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digitalmars.D - DIP1000 questions

I was trying to read DIP1000, and I've made about half way 
through it. I found it confusing/hard to follow, and sometimes 
inconsistent. So I want to ask for some clarification. Help would 
be appreciated.

 # Abstract
 A garbage collected language is inherently memory safe.
I think in order for this sentence to make sense, we need to define what is a "garbage collected language". Does any language that supports GC count? Because there's Boehm GC for C. Does D count? Because dmd has this compiler switch: -boundscheck=off, which clearly makes the language not memory safe.
 # Description
 ## Definitions
 We also define lifetime for each value, which is the extent 
 during which a value can be safely used.
 * For an unrestricted pointer, [...] lifetime is dictated by 
 the lifetime of the data to which the pointer points to.
Why? The pointer itself can be used safely in its lexical scope just like a value type. It's *pointer which has the lifetime of the data. Maybe 'using' a pointer means dereferencing it?
 ### Algebra of Lifetimes
 expression	lifetime	notes
 *e		∞		Lifetime is not transitive
Huh? I guess this is true if *e is a value type, since then it would be copied. But what about: int a; int *b = &a; int **c = &b; *c = b so lifetime(*c) = lifetime(b), right? And then as per the example given
 if (...) {
    int x;
    p = &x; // lifetime(p) is now equal to lifetime(x)
lifetime(b) = lifetime(a). So lifetime(*c) = lifetime(a) != ∞. Maybe that example is poorly written? Because:
 ## Fundamentals of scope
     scope int* a = &global_var; // OK per rule 1, 
 lifetime(&global_var) > lifetime(a)
     a = &global_var;       // OK per rule 1, 
 lifetime(&global_var) > lifetime(a)
As per the previous example. lifetime(a) will become lifetime(&global_var) after first assignment. Would it be better if we say lifetime(&global_var) > reachability(a)? BTW, reachability() is defined at the beginning of this DIP, but never used afterwards. Why bother defining it?
Jan 05 2017