Re: move constructors likely a requirement

[Carlo De Falco]

> Il giorno 4 set 2019, alle ore 00:39, John W. Eaton <address@hidden> ha 
> scritto:
> 
> I pushed the following changes:
> 
>  http://hg.savannah.gnu.org/hgweb/octave/rev/5bf76ab4cce3
>  http://hg.savannah.gnu.org/hgweb/octave/rev/a2d3fa82b730
>  http://hg.savannah.gnu.org/hgweb/octave/rev/fcaecdbc8d8a

Hi,

Since this changesets, when compiling with clang++ I see lot of warnings of the 
form :

octave/libinterp/parse-tree/pt-colon.cc:67:41: warning: moving a temporary 
object prevents copy elision
      [-Wpessimizing-move]
            octave_value ov_increment = std::move (m_increment->evaluate (tw));

AFAIU this warning means that, in this case, automatic return value 
optimization performed by the compiler
would result in code that is more efficient than that produced using move 
constructor.

I'm just reporting this in case it may be of interest, bu I don't know whether 
it is worth making any changes to
remove the warning.

c.