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| <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 5. Dynamic Memory</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="start" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="support.html" title="Part II. Support" /><link rel="prev" href="bk01pt02ch04s03.html" title="NULL" /><link rel="next" href="bk01pt02ch06.html" title="Chapter 6. Termination" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 5. Dynamic Memory</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt02ch04s03.html">Prev</a> </td><th width="60%" align="center">Part II. Support</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt02ch06.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="manual.support.memory"></a>Chapter 5. 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 type="disc"><li><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><p> |
| Single object "nothrow" form, returning NULL on errors |
| </p></li><li><p> |
| Array <code class="function">new</code>, throwing |
| <code class="classname">bad_alloc</code> on errors |
| </p></li><li><p> |
| Array nothrow <code class="function">new</code>, returning |
| <code class="constant">NULL</code> on errors |
| </p></li><li><p> |
| Placement <code class="function">new</code>, which does nothing (like |
| it's supposed to) |
| </p></li><li><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">throwing <code class="function">new</code>s</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 Chapter 19. |
| </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt02ch04s03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="support.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt02ch06.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">NULL </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 6. Termination</td></tr></table></div></body></html> |
