Re: Issue 5368: Reduce allocations in Grob dimension caching (issue 359770043 by address@hidden)

[Hans Åberg]

> On 7 Jul 2018, at 09:35, David Kastrup <address@hidden> wrote:
> 
> Hans Åberg <address@hidden> writes:
> 
>>> On 6 Jul 2018, at 11:12, address@hidden wrote:
>>> 
>>> On 2018/07/05 21:32:25, Dan Eble wrote:
>>> 
>>>> The rationale is that std::optional is fit for this situation and if
>>>> LilyPond were built with C++17 I would simply have used it.
>>> 
>>> Any C++17 lookalike package is _not_ "simply using it" but a maintenance
>>> sink of itself.  And a semi-lookalike always requires double-checking in
>>> what respects it does and does not do the same job.  Write code once,
>>> debug it twice.  Not to mention profile it twice.
>>> 
>>> Reimplementing and then maintaining C++17 features and eventually
>>> possibly phasing out and replacing them by "the real thing" in 4 years
>>> or so is not the same as "simply using them".
>> 
>> Use __cplusplus. Later C++ versions also have a 'using' version of
>> typedef, which I found useful for transforming code.
> 
> This is totally not addressing the objection at all.

The idea is to do it all now, then the change is automatic and the old code can 
just be removed at some point in time, but you would need a compiler that can 
do C++17, too.