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diff --git a/libstdc++-v3/doc/xml/manual/using.xml b/libstdc++-v3/doc/xml/manual/using.xml new file mode 100644 index 00000000000..2782596201f --- /dev/null +++ b/libstdc++-v3/doc/xml/manual/using.xml @@ -0,0 +1,1024 @@ +<?xml version='1.0'?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" +[ ]> + +<chapter id="manual.intro.using" xreflabel="Using"> +<?dbhtml filename="using.html"?> + +<title>Using</title> + + <sect1 id="manual.intro.using.lib" xreflabel="Lib"> + <title>Linking Library Binary Files</title> + + <para> + If you only built a static library (libstdc++.a), or if you + specified static linking, you don't have to worry about this. + But if you built a shared library (libstdc++.so) and linked + against it, then you will need to find that library when you run + the executable. + </para> + <para> + Methods vary for different platforms and different styles, but + the usual ones are printed to the screen during installation. + They include: + </para> + <itemizedlist> + <listitem> + <para> + At runtime set LD_LIBRARY_PATH in your environment + correctly, so that the shared library for libstdc++ can be + found and loaded. Be certain that you understand all of the + other implications and behavior of LD_LIBRARY_PATH first + (few people do, and they get into trouble). + </para> + </listitem> + <listitem> + <para> + Compile the path to find the library at runtime into the + program. This can be done by passing certain options to + g++, which will in turn pass them on to the linker. The + exact format of the options is dependent on which linker you + use: + </para> + <itemizedlist> + <listitem> + <para> + GNU ld (default on Linux):<literal>-Wl,--rpath,<filename class="directory">destdir</filename>/lib</literal> + </para> + </listitem> + <listitem> + <para> + IRIX ld:<literal> + -Wl,-rpath,<filename class="directory">destdir</filename>/lib</literal> + </para> + </listitem> + <listitem> + <para> + Solaris ld:<literal>-Wl,-R<filename class="directory">destdir</filename>/lib</literal> + </para> + </listitem> + <listitem> + <para> + More...? Let us know! + </para> + </listitem> + </itemizedlist> + </listitem> + </itemizedlist> + <para> + Use the <command>ldd</command> utility to show which library the + system thinks it will get at runtime. + </para> + <para> + A libstdc++.la file is also installed, for use with Libtool. If + you use Libtool to create your executables, these details are + taken care of for you. + </para> + </sect1> + + <sect1 id="manual.intro.using.headers" xreflabel="Headers"> + <title>Headers</title> + + <sect2 id="manual.intro.using.headers.all" xreflabel="Header Files"> + <title>Header Files</title> + + <para> + The C++ standard specifies the entire set of header files that + must be available to all hosted implementations. Actually, the + word "files" is a misnomer, since the contents of the + headers don't necessarily have to be in any kind of external + file. The only rule is that when one <code>#include</code>'s a + header, the contents of that header become available, no matter + how. + </para> + + <para> + That said, in practice files are used. + </para> + + <para> + There are two main types of include files: header files related + to a specific version of the ISO C++ standard (called Standard + Headers), and all others (TR1, C++ ABI, and Extensions). + </para> + + <para> + Two dialects of standard headers are supported, corresponding to + the 1998 standard as updated for 2003, and the draft of the + upcoming 200x standard. + </para> + + <para> + C++98/03 include files. These are available in the default compilation mode, ie <code>-std=c++98</code> or <code>-std=gnu++98</code>. + </para> + +<table frame='all'> +<title>C++ 1998 Library Headers</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<tbody> +<row><entry><filename class="headerfile">algorithm</filename></entry><entry><filename class="headerfile">iomanip</filename></entry><entry><filename class="headerfile">list</filename></entry><entry><filename class="headerfile">ostream</filename></entry><entry><filename class="headerfile">streambuf</filename></entry></row> +<row><entry><filename class="headerfile">bitset</filename></entry><entry><filename class="headerfile">ios</filename></entry><entry><filename class="headerfile">locale</filename></entry><entry><filename class="headerfile">queue</filename></entry><entry><filename class="headerfile">string</filename></entry></row> +<row><entry><filename class="headerfile">complex</filename></entry><entry><filename class="headerfile">iosfwd</filename></entry><entry><filename class="headerfile">map</filename></entry><entry><filename class="headerfile">set</filename></entry><entry><filename class="headerfile">typeinfo</filename></entry></row> +<row><entry><filename class="headerfile">deque</filename></entry><entry><filename class="headerfile">iostream</filename></entry><entry><filename class="headerfile">memory</filename></entry><entry><filename class="headerfile">sstream</filename></entry><entry><filename class="headerfile">utility</filename></entry></row> +<row><entry><filename class="headerfile">exception</filename></entry><entry><filename class="headerfile">istream</filename></entry><entry><filename class="headerfile">new</filename></entry><entry><filename class="headerfile">stack</filename></entry><entry><filename class="headerfile">valarray</filename></entry></row> +<row><entry><filename class="headerfile">fstream</filename></entry><entry><filename class="headerfile">iterator</filename></entry><entry><filename class="headerfile">numeric</filename></entry><entry><filename class="headerfile">stdexcept</filename></entry><entry><filename class="headerfile">vector</filename></entry></row> +<row><entry><filename