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

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  19
  20 <h1 class="centered">libstdc++ Frequently Asked Questions</h1>
  21
  22 <p>The latest version of this document is always available at
  23    <a href="http://gcc.gnu.org/onlinedocs/libstdc++/faq/">
  24    http://gcc.gnu.org/onlinedocs/libstdc++/faq/</a>.  The main documentation
  25    page is at
  26    <a href="http://gcc.gnu.org/onlinedocs/libstdc++/documentation.html">
  27    http://gcc.gnu.org/onlinedocs/libstdc++/documentation.html</a>.
  28 </p>
  29
  30 <p>To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
  31 </p>
  32
  33 <!-- ####################################################### -->
  34 <hr />
  35 <h1>Questions</h1>
  36 <ol>
  37    <li><a href="#1_0">General Information</a>
  38    <!-- I suspect these will mostly be links to/into existing documents. -->
  39    <ol>
  40       <li><a href="#1_1">What is libstdc++-v3?</a> </li>
  41       <li><a href="#1_2">Why should I use libstdc++?</a> </li>
  42       <li><a href="#1_3">Who's in charge of it?</a> </li>
  43       <li><a href="#1_4">How do I get libstdc++?</a> </li>
  44       <li><a href="#1_5">When is libstdc++ going to be finished?</a> </li>
  45       <li><a href="#1_6">How do I contribute to the effort?</a> </li>
  46       <li><a href="#1_7">What happened to libg++?  I need that!</a> </li>
  47       <li><a href="#1_8">What if I have more questions?</a> </li>
  48       <li><a href="#1_9">What are the license terms for libstdc++-v3?</a> </li>
  49    </ol>
  50    </li>
  51
  52    <li><a href="#2_0">Installation</a>
  53       <ol>
  54          <li><a href="#2_1">How do I install libstdc++-v3?</a> </li>
  55          <li><a href="#2_2">[removed]</a> </li>
  56          <li><a href="#2_3">What is this CVS thing that you keep
  57                             mentioning?</a> </li>
  58          <li><a href="#2_4">How do I know if it works?</a> </li>
  59          <li><a href="#2_5">This library is HUGE!  And what's libsupc++?</a> </li>
  60       </ol>
  61    </li>
  62
  63    <li><a href="#3_0">Platform-Specific Issues</a>
  64       <ol>
  65          <li><a href="#3_1">Can libstdc++-v3 be used with &lt;my
  66                             favorite compiler&gt;?</a> </li>
  67          <li><a href="#3_2">[removed]</a> </li>
  68          <li><a href="#3_3">[removed]</a> </li>
  69          <li><a href="#3_4">I can't use 'long long' on Solaris</a> </li>
  70          <li><a href="#3_5"><code>_XOPEN_SOURCE</code> /
  71                             <code>_GNU_SOURCE</code> / etc is always defined</a>
  72          </li>
  73          <li><a href="#3_6">OS X ctype.h is broken!  How can I hack it?</a></li>
  74          <li><a href="#3_7">Threading is broken on i386</a></li>
  75       </ol>
  76    </li>
  77
  78    <li><a href="#4_0">Known Bugs and Non-Bugs</a>
  79       <ol>
  80          <li><a href="#4_1">What works already?</a> </li>
  81          <li><a href="#4_2">Bugs in gcc/g++ (not libstdc++-v3)</a> </li>
  82          <li><a href="#4_3">Bugs in the C++ language/lib specification</a> </li>
  83          <li><a href="#4_4">Things in libstdc++ that only look like bugs</a><ul>
  84            <li><a href="#4_4_iostreamclear">reopening a stream fails</a> </li>
  85            <li><a href="#4_4_Weff">-Weffc++ complains too much</a> </li>
  86            <li><a href="#4_4_rel_ops">&quot;ambiguous overloads&quot;
  87                                after including an old-style header</a> </li>
  88            <li><a href="#4_4_interface">The g++-3 headers are
  89                                <strong>not ours</strong></a> </li>
  90            <li><a href="#4_4_glibc">compilation errors from streambuf.h</a> </li>
  91            <li><a href="#4_4_checks">errors about <em>*Concept</em> and
  92                                <em>constraints</em> in the STL...</a> </li>
  93            <li><a href="#4_4_dlsym">program crashes when using library code
  94                                in a dynamically-loaded library</a> </li>
  95          </ul>
  96          </li>
  97          <li><a href="#4_5">Aw, that's easy to fix!</a> </li>
  98       </ol>
  99    </li>
 100
 101    <li><a href="#5_0">Miscellaneous</a>
 102       <ol>
 103          <li><a href="#5_1">string::iterator is not char*;
 104                             vector&lt;T&gt;::iterator is not T*</a> </li>
 105          <li><a href="#5_2">What's next after libstdc++-v3?</a> </li>
 106          <li><a href="#5_3">What about the STL from SGI?</a> </li>
 107          <li><a href="#5_4">Extensions and Backward Compatibility</a> </li>
 108          <li><a href="#5_5">[removed]</a> </li>
 109          <li><a href="#5_6">Is libstdc++-v3 thread-safe?</a> </li>
 110          <li><a href="#5_7">How do I get a copy of the ISO C++ Standard?</a> </li>
 111          <li><a href="#5_8">What's an ABI and why is it so messy?</a> </li>
 112       </ol>
 113    </li>
 114
 115 </ol>
 116
 117 <hr />
 118
 119 <!-- ####################################################### -->
 120
 121 <h1><a name="1_0">1.0 General Information</a></h1>
 122 <!-- I suspect these will mostly be links to/into existing documents. -->
 123    <h2><a name="1_1">1.1 What is libstdc++-v3?</a></h2>
 124       <p>The GNU Standard C++ Library v3 is an
 125          ongoing project to implement the ISO 14882 Standard C++ library
 126          as described in chapters 17 through 27 and annex D.  As the
 127          library reaches stable plateaus, it is captured in a snapshot
 128          and released.  The latest release is
 129          <a href="http://gcc.gnu.org/libstdc++/index.html#download">the
 130          fourteenth snapshot</a> but newer versions have been included
 131          in recent GCC releases.  For those who want to see exactly how
 132          far the project has come, or just want the latest
 133          bleeding-edge code, the up-to-date source is available over
 134          anonymous CVS, and can even be browsed over the Web (see
 135          <a href="#1_4">1.4</a> below).
 136       </p>
 137       <p>The older libstdc++-v2 project is no longer maintained; the code
 138          has been completely replaced and rewritten.
