Re: extdebug now implies errtrace which implies `trap ... ERR` execution w/out `set -e`

[Chet Ramey]

On 2/9/21 11:51 AM, Mike Frysinger wrote:
> On 09 Feb 2021 11:12, Chet Ramey wrote:
> > On 2/8/21 11:54 PM, Mike Frysinger wrote:
> > > this set of changes between bash-4.3 & bash-4.4:
> > > https://git.savannah.gnu.org/cgit/bash.git/commit/?h=814e1ff513ceca5d535b92f6c8dd9af7554fe83e
> >
> > I'm glad you're upgrading to bash-4.4. This change was made nearly five
> > years ago; the time to relitigate it has long passed.
>
> we're on bash-4.3 atm.  we would upgrade to the latest if that were actually
> a reliable process.  unfortunately, moving between bash versions is often full
> of random regressions or changes in behavior.  like this one.

Interesting. I suppose one person's bug fix is another's "random change." I
don't see it in this case, though, since it's a bug fix and making bash do
what its documentation said it did.

> i understand your point, but the real world of shipping code doesn't have the
> luxury of burning the house down for the latest shiny features.

I understand that distribution stability means that you'd like to encase
the shell in amber. That's just never going to happen -- taking this
argument to its logical conclusion would prohibit all bug fixes because
someone might be relying on the buggy behavior.

> > > has this buried nugget:
> > > +       - shopt_set_debug_mode: make sure error_trace_mode reflects the setting
> > > +         of extdebug.  This one is tentative.  Fix from Grisha Levit > +      
> > > <grishalevit@gmail.com>
> > > +       - shopt_set_debug_mode: call set_shellopts after setting 
> > > error_trace_mode
> > > +         or function_trace_mode.  Fix from Grisha Levit <grishalevit@gmail.com>

You could also have looked in the CHANGES file:

oooo. Fixed a bug that caused the shell to not enable and disable function
      tracing with changes to the `extdebug' shell option.

> it looks like we can mitigate this with `set -E` after we turn on extdebug.
> it's unfortunate that there's no way to get extended debug info without also
> opting in to side-effects like this.  all we really want is to get backtrace
> info for logging messages when we abort down a few layers.

If it works for you, great. But extdebug is always going to be for the
benefit of the shell debugger.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/