class="headerfile">functional</filename></entry><entry><filename class="headerfile">limits</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para></para> +<table frame='all'> +<title>C++ 1998 Library Headers for C Library Facilities</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<tbody> +<row><entry><filename class="headerfile">cassert</filename></entry><entry><filename class="headerfile">ciso646</filename></entry><entry><filename class="headerfile">csetjmp</filename></entry><entry><filename class="headerfile">cstdio</filename></entry><entry><filename class="headerfile">ctime</filename></entry></row> +<row><entry><filename class="headerfile">cctype</filename></entry><entry><filename class="headerfile">climits</filename></entry><entry><filename class="headerfile">csignal</filename></entry><entry><filename class="headerfile">cstdlib</filename></entry><entry><filename class="headerfile">cwchar</filename></entry></row> +<row><entry><filename class="headerfile">cerrno</filename></entry><entry><filename class="headerfile">clocale</filename></entry><entry><filename class="headerfile">cstdarg</filename></entry><entry><filename class="headerfile">cstring</filename></entry><entry><filename class="headerfile">cwctype</filename></entry></row> +<row><entry><filename class="headerfile">cfloat</filename></entry><entry><filename class="headerfile">cmath</filename></entry><entry><filename class="headerfile">cstddef</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para>C++0x include files. These are only available in C++0x compilation mode, ie <code>-std=c++0x</code> or <code>-std=gnu++0x</code>. +</para> + +<para></para> +<table frame='all'> +<title>C++ 200x Library Headers</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<tbody> +<row><entry><filename class="headerfile">algorithm</filename></entry><entry><filename class="headerfile">iomanip</filename></entry><entry><filename class="headerfile">locale</filename></entry><entry><filename class="headerfile">regex</filename></entry><entry><filename class="headerfile">tuple</filename></entry></row> +<row><entry><filename class="headerfile">array</filename></entry><entry><filename class="headerfile">ios</filename></entry><entry><filename class="headerfile">map</filename></entry><entry><filename class="headerfile">set</filename></entry><entry><filename class="headerfile">typeinfo</filename></entry></row> +<row><entry><filename class="headerfile">bitset</filename></entry><entry><filename class="headerfile">iosfwd</filename></entry><entry><filename class="headerfile">memory</filename></entry><entry><filename class="headerfile">sstream</filename></entry><entry><filename class="headerfile">type_traits</filename></entry></row> +<row><entry><filename class="headerfile">complex</filename></entry><entry><filename class="headerfile">iostream</filename></entry><entry><filename class="headerfile">new</filename></entry><entry><filename class="headerfile">stack</filename></entry><entry><filename class="headerfile">unordered_map</filename></entry></row> +<row><entry><filename class="headerfile">deque</filename></entry><entry><filename class="headerfile">istream</filename></entry><entry><filename class="headerfile">numeric</filename></entry><entry><filename class="headerfile">stdexcept</filename></entry><entry><filename class="headerfile">unordered_set</filename></entry></row> +<row><entry><filename class="headerfile">exception</filename></entry><entry><filename class="headerfile">iterator</filename></entry><entry><filename class="headerfile">ostream</filename></entry><entry><filename class="headerfile">streambuf</filename></entry><entry><filename class="headerfile">utility</filename></entry></row> +<row><entry><filename class="headerfile">fstream</filename></entry><entry><filename class="headerfile">limits</filename></entry><entry><filename class="headerfile">queue</filename></entry><entry><filename class="headerfile">string</filename></entry><entry><filename class="headerfile">valarray</filename></entry></row> +<row><entry><filename class="headerfile">functional</filename></entry><entry><filename class="headerfile">list</filename></entry><entry><filename class="headerfile">random</filename></entry><entry><filename class="headerfile">system_error</filename></entry><entry><filename class="headerfile">vector</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para></para> + +<table frame='all'> +<title>C++ 200x Library Headers for C Library Facilities</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<colspec colname='c5'></colspec> +<tbody> +<row><entry><filename class="headerfile">cassert</filename></entry><entry><filename class="headerfile">cfloat</filename></entry><entry><filename class="headerfile">cmath</filename></entry><entry><filename class="headerfile">cstddef</filename></entry><entry><filename class="headerfile">ctgmath</filename></entry></row> +<row><entry><filename class="headerfile">ccomplex</filename></entry><entry><filename class="headerfile">cinttypes</filename></entry><entry><filename class="headerfile">csetjmp</filename></entry><entry><filename class="headerfile">cstdint</filename></entry><entry><filename class="headerfile">ctime</filename></entry></row> +<row><entry><filename class="headerfile">cctype</filename></entry><entry><filename class="headerfile">ciso646</filename></entry><entry><filename class="headerfile">csignal</filename></entry><entry><filename class="headerfile">cstdio</filename></entry><entry><filename class="headerfile">cuchar</filename></entry></row> +<row><entry><filename class="headerfile">cerrno</filename></entry><entry><filename class="headerfile">climits</filename></entry><entry><filename class="headerfile">cstdarg</filename></entry><entry><filename class="headerfile">cstdlib</filename></entry><entry><filename