C++: QLDoc for VirtualVariable in IR construction

Author: Robert Marsh

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll

@@ -133,6 +133,12 @@ abstract class MemoryLocation extends TMemoryLocation {
   predicate isAlwaysAllocatedOnStack() { none() }
 }
 
+/**
+ * Represents a set of `MemoryLocation`s that cannot overlap with
+ * `MemoryLocation`s outside of the set. The `VirtualVariable` will be
+ * represented by a `MemoryLocation` that totally overlaps all other
+ * `MemoryLocations` in the set.
+ */
 abstract class VirtualVariable extends MemoryLocation { }
 
 abstract class AllocationMemoryLocation extends MemoryLocation {

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SimpleSSA.qll

@@ -59,6 +59,12 @@ class MemoryLocation extends TMemoryLocation {
   final string getUniqueId() { result = var.getUniqueId() }
 }
 
+/**
+ * Represents a set of `MemoryLocation`s that cannot overlap with
+ * `MemoryLocation`s outside of the set. The `VirtualVariable` will be
+ * represented by a `MemoryLocation` that totally overlaps all other
+ * `MemoryLocations` in the set.
+ */
 class VirtualVariable extends MemoryLocation { }
 
 /** A virtual variable that groups all escaped memory within a function. */