Re: [RFA take 4] Allow setting breakpoints on inline functions (PR 10738)

[Doug Evans <dje@google.com>]

On Thu, Feb 16, 2012 at 2:37 AM, Gary Benson <gbenson@redhat.com> wrote:
>> > > The user's build procedure may involve building the index in a
>> > > way that is not easily updated in a timely manner.  Thus all the
>> > > speed improvements are (at least temporarily, but for a long
>> > > enough time to be troublesome) wiped out simply by using a
>> > > *newer* version of gdb.  And that makes me uncomfortable.
>> >
>> > How would it be if there the default behaviour was be to reject
>> > old indexes (as the patch does now) but with the addition of a
>> > flag ("maint set allow-old-gdb-indexes" perhaps?) that would allow
>> > users in this particular situation to get around it?  That way,
>> > our response to complaints can be "rebuild the index *or* use this
>> > flag (which by the way will lose you such and such a
>> > functionality)"  Inconsistent behaviour doesn't seem so bad if the
>> > user asked for it.
>>
>> IWBN if one could do "gdb my-binary-with-older-index" (as opposed
>> to, e.g., "gdb ; maint set ... ; file my-binary-with-older-index",
>> or the equivalent with -x/-ex foo, and setting the flag in
>> ./.gdbinit won't work).  That pretty much means passing gdb an
>> option ("gdb --use-old-index my-binary" or some such).  At Google
>> we've added --disable-gdb-index as an escape hatch against broken
>> indices.  I'm happy to replace it with something that will do the
>> same thing.
>>
>> As for what the default behaviour should be, I don't have a strong
>> enough opinion to want to defend it.  I can easily enough change it
>> here if desired.  [Not something unfamiliar to Redhat. :-)]
>
> Ok, so my plan is to implement an --allow-incomplete-gdb-index option
> that will turn on support for version 4 and 5 indexes.

[recognizing one tries not to bikeshed except when one thinks it's
important enough ...]
--allow-deprecated-gdb-index ?

> I am unsure
> as to whether to add printed warnings, but I'm leaning towards not
> having warnings in either configuration.  With the default setting
> GDB will work correctly, but may possibly be slow which would be the
> (admittedly not very direct) trigger for the user to investigate.
> With the option supplied I assume the user knows what they're doing,
> so they don't need pestering!

"works for me"

> I like the *idea* of warning users
> that their .gdb-index sections are being skipped, but I think of the
> case where somebody uses a new GDB on an older version of Fedora (say)
> being flooded with warning messages about every single shared library
> their program is linked to.

One can solve that by printing the warning at most once and providing
a way to see the entire list.  But I don't have a strong enough
opinion to push for implementing it.