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diff --git a/libstdc++-v3/docs/html/faq/index.html b/libstdc++-v3/docs/html/faq/index.html index f472bfc9dc6..29a1d2fa369 100644 --- a/libstdc++-v3/docs/html/faq/index.html +++ b/libstdc++-v3/docs/html/faq/index.html @@ -10,25 +10,27 @@ <meta name="DESCRIPTION" content="FAQ for the GNU libstdc++ effort." /> <title>libstdc++-v3 FAQ</title> <link rel="StyleSheet" href="../lib3styles.css" /> -<!-- - ** Locations of "the most recent snapshot is the Nth" text are - ** answers 1_1, 1_4, 4_1. +<!-- + ** Locations of "the most recent snapshot is the Nth" text are + ** answers 1_1, . --> </head> <body> <h1 class="centered">libstdc++ Frequently Asked Questions</h1> -<p>The latest version of this document is always available at +<p class="fineprint"><em> + The latest version of this document is always available at <a href="http://gcc.gnu.org/onlinedocs/libstdc++/faq/"> http://gcc.gnu.org/onlinedocs/libstdc++/faq/</a>. The main documentation page is at <a href="http://gcc.gnu.org/onlinedocs/libstdc++/documentation.html"> http://gcc.gnu.org/onlinedocs/libstdc++/documentation.html</a>. -</p> +</em></p> -<p>To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>. -</p> +<p><em> + To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>. +</em></p> <!-- ####################################################### --> <hr /> @@ -53,7 +55,7 @@ <ol> <li><a href="#2_1">How do I install libstdc++-v3?</a> </li> <li><a href="#2_2">[removed]</a> </li> - <li><a href="#2_3">What is this CVS thing that you keep + <li><a href="#2_3">What is this CVS thing that you keep mentioning?</a> </li> <li><a href="#2_4">How do I know if it works?</a> </li> <li><a href="#2_5">This library is HUGE! And what's libsupc++?</a> </li> @@ -72,6 +74,9 @@ </li> <li><a href="#3_6">OS X ctype.h is broken! How can I hack it?</a></li> <li><a href="#3_7">Threading is broken on i386</a></li> + <li><a href="#3_8">Recent GNU/Linux glibc required?</a></li> + <li><a href="#3_9">Can't use wchar_t/wstring on FreeBSD</a></li> + <li><a href="#3_10">MIPS atomic operations</a></li> </ol> </li> @@ -92,6 +97,7 @@ <em>constraints</em> in the STL...</a> </li> <li><a href="#4_4_dlsym">program crashes when using library code in a dynamically-loaded library</a> </li> + <li><a href="#4_4_leak">"memory leaks" in containers</a> </li> </ul> </li> <li><a href="#4_5">Aw, that's easy to fix!</a> </li> @@ -122,8 +128,8 @@ <!-- I suspect these will mostly be links to/into existing documents. --> <h2><a name="1_1">1.1 What is libstdc++-v3?</a></h2> <p>The GNU Standard C++ Library v3 is an - ongoing project to implement the ISO 14882 Standard C++ library - as described in chapters 17 through 27 and annex D. As the + ongoing project to implement the ISO 14882 Standard C++ library + as described in chapters 17 through 27 and annex D. As the library reaches stable plateaus, it is captured in a snapshot and released. The latest release is <a href="http://gcc.gnu.org/libstdc++/index.html#download">the @@ -132,7 +138,7 @@ far the project has come, or just want the latest bleeding-edge code, the up-to-date source is available over anonymous CVS, and can even be browsed over the Web (see - <a href="#1_4">1.4</a> below). + <a href="#1_4">1.4</a> below). </p> <p>The older libstdc++-v2 project is no longer maintained; the code has been completely replaced and rewritten. @@ -140,7 +146,7 @@ report bugs to your system vendor, not to the V3 list. </p> <p>A more formal description of the V3 goals can be found in the - official <a href="../17_intro/DESIGN">design document</a>. + official <a href="../17_intro/DESIGN">design document</a>. </p> <hr /> @@ -151,11 +157,11 @@ implementations are (as the Draft Standard used to say) "incomplet and incorrekt," and many suffer from limitations of the compilers that use them. - </p> + </p> <p>The GNU C/C++/FORTRAN/<pick-a-language> compiler (<code>gcc</code>, <code>g++</code>, etc) is widely considered to be one of the leading compilers in the world. Its development - has recently been taken over by the + has recently been taken over by the <a href="http://gcc.gnu.org/">GCC team</a>. All of the rapid development and near-legendary <a href="http://gcc.gnu.org/gcc-3.0/buildstat.html">portability</a> @@ -173,8 +179,8 @@ <h2><a name="1_3">1.3 Who's in charge of it?