improve std::deque::_M_reallocate_map

[Michael Matz]

Hello,

On Tue, 26 Nov 2024, Jonathan Wakely wrote:

> So the 'const int' doesn't really matter for any -On level, as you
> say, but just avoiding two separate uses of the __deque_buf_size
> function is worthwhile for -std=c++98 -O0

Oh, definitely.  Avoiding duplicate calls in C++ sources (no matter which 
version) is always good, even if for nothing else than to avoid parsing 
two call expressions in later versions ;-)

> You were right to be triggered, I was wrong to say that making it a 
> constant expression mattered. For C++98 it's not a constant expression 
> (because the function is just 'inline' but not 'constexpr') and for 
> C++11 the fact it's 'constexpr' is enough for it to be constant-folded 
> whether the LHS is const or not.

Cool cool, thanks again for bearing with me!


Ciao,
Michael.