Suppose the following generic procedure to print the elements of an array indexed by a discreet type (note the slight logic added to prevent the printing of an extra , past the end of the last element):

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;

procedure Array_Printer is
   
   generic
      type Index is (<>);
      type Int_Array is array (Index range <>) of Integer;
   procedure Print(IA: Int_Array); 
   
   procedure Print(IA: Int_Array) is
      -- Penultimate: Index := Index'Pred(IA'Last); -- raises CONSTRAINT_ERROR for IA'Length = 1
   begin
      Put("[");
      for I in IA'First .. Index'Pred(IA'Last) loop
         Put(IA(I), 0);Put(",");
      end loop;
      Put(IA(IA'Last), 0);
      Put("]");      
   end Print;
   
   type Int_Array is array(Positive range <>) of Integer;
   
   IA: Int_Array := (-3, -2, -1, 0, 1, 2, 3);
   IA2: Int_Array := (1 => 0);
   
   procedure Print_Int_Array is new Print(Index => Positive,
                                          Int_Array => Int_Array);
   
   begin
      Print_Int_Array(IA);   
end Array_Printer;

When this procedure runs with an array of length > 1 (e.g. IA) it correctly prints the array ([-3,-2,-1,0,1,2,3]). However, when it is given an array of length = 1 (e.g. IA2) then, perhaps surprisingly, the penultimate index calculation in the for-loop doesn't raise a CONSTRAINT_ERROR (due to a predecessor not existing) and the expected result ([0]) gets printed.

When that calculation is done elsewhere however (e.g. in the declarative section of the procedure) then that exception is raised, indeed.

Is the compiler smart enough to figure-out there's only one element in the array and hence generates a null range for the for loop?

Gnatstudio seems to be invoking gprbuild with -cargs -g -O0

Any thoughts? - Thanks