
 237          send a message to it.  More information is available on the
 238          homepage (including how to browse the list archives); to send
 239          to the list, use <a href="mailto:libstdc++@gcc.gnu.org">
 240          <CODE>libstdc++@gcc.gnu.org</CODE></a>.
 241       </p>
 242       <p>If you have a question that you think should be included here,
 243          or if you have a question <em>about</em> a question/answer here,
 244          contact <a href="mailto:pme@gcc.gnu.org">Phil Edwards</a>
 245          or <a href="mailto:gdr@gcc.gnu.org">Gabriel Dos Reis</a>.
 246       </p>
 247
 248 <hr>
 249    <h2><a name="1_9">1.9 What are the license terms for libstdc++-v3?</a></h2>
 250       <p>See <a href="../17_intro/license.html">our license description</a>
 251          for these and related questions.
 252       </p>
 253
 254 <hr>
 255 <h1><a name="2_0">2.0 Installation</a></h1>
 256    <h2><a name="2_1">2.1 How do I install libstdc++-v3?</a></h2>
 257       <p>Complete instructions are not given here (this is a FAQ, not
 258          an installation document), but the tools required are few:
 259       </p>
 260          <ul>
 261             <li> A 3.x release of GCC.  Note that building GCC is much
 262                  easier and more automated than building the GCC 2.[78]
 263                  series was.  If you are using GCC 2.95, you can still
 264                  build earlier snapshots of libstdc++.
 265             <li> GNU Make is recommended, but should not be required.
 266             <li> The GNU Autotools are needed if you are messing with
 267                  the configury or makefiles.
 268          </ul>
 269       <p>The file <a href="../documentation.html">documentation.html</a>
 270          provides a good overview of the steps necessary to build, install,
 271          and use the library.  Instructions for configuring the library
 272          with new flags such as --enable-threads are there also, as well as
 273          patches and instructions for working with GCC 2.95.
 274       </p>
 275       <p>The top-level install.html and
 276          <a href="../17_intro/RELEASE-NOTES">RELEASE-NOTES</a> files contain
 277          the exact build and installation instructions.  You may wish to
 278          browse those files over CVSweb ahead of time to get a feel for
 279          what's required.  RELEASE-NOTES is located in the
 280          &quot;.../docs/17_intro/&quot; directory of the distribution.
 281       </p>
 282
 283 <hr>
 284    <h2><a name="2_2">2.2 [removed]</a></h2>
 285       <p>This question has become moot and has been removed.  The stub
 286          is here to preserve numbering (and hence links/bookmarks).
 287       </p>
 288
 289 <hr>
 290    <h2><a name="2_3">2.3 What is this CVS thing that you
 291                          keep mentioning?</a></h2>
 292       <p>The <em>Concurrent Versions System</em> is one of several revision
 293          control packages.  It was selected for GNU projects because it's
 294          free (speech), free (beer), and very high quality.  The <A
 295          HREF="http://www.gnu.org/software/cvs/cvs.html">CVS entry in
 296          the GNU software catalogue</a> has a better description as
 297          well as a
 298          <a href="http://www.cvshome.org/">link to the makers of CVS</a>.
 299       </p>
 300       <p>The &quot;anonymous client checkout&quot; feature of CVS is
 301          similar to anonymous FTP in that it allows anyone to retrieve
 302          the latest libstdc++ sources.
 303       </p>
 304       <p>After the first of April, American users will have a
 305          &quot;/pharmacy&quot; command-line option...
 306          <!-- wonder how long that'll live -->
 307       </p>
 308
 309 <hr>
 310    <h2><a name="2_4">2.4 How do I know if it works?</a></h2>
 311       <p>libstdc++-v3 comes with its own testsuite.  You do not need
 312          to actually install the library (&quot;<code>make
 313          install</code>&quot;) to run the testsuite.
