[gcc r16-5378] ada: Don't generate function that violates No_Dynamic_Sized_Objects restriction

[Marc Poulhies]

https://gcc.gnu.org/g:6651ce055d40d0aab06a51f9cd5028478bb8d9b4

commit r16-5378-g6651ce055d40d0aab06a51f9cd5028478bb8d9b4
Author: Steve Baird <baird@adacore.com>
Date:   Thu Oct 30 14:40:06 2025 -0700

    ada: Don't generate function that violates No_Dynamic_Sized_Objects restriction
    
    In some cases, the compiler implicitly generates a hash function for an
    enumeration type. If a No_Dynamic_Sized_Objects restriction is in effect then
    that hash function violates the restriction, resulting in a compilation
    failure. Therefore, do not generate the hash function in that case.
    
    gcc/ada/ChangeLog:
    
            * exp_imgv.adb (Build_Enumeration_Image_Tables): If a
            No_Dynamic_Sized_Objects restriction is in effect, then choose a large
            value for Threshold so that no Lit_Hash function is generated.

Diff:
---
 gcc/ada/exp_imgv.adb | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gcc/ada/exp_imgv.adb b/gcc/ada/exp_imgv.adb
index 3fef6fabe64e..ea7b18582179 100644
--- a/gcc/ada/exp_imgv.adb
+++ b/gcc/ada/exp_imgv.adb
@@ -112,13 +112,18 @@ package body Exp_Imgv is
       --  exactly spent on all possible paths from this point.
 
       Threshold : constant Nat :=
-        (if Is_Library_Level_Entity (E)
+        (if Restriction_Active (No_Dynamic_Sized_Objects)
+         then Nat'Last
+         elsif Is_Library_Level_Entity (E)
            or else not Always_Compatible_Rep_On_Target
          then 3
          else Nat'Last);
       --  Threshold above which we want to generate the hash function in the
       --  default case. We avoid doing it if this would cause a trampoline to
       --  be generated because the type is local and descriptors are not used.
+      --  We also avoid doing it if a No_Dynamic_Sized_Objects restriction is
+      --  in effect because the hash function will violate the restriction
+      --  by declaring an array subtype with dynamic bounds.
 
       Threshold_For_Size : constant Nat := Nat'Max (Threshold, 9);
       --  But the function and its tables take a bit of space so the threshold