@@ -72,7 +72,14 @@ package body Exp_Ch8 is
-- clause applies (that can specify an arbitrary bit boundary), or where
-- the enclosing record itself has a non-standard representation.
- -- In these two cases, we pre-evaluate the renaming expression, by
+ -- In Ada 2020, a third case arises when the renamed object is a nonatomic
+ -- subcomponent of an atomic object, because reads of or writes to it must
+ -- access the enclosing atomic object. That's also the case for an object
+ -- subject to the Volatile_Full_Access GNAT aspect/pragma in any language
+ -- version. For the sake of simplicity, we treat any subcomponent of an
+ -- atomic or Volatile_Full_Access object in any language version this way.
+
+ -- In these three cases, we pre-evaluate the renaming expression, by
-- extracting and freezing the values of any subscripts, and then we
-- set the flag Is_Renaming_Of_Object which means that any reference
-- to the object will be handled by macro substitution in the front
@@ -102,10 +109,10 @@ package body Exp_Ch8 is
-- Determines whether it is necessary to do static name evaluation for
-- renaming of Nam. It is considered necessary if evaluating the name
-- involves indexing a packed array, or extracting a component of a
- -- record to which a component clause applies. Note that we are only
- -- interested in these operations if they occur as part of the name
- -- itself, subscripts are just values that are computed as part of the
- -- evaluation, so their form is unimportant.
+ -- record to which a component clause applies, or a subcomponent of an
+ -- atomic object. Note that we are only interested in these operations
+ -- if they occur as part of the name itself, subscripts are just values
+ -- that are computed as part of the evaluation, so they are unimportant.
-- In addition, always return True for Modify_Tree_For_C since the
-- code generator doesn't know how to handle renamings.
@@ -121,6 +128,10 @@ package body Exp_Ch8 is
elsif Nkind_In (Nam, N_Indexed_Component, N_Slice) then
if Is_Packed (Etype (Prefix (Nam))) then
return True;
+
+ elsif Is_Atomic_Or_VFA_Object (Prefix (Nam)) then
+ return True;
+
else
return Evaluation_Required (Prefix (Nam));
end if;
@@ -141,6 +152,9 @@ package body Exp_Ch8 is
then
return True;
+ elsif Is_Atomic_Or_VFA_Object (Prefix (Nam)) then
+ return True;
+
else
return Evaluation_Required (Prefix (Nam));
end if;