 139          <a href="#4_4_interface">If you are using V2</a>, then you need to
 140          report bugs to your system vendor, not to the V3 list.
 141       </p>
 142       <p>A more formal description of the V3 goals can be found in the
 143          official <a href="../17_intro/DESIGN">design document</a>.
 144       </p>
 145
 146 <hr />
 147    <h2><a name="1_2">1.2 Why should I use libstdc++?</a></h2>
 148       <p>The completion of the ISO C++ standardization gave the
 149          C++ community a powerful set of reuseable tools in the form
 150          of the C++ Standard Library.  However, all existing C++
 151          implementations are (as the Draft Standard used to say)
 152          &quot;incomplet and incorrekt,&quot; and many suffer from
 153          limitations of the compilers that use them.
 154       </p>
 155       <p>The GNU C/C++/FORTRAN/&lt;pick-a-language&gt; compiler
 156          (<code>gcc</code>, <code>g++</code>, etc) is widely considered to be
 157          one of the leading compilers in the world.  Its development
 158          has recently been taken over by the
 159          <a href="http://gcc.gnu.org/">GCC team</a>.  All of
 160          the rapid development and near-legendary
 161          <a href="http://gcc.gnu.org/gcc-3.0/buildstat.html">portability</a>
 162          that are the hallmarks of an open-source project are being
 163          applied to libstdc++.
 164       </p>
 165       <p>That means that all of the Standard classes and functions
 166          (such as <code>string</code>, <code>vector&lt;&gt;</code>, iostreams,
 167          and algorithms) will be freely available and fully compliant.
 168          Programmers will no longer need to &quot;roll their own&quot;
 169          nor be worried about platform-specific incompatibilities.
 170       </p>
 171
 172 <hr />
 173    <h2><a name="1_3">1.3 Who's in charge of it?</a></h2>
 174       <p>The libstdc++ project is contributed to by several developers
 175          all over the world, in the same way as GCC or Linux.
 176          Benjamin Kosnik, Gabriel Dos Reis, Phil Edwards, Ulrich Drepper,
 177          Loren James Rittle, and Paolo Carlini are the lead maintainers of
 178          the CVS archive.
 179       </p>
 180       <p>Development and discussion is held on the libstdc++ mailing
 181          list.  Subscribing to the list, or searching the list
 182          archives, is open to everyone.  You can read instructions for
 183          doing so on the <a href="http://gcc.gnu.org/libstdc++/">homepage</a>.
 184          If you have questions, ideas, code, or are just curious, sign up!
 185       </p>
 186
 187 <hr />
 188    <h2><a name="1_4">1.4 How do I get libstdc++?</a></h2>
 189       <p>The fourteenth (and latest) snapshot of libstdc++-v3 is
 190          <a href="http://gcc.gnu.org/libstdc++/index.html#download">available
 191          via ftp</a>.
 192       </p>
 193       <p>The <a href="http://gcc.gnu.org/libstdc++/">homepage</a>
 194          has instructions for retrieving the latest CVS sources, and for
 195          browsing the CVS sources over the web.
 196       </p>
 197       <p>The subset commonly known as the Standard Template Library
 198          (chapters 23 through 25, mostly) is adapted from the final release
 199          of the SGI STL.
 200       </p>
 201
 202 <hr />
 203    <h2><a name="1_5">1.5 When is libstdc++ going to be finished?</a></h2>
 204 <!--      <p>Nathan Myers gave the best of all possible answers in <a
 205          href="http://www.deja.com/getdoc.xp?AN=469581698&fmt=text">a
 206          Usenet article</a>.</p>
 207 which is no longer available, thanks deja...-->
 208       <p>Nathan Myers gave the best of all possible answers, responding to a
 209          Usenet article asking this question:  <em>Sooner, if you help.</em>
 210       </p>
 211
 212 <hr />
 213    <h2><a name="1_6">1.6 How do I contribute to the effort?</a></h2>
 214       <p>Here is <a href="../17_intro/contribute.html">a
 215          page devoted to this topic</a>.  Subscribing to the mailing
 216          list (see above, or the homepage) is a very good idea if you
 217          have something to contribute, or if you have spare time and
 218          want to help.  Contributions don't have to be in the form of
 219          source code; anybody who is willing to help write
 220          documentation, for example, or has found a bug in code that
 221          we all thought was working, is more than welcome!
 222       </p>
 223
 224 <hr />
 225    <h2><a name="1_7">1.7 What happened to libg++?  I need that!</a></h2>
 226       <p>The most recent libg++ README states that libg++ is no longer
 227          being actively maintained.  It should not be used for new
 228          projects, and is only being kicked along to support older code.
 229       </p>
 230       <p>The libg++ was designed and created when there was no Standard
 231          to provide guidance.  Classes like linked lists are now provided
 232          for by <code>list&lt;T&gt;</code> and do not need to be created by
 233          <code>genclass</code>.  (For that matter, templates exist now and
 234          are well-supported, whereas genclass (mostly) predates them.)
 235       </p>
 236       <p>There are other classes in libg++ that are not specified in the
 237          ISO Standard (e.g., statistical analysis).  While there are a
 238          lot of really useful things that are used by a lot of people
 239          (e.g., statistics :-), the Standards Committee couldn't include
 240          everything, and so a lot of those &quot;obvious&quot; classes
 241          didn't get included.
 242       </p>
 243       <p>Since libstdc++ is an implementation of the Standard Library, we
 244          have no plans at this time to include non-Standard utilities
 245          in the implementation, however handy they are.  (The extensions
 246          provided in the SGI STL aren't maintained by us and don't get
 247          a lot of our attention, because they don't require a lot of our
 248          time.)  It is entirely plausable that the &quot;useful stuff&quot;
 249          from libg++ might be extracted into an updated utilities library,
 250          but nobody has stated such a project yet.
 251       </p>
 252       <!-- The advertisement, so to speak, might have to go.  Hmmmmm.  -->
 253       <p>(The <a href="http://www.boost.org/">Boost</a> site houses free
 254          C++ libraries that do varying things, and happened to be started
 255          by members of the Standards Committee.  Certain &quot;useful
 256          stuff&quot; classes will probably migrate there.)
 257       </p>
 258       <p>For the bold and/or desperate, the
 259          <a href="http://gcc.gnu.org/extensions.html">GCC extensions page</a>
 260          describes where to find the last libg++ source.
