[gcc r10-9402] Fix PR ada/99095

[Eric Botcazou]

https://gcc.gnu.org/g:7297af89ea22c1a1da8609d811e100cf73e574d6

commit r10-9402-g7297af89ea22c1a1da8609d811e100cf73e574d6
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Tue Mar 2 17:58:46 2021 +0100

    Fix PR ada/99095
    
    This is a regression present on the mainline and 10 branch, where we fail
    to make the bounds explicit for the return value of a function returning
    an unconstrained array of a limited record type.
    
    gcc/ada/
            PR ada/99095
            * sem_ch8.adb (Check_Constrained_Object): Restrict again the special
            optimization for limited types to non-array types except in the case
            of an extended return statement.
    gcc/testsuite/
            * gnat.dg/limited5.adb: New test.

Diff:
---
 gcc/ada/sem_ch8.adb                | 10 +++++++++-
 gcc/testsuite/gnat.dg/limited5.adb | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/gcc/ada/sem_ch8.adb b/gcc/ada/sem_ch8.adb
index f083f7c16e7..baba51933ae 100644
--- a/gcc/ada/sem_ch8.adb
+++ b/gcc/ada/sem_ch8.adb
@@ -810,11 +810,19 @@ package body Sem_Ch8 is
             --  that are used in iterators. This is an optimization, but it
             --  also prevents typing anomalies when the prefix is further
             --  expanded.
+
             --  Note that we cannot just use the Is_Limited_Record flag because
             --  it does not apply to records with limited components, for which
             --  this syntactic flag is not set, but whose size is also fixed.
 
-            elsif Is_Limited_Type (Typ) then
+            --  Note also that we need to build the constrained subtype for an
+            --  array in order to make the bounds explicit in most cases, but
+            --  not if the object comes from an extended return statement, as
+            --  this would create dangling references to them later on.
+
+            elsif Is_Limited_Type (Typ)
+              and then (not Is_Array_Type (Typ) or else Is_Return_Object (Id))
+            then
                null;
 
             else
diff --git a/gcc/testsuite/gnat.dg/limited5.adb b/gcc/testsuite/gnat.dg/limited5.adb
new file mode 100644
index 00000000000..ded8aa3b4b1
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/limited5.adb
@@ -0,0 +1,17 @@
+--  { dg-do compile }
+
+procedure Limited5 is
+
+   type Command       is limited null record;
+   type Command_Array is array (Positive range <>) of Command;
+      
+   function To_Commands return Command_Array is
+   begin
+      return Result : Command_Array (1 .. 2);
+   end To_Commands;
+   
+   The_Commands : aliased Command_Array := To_Commands;
+
+begin
+   null;
+end;