[Bug c++/121174] New: std::dextents was not found, which prevented std::mdspan from specifying dimensions at runtime

[printfne at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121174

            Bug ID: 121174
           Summary: std::dextents was not found, which prevented
                    std::mdspan from specifying dimensions at runtime
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: printfne at gmail dot com
  Target Milestone: ---

// main.cpp

import std;

int main() {

    int v[] = {1, 2, 3, 4, 5, 6};

    std::mdspan<int, std::dextents<std::size_t, 2>> view{v, 2, 3};

    return 0;
}


// command
g++-latest -std=gnu++26 -c -fmodules -fsearch-include-path bits/std.cc
g++-latest -std=gnu++26 -fmodules main.cpp  


// error message
ain.cpp: In function 'int main()':
main.cpp:7:27: error: 'dextents' is not a member of 'std'
    7 |     std::mdspan<int, std::dextents<std::size_t, 2>> view{v, 2, 3};
      |                           ^~~~~~~~
main.cpp:7:49: error: template argument 2 is invalid
    7 |     std::mdspan<int, std::dextents<std::size_t, 2>> view{v, 2, 3};
      |                                                 ^
main.cpp:7:49: error: template argument 3 is invalid
main.cpp:7:50: error: expected unqualified-id before '>' token
    7 |     std::mdspan<int, std::dextents<std::size_t, 2>> view{v, 2, 3};
      |