[gcc r12-5025] [Ada] Reference in Unbounded_String is almost never null

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:f4665dc4fb511a40a104f1986488861fee8b24f7

commit r12-5025-gf4665dc4fb511a40a104f1986488861fee8b24f7
Author: Piotr Trojanek <trojanek@adacore.com>
Date:   Wed Oct 27 10:33:32 2021 +0200

    [Ada] Reference in Unbounded_String is almost never null
    
    gcc/ada/
    
            * libgnat/a-strunb.adb (Deallocate): Rename Reference_Copy to
            Old, to make the code similar to other routines in this package.
            (Realloc_For_Chunk): Use a temporary, deallocate the previous
            string using a null-allowing copy of the string reference.

Diff:
---
 gcc/ada/libgnat/a-strunb.adb | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/libgnat/a-strunb.adb b/gcc/ada/libgnat/a-strunb.adb
index 0d62e4b379f..b0e455b9edb 100644
--- a/gcc/ada/libgnat/a-strunb.adb
+++ b/gcc/ada/libgnat/a-strunb.adb
@@ -506,11 +506,11 @@ package body Ada.Strings.Unbounded is
 
       if Object.Reference /= Null_String'Access then
          declare
-            Reference_Copy : String_Access := Object.Reference;
+            Old : String_Access := Object.Reference;
             --  The original reference cannot be null, so we must create a
             --  copy which will become null when deallocated.
          begin
-            Deallocate (Reference_Copy);
+            Deallocate (Old);
             Object.Reference := Null_Unbounded_String.Reference;
          end;
          Object.Last := 0;
@@ -833,9 +833,13 @@ package body Ada.Strings.Unbounded is
             Tmp : constant String_Access :=
               new String (1 .. New_Rounded_Up_Size);
 
+            Old : String_Access := Source.Reference;
+            --  The original reference cannot be null, so we must create a copy
+            --  which will become null when deallocated.
+
          begin
             Tmp (1 .. Source.Last) := Source.Reference (1 .. Source.Last);
-            Free (Source.Reference);
+            Free (Old);
             Source.Reference := Tmp;
          end;
       end if;