 261       </p>
 262
 263 <hr />
 264    <h2><a name="1_8">1.8 What if I have more questions?</a></h2>
 265       <p>If you have read the README and RELEASE-NOTES files, and your
 266          question remains unanswered, then just ask the mailing list.
 267          At present, you do not need to be subscribed to the list to
 268          send a message to it.  More information is available on the
 269          homepage (including how to browse the list archives); to send
 270          to the list, use <a href="mailto:libstdc++@gcc.gnu.org">
 271          <code>libstdc++@gcc.gnu.org</code></a>.
 272       </p>
 273       <p>If you have a question that you think should be included here,
 274          or if you have a question <em>about</em> a question/answer here,
 275          contact <a href="mailto:pme@gcc.gnu.org">Phil Edwards</a>
 276          or <a href="mailto:gdr@gcc.gnu.org">Gabriel Dos Reis</a>.
 277       </p>
 278
 279 <hr />
 280    <h2><a name="1_9">1.9 What are the license terms for libstdc++-v3?</a></h2>
 281       <p>See <a href="../17_intro/license.html">our license description</a>
 282          for these and related questions.
 283       </p>
 284
 285 <hr />
 286 <h1><a name="2_0">2.0 Installation</a></h1>
 287    <h2><a name="2_1">2.1 How do I install libstdc++-v3?</a></h2>
 288       <p>Complete instructions are not given here (this is a FAQ, not
 289          an installation document), but the tools required are few:
 290       </p>
 291          <ul>
 292             <li> A 3.x release of GCC.  Note that building GCC is much
 293                  easier and more automated than building the GCC 2.[78]
 294                  series was.  If you are using GCC 2.95, you can still
 295                  build earlier snapshots of libstdc++.
 296             </li>
 297             <li> GNU Make is recommended, but should not be required.
 298             </li>
 299             <li> The GNU Autotools are needed if you are messing with
 300                  the configury or makefiles.
 301             </li>
 302          </ul>
 303       <p>The file <a href="../documentation.html">documentation.html</a>
 304          provides a good overview of the steps necessary to build, install,
 305          and use the library.  Instructions for configuring the library
 306          with new flags such as --enable-threads are there also, as well as
 307          patches and instructions for working with GCC 2.95.
 308       </p>
 309       <p>The top-level install.html and
 310          <a href="../17_intro/RELEASE-NOTES">RELEASE-NOTES</a> files contain
 311          the exact build and installation instructions.  You may wish to
 312          browse those files over CVSweb ahead of time to get a feel for
 313          what's required.  RELEASE-NOTES is located in the
 314          &quot;.../docs/17_intro/&quot; directory of the distribution.
 315       </p>
 316
 317 <hr />
 318    <h2><a name="2_2">2.2 [removed]</a></h2>
 319       <p>This question has become moot and has been removed.  The stub
 320          is here to preserve numbering (and hence links/bookmarks).
 321       </p>
 322
 323 <hr />
 324    <h2><a name="2_3">2.3 What is this CVS thing that you
 325                          keep mentioning?</a></h2>
 326       <p>The <em>Concurrent Versions System</em> is one of several revision
 327          control packages.  It was selected for GNU projects because it's
 328          free (speech), free (beer), and very high quality.  The <a
 329          href="http://www.gnu.org/software/cvs/cvs.html">CVS entry in
 330          the GNU software catalogue</a> has a better description as
 331          well as a
 332          <a href="http://www.cvshome.org/">link to the makers of CVS</a>.
 333       </p>
 334       <p>The &quot;anonymous client checkout&quot; feature of CVS is
 335          similar to anonymous FTP in that it allows anyone to retrieve
 336          the latest libstdc++ sources.
 337       </p>
 338       <p>After the first of April, American users will have a
 339          &quot;/pharmacy&quot; command-line option...
 340          <!-- wonder how long that'll live -->
 341       </p>
 342
 343 <hr />
 344    <h2><a name="2_4">2.4 How do I know if it works?</a></h2>
 345       <p>libstdc++-v3 comes with its own testsuite.  You do not need
 346          to actually install the library (&quot;<code>make
 347          install</code>&quot;) to run the testsuite.
 348       </p>
 349       <p>To run the testsuite on the library after building it, use
 350          &quot;make check&quot; while in your build directory.  To run
 351          the testsuite on the library after building and installing it,
 352          use &quot;make check-install&quot; instead.
 353       </p>
 354       <p>If you find bugs in the testsuite programs themselves, or if you
 355          think of a new test program that should be added to the suite,
 356          <strong>please</strong> write up your idea and send it to the list!
 357       </p>
 358
 359 <hr />
 360    <h2><a name="2_5">2.4 This library is HUGE!  And what's libsupc++?</a></h2>
 361       <p>Usually the size of libraries on disk isn't noticeable.  When a
 362          link editor (or simply &quot;linker&quot;) pulls things from a
 363          static archive library, only the necessary object files are copied
 364          into your executable, not the entire library.  Unfortunately, even
 365          if you only need a single function or variable from an object file,
 366          the entire object file is extracted.  (There's nothing unique to C++
 367          or libstdc++-v3 about this; it's just common behavior, given here
 368          for background reasons.)
 369       </p>
 370       <p>Some of the object files which make up libstdc++.a are rather large.
 371          If you create a statically-linked executable with
 372          <code> -static</code>, those large object files are suddenly part
 373          of your executable.  Historically the best way around this was to
 374          only place a very few functions (often only a single one) in each
 375          source/object file; then extracting a single function is the same
 376          as extracting a single .o file.  For libstdc++-v3 this is only
 377          possible to a certain extent; the object files in question contain
 378          template classes and template functions, pre-instantiated, and
 379          splitting those up causes severe maintenance headaches.
 380       </p>
 381       <p>It's not a bug, and it's not really a problem.  Nevertheless, some
 382          people don't like it, so here are two pseudo-solutions:
 383       </p>
 384       <p>If the only functions from libstdc++.a which you need are language
 385          support functions (those listed in
 386          <a href="../18_support/howto.html">clause 18</a> of the standard,
 387          e.g., <code>new</code> and <code>delete</code>), then try linking
 388          against <code>libsupc++.a</code> (usually specifying
 389          <code>-lsupc++</code> when calling g++ for the final link step will
 390          do it).  This library contains only those support routines, one per
 391          object file.  But if you are using anything from the rest of the
 392          library, such as IOStreams or vectors, then you'll still need
 393          pieces from <code>libstdc++.a</code>.