 314       </p>
 315       <p>To run the testsuite on the library after building it, use
 316          &quot;make check&quot; while in your build directory.  To run
 317          the testsuite on the library after building and installing it,
 318          use &quot;make check-install&quot; instead.
 319       </p>
 320       <p>If you find bugs in the testsuite programs themselves, or if
 321          you think of a new test program that should be added to the
 322          suite, <B>please</B> write up your idea and send it to the list!
 323       </p>
 324
 325 <hr>
 326 <h1><a name="3_0">3.0 Platform-Specific Issues</a></h1>
 327    <h2><a name="3_1">3.1 Can libstdc++-v3 be used with &lt;my
 328                          favorite compiler&gt;?</a></h2>
 329       <p>Probably not.  Yet.</p>
 330       <p>Because GCC advances so rapidly, development and testing of
 331          libstdc++ is being done almost entirely under that compiler.
 332          If you are curious about whether other, lesser compilers
 333          (*grin*) support libstdc++, you are more than welcome to try.
 334          Configuring and building the library (see above) will still
 335          require certain tools, however.  Also keep in mind that
 336          <em>building</em> libstdc++ does not imply that your compiler
 337          will be able to <em>use</em> all of the features found in the
 338          C++ Standard Library.
 339       </p>
 340       <p>Since the goal of ISO Standardization is for all C++
 341          implementations to be able to share code, the final libstdc++
 342          should, in theory, be useable under any ISO-compliant
 343          compiler.  It will still be targeted and optimized for
 344          GCC/g++, however.
 345       </p>
 346
 347 <hr>
 348    <h2><a name="3_2">3.2 [removed]</a></h2>
 349       <p>This question has become moot and has been removed.  The stub
 350          is here to preserve numbering (and hence links/bookmarks).
 351       </p>
 352
 353 <hr>
 354    <h2><a name="3_3">3.3 Building DEC OSF kills the assembler</a></h2>
 355       <p>The <code>atomicity.h</code> header for the Alpha processor
 356          currently uses pseudo-operators which the DEC assembler
 357          doesn't understand (in particular, .subsection and .previous).
 358          The simple solution is to install GNU <code>as</code> and arrange
 359          for the GCC build to use it (or merge the sources and build
 360          it during the bootstrap).
 361       </p>
 362       <p>Anyone who
 363          <a href="http://gcc.gnu.org/ml/libstdc++/2000-12/msg00279.html">knows
 364          the DEC assembler well enough</a> to provide the equivalent of
 365          these two pseudos would win praise and accolades from many.
 366       </p>
 367
 368
 369 <hr>
 370 <h1><a name="4_0">4.0 Known Bugs and Non-Bugs</a></h1>
 371    <em>Note that this section can get rapdily outdated -- such is the
 372    nature of an open-source project.  For the latest information, join
 373    the mailing list or look through recent archives.   The RELEASE-
 374    NOTES and BUGS files are generally kept up-to-date.</em>
 375
 376    <p>For 3.0.1, the most common &quot;bug&quot; is an apparently missing
 377       &quot;<code>../</code>&quot; in include/Makefile, resulting in files
 378       like gthr.h and gthr-single.h not being found.
 379    </p>
 380    <p>Please read
 381       <a href="http://gcc.gnu.org/install/configure.html">the configuration
 382       instructions for GCC</a>,
 383       specifically the part about configuring in a seperate build directory,
 384       and how strongly recommended it is.  Building in the source directory
 385       is fragile, is rarely tested, and tends to break, as in this case.
 386       Work has already gone into the source tree to make this less painful
 387       for the next release.
 388    </p>
 389    <p><strong>Please do not report this as a bug.  We know about it.</strong>
 390       Reporting this -- or any other problem that's already been fixed --
 391       hinders the development of GCC, because we have to take time to
 392       respond to your report.  Thank you.
