libstdc++-v3/doc/html/manual/dynamic_memory.html

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  15     There are six flavors each of <code class="function">new</code> and
  16     <code class="function">delete</code>, so make certain that you're using the right
  17     ones. Here are quickie descriptions of <code class="function">new</code>:
  18   </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
  19         single object form, throwing a
  20         <code class="classname">bad_alloc</code> on errors; this is what most
  21         people are used to using
  22       </p></li><li class="listitem"><p>
  23         Single object "nothrow" form, returning NULL on errors
  24       </p></li><li class="listitem"><p>
  25         Array <code class="function">new</code>, throwing
  26         <code class="classname">bad_alloc</code> on errors
  27       </p></li><li class="listitem"><p>
  28         Array nothrow <code class="function">new</code>, returning
  29         <code class="constant">NULL</code> on errors
  30       </p></li><li class="listitem"><p>
  31         Placement <code class="function">new</code>, which does nothing (like
  32         it's supposed to)
  33       </p></li><li class="listitem"><p>
  34         Placement array <code class="function">new</code>, which also does
  35         nothing
  36       </p></li></ul></div><p>
  37      They are distinguished by the parameters that you pass to them, like
  38      any other overloaded function.  The six flavors of <code class="function">delete</code>
  39      are distinguished the same way, but none of them are allowed to throw
  40      an exception under any circumstances anyhow.  (They match up for
  41      completeness' sake.)
  42    </p><p>
  43      Remember that it is perfectly okay to call <code class="function">delete</code> on a
  44      NULL pointer!  Nothing happens, by definition.  That is not the
  45      same thing as deleting a pointer twice.
  46    </p><p>
  47      By default, if one of the <span class="quote">“<span class="quote">throwing <code class="function">new</code>s</span>”</span> can't
  48      allocate the memory requested, it tosses an instance of a
  49      <code class="classname">bad_alloc</code> exception (or, technically, some class derived
  50      from it).  You can change this by writing your own function (called a
  51      new-handler) and then registering it with <code class="function">set_new_handler()</code>:
  52    </p><pre class="programlisting">
  53    typedef void (*PFV)(void);
  54
  55    static char*  safety;
  56    static PFV    old_handler;
  57
  58    void my_new_handler ()
  59    {
  60        delete[] safety;
  61        popup_window ("Dude, you are running low on heap memory.  You
  62                       should, like, close some windows, or something.
  63                       The next time you run out, we're gonna burn!");
  64        set_new_handler (old_handler);
  65        return;
  66    }
  67
  68    int main ()
  69    {
  70        safety = new char[500000];
  71        old_handler = set_new_handler (&amp;my_new_handler);
  72        ...
  73    }
  74    </pre><p>
  75      <code class="classname">bad_alloc</code> is derived from the base <code class="classname">exception</code>
  76      class defined in Sect1 19.
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