 394       </p>
 395       <p>The second method is one we hope to incorporate into the library
 396          build process.  Some platforms can place each function and variable
 397          into its own section in a .o file.  The GNU linker can then perform
 398          garbage collection on unused sections; this reduces the situation
 399          to only copying needed functions into the executable, as before,
 400          but all happens automatically.
 401       </p>
 402       <p>Unfortunately the garbage collection in GNU ld is buggy; sections
 403          (corresponding to functions and variables) which <em>are</em> used
 404          are mistakenly removed, leading to horrible crashes when your
 405          executable starts up.  For the time being, this feature is not used
 406          when building the library.
 407       </p>
 408
 409 <hr />
 410 <h1><a name="3_0">3.0 Platform-Specific Issues</a></h1>
 411    <h2><a name="3_1">3.1 Can libstdc++-v3 be used with &lt;my
 412                          favorite compiler&gt;?</a></h2>
 413       <p>Probably not.  Yet.</p>
 414       <p>Because GCC advances so rapidly, development and testing of
 415          libstdc++ is being done almost entirely under that compiler.
 416          If you are curious about whether other, lesser compilers
 417          (*grin*) support libstdc++, you are more than welcome to try.
 418          Configuring and building the library (see above) will still
 419          require certain tools, however.  Also keep in mind that
 420          <em>building</em> libstdc++ does not imply that your compiler
 421          will be able to <em>use</em> all of the features found in the
 422          C++ Standard Library.
 423       </p>
 424       <p>Since the goal of ISO Standardization is for all C++
 425          implementations to be able to share code, the final libstdc++
 426          should, in theory, be usable under any ISO-compliant
 427          compiler.  It will still be targeted and optimized for
 428          GCC/g++, however.
 429       </p>
 430
 431 <hr />
 432    <h2><a name="3_2">3.2 [removed]</a></h2>
 433       <p>This question has become moot and has been removed.  The stub
 434          is here to preserve numbering (and hence links/bookmarks).
 435       </p>
 436
 437 <hr />
 438    <h2><a name="3_3">3.3 [removed]</a></h2>
 439       <p>This question has become moot and has been removed.  The stub
 440          is here to preserve numbering (and hence links/bookmarks).
 441       </p>
 442
 443 <hr />
 444    <h2><a name="3_4">3.4 I can't use 'long long' on Solaris</a></h2>
 445       <p>By default we try to support the C99 <code>long long</code> type.
 446          This requires that certain functions from your C library be present.
 447       </p>
 448       <p>Up through release 3.0.2 the tests performed were too general, and
 449          this feature was disabled when it did not need to be.  The most
 450          commonly reported platform affected was Solaris.
 451       </p>
 452       <p>This has been fixed for 3.0.3 and onwards.
 453       </p>
 454
 455 <hr />
 456    <h2><a name="3_5">3.5 <code>_XOPEN_SOURCE</code> / <code>_GNU_SOURCE</code>
 457                          / etc is always defined</a></h2>
 458       <p>On Solaris, g++ (but not gcc) always defines the preprocessor
 459          macro <code>_XOPEN_SOURCE</code>.  On GNU/Linux, the same happens
 460          with <code>_GNU_SOURCE</code>.  (This is not an exhaustive list;
 461          other macros and other platforms are also affected.)
 462       </p>
 463       <p>These macros are typically used in C library headers, guarding new
 464          versions of functions from their older versions.  The C++ standard
 465          library includes the C standard library, but it requires the C90
 466          version, which for backwards-compatability reasons is often not the
 467          default for many vendors.
 468       </p>
 469       <p>More to the point, the C++ standard requires behavior which is only
 470          available on certain platforms after certain symbols are defined.
 471          Usually the issue involves I/O-related typedefs.  In order to
 472          ensure correctness, the compiler simply predefines those symbols.
 473       </p>
 474       <p>Note that it's not enough to #define them only when the library is
 475          being built (during installation).  Since we don't have an 'export'
 476          keyword, much of the library exists as headers, which means that
 477          the symbols must also be defined as your programs are parsed and
 478          compiled.
 479       </p>
 480       <p>To see which symbols are defined, look for CPLUSPLUS_CPP_SPEC in
 481          the gcc config headers for your target (and try changing them to
 482          see what happens when building complicated code).  You can also run
 483          <code>&quot;g++ -E -dM - &lt; /dev/null&quot;</code> to display
 484          a list of predefined macros for any particular installation.
 485       </p>
 486       <p>This has been discussed on the mailing lists
 487          <a href="http://gcc.gnu.org/cgi-bin/htsearch?method=and&amp;format=builtin-long&amp;sort=score&amp;words=_XOPEN_SOURCE+Solaris">quite a bit</a>.
 488       </p>
 489       <p>This method is something of a wart.  We'd like to find a cleaner
 490          solution, but nobody yet has contributed the time.
 491       </p>
 492
 493 <hr />
 494    <h2><a name="3_6">3.6 OS X ctype.h is broken!  How can I hack it?</a></h2>
 495       <p>This is a long-standing bug in the OS X support.  Fortunately,
 496          the patch is quite simple, and well-known.
 497          <a href="http://gcc.gnu.org/ml/gcc/2002-03/msg00817.html"> Here's a
 498          link to the solution.</a>
 499       </p>
 500
 501 <hr />
 502    <h2><a name="3_7">3.7 Threading is broken on i386</a></h2>
 503       <p>Support for atomic integer operations is/was broken on i386
 504          platforms.  The assembly code accidentally used opcodes that are
 505          only available on the i486 and later.  So if you configured GCC
 506          to target, for example, i386-linux, but actually used the programs
 507          on an i686, then you would encounter no problems.  Only when
 508          actually running the code on a i386 will the problem appear.
 509       </p>
 510       <p>This is fixed in 3.2.2.
 511       </p>
 512
 513 <hr />
 514    <h2><a name="3_8">3.8 Recent GNU/Linux glibc required?</a></h2>
 515       <p>For 3.2.1 (shared library version 5.0.1) and later, the library
 516          uses localization and formatting code from the system C library
 517          (glibc) version 2.2.5.  That version of glibc is over a year old
 518          and contains necessary bugfixes.  Many GNU/Linux distros make
 519          glibc version 2.3.x available now.
 520       </p>
 521       <p>The guideline is simple:  the more recent the C++ library, the
 522          more recent the C library.
