[RESEND PATCH] reader context: do not reuse current corpus and corpus_group

[Dodji Seketeli]

Hello Matthias, Giuliano,

Matthias Maennich <maennich@google.com> a écrit:

> libabigail's readers (abg-reader and abg-dwarf-reader) currently spare
> some allocations by reusing the reader context's existing current corpus
> and current corpus group. When building a corpus_group's vector of
> corpora, reusing the shared_ptr referring to a corpus means we are
> modifying the corpus data of a previously read corpus. As a user of the
> read*corpus functions, that isn't entirely transparent and when storing
> corpare like in the vector above, we might introduce subtle bugs.

[...]

Giuliano Procida <gprocida@google.com> a écrit:

> Does this change have any impact on incomplete (forward-declared) type
> differences?
> Does it significantly impact performance on large inputs?

Right.  That is my concern as well.  The reason why we avoid
instantiating a new dwarf reader context all the time is for performance
reasons, especially when analysing a kernel with lots of kernel
modules.  Example of kernels would be any of the known enterprise
kernels, I guess.


That being said, a lot of things have happened on the front of
performance for kernels with lots of modules, so maybe this particular
optimization is not useful anymore, I am not sure.

In any case, we should measure this first before we know if this can get
in.

I hope this makes sense.

Cheers,

-- 
		Dodji