Eigen::Vec2 is misaligned but condition cannot check it.

[recsater]

Eigen::Vec3, Eigen:: Mat3 and so on is ok except Eigen::Vec2

Make Eigen formattable

include "eigen3/Eigen/Core"

#define _FMTLOG_EIGEN_FORMAT(_Scalar, _Rows, _Cols)                          \
  template <>                                                                \
  struct fmt::formatter<Eigen::Matrix<_Scalar, _Rows, _Cols>>                \
      : formatter<std::string_view> {                                        \
                                                                             \
    auto format(const Eigen::Matrix<_Scalar, _Rows, _Cols>& c,               \
                format_context& ctx) const {                                 \
      std::stringstream ss;                                                  \
      ss << c.format(Eigen::IOFormat(5, 0, ", ", "\n", "[", "]", "[", "]")); \
      return fmt::formatter<fmt::string_view>::format(ss.str(), ctx);        \
    }                                                                        \
  };

_FMTLOG_EIGEN_FORMAT(double, -1, -1)
_FMTLOG_EIGEN_FORMAT(double, 2, -1)
_FMTLOG_EIGEN_FORMAT(double, 2, 1)
_FMTLOG_EIGEN_FORMAT(double, 2, 2)
_FMTLOG_EIGEN_FORMAT(double, 3, -1)
_FMTLOG_EIGEN_FORMAT(double, 3, 1)
_FMTLOG_EIGEN_FORMAT(double, 3, 2)
_FMTLOG_EIGEN_FORMAT(double, 3, 3)
_FMTLOG_EIGEN_FORMAT(double, 4, -1)
_FMTLOG_EIGEN_FORMAT(double, 4, 1)
_FMTLOG_EIGEN_FORMAT(double, 4, 2)
_FMTLOG_EIGEN_FORMAT(double, 4, 3)
_FMTLOG_EIGEN_FORMAT(double, 4, 4)

logi("{}", Eigen::Mat3); // OK
logi("{}", Eigen::Vec2); // Segfault

Segfault

// fmtlog.h :487
    if constexpr (std::is_trivially_copyable_v<fmt::remove_cvref_t<Arg>>) { // false for Eigen::Vec2 
        memcpy(out, &arg, sizeof(Arg)); // If run this line, formatting is successful.
      }
      else {
        new (out) fmt::remove_cvref_t<Arg>(std::forward<Arg>(arg));
      }
    return encodeArgs<CstringIdx>(cstringSize, out + sizeof(Arg), std::forward<Args>(args)...); // Segfault at this line.

[Mishura4]

Same issue with boost containers like boost::container::small_vector, which assert their alignment on construction.

This makes the library unusable on some ARM platforms which have strict alignment requirements.