 523       </p>
 524
 525 <hr />
 526 <h1><a name="4_0">4.0 Known Bugs and Non-Bugs</a></h1>
 527    <em>Note that this section can get rapdily outdated -- such is the
 528    nature of an open-source project.  For the latest information, join
 529    the mailing list or look through recent archives.   The RELEASE-
 530    NOTES and BUGS files are generally kept up-to-date.</em>
 531
 532    <p>For 3.0.1, the most common &quot;bug&quot; is an apparently missing
 533       &quot;<code>../</code>&quot; in include/Makefile, resulting in files
 534       like gthr.h and gthr-single.h not being found.  Please read
 535       <a href="http://gcc.gnu.org/install/configure.html">the configuration
 536       instructions for GCC</a>,
 537       specifically the part about configuring in a separate build directory,
 538       and how strongly recommended it is.  Building in the source directory
 539       is fragile, is rarely tested, and tends to break, as in this case.
 540       This was fixed for 3.0.2.
 541    </p>
 542
 543    <p>For 3.1, the most common &quot;bug&quot; is a parse error when using
 544       <code>&lt;fstream&gt;</code>, ending with a message,
 545       &quot;<code>bits/basic_file.h:52: parse error before `{'
 546       token</code>.&quot;  Please read
 547       <a href="http://gcc.gnu.org/install/">the installation instructions for
 548       GCC</a>, specifically the part about not installing newer versions on
 549       top of older versions.  If you install 3.1 over a 3.0.x release, then
 550       the wrong basic_file.h header will be found (its location changed
 551       between releases).
 552    </p>
 553
 554    <p><strong>Please do not report these as bugs.  We know about them.</strong>
 555       Reporting this -- or any other problem that's already been fixed --
 556       hinders the development of GCC, because we have to take time to
 557       respond to your report.  Thank you.
 558    </p>
 559
 560    <h2><a name="4_1">4.1 What works already?</a></h2>
 561       <p>This is a verbatim clip from the &quot;Status&quot; section
 562          of the RELEASE-NOTES for the latest snapshot.  For a list of
 563          fixed bugs, see that file.
 564       </p>
 565
 566 <!-- Yeah, I meant that "verbatim clip" thing literally... :-)  -->
 567
 568 <pre>
 569 New:
 570 ---
 571 (post 3.0.97)
 572 - more doxygen documentation
 573 - more named locale fixups
 574 - stdio_filebuf that takes fd, FILE
 575 - io performance tuning
 576 - allocation tuning, valgrind fixups
 577 - __cxa_demangle now supported
 578 (3.0.97)
 579 - more doxygen documentation.
 580 - more named locale bug fixes
 581 - support for symbol versioning when using GNU ld &gt;= 2.12
 582 - wide-io
 583 - tuning for executable size
 584 (3.0.96)
 585 - more doxygen documentation.
 586 - extensions moved out of namespace std
 587 - HPUX long long support
 588 - more string optimizations
 589 - support for NetBSD cross compiles
 590 - concept_check merge from boost
 591 - header simplification
 592 - named locale bug shakeout
 593 - thread testsuite
 594 (3.0.95)
 595 - add S390, m68k, x86-64 support.
 596 - doxygen documentation has been extended, including man pages.
 597 - verbose terminate handling has been added.
 598 - some libsupc++ tweaks
 599 - warnings for deprecated headers now active.
 600 - dejagnu testsuite preliminary documentation.
 601 - dejagnu testsuite default.
 602 - dejagnu testsuite cross compiler, multilib safe.
 603 - long long iostreams on by default, rework of ISO C99 support.
 604 - iterator re-write and testsuites.
 605 - container testsuites.
 606 - allocator revamp and testsuites.
 607 - more concept-checking work.
 608 - basic_string optimization and MT fixes.
 609 - new limits implementation.
 610 - update -fno-exceptions code, verify it works.
 611 - full named locale support fpr all facets, choice of gnu,
 612   ieee_1003.1-200x (POSIX 2), or generic models. Full support depends
 613   on target OS and underlying &quot;C&quot; library support.
 614 </pre>
 615
 616
 617 <hr />
 618    <h2><a name="4_2">4.2 Bugs in gcc/g++ (not libstdc++-v3)</a></h2>
 619       <p>This is by no means meant to be complete nor exhaustive, but
 620          mentions some problems that users may encounter when building
 621          or using libstdc++.  If you are experiencing one of these
 622          problems, you can find more information on the libstdc++ and
 623          the GCC mailing lists.
 624       </p>
 625       <p>Before reporting a bug, examine the
 626          <a href="http://gcc.gnu.org/bugs.html">bugs database</a> with the
 627          category set to &quot;libstdc++&quot;.  The BUGS file in the source
 628          tree also tracks known serious problems.
 629       </p>
 630       <ul>
 631          <li>Debugging is problematic, due to bugs in line-number generation
 632              (mostly fixed in the compiler) and gdb lagging behind the
 633              compiler (lack of personnel).  We recommend configuring the
 634              compiler using <code>--with-dwarf2</code> if the DWARF2
 635              debugging format is not already the default on your platform.
 636              Also,
 637 <a href="http://gcc.gnu.org/ml/libstdc++/2002-02/msg00034.html">changing your
 638              GDB settings</a> can have a profound effect on your C++ debugging
 639              experiences.  :-)</li>
 640       </ul>
 641
 642 <hr />
 643    <h2><a name="4_3">4.3 Bugs in the C++ language/lib specification</a></h2>
 644       <p>Yes, unfortunately, there are some.  In a
 645          <a href="http://gcc.gnu.org/ml/libstdc++/1998/msg00006.html">message
 646          to the list</a>, Nathan Myers announced that he has started a list of
 647          problems in the ISO C++ Standard itself, especially with
 648          regard to the chapters that concern the library.  The list
 649          itself is
 650          <a href="http://www.cantrip.org/draft-bugs.txt">posted on his
 651          website</a>.  Developers who are having problems interpreting
 652          the Standard may wish to consult his notes.
 653       </p>
 654       <p>For those people who are not part of the ISO Library Group
 655          (i.e., nearly all of us needing to read this page in the first
 656          place :-), a public list of the library defects is occasionally
 657          published <a href="http://anubis.dkuug.dk/jtc1/sc22/wg21/">here</a>.
 658          Some of these have resulted in <a href="#5_2">code changes</a>.
 659       </p>
 660
 661 <hr />
 662    <h2><a name="4_4">4.4 Things in libstdc++ that only look like bugs</a></h2>
 663       <p>There are things which are not bugs in the compiler (4.2) nor
 664          the language specification (4.3), but aren't really bugs in
 665          libstdc++, either.  Really!  Please do not report these as bugs.