class="headerfile">cwchar</filename></entry></row> +<row><entry><filename class="headerfile">cfenv</filename></entry><entry><filename class="headerfile">clocale</filename></entry><entry><filename class="headerfile">cstdbool</filename></entry><entry><filename class="headerfile">cstring</filename></entry><entry><filename class="headerfile">cwctype</filename></entry></row> +</tbody> +</tgroup> +</table> + + +<para> + In addition, TR1 includes as: +</para> + +<table frame='all'> +<title>C++ TR1 Library Headers</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<colspec colname='c5'></colspec> +<tbody> + +<row><entry><filename class="headerfile">tr1/array</filename></entry><entry><filename class="headerfile">tr1/memory</filename></entry><entry><filename class="headerfile">tr1/regex</filename></entry><entry><filename class="headerfile">tr1/type_traits</filename></entry><entry><filename class="headerfile">tr1/unordered_set</filename></entry></row> +<row><entry><filename class="headerfile">tr1/complex</filename></entry><entry><filename class="headerfile">tr1/random</filename></entry><entry><filename class="headerfile">tr1/tuple</filename></entry><entry><filename class="headerfile">tr1/unordered_map</filename></entry><entry><filename class="headerfile">tr1/utility</filename></entry></row> +<row><entry><filename class="headerfile">tr1/functional</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para></para> + + +<table frame='all'> +<title>C++ TR1 Library Headers for C Library Facilities</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<colspec colname='c5'></colspec> +<tbody> + +<row><entry><filename class="headerfile">tr1/cmath</filename></entry><entry><filename class="headerfile">tr1/cfloat</filename></entry><entry><filename class="headerfile">tr1/cstdarg</filename></entry><entry><filename class="headerfile">tr1/cstdio</filename></entry><entry><filename class="headerfile">tr1/ctime</filename></entry></row> +<row><entry><filename class="headerfile">tr1/ccomplex</filename></entry><entry><filename class="headerfile">tr1/cinttypes</filename></entry><entry><filename class="headerfile">tr1/cstdbool</filename></entry><entry><filename class="headerfile">tr1/cstdlib</filename></entry><entry><filename class="headerfile">tr1/cwchar</filename></entry></row> +<row><entry><filename class="headerfile">tr1/cfenv</filename></entry><entry><filename class="headerfile">tr1/climits</filename></entry><entry><filename class="headerfile">tr1/cstdint</filename></entry><entry><filename class="headerfile">tr1/ctgmath</filename></entry><entry><filename class="headerfile">tr1/cwctype</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para> + Also included are files for the C++ ABI interface: +</para> + +<table frame='all'> +<title>C++ ABI Headers</title> +<tgroup cols='2' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<tbody> +<row><entry><filename class="headerfile">cxxabi.h</filename></entry><entry><filename class="headerfile">cxxabi_forced.h</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para> + And a large variety of extensions. +</para> + +<table frame='all'> +<title>Extension Headers</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<colspec colname='c5'></colspec> +<tbody> + +<row><entry><filename class="headerfile">ext/algorithm</filename></entry><entry><filename class="headerfile">ext/debug_allocator.h</filename></entry><entry><filename class="headerfile">ext/mt_allocator.h</filename></entry><entry><filename class="headerfile">ext/pod_char_traits.h</filename></entry><entry><filename class="headerfile">ext/stdio_sync_filebuf.h</filename></entry></row> +<row><entry><filename class="headerfile">ext/array_allocator.h</filename></entry><entry><filename class="headerfile">ext/enc_filebuf.h</filename></entry><entry><filename class="headerfile">ext/new_allocator.h</filename></entry><entry><filename class="headerfile">ext/pool_allocator.h</filename></entry><entry><filename class="headerfile">ext/throw_allocator.h</filename></entry></row> +<row><entry><filename class="headerfile">ext/atomicity.h</filename></entry><entry><filename class="headerfile">ext/functional</filename></entry><entry><filename class="headerfile">ext/numeric</filename></entry><entry><filename class="headerfile">ext/rb_tree</filename></entry><entry><filename class="headerfile">ext/typelist.h</filename></entry></row> +<row><entry><filename class="headerfile">ext/bitmap_allocator.h</filename></entry><entry><filename class="headerfile">ext/iterator</filename></entry><entry><filename class="headerfile">ext/numeric_traits.h</filename></entry><entry><filename class="headerfile">ext/rope</filename></entry><entry><filename class="headerfile">ext/type_traits.h</filename></entry></row> +<row><entry><filename class="headerfile">ext/codecvt_specializations.h</filename></entry><entry><filename class="headerfile">ext/malloc_allocator.h</filename></entry><entry><filename class="headerfile">ext/pb_ds/assoc_container.h</filename></entry><entry><filename class="headerfile">ext/slist</filename></entry><entry><filename class="headerfile">ext/vstring.h</filename></entry></row> +<row><entry><filename class="headerfile">ext/concurrence.h</filename></entry><entry><filename class="headerfile">ext/memory</filename></entry><entry><filename class="headerfile">ext/pb_ds/priority_queue.h</filename></entry><entry><filename class="headerfile">ext/stdio_filebuf.h</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para></para> + +<table frame='all'> +<title>Extension Debug Headers</title> +<tgroup cols='5' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<colspec colname='c3'></colspec> +<colspec colname='c4'></colspec> +<colspec colname='c5'></colspec> +<tbody> + +<row><entry><filename class="headerfile">debug/bitset</filename></entry><entry><filename