Dynamic Memory

Dynamic Memory
Prev	Chapter 4. + Support + +	Next

+ There are six flavors each of new and + delete, so make certain that you're using the right + ones. Here are quickie descriptions of new: +

+ single object form, throwing a + bad_alloc on errors; this is what most + people are used to using +
+ Single object "nothrow" form, returning NULL on errors +
+ Array new, throwing + bad_alloc on errors +
+ Array nothrow new, returning + NULL on errors +
+ Placement new, which does nothing (like + it's supposed to) +
+ Placement array new, which also does + nothing +

+ They are distinguished by the parameters that you pass to them, like + any other overloaded function. The six flavors of delete + 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.) +

+ Remember that it is perfectly okay to call delete on a + NULL pointer! Nothing happens, by definition. That is not the + same thing as deleting a pointer twice. +

+ By default, if one of the “throwing news” can't + allocate the memory requested, it tosses an instance of a + bad_alloc 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 set_new_handler(): +

+   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);
+       ...
+   }
+

+ bad_alloc is derived from the base exception + class defined in Sect1 19. +