C++20: ‘class std::allocator’ has no member named ‘construct’

[mclow]

Taken from the -developers mailing list.

Problem description:
When compiling the following example:

#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/io.hpp>

int main () {
using namespace boost::numeric::ublas;
matrix m (3, 3);
for (unsigned i = 0; i < m.size1 (); ++ i)
  for (unsigned j = 0; j < m.size2 (); ++ j)
    m (i, j) = 3 * i + j;
std::cout << m << std::endl;
}

with gcc-10 with -std=gnu++2a flag, compilation breaks
Running the same compilation line with -std=gnu++17 passes

boost build command lines:
./bootstrap.sh --prefix="${PWD}/../boost-bin"
./b2
./b2 install

Compiled on ubuntu 18.04, added gcc-10:
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt install gcc-10 g++-10

Compilation error:
test_boost.cpp:9:27: required from here
/home/ubuntu/repos/cv-engine/externals/boost-bin/include/boost/numeric/ublas/storage.hpp:79:30: error: ‘class std::allocator’ has no member named ‘construct’
79 | alloc_.construct(d, value_type());

[mclow]

Duplicate. Sorry for the noise.

[jmarrec]

The duplicate is #96