 666       </p>
 667       <p><a name="4_4_Weff"><strong>-Weffc++</strong></a>
 668          The biggest of these is the quadzillions of warnings about the
 669          library headers emitted when <code>-Weffc++</code> is used.  Making
 670          libstdc++ &quot;-Weffc++-clean&quot; is not a goal of the project,
 671          for a few reasons.  Mainly, that option tries to enforce
 672          object-oriented programming, while the Standard Library isn't
 673          necessarily trying to be OO.
 674       </p>
 675       <p><a name="4_4_iostreamclear"><strong>reopening a stream fails</strong>
 676          </a> Did I just say that -Weffc++ was our biggest false-bug report?
 677          I lied.  (It used to be.)  Today it seems to be reports that after
 678          executing a sequence like
 679       </p>
 680       <pre>
 681     #include &lt;fstream&gt;
 682     ...
 683     std::fstream  fs(&quot;a_file&quot;);
 684     // .
 685     // . do things with fs...
 686     // .
 687     fs.close();
 688     fs.open(&quot;a_new_file&quot;);</pre>
 689       <p>all operations on the re-opened <code>fs</code> will fail, or at
 690          least act very strangely.  Yes, they often will, especially if
 691          <code>fs</code> reached the EOF state on the previous file.  The
 692          reason is that the state flags are <strong>not</strong> cleared
 693          on a successful call to open().  The standard unfortunately did
 694          not specify behavior in this case, and to everybody's great sorrow,
 695          the <a href="../ext/howto.html#5">proposed LWG resolution</a> (see
 696          DR #22) is to leave the flags unchanged.  You must insert a call
 697          to <code>fs.clear()</code> between the calls to close() and open(),
 698          and then everything will work like we all expect it to work.
 699       </p>
 700       <p><a name="4_4_rel_ops"><strong>rel_ops</strong></a>
 701          Another is the <code>rel_ops</code> namespace and the template
 702          comparison operator functions contained therein.  If they become
 703          visible in the same namespace as other comparison functions
 704          (e.g., '<code>using</code>' them and the &lt;iterator&gt; header),
 705          then you will suddenly be faced with huge numbers of ambiguity
 706          errors.  This was discussed on the -v3 list; Nathan Myers
 707          <a href="http://gcc.gnu.org/ml/libstdc++/2001-01/msg00247.html">sums
 708          things up here</a>.  The collisions with vector/string iterator
 709          types have been fixed for 3.1.  <!-- more links to email here -->
 710       </p>
 711       <h3><a name="4_4_interface">The g++-3 headers are <em>not ours</em></a></h3>
 712       <p>If you have found an extremely broken header file which is
 713          causing problems for you, look carefully before submitting a
 714          &quot;high&quot; priority bug report (which you probably shouldn't
 715          do anyhow; see the last paragraph of the page describing
 716          <a href="http://gcc.gnu.org/gnatswrite.html">the GCC bug database</a>).
 717       </p>
 718       <p>If the headers are in <code>${prefix}/include/g++-3</code>, or if
 719          the installed library's name looks like <code>libstdc++-2.10.a</code>
 720          or <code>libstdc++-libc6-2.10.so</code>,
 721          then you are using the old libstdc++-v2 library, which is nonstandard
 722          and unmaintained.  Do not report problems with -v2 to the -v3
 723          mailing list.
 724       </p>
 725       <p>Currently our header files are installed in
 726          <code>${prefix}/include/g++-v3</code> (see the 'v'?).  This may
 727          change with the next release of GCC, as it may be too confusing,
 728          but <a href="http://gcc.gnu.org/ml/gcc/2000-10/msg00732.html">the
 729          question has not yet been decided</a>.
 730       </p>
 731       <p><a name="4_4_glibc"><strong>glibc</strong></a>
 732          If you're on a GNU/Linux system and have just upgraded to
 733          glibc 2.2, but are still using gcc 2.95.2, then you should have
 734          read the glibc FAQ, specifically 2.34:
 735       </p>
 736       <pre>
 737 2.34.   When compiling C++ programs, I get a compilation error in streambuf.h.
 738
 739 {BH} You are using g++ 2.95.2? After upgrading to glibc 2.2, you need to
 740 apply a patch to the include files in /usr/include/g++, because the fpos_t
 741 type has changed in glibc 2.2.  The patch is at
 742 http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff
 743    </pre>
 744       <p>Note that 2.95.x shipped with the
 745          <a href="#4_4_interface">old v2 library</a> which is no longer
 746          maintained.  Also note that gcc 2.95.3 fixes this problem, but
 747          requires a separate patch for libstdc++-v3.
 748       </p>
 749       <p><a name="4_4_checks"><strong>concept checks</strong></a>
 750          If you see compilation errors containing messages about
 751          <code> <em>foo</em>Concept </code>and a<code> constraints </code>
 752          member function, then most likely you have violated one of the
 753          requirements for types used during instantiation of template
 754          containers and functions.  For example, EqualityComparableConcept
 755          appears if your types must be comparable with == and you have not
 756          provided this capability (a typo, or wrong visibility, or you
 757          just plain forgot, etc).
 758       </p>
 759       <p>More information, including how to optionally enable/disable the
 760          checks, is available
 761          <a href="../19_diagnostics/howto.html#3">here</a>.
 762       </p>
 763       <p><a name="4_4_dlsym"><strong>dlopen/dlsym</strong></a>
 764          If you are using the C++ library across dynamically-loaded
 765          objects, make certain that you are passing the correct options
 766          when compiling and linking:
 767       </p>
 768       <pre>
 769     // compile the library components
 770     g++ -fPIC -c a.cc
 771     g++ -fPIC -c b.cc
 772     ...
 773     g++ -fPIC -c z.cc
 774
 775     // create the library
 776     g++ -fPIC -shared -rdynamic -o libfoo.so a.o b.o ... z.o
 777
 778     // link the executable
 779     g++ -fPIC -rdynamic -o foo ... -L. -lfoo -ldl</pre>
 780
 781 <hr />
 782    <h2><a name="4_5">4.5 Aw, that's easy to fix!</a></h2>
 783       <p>If you have found a bug in the library and you think you have
 784          a working fix, then send it in!  The main GCC site has a page
 785          on <a href="http://gcc.gnu.org/contribute.html">submitting
 786          patches</a> that covers the procedure, but for libstdc++ you
 787          should also send the patch to our mailing list in addition to
 788          the GCC patches mailing list.  The libstdc++
 789          <a href="../17_intro/contribute.html">contributors' page</a>
 790          also talks about how to submit patches.
