Re: Conservative GC isn't safe

[Daniel Colascione <dancol@dancol.org>]

On 11/26/2016 07:05 AM, Stefan Monnier wrote:
>> How would you assert dynamically that if an interval is reachable, its
>> owning string or buffer must be too?
>
> You don't.  You check it statically (by a human).
>
>> It's not enough for the variable holding the reference to the string
>> or buffer to be in scope: you have to be sure that the reference
>> isn't dead.
>
> It should be: if it's in scope, it's not dead.

That's not the case.

struct foo* f = something();
int* x = f->&field;
something_else(); // invalidate global memory
*x = 5; // f is dead here, but still in scope

Even if you don't write this kind of code, the compiler is allowed to 
generate it.