Incompatibility with `libfmt10`? `error: 'fmt::v10::detail::type_is_unformattable_for<cppoptlib::Status, char> _' has incomplete type`

[barracuda156]

Is something wrong on my side or libfmt10 is unsupported?

/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_math_polysolve/polysolve/work/polysolve-73d98008631b8ae1617131cb4896f784ae2ec5fe/src/polysolve/nonlinear/Solver.cpp:511:21:   required from here
/opt/local/include/libfmt10/fmt/core.h:1576:63: error: 'fmt::v10::detail::type_is_unformattable_for<cppoptlib::Status, char> _' has incomplete type
 1576 |     type_is_unformattable_for<T, typename Context::char_type> _;
      |                                                               ^
/opt/local/include/libfmt10/fmt/core.h:1580:7: error: static assertion failed: Cannot format an argument. To make type T formattable provide a formatter<T> specialization: https://fmt.dev/latest/api.html#udt
 1580 |       formattable,
      |       ^~~~~~~~~~~
/opt/local/include/libfmt10/fmt/core.h:1580:7: note: 'formattable' evaluates to false

May be related to using outdated cppoptlib: #63

[barracuda156]

@zfergus Thank you very much for addressing this!

I will test this soon, need to rebase the patches to use external libfmt (it is still needed, right?).

[zfergus]

You should not need to use an external fmt as it is bundled with spdlog (downloaded and compiled through cmake).

[barracuda156]

As long as it is not strictly required, we would rather use existing ports than build multiple duplicates (and Macports supports several versions of libfmt, that can be chosen, and at least two versions of spdlog). But of course, if some non-standard commit-based version is needed, then using the bundled one is the only feasible option.

[barracuda156]

@zfergus Tried to build it from d65d1b1 – I get almost the same error, just without cppoptlib now:

/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_math_polysolve/polysolve/work/polysolve-d65d1b1dbfc06bfe2aa038349f382b80ca4082e3/src/polysolve/nonlinear/Solver.cpp:481:21:   required from here
/opt/local/include/libfmt10/fmt/core.h:1600:63: error: 'fmt::v10::detail::type_is_unformattable_for<polysolve::nonlinear::Status, char> _' has incomplete type
 1600 |     type_is_unformattable_for<T, typename Context::char_type> _;
      |                                                               ^
/opt/local/include/libfmt10/fmt/core.h:1604:7: error: static assertion failed: Cannot format an argument. To make type T formattable provide a formatter<T> specialization: https://fmt.dev/latest/api.html#udt
 1604 |       formattable,
      |       ^~~~~~~~~~~
/opt/local/include/libfmt10/fmt/core.h:1604:7: note: 'formattable' evaluates to false

Should I switch to an earlier libfmt?