On 3/19/19 4:57 PM, Ed Smith-Rowland via libstdc++ wrote:
On 3/18/19 6:18 PM, Jonathan Wakely wrote:
On 17/03/19 22:54 -0400, Ed Smith-Rowland via libstdc++ wrote:
Greetings,
This patch implements C++20 p0202 - Add Constexpr Modifiers to
Functions in <algorithm> and <utility> Headers
and C++20 p1023 - constexpr comparison operators for std::array.
The patch is large because of the testsuite additions. Basically,
the algorithms and the array comparison operators are all marked
constexpr for C++20. This has been built and tested on x86_64-linux.
As discussed on IRC< the tests need to be run with -std=gnu++2a to
ensure everything we test (which is not exhaustive, but is the best we
can do) still works in C++2a mode.
The indentation went bad here:
template<typename _FIter1, typename _FIter2, typename
_BinaryPredicate>
- _FIter1
+ _GLIBCXX20_CONSTEXPR
+ _FIter1
find_first_of(_FIter1, _FIter1, _FIter2, _FIter2, _BinaryPredicate);
Fixed.
I would have to look through old emails but I think there's a reason
the function objects like _Iter_comp_to_val take their arguments by
non-const reference.
I'm very surprised that none of the algos that dispatch to
__builtin_memove need changes, because those optimizations won't work
in constant expressions. I would expect to have to use
std::is_constant_evaluated to disable the optimizations when used in
constant expressions.
As am I. As I mentioned on IRC I could roll a constexpr memmove.
I was wondering if somehow I'm not checking what I think I'm checking
(but I don't see how.)
I wonder if the builtins are handled differently somehow by the front
end. I'm still not sure why __builtin_memcmp is OK for array == array
but not array != array. In that case I just do element by element
compare for constexpr now anyway.
Ed
Ignore this patch,
I'm not actually getting constexpr.
Ed
