And probably many other distributions.
Until now, ./configure would fail silently printing a warning
./configure: line 4621: AX_CXX_COMPILE_STDCXX_17: command not found
and then continuing, later failing with a C++ #error saying that some C++11
feature isn't supported (it didn't even get to the C++17 features).
This is because older distributions don't come with the
`AX_CXX_COMPILE_STDCXX_17` m4 macro.
This commit vendors that macro accordingly.
Now ./configure complains correctly:
configure: error: *** A compiler with support for C++17 language features is required.
On Ubuntu 16.04, ./configure completes if a newer compiler is used, e.g. with
gcc-7 from https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test
using:
./bootstrap.sh
./configure CXX=g++-7 --disable-doc-gen --with-boost=$(nix-build --no-link '<nixpkgs>' -A boost.dev)
eldritch horrors
