Build failure with GCC15 / C++23

[mattiaverga]

Fedora Linux has just introduced GCC15 with C++23 standard.
Ducc0 now fails to build with the following error:

g++ -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -march=z13 -mtune=z14 -fasynchronous-unwind-tables -fstack-clash-protection -fPIC -DPKGNAME=ducc0 -DPKGVERSION=0.36.0 -I. -I./src/ -I/usr/include/pybind11 -I/usr/include/pybind11 -I/usr/include/python3.13 -c python/ducc.cc -o build/temp.linux-s390x-cpython-313/python/ducc.o
  In file included from python/ducc.cc:9:
  ./src/ducc0/math/wigner3j.cc: In function ‘void ducc0::detail_wigner3j::wigner3j_00_internal(double, double, double, int, const ducc0::detail_mav::vmav<double, 1>&)’:
  ./src/ducc0/math/wigner3j.cc:110:6: error: call of ‘(const ducc0::detail_mav::vmav<double, 1>) (int)’ is ambiguous
    110 |   res(0) = 1.;
        |   ~~~^~~
  In file included from ./src/ducc0/infra/mav.cc:56,
                   from python/ducc.cc:3:
  ./src/ducc0/infra/mav.h:835:41: note: there are 2 candidates
    835 | template<typename T, size_t ndim> class vmav: public cmav<T, ndim>
        |                                         ^~~~
  ./src/ducc0/infra/mav.h:787:39: note: candidate 1: ‘const T& ducc0::detail_mav::cmav<T, ndim>::operator()(Ns ...) const [with Ns = {int}; T = double; long unsigned int ndim = 1]’
    787 |     template<typename... Ns> const T &operator()(Ns... ns) const
        |                                       ^~~~~~~~
  ./src/ducc0/infra/mav.h:885:33: note: candidate 2: ‘T& ducc0::detail_mav::vmav<T, ndim>::operator()(Ns ...) const [with Ns = {int}; T = double; long unsigned int ndim = 1]’
    885 |     template<typename... Ns> T &operator()(Ns... ns) const
        |                                 ^~~~~~~~
  ./src/ducc0/math/wigner3j.cc:111:35: error: call of ‘(const ducc0::detail_mav::vmav<double, 1>) (int)’ is ambiguous
    111 |   double sum = (2.*l1min+1.) * res(0)*res(0);
        |                                ~~~^~~

This is with ducc0 0.36.0 sources, I haven't tried if the main branch is already fixed.
A full build log is available here.

[mreineck]

Thanks a lot! I'll have a closer look tomorrow.

[mreineck]

Should be fixed on the main ducc0 branch.
Do you think this warrants a 0.36.1 release? My gut feeling is to wait for 0.37, which should not be too far off.

[mattiaverga]

I can wait for 0.37. Thanks!