boost 1.73.0 - boost::numeric::ublas::matrix compilation issues with gcc-10 with c++20 support

[eladedgy]

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: testboost.cpp:9:27: required from here 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());

[bassoy]

Thanks @eladedgy for using boost.ublas. We are aware of this issue and we already included a bugfix for the upcoming release boost release. Please have a look at the already merged PR https://github.com/boostorg/ublas/pull/83. I will close this issue as the bug is fixed with commit https://github.com/boostorg/ublas/commit/47a314dd01d1adacaaf7265c7c644f8f70afd402 on the development branch.

[mclow]

I see this commit in develop, but not in master.

[eladedgy]

Please notice I've tested it on 1.74 beta 1 as well as issue is reproducible on that branch

[bassoy]

I see this commit in develop, but not in master.

Yes. I am not sure if we can pull the commit into master as we are late for the 1.74 release which will be closed for merges in one day. We need two contributors to

@mclow what is your advise?

[eladedgy]

Hi, gcc-10 is already released for a couple of months, and it's supported out-of-the-box in Ubuntu 20.04 LTS releasing 1.74.0 with this bug means no one will be able to compile with C++20 on those machines or Ubuntu 20.04 based containers This is not a minor issue which can be released

[jwakely]

Fedora 32 (released three months ago) also uses GCC 10.

[glenfe]

Fixed in develop with #103.