 791       </p>
 792       <p>In addition to the description, the patch, and the ChangeLog
 793          entry, it is a Good Thing if you can additionally create a small
 794          test program to test for the presence of the bug that your
 795          patch fixes.  Bugs have a way of being reintroduced; if an old
 796          bug creeps back in, it will be caught immediately by the
 797          <a href="#2_4">testsuite</a> -- but only if such a test exists.
 798       </p>
 799
 800 <hr />
 801 <h1><a name="5_0">5.0 Miscellaneous</a></h1>
 802    <h2><a name="5_1">5.1 string::iterator is not char*;
 803                      vector&lt;T&gt;::iterator is not T*</a></h2>
 804       <p>If you have code that depends on container&lt;T&gt; iterators
 805          being implemented as pointer-to-T, your code is broken.
 806       </p>
 807       <p>While there are arguments for iterators to be implemented in
 808          that manner, A) they aren't very good ones in the long term,
 809          and B) they were never guaranteed by the Standard anyway.  The
 810          type-safety achieved by making iterators a real class rather
 811          than a typedef for <code>T*</code> outweighs nearly all opposing
 812          arguments.
 813       </p>
 814       <p>Code which does assume that a vector iterator <code> i </code>
 815          is a pointer can often be fixed by changing <code> i </code> in
 816          certain expressions to <code> &amp;*i </code>.  Future revisions
 817          of the Standard are expected to bless this usage for
 818          vector&lt;&gt; (but not for basic_string&lt;&gt;).
 819       </p>
 820
 821 <hr />
 822    <h2><a name="5_2">5.2 What's next after libstdc++-v3?</a></h2>
 823       <p>Hopefully, not much.  The goal of libstdc++-v3 is to produce
 824          a fully-compliant, fully-portable Standard Library.  After that,
 825          we're mostly done:  there won't <em>be</em> any more compliance
 826          work to do.  However:
 827       </p>
 828       <ol>
 829       <li><p>The ISO Committee will meet periodically to review Defect Reports
 830          in the C++ Standard.  Undoubtedly some of these will result in
 831          changes to the Standard, which will be reflected in patches to
 832          libstdc++.  Some of that is already happening, see 4.2.  Some of
 833          those changes are being predicted by the library maintainers, and
 834          we add code to the library based on what the current proposed
 835          resolution specifies.  Those additions are listed in
 836          <a href="../ext/howto.html#5">the extensions page</a>.
 837       </p></li>
 838       <li><p>Performance tuning.  Lots of performance tuning.  This too is
 839          already underway for post-3.0 releases, starting with memory
 840          expansion in container classes and buffer usage in synchronized
 841          stream objects.
 842       </p></li>
 843       <li><p>An ABI for libstdc++ is being developed, so that
 844          multiple binary-incompatible copies of the library can be replaced
 845          with a single backwards-compatible library, like libgcc_s.so is.
 846       </p></li>
 847       <li><p>The current libstdc++ contains extensions to the Library which
 848          must be explicitly requested by client code (for example, the
 849          hash tables from SGI).  Other extensions may be added to
 850          libstdc++-v3 if they seem to be &quot;standard&quot; enough.
 851          (For example, the &quot;long long&quot; type from C99.)
 852          Bugfixes and rewrites (to improve or fix thread safety, for
 853          instance) will of course be a continuing task.
 854       </p></li>
 855       </ol>
 856       <p><a href="http://gcc.gnu.org/ml/libstdc++/1999/msg00080.html">This
 857          question</a> about the next libstdc++ prompted some brief but
 858          interesting
 859          <a href="http://gcc.gnu.org/ml/libstdc++/1999/msg00084.html">speculation</a>.
 860       </p>
 861
 862 <hr />
 863    <h2><a name="5_3">5.3 What about the STL from SGI?</a></h2>
 864       <p>The <a href="http://www.sgi.com/Technology/STL/">STL from SGI</a>,
 865          version 3.3, was the most recent merge of the STL codebase.  The
 866          code in libstdc++ contains many fixes and changes, and it is
 867          very likely that the SGI code is no longer under active
 868          development.  We expect that no future merges will take place.
 869       </p>
 870       <p>In particular, <code>string</code> is not from SGI and makes no
 871          use of their &quot;rope&quot; class (which is included as an
 872          optional extension), nor is <code>valarray</code> and some others.
 873          Classes like <code>vector&lt;&gt;</code> are, however.
 874       </p>
 875       <p>The FAQ for SGI's STL (one jump off of their main page) is
 876          recommended reading.
 877       </p>
 878
 879 <hr />
 880    <h2><a name="5_4">5.4 Extensions and Backward Compatibility</a></h2>
 881       <p>Headers in the <code>ext</code> and <code>backward</code>
 882          subdirectories should be referred to by their relative paths:
 883          <!-- Careful, the leading spaces in PRE show up directly. -->
 884       </p>
 885       <pre>
 886       #include &lt;ext/hash_map&gt; </pre>
 887       <p>rather than using <code>-I</code> or other options.  This is more
 888          portable and forward-compatible.  (The situation is the same as
 889          that of other headers whose directories are not searched directly,
 890          e.g., <code>&lt;sys/stat.h&gt;</code>, <code>&lt;X11/Xlib.h&gt;</code>.
 891       </p>
 892
 893       <p>The extensions are no longer in the global or <code>std</code>
 894          namespaces, instead they are declared in the <code>__gnu_cxx</code>
 895          namespace. For maximum portability, consider defining a namespace
 896          alias to use to talk about extensions, e.g.:
 897       </p>
 898       <pre>
 899       #ifdef __GNUC__
 900       #if __GNUC__ &lt; 3
 901         #include &lt;hash_map.h&gt;
 902         namespace Sgi { using ::hash_map; }; // inherit globals
 903       #else
 904         #include &lt;ext/hash_map&gt;
 905         #if __GNUC_MINOR__ == 0
 906           namespace Sgi = std;               // GCC 3.0
 907         #else
 908           namespace Sgi = ::__gnu_cxx;       // GCC 3.1 and later
 909         #endif
 910       #endif
 911       #else      // ...  there are other compilers, right?
