Turn history saving on by default? (Re: GDB BoF notes - GNU Cauldron 2023)

Pedro Alves
2023-09-29T09:53:07Z

On 2023-09-29 10:24, Lancelot SIX wrote:
>>> - Revisiting defaults
>>>
>>> - Can we turn history saving on by default? Maybe default to
>>> history on home dir by default, too (~/.gdb_history). That would
>>> align us with bash. Some in the room have had this enabled in
>>> their gdbinits for so long they no longer remembered this wasn't
>>> on by default. Others weren't even aware you can turn this on.
>>
>> One issue I find with the bash approach is that you end up mixing history
>> between multiple unrelated sessions. Bash can't solve this but GDB possibly
>> could.
>>
>> My suggestion would be to use an approach similar to vim's swap files. As an
>> example, editing the maintainers file, I have the file ~/.local/state/nvim/swap/%home%blarsen%Documents%binutils-gdb%gdb%MAINTAINERS.swp;
>> This way you can have histories specific to any binary you're debugging
>> without mixing sessions.
>>
>
> Hi,
>
> With such approach, I am not really sure how to name/identify a session.
> Is that based on the name of the binary you're debugging? If so what
> happens if you use `file another_bin`? Either you switch to another
> "session", but really you never left GDB so that would seem odd to me,
> or you end up having history about another_bin in your first apparently
> unrelated session.

Of what happens if you start GDB without a binary at all?

>
> Similarly, when dealing with multiple inferiors, would running `inferior
> N` switch from session to session?
>
> I can see cases where such behavior could be helpful, but there seems
> to be a lot of edge cases where it could become strange.
>
> My feeling for now is that the best way to achieve this is to save the
> gdb history in the current directory, with the "risk" of having plenty
> of history files left all-over the place (as you mentioned already).
>
> I feel that having the default somewhere under $HOME / $XDG_STATE_HOME
> (as suggested by Tom) seems an "easier" default.
>

My thoughts exactly. +1.

On my bash for example, I got recently annoyed with
all my ssh shells overwriting the same history file, so I came up with a way to
have easy separate bash history sessions. But, I still think that the bash default
is OK.

The only viable options that I can think of for gdb are:

#1 - don't save history (current default)
#2 - save history in current dir
#3 - save history in $HOME (or somewhere XDG if it makes system for the system)

#1 is of course the current default.

#2 is what I do in my .gdbinit:

set history save on
set history filename .gdb_history
set history size unlimited

This works well enough for me. It does have the downside of sprinkling .gdb_history files all
over the place, which gets a bit annoying at times. E.g., sometimes I'll spawn gdb in a random
directory because I often use gdb as my calculator :-) ("(gdb) p 1 + 2 * 3", etc.),
which ends up with a .gdb_history file in that dir. Still, it's my choice, and
I am aware of the consequences.

#3 seems like a reasonable default to me, which doesn't have that "sprinkle files
throughout the filesystem" issue.