Thomas Løcke Being Incoherent

While trying out the new Ada 2012 loop syntax, I discovered what appeared to be a bug in the compiler: I could not use labeled exit statements when using the new loop syntax. Observe this simple example:

with Ada.Text_IO;
 
procedure Loopy is
   use Ada.Text_IO;
 
   Foo : array (1 .. 3) of String (1 .. 3)
     := (2 => "Bar", others => "Foo");
begin
   --  Classic loop syntax
   for I in Foo'Range loop
      Put_Line (Foo (I));
   end loop;
 
   --  New loop syntax
   for K of Foo loop
      Put_Line (K);
   end loop;
end Loopy;

Compiling this with the -gnat2012 works like a charm and output from the program is as expected:

Foo
Bar
Foo
Foo
Bar
Foo

Obviously using labeled loops/exits in this example is more or less completely pointless, but since I’m a bit of a renegade (and for the sake of the argument), I’m going to do it anyway. Lets see what happens:

with Ada.Text_IO;
 
procedure Loopy is
   use Ada.Text_IO;
 
   Foo : array (1 .. 3) of String (1 .. 3)
     := (2 => "Bar", others => "Foo");
begin
   --  Classic loop syntax
   Loop_Classic : for I in Foo'Range loop
      exit Loop_Classic When Foo (I) = "Bar";	  
      Put_Line (Foo (I));
   end loop Loop_Classic;
 
   --  New loop syntax
   Loop_New : for K of Foo loop
      exit Loop_New when K = "Bar";    
      Put_Line (K);
   end loop Loop_New;
end Loopy;

Awesome labels I’ve come up with eh’?

Compiling the above example yields this little puppy:

gcc -c -gnat2012 loopy.adb
loopy.adb:17:07: invalid loop name in exit statement
gnatmake: "loopy.adb" compilation error

Gaagle! The horror! The pain! The bug has been reported to AdaCore by Marc A. Criley, and according to this notice they’ve sorta/kinda acknowledged it.

So all we have to do now is wait for a fix. When I cried out on comp.lang.ada that I wanted my labeled exit statements back, he replied with this:

GNAT GPL 2013

Hehe.. Dry fellow that Marc. But he’s probably right. I’m just going to have to patiently wait an entire year before I can actually use the new loop syntax and labeled exit statements at the same time. I can handle that. I think.