First, this change is reducing undefined behavior* (EDIT: see below), and that undefined behavior (most casts between pointers and integers) did _not_ work reliably in practice. And in fact, the semantics they chose is rather sensible.
But yes, some code with UB which works for now might break. But that’s true whenever you upgrade your C compiler or use optimizations, so for correctness you shouldn’t do either! People working on certified embedded software have known that for long.
The real problem is that C users have been lied to. They’ve been taught the lie that C pointers are just addresses, that memory is an array of bytes, that relying on this lie is robust, and that this combination is fast. But this combination is impossible.
EDIT: officially some behavior was implementation-defined, but implementations made it undefined anyway — either officially or via bugs; links in subthread.
But yes, some code with UB which works for now might break. But that’s true whenever you upgrade your C compiler or use optimizations, so for correctness you shouldn’t do either! People working on certified embedded software have known that for long.
The real problem is that C users have been lied to. They’ve been taught the lie that C pointers are just addresses, that memory is an array of bytes, that relying on this lie is robust, and that this combination is fast. But this combination is impossible.
EDIT: officially some behavior was implementation-defined, but implementations made it undefined anyway — either officially or via bugs; links in subthread.