Re: What do you think about this?

[Simon Wright <simon@pushface.org>]

Laurent <lutgenl@icloud.com> writes:

> Houston we have a problem: Exception name: SYSTEM.ASSERTIONS.ASSERT_FAILURE
> Message: failed precondition from common_defs_bci.ads:19
> Load address: 0x1070dc000
> Call stack traceback locations:
> 0x107111931 0x1070e35f1 0x1070ddf8c 0x1070de763 0x1070de147 0x1070df063
>
> 0x0000000107111931
> 0x00000001070E35F1
> 0x00000001070DDF8C
> 0x00000001070DE763
> 0x00000001070DE147
> 0x00000001070DF063
>
> I can interpret the 3 first lines. For the rest I will ask my cat(s).

GNAT.Traceback.Symbolic isn't useful on Mac OS X; all it does is report
the absolute addresses of the stack trace without interpretation. The
fact it does so on multiple lines addes to the inconvenience.

My little example (written for another purpose) is:

   with Ada.Exceptions;
   with Ada.Text_IO; use Ada.Text_IO;
   procedure Raiser is
   begin
      begin
         raise Constraint_Error;
      exception
         when E : Constraint_Error =>
            Put_Line ("CE raised.");
            Put_Line (Ada.Exceptions.Exception_Information (E));
            raise;
      end;
   end Raiser;

and when I run it I get (GNAT GPL 201[4,5], FSF GCC)

   $ ./raiser 
   CE raised.
   Exception name: CONSTRAINT_ERROR
   Message: raiser.adb:6 explicit raise
   Load address: 0x101819000
   Call stack traceback locations:
   0x10181a987 0x10181a925


   Execution terminated by unhandled exception
   Exception name: CONSTRAINT_ERROR
   Message: raiser.adb:6 explicit raise
   Load address: 0x101819000
   Call stack traceback locations:
   0x10181a987 0x10181a925

The first set of messages is from Exception_Information, the last
because of dropping out of the main program.

The linker, by default, generates position-independent executables
(protection against viruses); the Load address line is where we happened
to get loaded this time.

To decode the stack traceback, use atos

   $ atos -d -o raiser -l 0x101819000 0x10181a987 0x10181a925
   got symbolicator for raiser, base address 100000000
   _ada_raiser (in raiser) (raiser.adb:6)
   main (in raiser) (b~raiser.adb:197)

(run atos without -d to see why it's there!)