</a></h2> <p>The libstdc++ project is contributed to by several developers all over the world, in the same way as GCC or Linux. - Benjamin Kosnik, Gabriel Dos Reis, Phil Edwards, Ulrich Drepper, - Loren James Rittle, and Paolo Carlini are the lead maintainers of + Benjamin Kosnik, Gabriel Dos Reis, Phil Edwards, Ulrich Drepper, + Loren James Rittle, and Paolo Carlini are the lead maintainers of the CVS archive. </p> <p>Development and discussion is held on the libstdc++ mailing @@ -186,23 +192,22 @@ <hr /> <h2><a name="1_4">1.4 How do I get libstdc++?</a></h2> - <p>The fourteenth (and latest) snapshot of libstdc++-v3 is - <a href="http://gcc.gnu.org/libstdc++/index.html#download">available - via ftp</a>. - </p> <p>The <a href="http://gcc.gnu.org/libstdc++/">homepage</a> has instructions for retrieving the latest CVS sources, and for browsing the CVS sources over the web. </p> + <p>Stable versions of libstdc++-v3 are included with releases of + <a href="http://gcc.gnu.org/releases.html">the GCC compilers</a>. + </p> <p>The subset commonly known as the Standard Template Library (chapters 23 through 25, mostly) is adapted from the final release of the SGI STL. - </p> + </p> <hr /> <h2><a name="1_5">1.5 When is libstdc++ going to be finished?</a></h2> -<!-- <p>Nathan Myers gave the best of all possible answers in <a - href="http://www.deja.com/getdoc.xp?AN=469581698&fmt=text">a +<!-- <p>Nathan Myers gave the best of all possible answers in <a + href="http://www.deja.com/getdoc.xp?AN=469581698&fmt=text">a Usenet article</a>.</p> which is no longer available, thanks deja...--> <p>Nathan Myers gave the best of all possible answers, responding to a @@ -219,7 +224,7 @@ which is no longer available, thanks deja...--> source code; anybody who is willing to help write documentation, for example, or has found a bug in code that we all thought was working, is more than welcome! - </p> + </p> <hr /> <h2><a name="1_7">1.7 What happened to libg++? I need that!</a></h2> @@ -249,14 +254,13 @@ which is no longer available, thanks deja...--> from libg++ might be extracted into an updated utilities library, but nobody has stated such a project yet. </p> - <!-- The advertisement, so to speak, might have to go. Hmmmmm. --> <p>(The <a href="http://www.boost.org/">Boost</a> site houses free C++ libraries that do varying things, and happened to be started by members of the Standards Committee. Certain "useful stuff" classes will probably migrate there.) </p> <p>For the bold and/or desperate, the - <a href="http://gcc.gnu.org/fom_serv/cache/33.html">GCC FAQ</a> + <a href="http://gcc.gnu.org/extensions.html">GCC extensions page</a> describes where to find the last libg++ source. </p> @@ -312,7 +316,7 @@ which is no longer available, thanks deja...--> browse those files over CVSweb ahead of time to get a feel for what's required. RELEASE-NOTES is located in the ".../docs/17_intro/" directory of the distribution. - </p> + </p> <hr /> <h2><a name="2_2">2.2 [removed]</a></h2> @@ -327,9 +331,9 @@ which is no longer available, thanks deja...--> control packages. It was selected for GNU projects because it's free (speech), free (beer), and very high quality. The <a href="http://www.gnu.org/software/cvs/cvs.html">CVS entry in - the GNU software catalogue</a> has a better description as + the GNU software catalogue</a> has a better description as well as a - <a href="http://www.cvshome.org/">link to the makers of CVS</a>. + <a href="http://www.cvshome.org/">link to the makers of CVS</a>. </p> <p>The "anonymous client checkout" feature of CVS is similar to anonymous FTP in that it allows anyone to retrieve @@ -344,7 +348,9 @@ which is no longer available, thanks deja...--> <h2><a name="2_4">2.4 How do I know if it works?</a></h2> <p>libstdc++-v3 comes with its own testsuite. You do not need to actually install the library ("<code>make - install</code>") to run the testsuite. + install</code>") to run the testsuite, but you do need + DejaGNU, as described + <a href="http://gcc.gnu.org/install/test.html">here</a>. </p> <p>To run the testsuite on the library after building it, use "make check" while in your build directory. To run @@ -357,7 +363,7 @@ which is no longer available, thanks deja...--> </p> <hr /> - <h2><a name="2_5">2.4 This library is HUGE! And what's libsupc++?</a></h2> + <h2><a name="2_5">2.5 This library is HUGE! And what's libsupc++?</a></h2> <p>Usually the size of libraries on disk isn't noticeable. When a link editor (or simply "linker") pulls things from a static archive library, only the necessary object files are copied @@ -426,7 +432,7 @@ which is no longer available, thanks deja...