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authorbkoz <bkoz@138bc75d-0d04-0410-961f-82ee72b054a4>2008-02-11 00:01:33 +0000
committerbkoz <bkoz@138bc75d-0d04-0410-961f-82ee72b054a4>2008-02-11 00:01:33 +0000
commit2aad0282e79bee5d49dfd0f76d5c72f6c6912156 (patch)
tree9c37bc44363d015d83f53e9ff733daf4affc1973 /libstdc++-v3/doc/xml/manual/auto_ptr.xml
parent90a6366aaa90e4e3c7bf9af1b57df621241589a0 (diff)
downloadppe42-gcc-2aad0282e79bee5d49dfd0f76d5c72f6c6912156.tar.gz
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2008-02-10 Benjamin Kosnik <bkoz@redhat.com>
Convert documentation to DocBook. * doc/Makefile.am (doc-doxygen-html): Changed to doc-html-doxygen. (doc-doxygen-man): Changed to doc-man-doxygen. (doc-performance): Changed to doc-html-performance. (doc-xml-doxygen): New. (doc-xml-single): New. (doc-xml-validate): New. (doc-html): New. (doc-html-single): New. (doc-fo): New. (doc-pdf): New. (doc-pdf-fop-xml): New. (doc-pdf-fop-fo): New. (doc-pdf-xmlto): New. (doc-pdf-xmlroff): New. (doc-pdf-prince): New. * doc/xml: New directory. * doc/xml/authors.xml: New. * doc/xml/images: New directory. * doc/xml/images/confdeps.png: Add. * doc/xml/images/confdeps.dot: Add. * doc/xml/faq.xml: New. * doc/xml/api.xml: New. * doc/xml/gnu: New directory. * doc/xml/gnu/gpl-3.0.xml: New. * doc/xml/gnu/fdl-1.2.xml: New. * doc/xml/gnu/gpl-2.0.xml: New. * doc/xml/manual: New directory. * doc/xml/manual/mt_allocator.xml: New. * doc/xml/manual/allocator.xml: New. * doc/xml/manual/ctype.xml: New. * doc/xml/manual/numerics.xml: New. * doc/xml/manual/codecvt.xml: New. * doc/xml/manual/concurrency.xml: New. * doc/xml/manual/backwards_compatibility.xml: New. * doc/xml/manual/intro.xml: New. * doc/xml/manual/shared_ptr.xml: New. * doc/xml/manual/abi.xml: New. * doc/xml/manual/status_cxxtr1.xml: New. * doc/xml/manual/auto_ptr.xml: New. * doc/xml/manual/build.xml: New. * doc/xml/manual/internals.xml: New. * doc/xml/manual/parallel_mode.xml: New. * doc/xml/manual/status_cxx1998.xml: New. * doc/xml/manual/containers.xml: New. * doc/xml/manual/io.xml: New. * doc/xml/manual/appendix_porting.xml: New. * doc/xml/manual/utilities.xml: New. * doc/xml/manual/bitmap_allocator.xml: New. * doc/xml/manual/support.xml: New. * doc/xml/manual/configure.xml: New. * doc/xml/manual/build_hacking.xml: New. * doc/xml/manual/evolution.xml: New. * doc/xml/manual/using.xml: New. * doc/xml/manual/debug.xml: New. * doc/xml/manual/localization.xml: New. * doc/xml/manual/strings.xml: New. * doc/xml/manual/debug_mode.xml: New. * doc/xml/manual/locale.xml: New. * doc/xml/manual/extensions.xml: New. * doc/xml/manual/appendix_contributing.xml: New. * doc/xml/manual/messages.xml: New. * doc/xml/manual/diagnostics.xml: New. * doc/xml/manual/appendix_free.xml: New. * doc/xml/manual/algorithms.xml: New. * doc/xml/manual/iterators.xml: New. * doc/xml/manual/spine.xml: New. * doc/xml/manual/test.xml: New. * doc/xml/manual/status_cxx200x.xml: New. * doc/xml/spine.xml: New. * doc/xml/book.txml: New. Template file. * doc/xml/chapter.txml: Same. * doc/xml/class.txml: Same. * doc/doxygen/guide.html: Removed, integrated into other docs. * doc/doxygen/user.cfg.in: Clean up XML generation. * doc/doxygen/run_doxygen: Move to.. * scripts/run_doxygen: ...here. * configure: Regenerate. * Makefile.in: Regenerate. * src/Makefile.in: Regenerate. * doc/Makefile.in: Regenerate. * po/Makefile.in: Regenerate. * libmath/Makefile.in: Regenerate. * include/Makefile.in: Regenerate. * libsupc++/Makefile.in: Regenerate. * testsuite/Makefile.in: Regenerate. * aclocal.m4: Regenerate. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@132226 138bc75d-0d04-0410-961f-82ee72b054a4
