Re: What do you think about this?

[Laurent <lutgenl@icloud.com>]

On Thursday, 25 June 2015 09:29:45 UTC+2, Simon Wright  wrote:
> 
> > 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!)

Hm I checked the man pages for atos on Yosemite. No -d option. The whole thing is just providing some clues where to look for the error. In my case I have assigned a string which is longer than max length. I know where to find the error because it was intentional. But if not and the program is much larger, well good luck then to find it.