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Re: [PATCH] Tweak the handling of $HISTSIZE edge cases [PR gdb/16999]
- From: Pedro Alves <palves at redhat dot com>
- To: Patrick Palka <patrick at parcs dot ath dot cx>
- Cc: "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>
- Date: Fri, 22 May 2015 01:41:54 +0100
- Subject: Re: [PATCH] Tweak the handling of $HISTSIZE edge cases [PR gdb/16999]
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- References: <1432248648-7402-1-git-send-email-patrick at parcs dot ath dot cx> <555E6B60 dot 8040802 at redhat dot com> <CA+C-WL-89Y2_CaOpKe_tYP1S2BvKvwgFjW-NQ90tEN6MWW7VUg at mail dot gmail dot com>
On 05/22/2015 01:26 AM, Patrick Palka wrote:
> On Thu, May 21, 2015 at 7:33 PM, Pedro Alves <palves@redhat.com> wrote:
>> If I'm reading correctly, this treats HISTSIZE=" " as "disable history".
>> Is that intended?
>
> It's not really intended. The motivation was to make sure that an
> obvious typo in HISTSIZE (e.g. HISTSIZE="1000-") will not truncate the
> history size, but HISTSIZE=" " is not really a typo. But IMO adding a
> more intelligent typo heuristic (one to replace *endptr != '\0') is
> not worth it -- it's just a history file after all.
I haven't gone back to recheck what bash does, but, I can see
that happening in scripts, like:
if whatever; then
mysize=1000
fi
HISTSIZE="$mysize " HISTFILESIZE="$mysize"
and then mysize ends up unset.
>
> But that reminds me that the strings " 10" and "10 " should not be
> considered non-numeric. That could easily be achieved via a couple of
> calls to isspace().
Exactly, I was thinking of those too, but I didn't want to call
out what the behavior should be. :-)
>
>>
>> Also, a nit: I find it a bit odd to see strlen to check empty string
>> in one case, and != '\0' in another, instead of:
>>
>> if (*tmpenv == '\0'
>> || var < 0
>> || *endptr != '\0')
>>
>>> + history_size_setshow_var = -1;
>>> + else
>>> + history_size_setshow_var = var;
>>> }
>>> /* If the init file hasn't set a size yet, pick the default. */
>>> else if (history_size_setshow_var == -2)
>
> Well semantically endptr is less of a string and more of a pointer to
> a char within a string -- at least that's how I view it. But I will
> change the first condition to check for '\0'.
Ah. Good point. I'm fine either way then.
>
> On a related note, I wonder whether it is a good idea for GDB to look
> at HISTSIZE at all. As the buildbots and you have shown, some distros
> export HISTSIZE by default and by doing so it renders useless GDB's
> internal "history size" setting (as far as .gdbinit is concerned). I
> think people expect HISTSIZE to only affect shells, not e.g. readline
> applications. (Otherwise, I would expect the readline library to
> already extract the default history size from HISTSIZE or from another
> environment variable, something it currently has no support for.) So
> I wonder whether it would be better to stop reading HISTSIZE, to
> instead read GDBHISTSIZE or something.
Yeah, I'm inclined to agree.
Thanks,
Pedro Alves