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+<sect1 id="manual.util.memory.auto_ptr" xreflabel="auto_ptr">
+<?dbhtml filename="auto_ptr.html"?>
+
+<sect1info>
+ <keywordset>
+ <keyword>
+ ISO C++
+ </keyword>
+ <keyword>
+ auto_ptr
+ </keyword>
+ </keywordset>
+</sect1info>
+
+<title>auto_ptr</title>
+
+<sect2 id="auto_ptr.limitations" xreflabel="auto_ptr.limitations">
+<title>Limitations</title>
+
+ <para>Explaining all of the fun and delicious things that can
+ happen with misuse of the <classname>auto_ptr</classname> class
+ template (called <acronym>AP</acronym> here) would take some
+ time. Suffice it to say that the use of <acronym>AP</acronym>
+ safely in the presence of copying has some subtleties.
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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 <emphasis>not</emphasis>be used for arrays!
+ </para>
+ <para>
+ <acronym>AP</acronym> is meant to prevent nasty leaks in the
+ presence of exceptions. That's <emphasis>all</emphasis>. This
+ code is AP-friendly:
+ </para>
+ <programlisting>
+ // Not a recommend naming scheme, but good for web-based FAQs.
+ typedef std::auto_ptr&lt;MyClass&gt; 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());
+ }
+ </programlisting>
+ <para>When an exception gets thrown, the instance of MyClass that's
+ been created on the heap will be <function>delete</function>'d as the stack is
+ unwound past <function>func()</function>.
+ </para>
+ <para>Changing that code as follows is not <acronym>AP</acronym>-friendly:
+ </para>
+ <programlisting>
+ APMC ap (new MyClass[22]);
+ </programlisting>
+ <para>You will get the same problems as you would without the use
+ of <acronym>AP</acronym>:
+ </para>
+ <programlisting>
+ char* array = new char[10]; // array new...
+ ...
+ delete array; // ...but single-object delete
+ </programlisting>
+ <para>
+ 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>auto_array_ptr</code> for that situation (in fact, this has
+ been done many times; check the mailing lists, Usenet, Boost, etc).
+ </para>
+</sect2>
+
+<sect2 id="auto_ptr.using" xreflabel="auto_ptr.using">
+<title>Use in Containers</title>
+
+ <para>
+ </para>
+ <para>All of the <ulink url="../23_containers/howto.html">containers</ulink>
+ described in the standard library require their contained types
+ to have, among other things, a copy constructor like this:
+ </para>
+ <programlisting>
+ struct My_Type
+ {
+ My_Type (My_Type const&amp;);
+ };
+ </programlisting>
+ <para>
+ Note the const keyword; the object being copied shouldn't change.
+ The template 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.
+ </para>
+ <para>
+ The resulting rule is simple: <emphasis>Never ever use a
+ container of auto_ptr objects</emphasis>. The standard says that
+ <quote>undefined</quote> behavior is the result, but it is
+ guaranteed to be messy.
+ </para>
+ <para>
+ To prevent you from doing this to yourself, the
+ <ulink url="../19_diagnostics/howto.html#3">concept checks</ulink> built
+ in to this implementation will issue an error if you try to
+ compile code like this:
+ </para>
+ <programlisting>
+ #include &lt;vector&gt;
+ #include &lt;memory&gt;
+
+ void f()
+ {
+ std::vector&lt; std::auto_ptr&lt;int&gt; &gt; vec_ap_int;
+ }
+ </programlisting>
+ <para>
+Should you try this with the checks enabled, you will see an error.
+ </para>
+</sect2>
+
+</sect1> \ No newline at end of file
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