Re: [PATCH 00/19] libctf, and CTF support for objdump and readelf

[Florian Weimer <fweimer at redhat dot com>]

* Nick Alcock:

> On 3 May 2019, Florian Weimer verbalised:
>
>> * Nick Alcock:
>>
>>>   - a very compact association between the ELF symbol table and CTF.
>>>     No symbol table indexes are recorded: all are implied: the
>>>     data-object section is as compact as possible, containing nothing
>>>     but a stream of type IDs describing the type of data symbols in
>>>     symbol table order.
>>
>> Is this for GNU/Linux?
>>
>> On GNU/Linux, DWARF unwinding information (in the form of
>> PT_GNU_EH_FRAME) is not optional, it is required by the ABI (although
>> many people pretend it's not, resulting in crashes or worse).
>> 
>> I'm worried that we have to add both in the future, DWARF data and CTF
>> data, which would be rather bad.
>
> I'm fairly sure they are quite distinct. CTF doesn't even try to record
> unwinding information, or anything like it, but rather lets you
> introspect into datatypes (not into the call stack, not into function
> arguments, but into C types).

I don't know what happened on Friday.  I must have had a bad day.  (I
did have trouble backporting something that should have been a
straightforward fix, too.)  I suppose I somehow mixed up CTF and CFI
in my mind.  Sorry about that.

You are of course right, CTF isn't related to unwinding.

Thanks,
Florian