1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html 3 PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 4 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 5 6<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 7<head> 8 <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" /> 9 <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++" /> 10 <meta name="DESCRIPTION" content="Explanatory notes about libstdc++-v3." /> 11 <meta name="GENERATOR" content="vi and eight fingers" /> 12 <title>Explanatory notes about libstdc++-v3 design</title> 13<link rel="StyleSheet" href="lib3styles.css" type="text/css" /> 14<link rel="Copyright" href="17_intro/license.html" type="text/html" /> 15</head> 16<body> 17 18<h1 class="centered"><a name="top">Explanatory notes about libstdc++-v3 19design</a></h1> 20 21<p class="fineprint"><em> 22 The latest version of this document is always available at 23 <a href="http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html"> 24 http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html</a>. 25</em></p> 26 27<p><em> 28 To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>. 29</em></p> 30 31 32<!-- ####################################################### --> 33<hr /> 34<h3><a name="cstdio">"I/O packages", <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 "FILE*") 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>. 72</p> 73 74 75<!-- ####################################################### --> 76 77<hr /> 78<p class="fineprint"><em> 79See <a href="17_intro/license.html">license.html</a> for copying conditions. 80Comments 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> 83 84 85</body> 86</html> 87