Re: [PATCH] Fix PR gdb/17820

[Patrick Palka <patrick@parcs.ath.cx>]

On Wed, Apr 29, 2015 at 6:44 AM, Pedro Alves <palves@redhat.com> wrote:
> On 04/28/2015 02:05 AM, Patrick Palka wrote:
>> On Mon, Apr 27, 2015 at 2:39 PM, Pedro Alves <palves@redhat.com> wrote:
>
>>> But now we see that "set history size unlimited" in .gdbinit never
>>> really worked.  Bummer.  So this means that users must have kept
>>> using "set history size 0" instead...
>>
>> "set history size 0" (in the .gdbinit) doesn't set history to
>> unlimited either -- it sets it to 256!  So users currently have no
>> choice but to use "set history size BIGINT" for
>> approximately-unlimited history.
>
> Indeed, looks like that has already been the case...
>
>>> So if we change this now, there's no way to have a single
>>> "set history size FOO" setting that means unlimited with
>>> both gdb <= 7.9 and the next gdb release.  :-/  Oh well.  Maybe we should
>>> just tell users to do "set history size BIGINT" instead?
>>
>> But currently, neither "set history size 0" nor "set history size
>> unlimited" mean unlimited (in the .gdbinit).  So users today cannot
>> set an unlimited history size at all.  Changing this now will now at
>> least make "set history size unlimited".  So whether or not we change
>> this now, there will be no way to have a single "set history size FOO"
>> setting that means unlimited across current and future GDB versions.
>> Am I misunderstanding?
>>
>>>
>>> I'd definitely like to make "set history size 0" really
>>> disable history.
>>>
>>> So I think that if goes forward, it'd be good to have a NEWS entry.
>>
>> I can think of two things to mention.  One is that "set history size
>> 0" now really disables history.  The other is that "set history size
>> unlimited" now really does not truncate history.  Do you have anything
>> else in mind?
>
> That's good.  Maybe add the suggestion to
> use "set history size BIGINT" in .gdbinit, if compatibility
> with previous releases is desired.
>
>>>>       PR gdb/17820
>>>>       * top.c (history_size_setshow_var): Change type to signed.
>>>>       Initialize to -2.  Update documentation.
>>>>       (set_readline_history_size): Define.
>>>>       (set_history_size_command): Use it.  Remove logic for handling
>>>>       out-of-range sizes.
>>>>       (init_history): Use set_readline_history_size().  Test for a
>>>>       value of -2 instead of 0 when determining whether to set a
>>>>       default history size.
>>>>       (init_main): Decode the argument of the "size" command as a
>>>>       zuinteger_unlimited.
>>>
>>> Looks good to me.
>>>
>>> Adding a testcase would be ideal, but I'll not make it a requirement.
>>> I think we should be able to write one making use of GDBFLAGSs.  (and
>>> IWBN to test the  GDBHISTSIZE/HISTSIZE environment variables too, which
>>> we can do with "set env(HISTSIZE)", etc.)
>>
>> Do you have in mind a test that creates a dummy .gdbinit file to be
>> read by GDB?  Or is there another way to test this code path?
>
> It may be testable with -x or -ix on the command line too, not
> sure, gdb.base/bp-cmds-execution-x-script.exp is an example, though
> given "set history size" already behaves different today depending on when
> it is called, an alternate way to test the issue that happens to use
> the same path today may change in the future, and we may (re)introducing
> unnoticed bugs.  So I think we should test that path exactly.  I was
> thinking of creating a dir, put a test .gdbinit file there, and point
> HOME at that dir.  We'd just skip the test on remote host testing.

I tried this but the problem is that the testsuite seems to always
pass -nx to invocations of GDB meaning that .gdbinit files are not
read.  Would you know how to work around this?

>
> Thanks,
> Pedro Alves
>