[Bug c++/91780] Discrepancy between gcc 7.4, through 9.2, compared to clang.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91780 --- Comment #10 from Mikael Persson --- Thats great. Saw the dates on the other pr, jikes this has been around a while. Testing z.containers_[0]->i is clever, ill add a test for that ( or more generally z.containers_[0]->begin(), static_assert if i can figure out how. Is there a way to make the syntax for a zip iterator for(auto& [a,b...] :zip(...))? So for(auto [a,...] : zip(...)) Would create local copies as expected? As is i renamed it to zip::view, which seemed easier to read. ( And fixed a bunch of other things too, but adding static assert clang only meant its been practically unused. In particular as clang is still horrendously slow for std::random compared to gcc. ) On Fri, 17 Dec 2021, 11:51 redi at gcc dot gnu.org, < gcc-bugzi...@gcc.gnu.org> wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91780 > > --- Comment #9 from Jonathan Wakely --- > GCC 10.1 isn't using the deduction guide at all, it seems to prefer to > deduce > the class type using the zip(Containers...) constructor, which deduces > non-reference types. > > If I change the deduction guide to: > > template > zip(Container_types&&... containers) -> zip; > > Then GCC 10.1 still compiles it, because it doesn't use that guide anyway. > Whereas GCC 10.2 gives an error, because it does deduce as zip and so > z.containers_[0]->i is invalid. > > -- > You are receiving this mail because: > You reported the bug.
[Bug c++/91780] Discrepancy between gcc 7.4, through 9.2, compared to clang.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91780
--- Comment #12 from Mikael Persson ---
Looking at it now, not sure why i didnt.
On Sun, 19 Dec 2021, 14:00 redi at gcc dot gnu.org, <
gcc-bugzi...@gcc.gnu.org> wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91780
>
> --- Comment #11 from Jonathan Wakely ---
> Can't you just change your constructor to this?
>
> zip(Containers&&... containers) :
> containers_(std::forward(containers)...) { }
>
>
> The problematic deduction seems to only happen because of the odd
> constructor
> with an unused parameter pack that gets deduced as empty.
>
> --
> You are receiving this mail because:
> You reported the bug.
[Bug c++/91780] Discrepancy between gcc 7.4, through 9.2, compared to clang.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91780
--- Comment #13 from Mikael Persson ---
Ah right lifetime
On Sun, 19 Dec 2021, 16:02 Mikael Persson,
wrote:
> Looking at it now, not sure why i didnt.
>
> On Sun, 19 Dec 2021, 14:00 redi at gcc dot gnu.org, <
> gcc-bugzi...@gcc.gnu.org> wrote:
>
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91780
>>
>> --- Comment #11 from Jonathan Wakely ---
>> Can't you just change your constructor to this?
>>
>> zip(Containers&&... containers) :
>> containers_(std::forward(containers)...) { }
>>
>>
>> The problematic deduction seems to only happen because of the odd
>> constructor
>> with an unused parameter pack that gets deduced as empty.
>>
>> --
>> You are receiving this mail because:
>> You reported the bug.
>
>
