Re: [PATCH] Make running git under other debugger-like programs easy

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Elijah,

On Thu, 5 Apr 2018, Elijah Newren wrote:

> On Thu, Apr 5, 2018 at 12:57 PM, Johannes Schindelin
> <Johannes.Schindelin@gmx.de> wrote:
> 
> > I wonder whether a better approach would be to add an optional argument to
> > that `debug` function (which is intended to have `git` as first argument,
> > anyway, or at least a command/function that does not start with a dash):
> >
> > debug_aux () {
> >         shift
> >         "$@" <&6 >&5 2>&7
> > }
> >
> > debug () {
> >         case "$1" in
> >         -d)
> >                 shift &&
> >                 GIT_TEST_GDB="$1" debug_aux "$@"
> >                 ;;
> >         --debugger=*)
> >                 GIT_TEST_GDB="${1#*=}" debug_aux "$@"
> >                 ;;
> >         *)
> >                 GIT_TEST_GDB=1 "$@" <&6 >&5 2>&7
> >                 ;;
> >         esac
> > }
> >
> > ... and then in wrap-for-bin.sh, we would replace the last lines
> >
> > if test -n "$GIT_TEST_GDB"
> > then
> >         unset GIT_TEST_GDB
> >         exec gdb --args "${GIT_EXEC_PATH}/@@PROG@@" "$@"
> > else
> >         exec "${GIT_EXEC_PATH}/@@PROG@@" "$@"
> > fi
> >
> > by
> >
> > case "$GIT_TEST_GDB" in
> > '')
> >         exec "${GIT_EXEC_PATH}/@@PROG@@" "$@"
> >         ;;
> > 1)
> >         unset GIT_TEST_GDB
> >         exec gdb --args "${GIT_EXEC_PATH}/@@PROG@@" "$@"
> >         ;;
> > *)
> >         GIT_TEST_GDB_$$="$GIT_TEST_GDB"
> >         unset GIT_TEST_GDB
> >         exec $GIT_TEST_GDB_$$ "${GIT_EXEC_PATH}/@@PROG@@" "$@"
> >         ;;
> > esac
> >
> > or some such.
> 
> That all looks great to me.  But at this point, it seems like it's a
> full rewrite and your patch to submit (which I'd be happy to endorse
> in lieu of my own)...

:-)

> or do you want me to submit with you as author and me as committer?

That would be my preference. I have not even tested what I wrote above...

> Also, a side question: if we go this route, do we want to rename
> GIT_TEST_GDB to reflect its expanded usage?

Sure. Probably GIT_TEST_DEBUGGER? Or GIT_TEST_DBG? Or GIT_TEST_DEBUG?

> > Then your magic "GIT_WRAPPER" invocation would become a bit more explicit:
> >
> >     debug --debugger=nemiver git $ARGS
> >     debug -d "valgrind --tool=memcheck --track-origins=yes" git $ARGS
> 
> No, for most (60-80%?) of my invocations, I wouldn't be able to use
> the debug function; only a minority of my uses are from within the
> testsuite.  The rest are from the command line (I have
> git/bin-wrappers/ in my $PATH),

Oy vey. bin-wrappers in your PATH? That's even worse than what I did in
the first two years of developing Git: I always ran `git` in-place.
However, I was bitten by a couple of bugs introduced while developing that
made it hard to recover (if I don't have a functional Git, I cannot use it
to go back to a working version, can I?). How do *you* deal with these
things?

> so the above suggestions would mean that my invocation would become:
> 
> GIT_TEST_GDB="nemiver" git $ARGS
> GIT_TEST_GDB="valgrind --tool-memcheck --track-origins=yes" git $ARGS

Right.

> > (In any case, "GIT_WRAPPER" is probably a name in want of being renamed.)
> 
> Well, with your suggestion, it'd just be whatever that environment
> variable is named.  I'm perfectly happy with something other than
> GIT_WRAPPER (or GIT_TEST_GDB).  I'm not so good at coming up with such
> myself, but maybe something like GIT_DEBUGGER or GIT_DEBUG_WITH?

I like both. Pick whatever you like, as long as it starts with `GIT_` and
is descriptive enough. Even `GIT_LAUNCH_THROUGH` would work, but
`GIT_DEBUGGER` seems to be the shortest that still makes sense.

Ciao,
Dscho