class="headerfile">debug/list</filename></entry><entry><filename class="headerfile">debug/set</filename></entry><entry><filename class="headerfile">debug/unordered_map</filename></entry><entry><filename class="headerfile">debug/vector</filename></entry></row> +<row><entry><filename class="headerfile">debug/deque</filename></entry><entry><filename class="headerfile">debug/map</filename></entry><entry><filename class="headerfile">debug/string</filename></entry><entry><filename class="headerfile">debug/unordered_set</filename></entry></row> +</tbody> +</tgroup> +</table> + +<para></para> + +<table frame='all'> +<title>Extension Parallel Headers</title> +<tgroup cols='2' align='left' colsep='1' rowsep='1'> +<colspec colname='c1'></colspec> +<colspec colname='c2'></colspec> +<tbody> +<row><entry><filename class="headerfile">parallel/algorithm</filename></entry><entry><filename class="headerfile">parallel/numeric</filename></entry></row> +</tbody> +</tgroup> +</table> + + </sect2> + + <sect2 id="manual.intro.using.headers.mixing" xreflabel="Mixing Headers"> + <title>Mixing Headers</title> + +<para> A few simple rules. +</para> + +<para>First, mixing different dialects of the standard headers is not +possible. It's an all-or-nothing affair. Thus, code like +</para> + +<programlisting> +#include <array> +#include <functional> +</programlisting> + +<para>Implies C++0x mode. To use the entities in <array>, the C++0x +compilation mode must be used, which implies the C++0x functionality +(and deprecations) in <functional> will be present. +</para> + +<para>Second, the other headers can be included with either dialect of +the standard headers, although features and types specific to C++0x +are still only enabled when in C++0x compilation mode. So, to use +rvalue references with <code>__gnu_cxx::vstring</code>, or to use the +debug-mode versions of <code>std::unordered_map</code>, one must use +the <code>std=gnu++0x</code> compiler flag. (Or <code>std=c++0x</code>, of course.) +</para> + +<para>A special case of the second rule is the mixing of TR1 and C++0x +facilities. It is possible (although not especially prudent) to +include both the TR1 version and the C++0x version of header in the +same translation unit: +</para> + +<programlisting> +#include <tr1/type_traits> +#include <type_traits> +</programlisting> + +<para> Several parts of C++0x diverge quite substantially from TR1 predecessors. +</para> + </sect2> + + <sect2 id="manual.intro.using.headers.cheaders" xreflabel="C Headers and"> + <title>The C Headers and <code>namespace std</code></title> + +<para> + The standard specifies that if one includes the C-style header + (<math.h> in this case), the symbols will be available + in the global namespace and perhaps in + namespace <code>std::</code> (but this is no longer a firm + requirement.) One the other hand, including the C++-style + header (<cmath>) guarantees that the entities will be + found in namespace std and perhaps in the global namespace. + </para> + +<para> +Usage of C++-style headers is recommended, as then +C-linkage names can be disambiguated by explicit qualification, such +as by <code>std::abort</code>. In addition, the C++-style headers can +use function overloading to provide a simpler interface to certain +families of C-functions. For instance in <cmath>, the +function <code>std::sin</code> has overloads for all the builtin +floating-point types. This means that <code>std::sin</code> can be +used uniformly, instead of a combination +of <code>std::sinf</code>, <code>std::sin</code>, +and <code>std::sinl</code>. +</para> + </sect2> + + <sect2 id="manual.intro.using.headers.pre" xreflabel="Precompiled Headers"> + <title>Precompiled Headers</title> + + +<para>There are three base header files that are provided. They can be +used to precompile the standard headers and extensions into binary +files that may the be used to speed compiles that use these headers. +</para> + + +<itemizedlist> +<listitem> + <para>stdc++.h</para> +<para>Includes all standard headers. Actual content varies depending on +language dialect. +</para> +</listitem> + +<listitem> + <para>stdtr1c++.h</para> +<para>Includes all of <stdc++.h>, and adds all the TR1 headers. +</para> +</listitem> + +<listitem><para>extc++.h</para> +<para>Includes all of <stdtr1c++.h>, and adds all the Extension headers. +</para></listitem> +</itemizedlist> + +<para>How to construct a .gch file from one of these base header files.</para> + +<para>First, find the include directory for the compiler. One way to do +this is:</para> + +<programlisting> +g++ -v hello.cc + +#include <...> search starts here: + /mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0 +... +End of search list. +</programlisting> + + +<para>Then, create a precompiled header file with the same flags that +will be used to compile other projects.</para> + +<programlisting> +g++ -Winvalid-pch -x c++-header -g -O2 -o ./stdc++.h.gch /mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0/x86_64-unknown-linux-gnu/bits/stdc++.h +</programlisting> + +<para>The resulting file will be quite large: the current size is around +thirty megabytes. </para> + +<para>How to use the resulting file.