--> should, in theory, be usable under any ISO-compliant compiler. It will still be targeted and optimized for GCC/g++, however. - </p> + </p> <hr /> <h2><a name="3_2">3.2 [removed]</a></h2> @@ -499,23 +505,62 @@ which is no longer available, thanks deja...--> </p> <hr /> - <h2><a name="3_7">Threading is broken on i386</a></h2> + <h2><a name="3_7">3.7 Threading is broken on i386</a></h2> <p>Support for atomic integer operations is/was broken on i386 platforms. The assembly code accidentally used opcodes that are only available on the i486 and later. So if you configured GCC to target, for example, i386-linux, but actually used the programs - on an i686, then you would encounter no problems. Only when - actually running the code on a i386 will the problem appear. + on an i686, then you would encounter no problems. Only when + actually running the code on a i386 will the problem appear. </p> <p>This is fixed in 3.2.2. </p> <hr /> + <h2><a name="3_8">3.8 Recent GNU/Linux glibc required?</a></h2> + <p>When running on GNU/Linux, libstdc++ 3.2.1 (shared library version + 5.0.1) and later uses localization and formatting code from the system + C library (glibc) version 2.2.5. That version of glibc is over a + year old and contains necessary bugfixes. Many GNU/Linux distros make + glibc version 2.3.x available now. + </p> + <p>The guideline is simple: the more recent the C++ library, the + more recent the C library. (This is also documented in the main + GCC installation instructions.) + </p> + +<hr /> + <h2><a name="3_9">3.9 Can't use wchar_t/wstring on FreeBSD</a></h2> + <p>At the moment there are a few problems in FreeBSD's support for + wide character functions, and as a result the libstdc++ configury + decides that wchar_t support should be disabled. Once the underlying + problems are fixed in FreeBSD (soon), the library support will + automatically enable itself. + </p> + <p>You can fix the problems yourself, and learn more about the situation, + by reading + <a href="http://gcc.gnu.org/ml/libstdc++/2003-02/subjects.html#00286"> + this short thread</a> ("_GLIBCPP_USE_WCHAR_T undefined in + FreeBSD's c++config.h?"). + </p> + +<hr /> + <h2><a name="3_10">3.10 MIPS atomic operations</a></h2> + <p>The atomic locking routines for MIPS targets requires MIPS II + and later. A patch went in just after the 3.3 release to + make mips* use the generic implementation instead. You can also + configure for mipsel-elf as a workaround. + </p> + <p>mips*-*-linux* continues to use the MIPS II routines, and more + work in this area is expected. + </p> + +<hr /> <h1><a name="4_0">4.0 Known Bugs and Non-Bugs</a></h1> <em>Note that this section can get rapdily outdated -- such is the - nature of an open-source project. For the latest information, join - the mailing list or look through recent archives. The RELEASE- - NOTES and BUGS files are generally kept up-to-date.</em> + nature of an open-source project. For the latest information, join + the mailing list or look through recent archives. The RELEASE- + NOTES and BUGS files are generally kept up-to-date.</em> <p>For 3.0.1, the most common "bug" is an apparently missing "<code>../</code>" in include/Makefile, resulting in files @@ -546,59 +591,22 @@ which is no longer available, thanks deja...--> </p> <h2><a name="4_1">4.1 What works already?</a></h2> - <p>This is a verbatim clip from the "Status" section + <p>Short answer: Pretty much everything <em>works</em> except for some + corner cases. Also, localization is incomplete. For whether it works + well, or as you expect it to work, see 5.2. + </p> + <p>Long answer: See the docs/html/17_intro/CHECKLIST file, which is + badly outdated... + </p> + <p>What follows is a verbatim clip from the "Status" section of the RELEASE-NOTES for the latest snapshot. For a list of fixed bugs, see that file. - </p> + </p> <!