Re: segmentation violation in debug mode when watching for an index of an array and rerunning

[arnold]

Hello.

Thanks for the report.

Please try the latest release, 5.2.0, made about 2 weeks ago. Here
is what I get:

        $ cat a.awk
        a[1] = 2

        $ ./gawk --debug -f a.awk 
        gawk> b 1
        Breakpoint 1 set at file `a.awk', line 1
        gawk> run
        Starting program:
        
        Stopping in Rule ...
        Breakpoint 1, main() at `a.awk':1
        1       a[1] = 2
        gawk> watch a[1]
        Watchpoint 2: a["1"]
        gawk> run
        Program already running. Restart from beginning (y/n)? y
        Restarting ...
        Starting program:
        Program exited normally with exit value: 0

Now, exiting right away isn't lovely, but at least it's not a core dump.
(I will explore it further.)

In general, watchpoints are pretty fragile.  The debugger was written
by another developer who abandoned the project a long time ago, and is
perhaps the part of gawk I am least familiar with, unfortunately.

Arnold

Pascal Maugis <pascal.maugis@lsce.ipsl.fr> wrote:

> In debug mode, watching for operation on the index of an array is 
> possible (et very usefull). However, when rerunning the program while 
> the watch is still active leads to segmentation violation :
>
>     zsh> echo "a[1]=2" >! a.awk
>     zsh> gawk -D -f ./a.awk
>     *gawk> b *1
>      ?????? Point d'arret 1 defini dans le fichier ????./a.awk???? ligne 1
>     *gawk> r*
>      ?????? Demarrage du programme??:
>      ?????? Arr??t dans Rule...
>      ?????? Breakpoint 1, main() ?? ????./a.awk????:1
>      ?????? 1???????????? a[1]
>     gawk> n
>     gawk> w a[1]
>     Watchpoint 2: a["1"]
>     gawk> r
>      ?????? Programme en cours. Reprendre depuis le debut (o/n)??? o
>     *?????? gawk: fatal??: erreur interne??: erreur de segmentation*
>      ?????? [2]?????? 1001153 abort (core dumped)?? gawk -D -f ./a.awk
>
> Obviously, after rerun, 'watch' points to an adress which is not 
> allocated anymore (which is logic). I guess watchpoints on array indexes 
> should be disabled on rerun, or reenabled only when the array is defined 
> again as such. Watching a whole array ('watch a') works fine.
>
> Cheers,
>
> Pascal.
>
> Le 13/09/2022 ?? 12:42, Pascal Maugis a ??crit??:
> >
> > Hi, as promised here is the strange, unexpected behavior of ++ that 
> > looks like an error to me, because in "a ++b", a is incremented 
> > instead of b. "a b++" and "a++ b" produce the correct results however :
> >
> >     touch a.awk
> >     gawk -D -f ./a.awk
> >     eval "a=1 ; b=2"
> >     eval "print a ++b"???? ; output = 12 : (variables will be
> >     incremented after the operation, ok with me as documented)
> >     eval "print a b"???????? ; output = 22 : a has been incremented
> >     instead of b
> >     eval "print a++b"?????? ; output = 22 :
> >     eval "print a b"???????? ; output = 32 : a has been incremented
> >
> > The operation seems to be interpreted as "a++b", the space been 
> > uninterpreted as a separator
> >
> > Thanks for your insight,
> >
> > Cheers,
> >
> > Pascal.
> >
> > -- 
> > ------------------------------------------------------------------------
> >
> > *Pascal MAUGIS*
> > Mod??lisation hydrologique et changement climatique, PhD
> >
> > LSCE
> >
> > Laboratoire des Sciences du Climat et de l'Environnement 
> > <http://www.lsce.ipsl.fr/>
> >
> > Unit?? Mixte de Recherche CEA-CNRS-UVSQ (UMR 8212), IPSL, Paris-Saclay
> > Equipe MOSAIC : MOdelisation des SurfAces et Interfaces Continentales
> > B??t. 714, pi??ce 2115
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> >
> > e-mail : pascal.maugis@lsce.ipsl.fr
> > Page perso : FR <http://www.lsce.ipsl.fr/Pisp/pascal.maugis/> - EN 
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> > Tel./Fax : +33 1 69 08 75 24 / +33 1 69 08 77 16
> >
> > ------------------------------------------------------------------------
> -- 
> ------------------------------------------------------------------------
>
> *Pascal MAUGIS*
> Mod??lisation hydrologique et changement climatique, PhD
>
> LSCE
>
> Laboratoire des Sciences du Climat et de l'Environnement 
> <http://www.lsce.ipsl.fr/>
>
> Unit?? Mixte de Recherche CEA-CNRS-UVSQ (UMR 8212), IPSL, Paris-Saclay
> Equipe MOSAIC : MOdelisation des SurfAces et Interfaces Continentales
> B??t. 714, pi??ce 2115
> C.E. Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, FRANCE
>
> e-mail : pascal.maugis@lsce.ipsl.fr
> Page perso : FR <http://www.lsce.ipsl.fr/Pisp/pascal.maugis/> - EN 
> <http://www.lsce.ipsl.fr/en/Phocea/Pisp/index.php?nom=pascal.maugis>
> Tel./Fax : +33 1 69 08 75 24 / +33 1 69 08 77 16
>
> ------------------------------------------------------------------------