Clarifying attribute-const

[Alexander Monakov]

On Fri, 25 Sep 2015, Eric Botcazou wrote:

> > First, a belated follow-up to https://gcc.gnu.org/PR66512 . The bug is
> > asking why attribute-const appears to have a weaker effect in C++, compared
> > to C. The answer in that bug is that GCC assumes that attribute-const
> > function can terminate by throwing an exception.
> 
> FWIW there is an equivalent semantics in Ada: the "const" functions can throw 
> and the language explicitly allows them to be CSEd in this case, etc.

Can you expand on the "etc." a bit, i.e., may the compiler ...

  - move a call to a "const" function above a conditional branch, 
    causing a conditional throw to happen unconditionally?

  - move a call to a "const" function below a conditional branch, 
    causing an unconditional throw to happen only conditionally?

  - reorder calls to "const" functions  w.r.t. code with side effects, or
    other throwing functions?

(all of the above in the context of Ada)

Thanks.
Alexander