<?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" /> <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++" /> <meta name="DESCRIPTION" content="Explanatory notes about libstdc++-v3." /> <meta name="GENERATOR" content="vi and eight fingers" /> <title>Explanatory notes about libstdc++-v3 design</title> <link rel="StyleSheet" href="lib3styles.css" type="text/css" /> <link rel="Copyright" href="17_intro/license.html" type="text/html" /> </head> <body> <h1 class="centered"><a name="top">Explanatory notes about libstdc++-v3 design</a></h1> <p class="fineprint"><em> The latest version of this document is always available at <a href="http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html"> http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html</a>. </em></p> <p><em> To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>. </em></p> <!-- ####################################################### --> <hr /> <h3><a name="cstdio">"I/O packages", <code>--enable-cstdio</code></a></h3> <p>In addition to all the nifty things which C++ can do for I/O, its library also includes all of the I/O capabilites of C. Making them work together can be a challenge, not only <a href="27_io/howto.html#8">for the programmer</a> but for the implementors as well. </p> <p>There are two ways to do a C++ library: the cool way, and the easy way. More specifically, the cool-but-easy-to-get-wrong way, and the easy-to-guarantee-correct-behavior way. For 3.0, the easy way is used. </p> <p>Choosing 'stdio' is the easy way. It builds a C++ library which forwards all operations to the C library. Many of the C++ I/O functions are specified in the standard 'as if' they called a certain C function; the easiest way to get it correct is to actually call that function. The disadvantage is that the C++ code will run slower (fortunately, the layer is thin). </p> <p>Other packages are possible. For a new package, a header must be written to provide types like streamsize (usually just a typedef), as well as some internal types like<code> __c_file_type </code> and <code> __c_lock </code> (for the stdio case, these are FILE (as in "FILE*") and a simple POSIX mutex, respectively). An interface class called <code> __basic_file </code> must also be filled in; as an example, for the stdio case, these member functions are all inline calles to fread, fwrite, etc. </p> <p>Return <a href="#top">to the top of the page</a> or <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>. </p> <hr /> <h3><a name="alloc">Internal Allocators</a></h3> <p> </p> <p>Return <a href="#top">to the top of the page</a> or <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>. </p> <!-- ####################################################### --> <hr /> <p class="fineprint"><em> See <a href="17_intro/license.html">license.html</a> for copying conditions. Comments and suggestions are welcome, and may be sent to <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>. </em></p> </body> </html>