 912         namespace Sgi = std;
 913       #endif
 914
 915       Sgi::hash_map&lt;int,int&gt; my_map; </pre>
 916       <p>This is a bit cleaner than defining typedefs for all the
 917          instantiations you might need.
 918       </p>
 919
 920       <p>Extensions to the library have
 921          <a href="../ext/howto.html">their own page</a>.
 922       </p>
 923
 924 <hr />
 925    <h2><a name="5_5">5.5 [removed]</a></h2>
 926       <p>This question has become moot and has been removed.  The stub
 927          is here to preserve numbering (and hence links/bookmarks).
 928       </p>
 929
 930 <hr />
 931    <h2><a name="5_6">5.6 Is libstdc++-v3 thread-safe?</a></h2>
 932       <p>When the system's libc is itself thread-safe, a non-generic
 933          implementation of atomicity.h exists for the architecture, and gcc
 934          itself reports a thread model other than single; libstdc++-v3
 935          strives to be thread-safe.  The user-code must guard against
 936          concurrent method calls which may access any particular library
 937          object's state.  Typically, the application programmer may infer
 938          what object locks must be held based on the objects referenced in
 939          a method call.  Without getting into great detail, here is an
 940          example which requires user-level locks:
 941       </p>
 942       <pre>
 943      library_class_a shared_object_a;
 944
 945      thread_main () {
 946        library_class_b *object_b = new library_class_b;
 947        shared_object_a.add_b (object_b);   // must hold lock for shared_object_a
 948        shared_object_a.mutate ();          // must hold lock for shared_object_a
 949      }
 950
 951      // Multiple copies of thread_main() are started in independent threads.</pre>
 952       <p>Under the assumption that object_a and object_b are never exposed to
 953          another thread, here is an example that should not require any
 954          user-level locks:
 955       </p>
 956       <pre>
 957      thread_main () {
 958        library_class_a object_a;
 959        library_class_b *object_b = new library_class_b;
 960        object_a.add_b (object_b);
 961        object_a.mutate ();
 962      } </pre>
 963       <p>All library objects are safe to use in a multithreaded program as
 964          long as each thread carefully locks out access by any other thread
 965          while it uses any object visible to another thread.  In general,
 966          this requirement includes both read and write access to objects;
 967          unless otherwise documented as safe, do not assume that two
 968          threads may access a shared standard library object at the
 969          same time.
 970       </p>
 971       <p>See chapters <a href="../17_intro/howto.html#3">17</a> (library
 972          introduction), <a href="../23_containers/howto.html#3">23</a>
 973          (containers), and <a href="../27_io/howto.html#9">27</a> (I/O) for
 974          more information.
 975       </p>
 976
 977 <hr />
 978    <h2><a name="5_7">5.7 How do I get a copy of the ISO C++ Standard?</a></h2>
 979       <p>Copies of the full ISO 14882 standard are available on line via the
 980          ISO mirror site for committee members.  Non-members, or those who
 981          have not paid for the privilege of sitting on the committee and
 982          sustained their two-meeting commitment for voting rights, may get a
 983          copy of the standard from their respective national standards
 984          organization.  In the USA, this national standards organization is
 985          ANSI and their website is right <a href="http://www.ansi.org">here</a>.
 986          (And if you've already registered with them, clicking this link will
 987          take you to directly to the place where you can
 988 <a href="http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO%2FIEC+14882%2D1998">buy
 989          the standard on-line</a>.
 990       </p>
 991       <p>Who is your country's member body?  Visit the
 992          <a href="http://www.iso.ch/">ISO homepage</a> and find out!
 993       </p>
 994
 995 <hr />
 996    <h2><a name="5_8">5.8 What's an ABI and why is it so messy?</a></h2>
 997       <p>&quot;ABI&quot; stands for &quot;Application Binary Interface.&quot;
 998          Conventionally, it refers to a great mass of details about how
 999          arguments are arranged on the call stack and/or in registers, and
1000          how various types are arranged and padded in structs.  A single CPU
1001          design may suffer multiple ABIs designed by different development
1002          tool vendors who made different choices, or even by the same vendor
1003          for different target applications or compiler versions.  In ideal
1004          circumstances the CPU designer presents one ABI and all the OSes and
1005          compilers use it.  In practice every ABI omits details that compiler
1006          implementers (consciously or accidentally) must choose for themselves.
1007       </p>
1008       <p>That ABI definition suffices for compilers to generate code so a
1009          program can interact safely with an OS and its lowest-level libraries.
1010          Users usually want an ABI to encompass more detail, allowing libraries
1011          built with different compilers (or different releases of the same
1012          compiler!) to be linked together.  For C++, this includes many more
1013          details than for C, and CPU designers (for good reasons elaborated
1014          below) have not stepped up to publish C++ ABIs.  The details include
1015          virtual function implementation, struct inheritance layout, name
1016          mangling, and exception handling.  Such an ABI has been defined for
1017          GNU C++, and is immediately useful for embedded work relying only on
1018          a &quot;free-standing implementation&quot; that doesn't include (much
1019          of) the standard library.  It is a good basis for the work to come.
1020       </p>
1021       <p>A useful C++ ABI must also incorporate many details of the standard
1022          library implementation.  For a C ABI, the layouts of a few structs
1023          (such as FILE, stat, jmpbuf, and the like) and a few macros suffice.
1024          For C++, the details include the complete set of names of functions
1025          and types used, the offsets of class members and virtual functions,
1026          and the actual definitions of all inlines.  C++ exposes many more
1027          library details to the caller than C does.  It makes defining
1028          a complete ABI a much bigger undertaking, and requires not just
1029          documenting library implementation details, but carefully designing
1030          those details so that future bug fixes and optimizations don't
1031          force breaking the ABI.
1032       </p>
1033       <p>There are ways to help isolate library implementation details from the
1034          ABI, but they trade off against speed.  Library details used in
1035          inner loops (e.g., getchar) must be exposed and frozen for all
1036          time, but many others may reasonably be kept hidden from user code,
1037          so they may later be changed.  Deciding which, and implementing
1038          the decisions, must happen before you can reasonably document a
1039          candidate C++ ABI that encompasses the standard library.
1040       </p>
1041
1042 <!-- ####################################################### -->
1043
1044 <hr />
1045 <p class="fineprint"><em>
1046 See <a href="../17_intro/license.html">license.html</a> for copying conditions.
1047 Comments and suggestions are welcome, and may be sent to
1048 <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.
1049 </em></p>
1050
1051
1052 </body>
1053 </html>
1054