John Marino has packaged GNAT 6 from FSF for FreeBSD and DragonFly.
I’ve installed FreeBSD with GNAT 6, and tried to see if there were any obvious differences to the older versions (I use GNAT 4.9 and 5 on Debian).
So far the result is that it is more picky about anonymous access types. (Maybe even too picky. I’m trying to figure that out.)
Here is an example:
GNAT 6.0.0 20151129 (snapshot) -=> GNAT AUX [FreeBSD64] Copyright 1992-2015, Free Software Foundation, Inc. Compiling: /usr/home/sparre/org.opentoken-6.0b/opentoken-production-parser-lalr-parser_lists.adb Source file time stamp: 2015-12-10 10:32:39 Compiled at: 2015-12-24 13:56:17 487. return (Element => Position.Item'Access); | >>> access discriminant in return aggregate would be a dangling reference 746 lines: 1 error gnatmake: "/usr/home/sparre/org.opentoken-6.0b/opentoken-production-parser-lalr-parser_lists.adb" compilation error
The subroutine which causes the problem is:
480 function Constant_Reference 481 (Container : aliased in List'Class; 482 Position : in Parser_Node_Access) 483 return Constant_Reference_Type 484 is 485 pragma Unreferenced (Container); 486 begin 487 return (Element => Position.Item'Access); 488 end Constant_Reference;
'Unrestricted_Access makes the compiler accept the function, but is it safe?
(Debian/experimental also has GNAT-6.)