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* sem_attr.adb: Add some ??? comments for previous change

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From-SVN: r135949
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Arnaud Charlet 2008-05-26 17:52:16 +02:00
parent 45c87b72c7
commit edde779b94
1 changed files with 19 additions and 1 deletions
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gcc/ada/sem_attr.adb
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@ -8089,8 +8089,26 @@ package body Sem_Attr is
-- Arr (X .. Y)'address is identical to Arr (X)'address,
-- even if the array is packed and the slice itself is not
-- addressable. Transform the prefix into an indexed component.
-- Note that the transformation is safe only if we know that
-- the slice is non-null.
-- the slice is non-null. That is because a null slice can have
-- an out of bounds index value.
-- Right now, gigi blows up if given 'Address on a slice, and
-- this covers up that bug in one case, but the bug is likely
-- still there in the cases not transformed by this code ???
-- It's not clear what 'Address *should* return for a null
-- slice with out of bounds indexes, this might be worth an ARG
-- discussion ???
-- One approach would be to do a length check unconditionally,
-- and then do the transformation below unconditionally, but
-- analyze with checks off, avoiding the problem of the out of
-- bounds index. This approach would interpret the address of
-- an out of bounds null slice as being the address where the
-- array element would be if there was one, which is probably
-- as reasonable an interpretation as any ???
declare
Loc : constant Source_Ptr := Sloc (P);