Re: [PATCH v2] Make running git under other debugger-like programs easy

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

Hi Elijah,

On Mon, 9 Apr 2018, Elijah Newren wrote:

> On Mon, Apr 9, 2018 at 2:19 PM, Johannes Schindelin
> <Johannes.Schindelin@gmx.de> wrote:
> >
> > On Mon, 9 Apr 2018, Elijah Newren wrote:
> >
> >>  debug () {
> >> -      GIT_TEST_GDB=1 "$@" <&6 >&5 2>&7
> >> +     case "$1" in
> >> +     -d)
> >> +             DBG_FLAGS="$2" &&
> >
> > Maybe we can find a way that does not require setting a variable other
> > than GIT_DEBUGGER? After all, DBG_FLAGS will be visible to the script
> > calling `debug`...
> 
> I guess we could instead do a
>    export GIT_DEBUGGER="$2"
> here.  Short of explicitly using 'export', I think we'd need another
> environment variable.

I suppose so. The GIT_DEBUGGER variable has to be exported *anyway*,
otherwise the bin-wrappers/* won't see it.

> I would have stuck with your original suggestion, except that by running:
>     GIT_DEBUGGER="$1" debug_aux "$@"
> GIT_DEBUGGER would be set within the debug_aux function and would NOT
> be set once bin-wrappers/git was called, making git not run under the
> debugger as desired.

Oh, so in debug_aux, you'd have to do some funny

	GIT_DEBUGGER="$GIT_DEBUGGER" "$@"

to export that variable to the process... Ugly.

> >> +*)
> >> +     GIT_DEBUGGER_ARGS="$GIT_DEBUGGER"
> >> +     unset GIT_DEBUGGER
> >> +     exec ${GIT_DEBUGGER_ARGS} "${GIT_EXEC_PATH}/@@PROG@@" "$@"
> >
> > It may not be a big deal, bug GIT_DEBUGGER_ARGS (if it was exported e.g.
> > by the user calling the script) is now visible by the called process... (I
> > thought I had tried my best to avoid such a leaking variable in my
> > patch...)
> 
> You had a separate, per-process variable:
> GIT_DEBUGGER_$$="$GIT_DEBUGGER"

Right. And I guess it does not work because the _$$ is not expanded, you'd
have to eval it, and then you'd have to quote the right side
appropriately, and it's all not worth it.

> The problem with that line is that the $$ apparently makes bash treat
> it as a command to run rather than as a variable and a value with the
> desire to set one to the other.  Prepending the line with 'declare' or
> 'local' or perhaps 'readonly' would fix that, but those aren't posix
> and my reading suggested that while some other shells did support some
> of those builtins, the support was somewhat spotty.  Since
> wrap-for-bin.sh runs under /bin/sh, not /bin/bash, I didn't have a way
> of making the per-process piece work and just fell back to a separate
> variable.  Maybe we want to change that script to /bin/bash?
> 
> Do you see any alternatives I'm missing?

No, not really.

Well, let's stick with your patch (with s/DBG_FLAGS/GIT_DEBUGGER/).

Thanks,
Dscho