-- Yeah, I meant that "verbatim clip" thing literally... :-) --> <pre> New: ---- -(post 3.0.97) -- more doxygen documentation -- more named locale fixups -- stdio_filebuf that takes fd, FILE -- io performance tuning -- allocation tuning, valgrind fixups -- __cxa_demangle now supported -(3.0.97) -- more doxygen documentation. -- more named locale bug fixes -- support for symbol versioning when using GNU ld >= 2.12 -- wide-io -- tuning for executable size -(3.0.96) -- more doxygen documentation. -- extensions moved out of namespace std -- HPUX long long support -- more string optimizations -- support for NetBSD cross compiles -- concept_check merge from boost -- header simplification -- named locale bug shakeout -- thread testsuite -(3.0.95) -- add S390, m68k, x86-64 support. -- doxygen documentation has been extended, including man pages. -- verbose terminate handling has been added. -- some libsupc++ tweaks -- warnings for deprecated headers now active. -- dejagnu testsuite preliminary documentation. -- dejagnu testsuite default. -- dejagnu testsuite cross compiler, multilib safe. -- long long iostreams on by default, rework of ISO C99 support. -- iterator re-write and testsuites. -- container testsuites. -- allocator revamp and testsuites. -- more concept-checking work. -- basic_string optimization and MT fixes. -- new limits implementation. -- update -fno-exceptions code, verify it works. -- full named locale support fpr all facets, choice of gnu, - ieee_1003.1-200x (POSIX 2), or generic models. Full support depends - on target OS and underlying "C" library support. </pre> @@ -680,8 +688,8 @@ New: reason is that the state flags are <strong>not</strong> cleared on a successful call to open(). The standard unfortunately did not specify behavior in this case, and to everybody's great sorrow, - the <a href="../ext/howto.html#5">proposed LWG resolution</a> (see - DR #22) is to leave the flags unchanged. You must insert a call + the <a href="../ext/howto.html#5">proposed LWG resolution in + DR #22</a> is to leave the flags unchanged. You must insert a call to <code>fs.clear()</code> between the calls to close() and open(), and then everything will work like we all expect it to work. </p> @@ -705,16 +713,15 @@ New: </p> <p>If the headers are in <code>${prefix}/include/g++-3</code>, or if the installed library's name looks like <code>libstdc++-2.10.a</code> - or <code>libstdc++-libc6-2.10.so</code>, - then you are using the old libstdc++-v2 library, which is nonstandard - and unmaintained. Do not report problems with -v2 to the -v3 - mailing list. + or <code>libstdc++-libc6-2.10.so</code>, then you are using the old + libstdc++-v2 library, which is nonstandard and unmaintained. Do not + report problems with -v2 to the -v3 mailing list. </p> - <p>Currently our header files are installed in - <code>${prefix}/include/g++-v3</code> (see the 'v'?). This may - change with the next release of GCC, as it may be too confusing, - but <a href="http://gcc.gnu.org/ml/gcc/2000-10/msg00732.html">the - question has not yet been decided</a>. + <p>For GCC versions 3.0 and 3.1 the libstdc++-v3 header files are + installed in <code>${prefix}/include/g++-v3</code> (see the 'v'?). + Starting with version 3.2 the headers are installed in + <code>${prefix}/include/c++/${version}</code> as this prevents + headers from previous versions being found by mistake. </p> <p><a name="4_4_glibc"><strong>glibc</strong></a> If you're on a GNU/Linux system and have just upgraded to @@ -754,17 +761,29 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff when compiling and linking: </p> <pre> - // compile the library components + // compile your library components g++ -fPIC -c a.cc g++ -fPIC -c b.cc ... g++ -fPIC -c z.cc - // create the library + // create your library g++ -fPIC -shared -rdynamic -o libfoo.so a.o b.o ... z.o // link the executable g++ -fPIC -rdynamic -o foo ... -L. -lfoo -ldl</pre> + <p><a name="4_4_leak"><strong>"memory leaks" in containers</strong></a> + A few people have reported that the standard containers appear + to leak memory when tested with memory checkers such as + <a href="http://developer.kde.org/~sewardj/">valgrind</a>. + The library's default allocators keep free memory in a pool + for later reuse, rather than returning it to the OS. Although + this memory is always reachable by the library and is never + lost, memory debugging tools can report it as a leak. If you + want to test the library for memory leaks please read + <a href="../debug.html#mem">Tips for memory leak hunting</a> + first. + </p> <hr /> <h2><a name="4_5">4.5 Aw, that's easy to fix!