From 2ae98c3a75102cb4dbb9b8da690952a9971d4e93 Mon Sep 17 00:00:00 2001
From: Piotr Trojanek <trojanek@adacore.com>
Date: Fri, 6 May 2022 17:23:25 +0200
Subject: [PATCH] [Ada] Propagate null-exclusion to anonymous access types
When analyzing an array or record type declaration whose component has a
constrained access type, e.g.:
type Buffer_Acc is not null access all String;
type Buffer_Rec is record
Data : Buffer_Acc (1 .. 10);
end record;
type Buffer_Arr is array (Boolean) of Buffer_Acc (1 .. 10);
we propagated various properties of the unconstrained access type (e.g.
the designated type, access-to-constant flag), but forgot to propagate
the null-exclusion.
For GNAT it didn't make a big difference, because the (anonymous)
component type was never subject to legality checks. The "value
tracking" optimisation machinery, which also deals with null values,
only works for entire objects and doesn't care about components.
However, GNATprove uses this flag when an access-to-component object is
dereferenced.
gcc/ada/
* sem_ch3.adb (Constrain_Access): Propagate null-exclusion flag
from parent type.
---
gcc/ada/sem_ch3.adb | 1 +
1 file changed, 1 insertion(+)
diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index b7f26a3a066f..f91d3edfefd1 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -13535,6 +13535,7 @@ package body Sem_Ch3 is
Set_Directly_Designated_Type (Def_Id, Desig_Subtype);
Set_Depends_On_Private (Def_Id, Has_Private_Component (Def_Id));
Set_Is_Access_Constant (Def_Id, Is_Access_Constant (T));
+ Set_Can_Never_Be_Null (Def_Id, Can_Never_Be_Null (T));
Conditional_Delay (Def_Id, T);
--
GitLab