 393    </p>
 394
 395    <h2><a name="4_1">4.1 What works already?</a></h2>
 396       <p>This is a verbatim clip from the &quot;Status&quot; section
 397           of the RELEASE-NOTES for the latest snapshot.
 398       </p>
 399
 400 <!-- Yeah, I meant that "verbatim clip" thing literally... :-)  -->
 401
 402 <pre>
 403 New:
 404 ---
 405 - preliminary doxygen documentation has been added. Running &quot;make
 406   doxygen&quot; in the libstdc++-v3 build directory will generate HTML
 407   documentation that can be used to cross-reference names and files in
 408   the library.
 409 - a dejagnu based testing framework has been added
 410 - a new implementation of the concept checking code has been ported
 411   from the boost libraries.
 412 - support for -fno-exceptions has been added
 413 - stdexcept was re-written
 414 - using deprecated or antiquated headers now gives a warning
 415 - the stdio interface to iostreams has been tweaked, and now works
 416   with synchronized c/c++ io
 417 - new libsupc++ routines implementing the IA-64 C++ ABI.
 418 - HPUX configuration files
 419 - support for AIX added
 420 - a lot of bugs were fixed.
 421 - preliminary named locales implemented
 422 - portability improvements made to generation of &lt;limits&gt;
 423 - speedups to improve configuration time.
 424 - DJGPP support added.
 425 - support for dlopening shared libstdc++
 426 </pre>
 427
 428
 429 <hr>
 430    <h2><a name="4_2">4.2 Bugs in gcc/g++ (not libstdc++-v3)</a></h2>
 431       <p>This is by no means meant to be complete nor exhaustive, but
 432          mentions some problems that users may encounter when building
 433          or using libstdc++.  If you are experiencing one of these
 434          problems, you can find more information on the libstdc++ and
 435          the GCC mailing lists.
 436       </p>
 437       <ul>
 438          <li>As of 2.91, these bugs have all been fixed.  We look forward
 439              to new ones, well, not exactly...
 440       </ul>
 441
 442 <hr>
 443    <h2><a name="4_3">4.3 Bugs in the C++ language/lib specification</a></h2>
 444       <p>Yes, unfortunately, there are some.  In a <A
 445 HREF="http://gcc.gnu.org/ml/libstdc++/1998/msg00006.html">message
 446 to the list</a>, Nathan Myers announced that he has started a list of
 447          problems in the ISO C++ Standard itself, especially with
 448          regard to the chapters that concern the library.  The list
 449          itself is <A
 450          HREF="http://www.cantrip.org/draft-bugs.txt">posted on his
 451          website</a>.  Developers who are having problems interpreting
 452          the Standard may wish to consult his notes.
 453       </p>
 454       <p>For those people who are not part of the ISO Library Group
 455          (i.e., nearly all of us needing to read this page in the first
 456          place :-), a public list of the library defects is occasionally
 457          published <a href="http://anubis.dkuug.dk/jtc1/sc22/wg21/">here</a>.
 458       </p>
 459
 460 <hr>
 461    <h2><a name="4_4">4.4 Things in libstdc++ that look like bugs</a></h2>
 462       <p>There are things which are not bugs in the compiler (4.2) nor
 463          the language specification (4.3), but aren't really bugs in
 464          libstdc++, either.  Really!  Please do not report these as bugs.
 465       </p>
 466       <a name="4_4_Weff">
 467         <p><strong>-Weffc++</strong>
 468            The biggest of these is the quadzillions of warnings about the
 469            library headers emitted when <code>-Weffc++</code> is used.  Making
 470            libstdc++ &quot;-Weffc++-clean&quot; is not a goal of the project,
 471            for a few reasons.  Mainly, that option tries to enforce
 472            object-oriented programming, while the Standard Library isn't
 473            necessarily trying to be OO.  There are multiple solutions
 474            under discussion.
