unmanaged resource

[George2]

Hello everyone,


I think unmanaged resource means the resources (e.g. memory and file handler) which is used directly (new, FILE*) other than using a wrapper class (Resource Acquisition Is Initialization) or auto_ptr to wrap it. Is my understanding correct?

Here is a sample about what is unmanaged resource.

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http://www.gotw.ca/gotw/066.htm

Moral #3: Always perform unmanaged resource acquisition in the constructor body, never in initializer lists. In other words, either use "resource acquisition is initialization" (thereby avoiding unmanaged resources entirely) or else perform the resource acquisition in the constructor body.
--------------------


thanks in advance,
George

[weaknessforcats]

Not true. You use function-try blocks for this.

[George2]

Sorry weaknessforcats, I am confused. My question is what is unmanaged resource and whether my understanding of unmanaged resource is correct. Your reply has relationship with my question? :-)

Not true. You use function-try blocks for this.

regards,
George

[weaknessforcats]

A resource managed by the compiler is a managed resource.

A resource managed by you is an unmanaged resource.

[George2]

Thanks weaknessforcats,


I think a pointer which is pointed to something allocated with new is unmanaged resource, and if we add a wrapper -- e.g. making the pointer as a member of a class, then the class is managed resource.

I am not sure whether my understanding is correct. It is appreciated if you could provide some samples about the two statement below.

A resource managed by the compiler is a managed resource.

A resource managed by you is an unmanaged resource.

have a good weekend,
George

[weaknessforcats]

You are making this too hard.

The compiler manages all resources not allocated by new. The resources allocated by new are unmanaged.

int* data = new int[30];
 

Here data is a pointer to an int. It is a local variable in a stack frame. It is managed by the compiler. When it goes out of scope, the destructor for the pointer will be called. Except in this case there is no destructor for an int* so the compiler just deletes it.

The fact that you did something without cleaning it up is irrelevant.

The int[30] is an unmanaged resource. It is your respnsibility to release it when you are finished with it.

If you put this in a class:

class George2
{
    int* data;
    public:
    George2() : data(new int[30]) {}
 
};
int main()
{
    George2 obj;
    George2* pobj = new George2;
}
 

Here obj is managed (the compiler allocated it). The fact that it has allocated other resources is irrelevant. When obj goes out of scope, the destructor will be called (except there isn't one) so if any problems arise where data is not delete, it will be your fault.

pobj is a managed resource (the compiler allocated it). the new George2 is unmanaged. When pobj goes out of scope, the pointer is destroyed. Pointers have no destructors so the George2 destrcutor (if there is one) will not be called. You have to delete the object yourself. And even here, you are responsible for cleanup of data members.

And please, do not drag in Microsoft's "managed C++" where they mean code running under the CLR.

[George2]

Thanks weaknessforcats,


Your sample is great! My question is answered.

You are making this too hard.

The compiler manages all resources not allocated by new. The resources allocated by new are unmanaged.

int* data = new int[30];
 

Here data is a pointer to an int. It is a local variable in a stack frame. It is managed by the compiler. When it goes out of scope, the destructor for the pointer will be called. Except in this case there is no destructor for an int* so the compiler just deletes it.

The fact that you did something without cleaning it up is irrelevant.

The int[30] is an unmanaged resource. It is your respnsibility to release it when you are finished with it.

If you put this in a class:

class George2
{
    int* data;
    public:
    George2() : data(new int[30]) {}
 
};
int main()
{
    George2 obj;
    George2* pobj = new George2;
}
 

Here obj is managed (the compiler allocated it). The fact that it has allocated other resources is irrelevant. When obj goes out of scope, the destructor will be called (except there isn't one) so if any problems arise where data is not delete, it will be your fault.

pobj is a managed resource (the compiler allocated it). the new George2 is unmanaged. When pobj goes out of scope, the pointer is destroyed. Pointers have no destructors so the George2 destrcutor (if there is one) will not be called. You have to delete the object yourself. And even here, you are responsible for cleanup of data members.

And please, do not drag in Microsoft's "managed C++" where they mean code running under the CLR.

regards,
George