Re: ADA.STRINGS.INDEX_ERROR : a-strunb.adb:782

[Anh Vo <anhvofrcaus@gmail.com>]

On Tuesday, January 16, 2018 at 8:06:33 AM UTC-8, Brian Drummond wrote:
> On Mon, 15 Jan 2018 09:22:34 -0800, Anh Vo wrote:
> 
> > On Monday, January 15, 2018 at 12:29:41 AM UTC-8, Dmitry A. Kazakov
> >> 
> >>     addr2line --exe=<program-name> <funny-numbers>
> >> 
> >> That will give you the stack trace.
> >  
> > It is even better to use GNAT addition to print out full stack trace as
> > shown in the snippet.
> > 
> > -- ...
> > 
> > exception
> > 
> > when Err : others =>
> > 
> >   Text_Io.Put_Line ("Houston we have a problem: " &
> >                                     Exceptions.Exception_Information
> >                                     (Err));
> >   Text_Io.Put_Line ("Traceback => " &
> >   GNAT.Traceback.Symbolic.Symbolic_Traceback(Err));
> > end [Ada Unit Name];
> 
> This has some issues with (FSF) Gnat 6.3 (at least on Debian Stretch).
> I asked about this on the Gnoga list, still working through the issues.
> 
> (1) It just prints out the same funny numbers, with capital letters in 
> the hex part.
> 
> (2) Feeding the funny numbers to addr2line just gives a bunch of question 
> marks.
> 
> The culprit appears to be something to do with Position Independent 
> Executables, and Address Space Randomization, which appear to have broken 
> a few things. 
> 
> Adding "-no-pie" (NOT "-Wl,-no_pie") to the Linker switches changes the 
> funny numbers, such that addr2line can now parse them, fixing (2).
> 
> However neither this nor explicitly linking libreadline (adding 
> "-lreadline" to teh linker options fixes (1). I have a feeling that when 
> (2) broke, a quick fix was added to GNAT.Traceback.Symbolic to "fix" (1).
> 
> (checking the RTS source I see a comment...
> --  This is the default implementation for platforms where the full 
> capability
> --  is not supported. It returns tracebacks as lists of hexadecimal 
> addresses
> --  of the form "0x...".
> 
> So, apparently not provided in recent-ish FSF Gnat compilers ... if it 
> ever was.

I trusted that switch -g passed during compilation, -E passed during binding and -g passed during linking.

Anh Vo