 475         </p>
 476       </a>
 477       <a name="4_4_rel_ops">
 478         <p><strong>rel_ops</strong>
 479            Another is the <code>rel_ops</code> namespace and the template
 480            comparison operator functions contained therein.  If they become
 481            visible in the same namespace as other comparison functions
 482            (e.g., '<code>using</code>' them and the &lt;iterator&gt; header),
 483            then you will suddenly be faced with huge numbers of ambiguity
 484            errors.  This was discussed on the -v3 list; Nathan Myers
 485            <a href="http://gcc.gnu.org/ml/libstdc++/2001-01/msg00247.html">sums
 486            things up here</a>.
 487         </p>
 488       </a>
 489       <a name="4_4_interface"><h3>The g++-3 headers are
 490                                       <em>not ours</em></h3>
 491         <p>If you have found an extremely broken header file which is
 492            causing problems for you, look carefully before submitting a
 493            &quot;high&quot; priority bug report (which you probably shouldn't
 494            do anyhow; see the last paragraph of the page describing
 495          <a href="http://gcc.gnu.org/gnatswrite.html">the GCC bug database</a>).
 496         </p>
 497         <p>If the headers are in <CODE>${prefix}/include/g++-3</CODE>, then
 498            you are using the old libstdc++-v2 library, which is nonstandard
 499            and unmaintained.  Do not report problems with -v2 to the -v3
 500            mailing list.
 501         </p>
 502         <p>Currently our header files are installed in
 503            <CODE>${prefix}/include/g++-v3</CODE> (see the 'v'?).  This may
 504            change with the next release of GCC, as it may be too confusing,
 505            but <a href="http://gcc.gnu.org/ml/gcc/2000-10/msg00732.html">the
 506            question has not yet been decided</a>.
 507         </p>
 508       </a>
 509       <a name="4_4_glibc">
 510         <p><strong>glibc</strong>
 511            If you're on a GNU/Linux system and have just upgraded to
 512            glibc 2.2, but are still using gcc 2.95.2, then you should have
 513            read the glibc FAQ, specifically 2.34:
 514    <PRE>
 515 2.34.   When compiling C++ programs, I get a compilation error in streambuf.h.
 516
 517 {BH} You are using g++ 2.95.2? After upgrading to glibc 2.2, you need to
 518 apply a patch to the include files in /usr/include/g++, because the fpos_t
 519 type has changed in glibc 2.2.  The patch is at
 520 http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
 521    </PRE>
 522            Note that 2.95.x shipped with the
 523            <a href="#4_4_interface">old v2 library</a> which is no longer
 524            maintained.  Also note that gcc 2.95.3 fixes this problem, but
 525            requires a separate patch for libstdc++-v3.
 526         </p>
 527       </a>
 528       <a name="4_4_checks">
 529         <p><strong>concept checks</strong>
 530            If you see compilation errors containing messages about
 531            <code> <em>foo</em>Concept </code>and a<code> constraints </code>
 532            member function, then most likely you have violated one of the
 533            requirements for types used during instantiation of template
 534            containers and functions.  For example, EqualityComparableConcept
 535            appears if your types must be comparable with == and you have not
 536            provided this capability (a typo, or wrong visibility, or you
 537            just plain forgot, etc).
 538         </p>
 539         <p>More information, including how to optionally enable/disable the
 540            checks, is available
 541            <a href="../19_diagnostics/howto.html#3">here</a>.
 542         </p>
 543       </a>
 544
 545 <hr>
 546    <h2><a name="4_5">4.5 Aw, that's easy to fix!</a></h2>
 547       <p>If you have found a bug in the library and you think you have
 548          a working fix, then send it in!  The main GCC site has a page
 549          on <a href="http://gcc.gnu.org/contribute.html">submitting
 550          patches</a> that covers the procedure, but for libstdc++ you
 551          should also send the patch to our mailing list in addition to
 552          the GCC patches mailing list.  The libstdc++
 553          <a href="../17_intro/contribute.html">contributors' page</a>
 554          also talks about how to submit patches.
