Is the pointer guaranteed to be > a certain value?

Question

In C++ when i do new (or even malloc) is there any guarantee that the return address will be greater than a certain value? Because... in this project i find it

Answer 1

It's very platform-specific, so I would discourage relying on this kind of information unless you have a very good reason and are aware of consequences for portability, maintainability etc.

NULL is guaranteed to be 0x0 always. If I recall correctly, x86 reserves the first 128 MB of address space as "NULL-equivalent", so that valid pointers can't take on values in this range. On x64 there are some additional addresses which you shouldn't encounter in practice, at least for now.

As for address space reserved for the operating system, it will clearly depend on the OS. On Linux, the kernel-user space division is configurable in the kernel, so at least the 3 splits: 1-3 GB, 2-2 GB and 3-1 GB are common on 32-bit systems. You can find more details on kerneltrap.