libstdc++-v3/docs/html/explanations.html

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   8    <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" />
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  10    <meta name="DESCRIPTION" content="Explanatory notes about libstdc++-v3." />
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  12    <title>Explanatory notes about libstdc++-v3 design</title>
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  18 <h1 class="centered"><a name="top">Explanatory notes about libstdc++-v3
  19 design</a></h1>
  20
  21 <p class="fineprint"><em>
  22    The latest version of this document is always available at
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  24    http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html</a>.
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  28    To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
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  34 <h3><a name="cstdio">&quot;I/O packages&quot;, <code>--enable-cstdio</code></a></h3>
  35 <p>In addition to all the nifty things which C++ can do for I/O, its library
  36    also includes all of the I/O capabilites of C.  Making them work together
  37    can be a challenge, not only
  38    <a href="27_io/howto.html#8">for the programmer</a> but for the
  39    implementors as well.
  40 </p>
  41 <p>There are two ways to do a C++ library:  the cool way, and the easy way.
  42    More specifically, the cool-but-easy-to-get-wrong way, and the
  43    easy-to-guarantee-correct-behavior way.  For 3.0, the easy way is used.
  44 </p>
  45 <p>Choosing 'stdio' is the easy way.  It builds a C++ library which forwards
  46    all operations to the C library.  Many of the C++ I/O functions are
  47    specified in the standard 'as if' they called a certain C function; the
  48    easiest way to get it correct is to actually call that function.  The
  49    disadvantage is that the C++ code will run slower (fortunately, the layer
  50    is thin).
  51 </p>
  52 <p>Other packages are possible.  For a new package, a header must be
  53    written to provide types like streamsize (usually just a typedef), as
  54    well as some internal types like<code> __c_file_type </code> and
  55    <code> __c_lock </code> (for the stdio case, these are FILE (as in
  56    &quot;FILE*&quot;) and a simple POSIX mutex, respectively).  An
  57    interface class called <code> __basic_file </code> must also be filled in;
  58    as an example, for the stdio case, these member functions are all
  59    inline calles to fread, fwrite, etc.
  60 </p>
  61 <p>Return <a href="#top">to the top of the page</a> or
  62    <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>.
  63 </p>
  64
  65
  66 <hr />
  67 <h3><a name="alloc">Internal Allocators</a></h3>
  68 <p>
  69 </p>
  70 <p>Return <a href="#top">to the top of the page</a> or
  71    <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>.
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  79 See <a href="17_intro/license.html">license.html</a> for copying conditions.
  80 Comments and suggestions are welcome, and may be sent to
  81 <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.
  82 </em></p>
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