Return value of memory allocation ?

[t048]

I'm reading a tutorial about c++ programming and it says "you should check the return value of every memory allocation". What does that mean?

#include <cassert>

ptr = new int[size] // dynamic allocate memory
assert(ptr != 0)    // terminate if memory not allocated

Like this ??

[t048]

Oh, I see. *I thought it had something to do with removing things from memory and then checking to see if the memor y was in fact freed.

Oh, I see. I thought it had something to do with removing things from memory and then checking to see if the memor y was in fact freed.

no no, delete should remove all traces of the data.

[t048]

So delete doesn't just remove the pointers to the memory and mark it free, it actually destroys the data?

So delete doesn't just remove the pointers to the memory and mark it free, it actually destroys the data?

Deleting the pointer is removing all traces, it's marked as usable space, to be overwritten.

[ndogg]

So delete doesn't just remove the pointers to the memory and mark it free, it actually destroys the data?

There is an easier way to say it than Lovechild (but he's not incorrect.)

free()'d memory is not necessarily destroyed, that's compiler/OS dependent. In some cases, it may be destroyed, in others, it may merely be marked as unused. In the latter case, you could, if you really wanted to, keep using that data, but you can't rely on that data staying the same.

[t048]

#include <cassert>

ptr = new int[size] *// dynamic allocate memory
assert(ptr != 0) * * * *// terminate if memory not allocated

Like this ??

Is this how one would declared the variable [tt]ptr[/tt]?

...
int *ptr;
...
ptr= new int[size];
...

Also, what is the difference between these two lines:

myclass->mymethod();
(*myclass).mymethod();

[Mor_gath]

I don't se any diffrence if it's the same as ansi c
there -> == (*variabel).(element)

[redhead]

Is this how one would declared the variable [tt]ptr[/tt]?

...
int *ptr;
...
ptr= new int[size];
...

Yes, that is the way to declare an int array, which is created with new, or you could use malloc() or calloc() or realloc() or alloca() any other memory allocating version.

Also, what is the difference between these two lines:

myclass->mymethod();
(*myclass).mymethod();

This is playing with pointers, the derefferencing method with '->' is my favorit.