 555       </p>
 556       <p>In addition to the description, the patch, and the ChangeLog
 557          entry, it is a Good Thing if you can additionally create a small
 558          test program to test for the presence of the bug that your
 559          patch fixes.  Bugs have a way of being reintroduced; if an old
 560          bug creeps back in, it will be caught immediately by the
 561          <a href="#2_4">testsuite</a> -- but only if such a test exists.
 562       </p>
 563
 564 <hr>
 565 <h1><a name="5_0">5.0 Miscellaneous</a></h1>
 566    <h2><a name="5_1">5.1 string::iterator is not char*;
 567                      vector&lt;T&gt;::iterator is not T*</a></h2>
 568       <p>If you have code that depends on container&lt;T&gt; iterators
 569          being implemented as pointer-to-T, your code is broken.
 570       </p>
 571       <p>While there are arguments for iterators to be implemented in
 572          that manner, A) they aren't very good ones in the long term,
 573          and B) they were never guaranteed by the Standard anyway.  The
 574          type-safety achieved by making iterators a real class rather
 575          than a typedef for <code>T*</code> outweighs nearly all opposing
 576          arguments.
 577       </p>
 578       <p>Code which does assume that a vector iterator <code> i </code>
 579          is a pointer can often be fixed by changing <code> i </code> in
 580          certain expressions to <code> &amp;*i </code>.  Future revisions
 581          of the Standard are expected to bless this usage for
 582          vector&lt;&gt; (but not for basic_string&lt;&gt;).
 583       </p>
 584
 585 <hr>
 586    <h2><a name="5_2">5.2 What's next after libstdc++-v3?</a></h2>
 587       <p>Hopefully, not much.  The goal of libstdc++-v3 is to produce
 588          a fully-compliant, fully-portable Standard Library.  After that,
 589          we're mostly done:  there won't <em>be</em> any more compliance
 590          work to do.  However:
 591       </p>
 592       <ol>
 593       <li><p>The ISO Committee will meet periodically to review Defect Reports
 594          in the C++ Standard.  Undoubtedly some of these will result in
 595          changes to the Standard, which will be reflected in patches to
 596          libstdc++.  Some of that is already happening, see 4.2.  Some of
 597          those changes are being predicted by the library maintainers, and
 598          we add code to the library based on what the current proposed
 599          resolution specifies.  Those additions are listed in
 600          <a href="../ext/howto.html#5">the extensions page</a>.
 601       </p>
 602       <li><p>Performance tuning.  Lots of performance tuning.  This too is
 603          already underway for post-3.0 releases, starting with memory
 604          expansion in container classes and buffer usage in synchronized
 605          stream objects.
 606       </p>
 607       <li><p>An ABI for libstdc++ will eventually be developed, so that
 608          multiple binary-incompatible copies of the library can be replaced
 609          with a single backwards-compatible library, like libgcc_s.so is.
 610       </p>
 611       <li><p>The current libstdc++ contains extensions to the Library which
 612          must be explicitly requested by client code (for example, the
 613          hash tables from SGI).  Other extensions may be added to
 614          libstdc++-v3 if they seem to be &quot;standard&quot; enough.
 615          (For example, the &quot;long long&quot; type from C99.)
 616          Bugfixes and rewrites (to improve or fix thread safety, for
 617          instance) will of course be a continuing task.
 618       </p>
 619       </ol>
 620       <p><A
 621 HREF="http://gcc.gnu.org/ml/libstdc++/1999/msg00080.html">This
 622          question</a> about the next libstdc++ prompted some brief but
 623          interesting <A
 624 HREF="http://gcc.gnu.org/ml/libstdc++/1999/msg00084.html">speculation</a>.
 625       </p>
 626
 627 <hr>
 628    <h2><a name="5_3">5.3 What about the STL from SGI?</a></h2>
 629       <p>The <a href="http://www.sgi.com/Technology/STL/">STL from SGI</a>,
 630          version 3.3, was the most recent merge of the STL codebase.  The
 631          code in libstdc++ contains many fixes and changes, and it is
 632          very likely that the SGI code is no longer under active
 633          development.  We expect that no future merges will take place.
