A Bug about GNAT 3.13p

A Bug about GNAT 3.13p

[wzm]

when I was writing a small example for my ada tutorials,I found a
bug,the sorce code is:

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

procedure comp is 
    function compare (A:Integer; B :Integer) return Integer is 
    begin 
    return (A - B);
    end compare;
    X,Y,Result:Integer;
 begin
    Put ("Enter A:"); Get (X);
     Put ("Enter B:"); Get (Y);
    Result := compare (X,Y);
    Put(Result);
    Put(Integer'Last); 
    case Result is
      when Integer'First..-1 => Put_Line (" A < B.");
      when 0 => Put_Line (" A = B.");
      when 1..Integer'Last => Put_Line (" A > B.");
      when others => null;
    end case;
 end comp;

the program can compile successfully&#65292;but when run:

Enter A:1234567890
Enter B:-1234567890
A < B

of course&#65292;it's wrong&#65292;and the value of Result became
-1825831516.
In this case&#65292;raising Constraint_error shoud be suitable

Re: A Bug about GNAT 3.13p

[tmoran]

> Enter A:1234567890
> Enter B:-1234567890
> A < B
   It's not a bug, it's a feature.  If you want the Gnat compiler to
implement Ada, you'll need the "-gnato" option.  Without that option, it
implements a slightly different language in which integer overflow is not
checked.  It's documented.  It also serves nicely to separate the
cognoscenti from the masses.

Re: A Bug about GNAT 3.13p

[wzm]

tmoran@acm.org wrote in message news:<99p28.35119$_t6.1630727346@newssvr14.news.prodigy.com>...
> > Enter A:1234567890
> > Enter B:-1234567890
> > A < B
>    It's not a bug, it's a feature.  If you want the Gnat compiler to
> implement Ada, you'll need the "-gnato" option.  Without that option, it
> implements a slightly different language in which integer overflow is not
> checked.  It's documented.  It also serves nicely to separate the
> cognoscenti from the masses.

Thank you!

Re: A Bug about GNAT 3.13p

[Robert Dewar]

wzm@clinux.org (wzm) wrote in message news:<5240f9fd.0201191650.2e71c7b1@posting.google.com>...
> when I was writing a small example for my ada tutorials,I 
> found a bug,the sorce code is:

This is not a bug, it is a test on whether you have read
the documentation. You failed the test :-)

Hint: look up -gnato, and while you are at it, check into
all the other compiler options since there are lots of nice
features there.