Unbounded string `ENCODING_ERROR : bad input at Item`

Why is the following code failing ?

I have picked Characters.Latin_1.Reserved_128 on purpose.

-- File 'print_non_graphic_character.adb'
with Ada.Characters.Latin_1;
with Ada.Text_IO;
with Ada.Strings.Unbounded;

procedure Print_Non_Graphic_Character is
   Text_String : constant String := "Non Graphic Character: " & Ada.Characters.Latin_1.Reserved_128;
   Text_Unbounded_String : constant Ada.Strings.Unbounded.Unbounded_String :=
      Ada.Strings.Unbounded.To_Unbounded_String (Text_String);
   Ada.Text_IO.Put_Line (Text_String);
   Ada.Text_IO.Put_Line (Ada.Strings.Unbounded.To_String (Text_Unbounded_String));
   Ada.Text_IO.Put_Line (Text_Unbounded_String'Image);
end Print_Non_Graphic_Character;

Note that it also fails with:

Ada.Text_IO.Put_Line (Ada.Strings.Unbounded.Unbounded_String'Image (Text_Unbounded_String));
-- File 'print_non_graphic_character.gpr'
project Print_Non_Graphic_Character is
   for Main use ("print_non_graphic_character.adb");
   for Object_Dir use ".objs";

   package Compiler is
      -- "-Og" -- Optimize for debug
      -- "-g" -- Generate debug info
      for Default_Switches ("Ada") use ("-g", "-gnat2020", "-Og");
   end Compiler;

   package Binder is
      for Switches ("Ada") use ("-Es"); --  Symbolic traceback
   end Binder;
end Print_Non_Graphic_Character;

It gives me with GNAT 12.2.0

Non Graphic Character: �
Non Graphic Character: �

raised ADA.STRINGS.UTF_ENCODING.ENCODING_ERROR : bad input at Item (25)
0x40e8fb Ada.Strings.Utf_Encoding.Raise_Encoding_Error at a-stuten.adb:126
0x40f38b Ada.Strings.Utf_Encoding.Strings.Decode at a-suenst.adb:163
0x4049a8 Print_Non_Graphic_Character at print_non_graphic_character.adb:13
0x404efa Main at b__print_non_graphic_character.adb:279
0x404658 _start at ???

It is annoying because, when I want to print a record which is commposed with Unbounded_String, I cannot use the 'Image attribute because of the above error and have to print each field and use To_String for Unbounded_String (which is annoying to have when I couple that with generic functions/packages).


  • I opened a bug on GCC Bugzilla: