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

[Doug Evans <dje@google.com>]

On Mon, Jun 22, 2015 at 8:46 AM, Patrick Palka <patrick@parcs.ath.cx> wrote:
> On Mon, Jun 22, 2015 at 9:21 AM, Doug Evans <dje@google.com> wrote:
>> 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.
>
> The env array is "magical" so I'm not sure if these techniques may work on it.

Well, that's unfortunate.

https://www.tcl.tk/man/tcl8.5/TclCmd/tclvars.htm

"If the entire env array is unset then Tcl will stop monitoring env
accesses and will not update environment variables."

Still, it should be possible to write the equivalent.
I'll look at the save_vars patch.