Why *mut?

[iampi31415]

In this chapter about Debug it says:

As expected, x contains the value 42. The command print &x prints the address of the variable x. The interesting bit here is that GDB output shows the type of the reference: *mut i32, a pointer to a mutable i32 value.

I know the pointer type *mut which is a raw pointer type. But x is not mutable. I tested locally, and got the same.

Why is it so?

[BartMassey]

GDB doesn't really understand Rust very well; further it doesn't want to be restricted by Rust's rules, which make debugging harder. Treating the location of x as a mutable raw pointer is what allows you to set x's value in GDB:

(gdb) set x = 52
(gdb) print x
$2 = 52

Probably some text to this effect should be added here somewhere.