</para> + +<programlisting> +g++ -I. -include stdc++.h -H -g -O2 hello.cc +</programlisting> + +<para>Verification that the PCH file is being used is easy:</para> + +<programlisting> +g++ -Winvalid-pch -I. -include stdc++.h -H -g -O2 hello.cc -o test.exe +! ./stdc++.h.gch +. /mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0/iostream +. /mnt/share/bld/H-x86-gcc.20071201include/c++/4.3.0/string +</programlisting> + +<para>The exclamation point to the left of the <code>stdc++.h.gch</code> listing means that the generated PCH file was used, and thus the </para> +<para></para> + +<para> Detailed information about creating precompiled header files can be found in the GCC <ulink url="http://gcc.gnu.org/onlinedocs/gcc/Precompiled-Headers.html">documentation</ulink>. +</para> + + + </sect2> + </sect1> + + <sect1 id="manual.intro.using.namespaces" xreflabel="Namespaces"> + <title>Namespaces</title> + + <sect2 id="manual.intro.using.namespaces.all" xreflabel="Available Namespaces"> + <title>Available Namespaces</title> + + + +<para> There are three main namespaces. +</para> + +<itemizedlist> + <listitem><para>std</para> +<para>The ISO C++ standards specify that "all library entities are defined +within namespace std." This includes namepaces nested +within <code>namespace std</code>, such as <code>namespace +std::tr1</code>. +</para> +</listitem> +<listitem><para>abi</para> +<para>Specified by the C++ ABI. This ABI specifies a number of type and +function APIs supplemental to those required by the ISO C++ Standard, +but necessary for interoperability. +</para> +</listitem> + +<listitem><para>__gnu_</para> +<para>Indicating one of several GNU extensions. Choices +include <code>__gnu_cxx</code>, <code>__gnu_debug</code>, <code>__gnu_parallel</code>, +and <code>__gnu_pbds</code>. +</para></listitem> +</itemizedlist> + +<para> A complete list of implementation namespaces (including namespace contents) is available in the generated source <ulink url="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/namespaces.html">documentation</ulink>. +</para> + + + </sect2> + + <sect2 id="manual.intro.using.namespaces.std" xreflabel="namespace std"> + <title>namespace std</title> + + +<para> + One standard requirement is that the library components are defined + in <code>namespace std::</code>. Thus, in order to use these types or + functions, one must do one of two things: +</para> + +<itemizedlist> + <listitem><para>put a kind of <emphasis>using-declaration</emphasis> in your source +(either <code>using namespace std;</code> or i.e. <code>using +std::string;</code>) This approach works well for individual source files, but +should not be used in a global context, like header files. + </para></listitem> <listitem><para>use a <emphasis>fully +qualified name</emphasis>for each library symbol +(i.e. <code>std::string</code>, <code>std::cout</code>) Always can be +used, and usually enhanced, by strategic use of typedefs. (In the +cases where the qualified verbiage becomes unwieldy.) + </para> + </listitem> +</itemizedlist> + + </sect2> + + <sect2 id="manual.intro.using.namespaces.comp" xreflabel="Using Namepace Composition"> + <title>Using Namespace Composition</title> + +<para> +Best practice in programming suggests sequestering new data or +functionality in a sanely-named, unique namespace whenever +possible. This is considered an advantage over dumping everything in +the global namespace, as then name look-up can be explicitly enabled or +disabled as above, symbols are consistently mangled without repetitive +naming prefixes or macros, etc. +</para> + +<para>For instance, consider a project that defines most of its classes in <code>namespace gtk</code>. It is possible to + adapt <code>namespace gtk</code> to <code>namespace std</code> by using a C++-feature called + <emphasis>namespace composition</emphasis>. This is what happens if + a <emphasis>using</emphasis>-declaration is put into a + namespace-definition: the imported symbol(s) gets imported into the + currently active namespace(s). For example: +</para> +<programlisting> +namespace gtk +{ + using std::string; + using std::tr1::array; + + class Window { ... }; +} +</programlisting> +<para> + In this example, <code>std::string</code> gets imported into + <code>namespace gtk</code>. The result is that use of + <code>std::string</code> inside namespace gtk can just use <code>string</code>, without the explicit qualification. + As an added bonus, + <code>std::string</code> does not get imported into + the global namespace. Additionally, a more elaborate arrangement can be made for backwards compatibility and portability, whereby the + <code>using</code>-declarations can wrapped in macros that + are set based on autoconf-tests to either "" or i.e. <code>using + std::string;</code> (depending on whether the system has + libstdc++ in <code>std::</code> or not). (ideas from + <email>llewelly@dbritsch.dsl.xmission.com</email>, Karl Nelson <email>kenelson@ece.ucdavis.edu</email>) +</para> + + + </sect2> + </sect1> + + <sect1 id="manual.intro.using.macros" xreflabel="Macros"> + <title>Macros</title> + + <para>All pre-processor switches and configurations are all gathered + in the file <code>c++config.h</code>, which is generated during + the libstdc++ configuration and build process, and included by + files part of the public libstdc++ API. Most of these macros + should not be used by consumers of libstdc++, and are reserved + for internal implementation use. <emphasis>These macros cannot be + redefined</emphasis>. However, a select handful of these macro + control libstdc++ extensions and extra features, or provide + versioning information for the API, and are able to be used. + </para> + + <para>All library macros begin with <code>_GLIBCXX_</code> (except for + versions 3.1.x to 3.3.x, which use <code>_GLIBCPP_</code>). + </para> + + <para>Below is the macro which users may check for library version + information. </para> + + <variablelist> + <varlistentry> + <term><code>__GLIBCXX__</code></term> + <listitem> + <para>The current version of + libstdc++ in compressed ISO date format, form of an unsigned + long. For details on the value of this particular macro for a + particular release, please consult this <ulink url="abi.html"> + document</ulink>. