<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><title>Dynamic Memory</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="support.html" title="Chapter 4. Support"/><link rel="prev" href="support.html" title="Chapter 4. Support"/><link rel="next" href="termination.html" title="Termination"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Dynamic Memory</th></tr><tr><td align="left"><a accesskey="p" href="support.html">Prev</a> </td><th width="60%" align="center">Chapter 4. Support </th><td align="right"> <a accesskey="n" href="termination.html">Next</a></td></tr></table><hr/></div><div class="section" title="Dynamic Memory"><div class="titlepage"><div><div><h2 class="title"><a id="std.support.memory"/>Dynamic Memory</h2></div></div></div><p> There are six flavors each of <code class="function">new</code> and <code class="function">delete</code>, so make certain that you're using the right ones. Here are quickie descriptions of <code class="function">new</code>: </p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p> single object form, throwing a <code class="classname">bad_alloc</code> on errors; this is what most people are used to using </p></li><li class="listitem"><p> Single object "nothrow" form, returning NULL on errors </p></li><li class="listitem"><p> Array <code class="function">new</code>, throwing <code class="classname">bad_alloc</code> on errors </p></li><li class="listitem"><p> Array nothrow <code class="function">new</code>, returning <code class="constant">NULL</code> on errors </p></li><li class="listitem"><p> Placement <code class="function">new</code>, which does nothing (like it's supposed to) </p></li><li class="listitem"><p> Placement array <code class="function">new</code>, which also does nothing </p></li></ul></div><p> They are distinguished by the parameters that you pass to them, like any other overloaded function. The six flavors of <code class="function">delete</code> are distinguished the same way, but none of them are allowed to throw an exception under any circumstances anyhow. (They match up for completeness' sake.) </p><p> Remember that it is perfectly okay to call <code class="function">delete</code> on a NULL pointer! Nothing happens, by definition. That is not the same thing as deleting a pointer twice. </p><p> By default, if one of the <span class="quote">“<span class="quote">throwing <code class="function">new</code>s</span>”</span> can't allocate the memory requested, it tosses an instance of a <code class="classname">bad_alloc</code> exception (or, technically, some class derived from it). You can change this by writing your own function (called a new-handler) and then registering it with <code class="function">set_new_handler()</code>: </p><pre class="programlisting"> typedef void (*PFV)(void); static char* safety; static PFV old_handler; void my_new_handler () { delete[] safety; popup_window ("Dude, you are running low on heap memory. You should, like, close some windows, or something. The next time you run out, we're gonna burn!"); set_new_handler (old_handler); return; } int main () { safety = new char[500000]; old_handler = set_new_handler (&my_new_handler); ... } </pre><p> <code class="classname">bad_alloc</code> is derived from the base <code class="classname">exception</code> class defined in Sect1 19. </p></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="support.html">Prev</a> </td><td align="center"><a accesskey="u" href="support.html">Up</a></td><td align="right"> <a accesskey="n" href="termination.html">Next</a></td></tr><tr><td align="left" valign="top">Chapter 4. Support </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Termination</td></tr></table></div></body></html>