On 3/29/19 11:12 AM, Jakub Jelinek wrote:
On Fri, Mar 29, 2019 at 11:07:53AM -0400, Jason Merrill wrote:
On Tue, Mar 19, 2019 at 4:57 PM Ed Smith-Rowland via gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
On 3/18/19 6:18 PM, Jonathan Wakely wrote:
On 17/03/19 22:54 -0400, Ed Smith-Rowland via libstdc++ wrote:
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.
Is there a PR about making these builtins work in constexpr?
Yes, PR80265.
Jakub
I see what you did there ;-) I could make my patch use the same idiom as
what you have in the char_traits patch if folks would prefer.
BTW, what does
(void) __s;
do?
In other news, assuming that it's official there was constexpr in
char_traits in some paper. I was going to try that but it looks like
you were starting.
Ed
