From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.5-pre1
Path: eternal-september.org!reader02.eternal-september.org!aioe.org!yy9MKEJN2ULhWGfnfq4v5w.user.gioia.aioe.org.POSTED!not-for-mail
From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: GCC 11 bug? lawyer needed
Date: Mon, 03 May 2021 17:08:20 +0100
Organization: Aioe.org NNTP Server
Message-ID: <lyh7jjztor.fsf@pushface.org>
NNTP-Posting-Host: yy9MKEJN2ULhWGfnfq4v5w.user.gioia.aioe.org
Mime-Version: 1.0
Content-Type: text/plain
X-Complaints-To: abuse@aioe.org
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (darwin)
Cancel-Lock: sha1:ggy9NsvdAIhCs/mIBeV3RMQl5EM=
X-Notice: Filtered by postfilter v. 0.9.2
Xref: reader02.eternal-september.org comp.lang.ada:61948
List-Id: <comp.lang.ada>

This code results in the error shown:

     1. package Aliased_Tagged_Types is
     2.
     3.    type T is tagged null record;
     4.
     5.    function P (Param : aliased T) return Boolean
     6.      is (False);
     7.
     8.    function F (Param : T) return Boolean
     9.      is (Param.P);
                 |
        >>> actual for explicitly aliased formal is too short lived

    10.
    11. end Aliased_Tagged_Types;

The compiler code that results in this error is at sem_ch4.adb:1490, and
was introduced for Ada202x accessibiity checking reasons.

   --  Check whether the formal is aliased and if the accessibility
   --  level of the actual is deeper than the accessibility level
   --  of the enclosing subprogam to which the current return
   --  statement applies.

   [...]

   if Is_Explicitly_Aliased (Form)
     and then Is_Entity_Name (Act)
     and then Static_Accessibility_Level
                (Act, Zero_On_Dynamic_Level)
                  > Subprogram_Access_Level (Current_Subprogram)
   then
      Error_Msg_N ("actual for explicitly aliased formal is too"
                    & " short lived", Act);
   end if;

----

For those interested, this issue affects Alire.