Re: Potential Coextension Bug in GNAT

[Jere <jhb.chat@gmail.com>]

On Thursday, December 20, 2018 at 10:59:02 AM UTC-5, Jere wrote:
> I was messing around and trying to learn coextensions and
> I came across some counter intuitive functionality.  If I
> directly initialize one via an aggregate, it works fine.
> However, if I initialize through a constructing function, 
> it seems to treat the access discriminant as a normal access
> type and finalizes it at the end of the program instead of
> when the object leaves scope.  I don't fully understand them
> yet and there isn't much on them listed in the RM but one
> section (at least according to the index)[1].  That one
> section does indicate that initialization via a function
> should be valid however, so maybe I am back to I am doing it
> wrong or potentially a GNAT bug.
> 
> I'm using GNAT 7.1.1
> 
> Here is my test program
> 
> ****************************************************
> 
> with Ada.Text_IO; use Ada.Text_IO;
> with Ada.Finalization; use Ada.Finalization;
> 
> procedure Hello is
> 
>     type Thing_1 is new Limited_Controlled with null record;
>     
>     overriding 
>     procedure Finalize(Self : in out Thing_1) is
>     begin
>         Put_Line("Finalize Thing_1");
>     end Finalize;
>     
>     type Thing_2
>         (Other : not null access Thing_1)
>     is limited null record;
>     
>     procedure Test_Coextension_1 is
>         The_Thing : Thing_2(new Thing_1);
>     begin
>         Put_Line("Coextenson directly initialized");
>     end Test_Coextension_1;
>     
>     function Make_Thing_2 return Thing_2 is
>     begin
>         return (Other => new Thing_1);
>     end Make_Thing_2;
>     
>     procedure Test_Coextension_2 is
>         The_Thing : Thing_2 := Make_Thing_2;
>     begin
>         Put_Line("Coextension initialized through build in place");
>     end Test_Coextension_2;
>     
> begin
>     Test_Coextension_1;
>     Test_Coextension_2;
>     Put_Line("Test Finished");
> end Hello;
> 
> ****************************************************
> 
> Any thoughts?
> 
> [1] Ada 2012 tc1 RM 3.10.2(14.4/3) - http://www.ada-auth.org/standards/rm12_w_tc1/html/RM-3-10-2.html#I2301

Sorry, forgot to put the program output:
**************************************************
$gnatmake -o hello *.adb
gcc -c hello.adb
gnatbind -x hello.ali
gnatlink hello.ali -o hello
$hello
Coextenson directly initialized
Finalize Thing_1
Coextension initialized through build in place
Test Finished
Finalize Thing_1