Correct way to express to the compiler "this does not get clobbered"?

[stefan@franke.ms]

Am 4. Dezember 2020 00:00:28 MEZ schrieb Andrea Corallo via Gcc-help <gcc-help@gcc.gnu.org>:
>David Brown <david.brown@hesbynett.no> writes:
>
>Hi David,
>
>> As "f()" runs, the value of "y->fun_ptr" changes with each step as
>you
>> get alternating "foo1", "foo2" outputs.  Thus it is clear (I hope)
>that
>> the compiler cannot assume that "y->fun_ptr" is not clobbered by the
>> function call.
>
>Indeed that's clear.  The question is more if there's some way to
>express
>this to the compiler qualifying the variables in discussion without
>changing the structure of the code.  This because as I wrote may be not
>trivial to modify the code generator for optimal results.
>
>I understand this is probably not possible and there's no magic
>attribute or qualifier to express this.
>
>Thanks
>
>  Andrea

IMHO it's a bug that const members referenced by a const pointer are reloaded inside the loop.

Regards

Stefan