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para>Below are the macros which users may change with #define/#undef or + with -D/-U compiler flags. The default state of the symbol is + listed.</para> + + <para><quote>Configurable</quote> (or <quote>Not configurable</quote>) means + that the symbol is initially chosen (or not) based on + --enable/--disable options at library build and configure time + (documented <link linkend="manual.intro.setup.configure">here</link>), with the + various --enable/--disable choices being translated to + #define/#undef). + </para> + + <para> <acronym>ABI</acronym> means that changing from the default value may + mean changing the <acronym>ABI</acronym> of compiled code. In other words, these + choices control code which has already been compiled (i.e., in a + binary such as libstdc++.a/.so). If you explicitly #define or + #undef these macros, the <emphasis>headers</emphasis> may see different code + paths, but the <emphasis>libraries</emphasis> which you link against will not. + Experimenting with different values with the expectation of + consistent linkage requires changing the config headers before + building/installing the library. + </para> + + <variablelist> + <varlistentry><term><code>_GLIBCXX_DEPRECATED</code></term> + <listitem> + <para> + Defined by default. Not configurable. ABI-changing. Turning this off + removes older ARM-style iostreams code, and other anachronisms + from the API. This macro is dependent on the version of the + standard being tracked, and as a result may give different results for + <code>-std=c++98</code> and <code>-std=c++0x</code>. This may + be useful in updating old C++ code which no longer meet the + requirements of the language, or for checking current code + against new language standards. + </para> + </listitem></varlistentry> + + <varlistentry><term><code>_GLIBCXX_FORCE_NEW</code></term> + <listitem> + <para> + Undefined by default. When defined, memory allocation and + allocators controlled by libstdc++ call operator new/delete + without caching and pooling. Configurable via + <code>--enable-libstdcxx-allocator</code>. ABI-changing. + </para> + </listitem></varlistentry> + + + <varlistentry><term><code>_GLIBCXX_CONCEPT_CHECKS</code></term> + <listitem> + <para> + Undefined by default. Configurable via + <code>--enable-concept-checks</code>. When defined, performs + compile-time checking on certain template instantiations to + detect violations of the requirements of the standard. This + is described in more detail <ulink + url="../19_diagnostics/howto.html#3">here</ulink>. + </para> + </listitem></varlistentry> + + <varlistentry><term><code>_GLIBCXX_DEBUG</code></term> + <listitem> + <para> + Undefined by default. When defined, compiles + user code using the <ulink url="../ext/debug.html#safe">libstdc++ debug + mode</ulink>. + </para> + </listitem></varlistentry> + <varlistentry><term><code>_GLIBCXX_DEBUG_PEDANTIC</code></term> + <listitem> + <para> + Undefined by default. When defined while + compiling with the <ulink url="../ext/debug.html#safe">libstdc++ debug + mode</ulink>, makes the debug mode extremely picky by making the use + of libstdc++ extensions and libstdc++-specific behavior into + errors. + </para> + </listitem></varlistentry> + <varlistentry><term><code>_GLIBCXX_PARALLEL</code></term> + <listitem> + <para>Undefined by default. When defined, compiles + user code using the <ulink url="../ext/parallel_mode.html">libstdc++ parallel + mode</ulink>. + </para> + </listitem></varlistentry> + </variablelist> + + + </sect1> + + <sect1 id="manual.intro.using.concurrency" xreflabel="Concurrency"> + <title>Concurrency</title> + + <para>This section discusses issues surrounding the proper compilation + of multithreaded applications which use the Standard C++ + library. This information is GCC-specific since the C++ + standard does not address matters of multithreaded applications. + </para> + + <sect2 id="manual.intro.using.concurrency.prereq" xreflabel="Thread Prereq"> + <title>Prerequisites</title> + + <para>All normal disclaimers aside, multithreaded C++ application are + only supported when libstdc++ and all user code was built with + compilers which report (via <code> gcc/g++ -v </code>) the same thread + model and that model is not <emphasis>single</emphasis>. As long as your + final application is actually single-threaded, then it should be + safe to mix user code built with a thread model of + <emphasis>single</emphasis> with a libstdc++ and other C++ libraries built + with another thread model useful on the platform. Other mixes + may or may not work but are not considered supported. (Thus, if + you distribute a shared C++ library in binary form only, it may + be best to compile it with a GCC configured with + --enable-threads for maximal interchangeability and usefulness + with a user population that may have built GCC with either + --enable-threads or --disable-threads.) + </para> + <para>When you link a multithreaded application, you will probably + need to add a library or flag to g++. This is a very + non-standardized area of GCC across ports. Some ports support a + special flag (the spelling isn't even standardized yet) to add + all required macros to a compilation (if any such flags are + required then you must provide the flag for all compilations not + just linking) and link-library additions and/or replacements at + link time. The documentation is weak. Here is a quick summary + to display how ad hoc this is: On Solaris, both -pthreads and + -threads (with subtly different meanings) are honored. On OSF, + -pthread and -threads (with subtly different meanings) are + honored. On Linux/i386, -pthread is honored. On FreeBSD, + -pthread is honored. Some other ports use other switches. + AFAIK, none of this is properly documented anywhere other than + in ``gcc -dumpspecs'' (look