generalize endless loops to resource exhaustion

Author: RalfJung

const_safety.md

@@ -9,8 +9,9 @@ four possible ways:
 * The program causes undefined behavior (e.g., dereferencing an out-of-bounds
   pointer).
 * The program panics (e.g., a failed bounds check).
-* The program loops forever, and this is detected by the loop detector.  Note
-  that this detection happens on a best-effort basis only.
+* The program exhausts its resources: It might overflow the stack, allocation
+  too much memory or loops forever.  Note that detecting these conditions
+  happens on a best-effort basis only.
 
 Just like panics and non-termination are acceptable in safe run-time Rust code,
 we also consider these acceptable in safe compile-time Rust code.  However, we

promotion.md

@@ -101,5 +101,5 @@ TODO: Fill this with information.
 
 ## Open questions
 
-* There is a fourth kind of CTFE failure -- and endless loop being detected.
-  What do we do when that happens while evaluating a promoted?
+* There is a fourth kind of CTFE failure -- resource exhaustion.  What do we do
+  when that happens while evaluating a promoted?