Question

If I have some stupid code like this:

int nBlah = 123;
int* pnBlah = &nBlah;
pnBlah += 80000;
*pnBlah = 65;

Can I change another app’s memory?

You have explained me this is evil, I know. But I was just interested.
And this isn’t something to simply try. I don’t know what would happen.

Thanks

Answer 1

In C++ terms, this is undefined behavior. What will actually happen depends on many factors, but most importantly it depends on the operating system (OS) you are using. On modern memory-managed OS’s, your application will be terminated with a “segmentation fault” (the actual term is OS-dependent) for attempting to access memory outside of your process address space. Some OS’s however don’t have this protection, and you can willy-nilly poke and destroy things that belong to other programs. This is also usually the case if your code is inside kernel space, e.g. in a device driver.