</a></h2> @@ -781,7 +800,7 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff entry, it is a Good Thing if you can additionally create a small test program to test for the presence of the bug that your patch fixes. Bugs have a way of being reintroduced; if an old - bug creeps back in, it will be caught immediately by the + bug creeps back in, it will be caught immediately by the <a href="#2_4">testsuite</a> -- but only if such a test exists. </p> @@ -858,7 +877,8 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff <p>In particular, <code>string</code> is not from SGI and makes no use of their "rope" class (which is included as an optional extension), nor is <code>valarray</code> and some others. - Classes like <code>vector<></code> are, however. + Classes like <code>vector<></code> are, however we have + made significant changes to them since then. </p> <p>The FAQ for SGI's STL (one jump off of their main page) is recommended reading. @@ -904,7 +924,6 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff <p>This is a bit cleaner than defining typedefs for all the instantiations you might need. </p> - <p>Extensions to the library have <a href="../ext/howto.html">their own page</a>. </p> @@ -917,15 +936,21 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff <hr /> <h2><a name="5_6">5.6 Is libstdc++-v3 thread-safe?</a></h2> - <p>When the system's libc is itself thread-safe, a non-generic - implementation of atomicity.h exists for the architecture, and gcc - itself reports a thread model other than single; libstdc++-v3 - strives to be thread-safe. The user-code must guard against - concurrent method calls which may access any particular library - object's state. Typically, the application programmer may infer - what object locks must be held based on the objects referenced in - a method call. Without getting into great detail, here is an - example which requires user-level locks: + <p>libstdc++-v3 strives to be thread-safe when all of the following + conditions are met: + </p> + <ul> + <li>The system's libc is itself thread-safe,</li> + <li><code>gcc -v</code> reports a thread model other than 'single',</li> + <li>[pre-3.3 only] a non-generic implementation of atomicity.h + exists for the architecture in question.</li> + </ul> + <p>The user-code must guard against concurrent method calls which may + access any particular library object's state. Typically, the + application programmer may infer what object locks must be held + based on the objects referenced in a method call. Without getting + into great detail, here is an example which requires user-level + locks: </p> <pre> library_class_a shared_object_a; @@ -949,12 +974,12 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff object_a.mutate (); } </pre> <p>All library objects are safe to use in a multithreaded program as - long as each thread carefully locks out access by any other thread - while it uses any object visible to another thread. In general, + long as each thread carefully locks out access by any other + thread while it uses any object visible to another thread, i.e., + treat library objects like any other shared resource. In general, this requirement includes both read and write access to objects; - unless otherwise documented as safe, do not assume that two - threads may access a shared standard library object at the - same time. + unless otherwise documented as safe, do not assume that two threads + may access a shared standard library object at the same time. </p> <p>See chapters <a href="../17_intro/howto.html#3">17</a> (library introduction), <a href="../23_containers/howto.html#3">23</a> @@ -1006,7 +1031,7 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff a "free-standing implementation" that doesn't include (much of) the standard library. It is a good basis for the work to come. </p> - <p>A useful C++ ABI must also incorporate many details of the standard + <p>A useful C++ ABI must also incorporate many details of the standard library implementation. For a C ABI, the layouts of a few structs (such as FILE, stat, jmpbuf, and the like) and a few macros suffice. For C++, the details include the complete set of names of functions @@ -1018,7 +1043,7 @@ http://clisp.cons.org/~haible/gccinclude-glibc-2.2-compat.diff those details so that future bug fixes and optimizations don't force breaking the ABI. </p> - <p>There are ways to help isolate library implementation details from the + <p>There are ways to help isolate library implementation details from the ABI, but they trade off against speed. Library details used in inner loops (e.g., getchar) must be exposed and frozen for all time, but many others may reasonably be kept hidden from user code, |