[Ada] Refine implementation of AI05-0149 missing conversion checks

Message ID 20200609081006.GA73782@adacore.com
State New
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Series
  • [Ada] Refine implementation of AI05-0149 missing conversion checks
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Commit Message

Pierre-Marie de Rodat June 9, 2020, 8:10 a.m.
We were accepting conversion from anon-access-T'Class to access-all-T
which is incorrect.

Tested on x86_64-pc-linux-gnu, committed on trunk

2020-06-09  Arnaud Charlet  <charlet@adacore.com>

gcc/ada/

	* sem_type.adb (Covers): Fix implementation of AI05-0149.
	* sem_res.adb: Fix typo.

Patch

--- gcc/ada/sem_res.adb
+++ gcc/ada/sem_res.adb
@@ -2852,7 +2852,7 @@  package body Sem_Res is
                return;
 
             --  Under relaxed RM semantics silently replace occurrences of null
-            --  by System.Address_Null.
+            --  by System.Null_Address.
 
             elsif Null_To_Null_Address_Convert_OK (N, Typ) then
                Replace_Null_By_Null_Address (N);

--- gcc/ada/sem_type.adb
+++ gcc/ada/sem_type.adb
@@ -1021,15 +1021,17 @@  package body Sem_Type is
 
       --  Ada 2012 (AI05-0149): Allow an anonymous access type in the context
       --  of a named general access type. An implicit conversion will be
-      --  applied. For the resolution, one designated type must cover the
-      --  other.
+      --  applied. For the resolution, the designated types must match if
+      --  untagged; further, if the designated type is tagged, the designated
+      --  type of the anonymous access type shall be covered by the designated
+      --  type of the named access type.
 
       elsif Ada_Version >= Ada_2012
         and then Ekind (BT1) = E_General_Access_Type
         and then Ekind (BT2) = E_Anonymous_Access_Type
-        and then (Covers (Designated_Type (T1), Designated_Type (T2))
-                    or else
-                  Covers (Designated_Type (T2), Designated_Type (T1)))
+        and then Covers (Designated_Type (T1), Designated_Type (T2))
+        and then (Is_Class_Wide_Type (Designated_Type (T1)) >=
+                  Is_Class_Wide_Type (Designated_Type (T2)))
       then
          return True;