at lib and cpp entries). + </para> + + </sect2> + + <sect2 id="manual.intro.using.concurrency.thread_safety" xreflabel="Thread Safety"> + <title>Thread Safety</title> + + +<para> +We currently use the <ulink url="http://www.sgi.com/tech/stl/thread_safety.html">SGI STL</ulink> definition of thread safety. +</para> + + + <para>The library strives to be thread-safe when all of the following + conditions are met: + </para> + <itemizedlist> + <listitem> + <para>The system's libc is itself thread-safe, + </para> + </listitem> + <listitem> + <para> + The compiler in use reports a thread model other than + 'single'. This can be tested via output from <code>gcc + -v</code>. Multi-thread capable versions of gcc output + something like this: + </para> +<programlisting> +%gcc -v +Using built-in specs. +... +Thread model: posix +gcc version 4.1.2 20070925 (Red Hat 4.1.2-33) +</programlisting> + +<para>Look for "Thread model" lines that aren't equal to "single."</para> + </listitem> + <listitem> + <para> + Requisite command-line flags are used for atomic operations + and threading. Examples of this include <code>-pthread</code> + and <code>-march=native</code>, although specifics vary + depending on the host environment. See <ulink + url="http://gcc.gnu.org/onlinedocs/gcc/Option-Summary.html">Machine + Dependent Options</ulink>. + </para> + </listitem> + <listitem> + <para> + An implementation of atomicity.h functions + exists for the architecture in question. See the internals documentation for more <ulink url="../ext/concurrence.html">details</ulink>. + </para> + </listitem> + + </itemizedlist> + <para>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: + </para> + <programlisting> + library_class_a shared_object_a; + + thread_main () { + library_class_b *object_b = new library_class_b; + shared_object_a.add_b (object_b); // must hold lock for shared_object_a + shared_object_a.mutate (); // must hold lock for shared_object_a + } + + // Multiple copies of thread_main() are started in independent threads.</programlisting> + <para>Under the assumption that object_a and object_b are never exposed to + another thread, here is an example that should not require any + user-level locks: + </para> + <programlisting> + thread_main () { + library_class_a object_a; + library_class_b *object_b = new library_class_b; + object_a.add_b (object_b); + object_a.mutate (); + } </programlisting> + <para>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, 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. + </para> + <para>See chapters <ulink url="../17_intro/howto.html#3">17</ulink> (library + introduction), <ulink url="../23_containers/howto.html#3">23</ulink> + (containers), and <ulink url="../27_io/howto.html#9">27</ulink> (I/O) for + more information. + </para> + + + </sect2> + <sect2 id="manual.intro.using.concurrency.atomics" xreflabel="Atomics"> + <title>Atomics</title> + <para> + </para> + </sect2> + + <sect2 id="manual.intro.using.concurrency.io" xreflabel="IO"> + <title>IO</title> + <para>I'll assume that you have already read the + <ulink url="../17_intro/howto.html#3">general notes on library threads</ulink>, + and the + <ulink url="../23_containers/howto.html#3">notes on threaded container + access</ulink> (you might not think of an I/O stream as a container, but + the points made there also hold here). If you have not read them, + please do so first. + </para> + <para>This gets a bit tricky. Please read carefully, and bear with me. + </para> + + <sect3 id="concurrency.io.structure" xreflabel="Structure"> + <title>Structure</title> + <para>A wrapper + type called <code>__basic_file</code> provides our abstraction layer + for the <code>std::filebuf</code> classes. Nearly all decisions dealing + with actual input and output must be made in <code>__basic_file</code>. + </para> + <para>A generic locking mechanism is somewhat in place at the filebuf layer, + but is not used in the current code. Providing locking at any higher + level is akin to providing locking within containers, and is not done + for the same reasons (see the links above). + </para> + </sect3> + + <sect3 id="concurrency.io.defaults" xreflabel="Defaults"> + <title>Defaults</title> + <para>The __basic_file type is simply a collection of small wrappers around + the C stdio layer (again, see the link under Structure). We do no + locking ourselves, but simply pass through to calls to <code>fopen</code>, + <code>fwrite</code>, and so forth. + </para> + <para>So, for 3.0, the question of "is multithreading safe for I/O" + must be answered with, "is your platform's C library threadsafe + for I/O?" Some are by default, some are not; many offer multiple + implementations of the C library with varying tradeoffs of threadsafety + and efficiency. You, the programmer, are always required to take care + with multiple threads. + </para> + <para>(As an example, the POSIX standard requires that C stdio FILE* + operations are atomic. POSIX-conforming C libraries (e.g, on Solaris + and GNU/Linux) have an internal mutex to serialize operations on + FILE*s. However, you still need to not do stupid things like calling + <code>fclose(fs)</code> in one thread followed by an access of + <code>fs</code> in another.) + </para> + <para>So, if your platform's C library is threadsafe, then your + <code>fstream</code> I/O operations will be threadsafe at the lowest + level. For higher-level operations, such as manipulating the data + contained in the stream formatting classes (e.g., setting up callbacks + inside an <code>std::ofstream</code>), you need to guard such accesses + like any other critical shared resource. + </para> + </sect3> + + <sect3 id="concurrency.io.future" xreflabel="Future"> + <title>Future</title> + <para> A + second choice may be available