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

[Carlos O'Donell via Libc-alpha <libc-alpha@sourceware.org>]

On 9/22/20 2:44 PM, Florian Weimer wrote:
> * 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.

Thank you for the clarification. I agree completely.

-- 
Cheers,
Carlos.