 634       </p>
 635       <p>In particular, <code>string</code> is not from SGI and makes no
 636          use of their &quot;rope&quot; class (which is included as an
 637          optional extension), nor is <code>valarray</code> and some others.
 638          Classes like <code>vector&lt;&gt;</code> are, however.
 639       </p>
 640       <p>The FAQ for SGI's STL (one jump off of their main page) is
 641          recommended reading.
 642       </p>
 643
 644 <hr>
 645    <h2><a name="5_4">5.4 Extensions and Backward Compatibility</a></h2>
 646       <p>Although you can specify <code>-I</code> options to make the
 647          preprocessor search the g++-v3/ext and /backward directories,
 648          it is better to refer to files there by their path, as in:
 649          <!-- Careful, the leading spaces in PRE show up directly. -->
 650       </p>
 651          <PRE>
 652        #include &lt;ext/hash_map&gt;
 653          </PRE>
 654       <p>Extensions to the library have
 655          <a href="../ext/howto.html">their own page</a>.
 656       </p>
 657
 658 <hr>
 659    <h2><a name="5_5">5.5 [removed]</a></h2>
 660       <p>This question has become moot and has been removed.  The stub
 661          is here to preserve numbering (and hence links/bookmarks).
 662       </p>
 663
 664 <hr>
 665    <h2><a name="5_6">5.6 Is libstdc++-v3 thread-safe?</a></h2>
 666       <p>Quick answer:  no, as of 2.92 (eleventh snapshot), the
 667          library is not appropriate for multithreaded access.  The
 668          string class is MT-safe.
 669       </p>
 670       <p>This is assuming that your idea of &quot;multithreaded&quot;
 671          is the same as ours...  The general question of multithreading
 672          and libstdc++-v3 is addressed in the chapter-specific advice for
 673 <a href="http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/howto.html#3">Library
 674          Introduction</a>.  Threadsafe containers are covered in
 675          more detail in
 676 <a href="http://gcc.gnu.org/onlinedocs/libstdc++/23_containers/howto.html">the
 677          Received Wisdom section on containers</a>.
 678          <!-- I have successfully evaded the topic; my work here is
 679               done- no, wait, I have to write those other sections... -->
 680       </p>
 681
 682 <hr>
 683    <h2><a name="5_7">5.7 How do I get a copy of the ISO C++ Standard?</a></h2>
 684       <p>Copies of the full ISO 14882 standard are available on line via the
 685          ISO mirror site for committee members.  Non-members, or those who
 686          have not paid for the privilege of sitting on the committee and
 687          sustained their two-meeting commitment for voting rights, may get a
 688          copy of the standard from their respective national standards
 689          organization.  In the USA, this national standards organization is
 690          ANSI and their website is right <a href="http://www.ansi.org">here</a>.
 691          (And if you've already registered with them, clicking this link will
 692          take you to directly to the place where you can
 693 <a href="http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO%2FIEC+14882%2D1998">buy
 694          the standard on-line</a>.
 695       </p>
 696       <p>Who is your country's member body?  Visit the
 697          <a href="http://www.iso.ch/">ISO homepage</a> and find out!
 698       </p>
 699
 700 <!-- ####################################################### -->
 701
 702 <hr>
 703 <P CLASS="fineprint"><em>
 704 See <a href="../17_intro/license.html">license.html</a> for copying conditions.
 705 Comments and suggestions are welcome, and may be sent to
 706 <a href="mailto:libstdc++@gcc.gnu.org">the mailing list</a>.
 707 </em></p>
 708
 709
 710 </body>
 711 </html>
 712