for I/O implementations: libio. This is + disabled by default, and in fact will not currently work due to other + issues. It will be revisited, however. + </para> + <para>The libio code is a subset of the guts of the GNU libc (glibc) I/O + implementation. When libio is in use, the <code>__basic_file</code> + type is basically derived from FILE. (The real situation is more + complex than that... it's derived from an internal type used to + implement FILE. See libio/libioP.h to see scary things done with + vtbls.) The result is that there is no "layer" of C stdio + to go through; the filebuf makes calls directly into the same + functions used to implement <code>fread</code>, <code>fwrite</code>, + and so forth, using internal data structures. (And when I say + "makes calls directly," I mean the function is literally + replaced by a jump into an internal function. Fast but frightening. + *grin*) + </para> + <para>Also, the libio internal locks are used. This requires pulling in + large chunks of glibc, such as a pthreads implementation, and is one + of the issues preventing widespread use of libio as the libstdc++ + cstdio implementation. + </para> + <para>But we plan to make this work, at least as an option if not a future + default. Platforms running a copy of glibc with a recent-enough + version will see calls from libstdc++ directly into the glibc already + installed. For other platforms, a copy of the libio subsection will + be built and included in libstdc++. + </para> + </sect3> + + <sect3 id="concurrency.io.alt" xreflabel="Alt"> + <title>Alternatives</title> + <para>Don't forget that other cstdio implementations are possible. You could + easily write one to perform your own forms of locking, to solve your + "interesting" problems. + </para> + </sect3> + + </sect2> + + <sect2 id="manual.intro.using.concurrency.containers" xreflabel="Containers"> + <title>Containers</title> + + <para>This section discusses issues surrounding the design of + multithreaded applications which use Standard C++ containers. + All information in this section is current as of the gcc 3.0 + release and all later point releases. Although earlier gcc + releases had a different approach to threading configuration and + proper compilation, the basic code design rules presented here + were similar. For information on all other aspects of + multithreading as it relates to libstdc++, including details on + the proper compilation of threaded code (and compatibility between + threaded and non-threaded code), see Chapter 17. + </para> + <para>Two excellent pages to read when working with the Standard C++ + containers and threads are + <ulink url="http://www.sgi.com/tech/stl/thread_safety.html">SGI's + http://www.sgi.com/tech/stl/thread_safety.html</ulink> and + <ulink url="http://www.sgi.com/tech/stl/Allocators.html">SGI's + http://www.sgi.com/tech/stl/Allocators.html</ulink>. + </para> + <para><emphasis>However, please ignore all discussions about the user-level + configuration of the lock implementation inside the STL + container-memory allocator on those pages. For the sake of this + discussion, libstdc++ configures the SGI STL implementation, + not you. This is quite different from how gcc pre-3.0 worked. + In particular, past advice was for people using g++ to + explicitly define _PTHREADS or other macros or port-specific + compilation options on the command line to get a thread-safe + STL. This is no longer required for any port and should no + longer be done unless you really know what you are doing and + assume all responsibility.</emphasis> + </para> + <para>Since the container implementation of libstdc++ uses the SGI + code, we use the same definition of thread safety as SGI when + discussing design. A key point that beginners may miss is the + fourth major paragraph of the first page mentioned above + ("For most clients,"...), which points out that + locking must nearly always be done outside the container, by + client code (that'd be you, not us). There is a notable + exceptions to this rule. Allocators called while a container or + element is constructed uses an internal lock obtained and + released solely within libstdc++ code (in fact, this is the + reason STL requires any knowledge of the thread configuration). + </para> + <para>For implementing a container which does its own locking, it is + trivial to provide a wrapper class which obtains the lock (as + SGI suggests), performs the container operation, and then + releases the lock. This could be templatized <emphasis>to a certain + extent</emphasis>, on the underlying container and/or a locking + mechanism. Trying to provide a catch-all general template + solution would probably be more trouble than it's worth. + </para> + <para>The STL implementation is currently configured to use the + high-speed caching memory allocator. Some people like to + test and/or normally run threaded programs with a different + default. For all details about how to globally override this + at application run-time see <ulink url="../ext/howto.html#3">here</ulink>. + </para> + <para>There is a better way (not standardized yet): It is possible to + force the malloc-based allocator on a per-case-basis for some + application code. The library team generally believes that this + is a better way to tune an application for high-speed using this + implementation of the STL. There is + <ulink url="../ext/howto.html#3">more information on allocators here</ulink>. + </para> + + </sect2> + </sect1> + + <sect1 id="manual.intro.using.exception_safety" xreflabel="Exception Safety"> + <title>Exception Safety</title> + <para></para> + </sect1> + +<!-- Section 0x : Debug --> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + parse="xml" href="debug.xml"> +</xi:include> + +</chapter> |