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diff --git a/gcc-4.4.3/libstdc++-v3/doc/html/manual/auto_ptr.html b/gcc-4.4.3/libstdc++-v3/doc/html/manual/auto_ptr.html new file mode 100644 index 000000000..9da480093 --- /dev/null +++ b/gcc-4.4.3/libstdc++-v3/doc/html/manual/auto_ptr.html @@ -0,0 +1,90 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!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"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>auto_ptr</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content=" ISO C++ , auto_ptr " /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="memory.html" title="Chapter 11. Memory" /><link rel="prev" href="memory.html" title="Chapter 11. Memory" /><link rel="next" href="shared_ptr.html" title="shared_ptr" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">auto_ptr</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="memory.html">Prev</a> </td><th width="60%" align="center">Chapter 11. Memory</th><td width="20%" align="right"> <a accesskey="n" href="shared_ptr.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.util.memory.auto_ptr"></a>auto_ptr</h2></div></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="auto_ptr.limitations"></a>Limitations</h3></div></div></div><p>Explaining all of the fun and delicious things that can + happen with misuse of the <code class="classname">auto_ptr</code> class + template (called <acronym class="acronym">AP</acronym> here) would take some + time. Suffice it to say that the use of <acronym class="acronym">AP</acronym> + safely in the presence of copying has some subtleties. + </p><p> + The AP class is a really + nifty idea for a smart pointer, but it is one of the dumbest of + all the smart pointers -- and that's fine. + </p><p> + AP is not meant to be a supersmart solution to all resource + leaks everywhere. Neither is it meant to be an effective form + of garbage collection (although it can help, a little bit). + And it can <span class="emphasis"><em>not</em></span>be used for arrays! + </p><p> + <acronym class="acronym">AP</acronym> is meant to prevent nasty leaks in the + presence of exceptions. That's <span class="emphasis"><em>all</em></span>. This + code is AP-friendly: + </p><pre class="programlisting"> + // Not a recommend naming scheme, but good for web-based FAQs. + typedef std::auto_ptr<MyClass> APMC; + + extern function_taking_MyClass_pointer (MyClass*); + extern some_throwable_function (); + + void func (int data) + { + APMC ap (new MyClass(data)); + + some_throwable_function(); // this will throw an exception + + function_taking_MyClass_pointer (ap.get()); + } + </pre><p>When an exception gets thrown, the instance of MyClass that's + been created on the heap will be <code class="function">delete</code>'d as the stack is + unwound past <code class="function">func()</code>. + </p><p>Changing that code as follows is not <acronym class="acronym">AP</acronym>-friendly: + </p><pre class="programlisting"> + APMC ap (new MyClass[22]); + </pre><p>You will get the same problems as you would without the use + of <acronym class="acronym">AP</acronym>: + </p><pre class="programlisting"> + char* array = new char[10]; // array new... + ... + delete array; // ...but single-object delete + </pre><p> + AP cannot tell whether the pointer you've passed at creation points + to one or many things. If it points to many things, you are about + to die. AP is trivial to write, however, so you could write your + own <code class="code">auto_array_ptr</code> for that situation (in fact, this has + been done many times; check the mailing lists, Usenet, Boost, etc). + </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="auto_ptr.using"></a>Use in Containers</h3></div></div></div><p> + </p><p>All of the <a class="ulink" href="../23_containers/howto.html" target="_top">containers</a> + described in the standard library require their contained types + to have, among other things, a copy constructor like this: + </p><pre class="programlisting"> + struct My_Type + { + My_Type (My_Type const&); + }; + </pre><p> + Note the const keyword; the object being copied shouldn't change. + The template class <code class="code">auto_ptr</code> (called AP here) does not + meet this requirement. Creating a new AP by copying an existing + one transfers ownership of the pointed-to object, which means that + the AP being copied must change, which in turn means that the + copy ctors of AP do not take const objects. + </p><p> + The resulting rule is simple: <span class="emphasis"><em>Never ever use a + container of auto_ptr objects</em></span>. The standard says that + “<span class="quote">undefined</span>” behavior is the result, but it is + guaranteed to be messy. + </p><p> + To prevent you from doing this to yourself, the + <a class="ulink" href="../19_diagnostics/howto.html#3" target="_top">concept checks</a> built + in to this implementation will issue an error if you try to + compile code like this: + </p><pre class="programlisting"> + #include <vector> + #include <memory> + + void f() + { + std::vector< std::auto_ptr<int> > vec_ap_int; + } + </pre><p> +Should you try this with the checks enabled, you will see an error. + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="memory.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="memory.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="shared_ptr.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 11. 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