Re: [RFC PATCH 0/3] implement dlmopen hooks for gdb

[Florian Weimer <fweimer@redhat.com>]

* Carlos O'Donell:

> On 9/22/20 2:04 PM, Florian Weimer wrote:
>> * Carlos O'Donell:
>> 
>>>> No, unlike GLIBC_PRIVATE, you can assume that if a GLIBC_DEBUG symbol is
>>>> there (and perhaps has the documented size), it has the documented
>>>> semantics.  But you can't assume that it is present.
>>>>
>>>> The semantics of GLIBC_PRIVATE symbols can change arbitrarily, even
>>>> between builds.
>>>
>>> Yes, absolutely, I agree completely, for it to be useful the semantics
>>> have to be:
>>>
>>> - If you detect a given symbol foo@GLIBC_DEBUG, then the feature is
>>>   present and has the semantics you expect.
>>>
>>> - If you want new semantics then you need to make a foo2@GLIBC_DEBUG
>>>   with the new semantics.
>>>
>>> What are the runtime semantics of the symbol? How do you access it?
>> 
>> That obviously depends on the symbol?  Sorry, I don't quite understand
>> these questions.
>
> You noted "not intended to be used for run-time linking?"
>
> Could you expand on what you're thinking there?

If there are no versioned dependencies on the symbol at the ELF level,
then the issues that require some distributions to backport whole symbol
sets do not apply.  The exact contents of the GLIBC_DEBUG symbol set
does not matter than.

Thanks,
Florian
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