Re: [PATCH] Test the interaction between GDBHISTSIZE and .gdbinit

[Doug Evans <dje at google dot com>]

On Thu, Jun 18, 2015 at 7:44 AM, Patrick Palka <patrick@parcs.ath.cx> wrote:
> On Thu, Jun 18, 2015 at 5:06 AM, Pedro Alves <palves@redhat.com> wrote:
>> On 06/17/2015 09:17 PM, Patrick Palka wrote:
>>> The value inside the GDBHISTSIZE environment variable, only if valid,
>>> should override setting the history size through one's .gdbinit file.
>>
>> Thanks, looks good.
>>
>>> +    unset -nocomplain env(GDBHISTSIZE)
>>>      array set env [array get old_env]
>>
>> Though this unset looks unnecessary, given that the following line
>> restores the whole array.
>
> It turns out that
>
>     array set env [array get old_env]
>
> does not completely restore the env array to its original state.  What
> it seems to do is to reset each pre-existing environment variable
> (existing in the saved env array) to its original value.  New
> environment variables that were set inside the env array in the
> meantime do not get unset after restoring.

http://tcl.tk/man/tcl8.5/TclCmd/array.htm

> So e.g. after doing
>
>     array set old_env [array get env]
>     set env(SOME_NEW_VAR) foo
>     array set env [array get old_env]
>
> the environment variable SOME_NEW_VAR=foo will still be in the env
> array.  So this "array set env" trick is insufficient.  That is why
> the unset of GDBHISTSIZE is necessary there.

I haven't read the save_vars patch yet, but how about:

array set old_env [array get env]
...
array unset env ;# <<<<<<<<<<<<<<<
array set env [array get old_env]
array unset old_env

It might be a teensy bit simpler to do:

set old_env [array get env]
...
array set env $old_env
unset old_env

Dunno.