std::vector::_Insert_n() contains a suboptimal check against max_size by Dmitry Me

As of version 10.0.40219.1 SP1Rel std::vector::_Insert_n() code goes like this:

if (_Count == 0)
;
else if (max_size() - size() < _Count)
_Xlen();    // result too long
else if (capacity() < size() + _Count)
//reallocate
else //skipped

Now capacity() <= max_size() at all times. Which means that if capacity() >= size() + _Count (enough room) then automatically max_size() >= size() + _Count. Which means that whenever that code is invoked when a vector already has room (that's quite often) the check max_size() >= size() + _Count is redundant.

_Insert_n() should be redesigned like this:

if (_Count == 0)
;
else if(capacity() - size() < _Count )
{
if( (max_size() - _Size < _Count)
     _Xlen();
//reallocate
} else //as previously

so that the check is done only if there's a need for reallocation in the first place.