[Bug tree-optimization/80794] constant objects can be assumed to be immutable

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80794

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #6)
> (In reply to Martin Sebor from comment #5)
> > S::i cannot change during the lifetime of an S object because S::i is
> > declared const.  This holds regardless of whether the S object itself is
> > const.
> 
> To be clear, the only way to change S::i is to destroy S or S::i and create
> a new object in its storage.  That can be relied on not to happen in s.foo()
> because the reference s is seen used after the function returns.

I agree about foo but not about the call in bar.
Also you cannot use the undefinedness found in foo (that is the call to f in
foo cannot change the object) with the bar [if they are in the same translation
unit] as foo might not be called at runtime (and it is only runtime
undefinedness).