Allocation of memory with using different operators

[Sun]

Can memory allocated by malloc be" new" by using "delete",<br>
and can memory allocated by new be deleted by "free()"<br>
if this is possible thenfor what reason is this possible ?

 

[chiph]

<br>
I think this is possible, but a bad idea.<br>
<br>
If you look in the CRT source code, eventually they both will call _nh_malloc(). This is today. Next week they could be totally different.<br>
<br>
You really ought to code these things in matching sets. A phrase I've heard is "sandwich code", where the memory allocation and the free form the bread of the sandwich, with all the meat & good stuff inbetween.<br>
<br>
Chip H.<br>

 

[Mart311]

It sure is a bad idea.<br>
<br>
malloc() and free() know nothing of constructors and destructors, which means they will not be called.<br>
<br>
That can lead to some very hard to find runtime bugs.<br>
<br>
Just to illustrate, take this example:<br>
<br>
class MyClass<br>
{<br>
public:<br>
<br>
MyClass();<br>
~MyClass();<br>
<br>
private:<br>
SomeOtherClass* _myCopy;<br>
};<br>
<br>
MyClass::MyClass()<br>
{<br>
_myCopy = new SomeOtherClass();<br>
}<br>
<br>
MyClass::~MyClass()<br>
{<br>
delete _myCopy;<br>
}<br>
<br>
now if you did the following, you'll be left with a leak:<br>
<br>
main()<br>
{<br>
MyClass* ptrMyClass = new MyClass();<br>
<br>
free(ptrMyClass); // Big problem: _myCopy was never deleted!<br>
<br>
}

 

[chiph]

Mart311 -<br>
<br>
Good point. Memory leaks from destructors not being called (for encapsulated objects) would also be a serious problem.<br>
<br>
Chip H.<br>

 

[Sun]

This was in case of container classes,<br>
what if a class did not have an object of<br>
some other class and u allocated memory for that class's<br>
object using &quot;new&quot; and deleted it using &quot;free&quot; ?

 

[Mart311]

<br>
Mixing &quot;new&quot; and &quot;delete&quot; with &quot;malloc&quot; and &quot;free&quot; is<br>
never a good idea, but if your class doesn't contain<br>
other classes (either by reference or pointer) then<br>
you could do what you said.<br>
<br>
Just be forewarned that you are in dangerous ground!<br>
<br>
-Mart311<br>