FMT_DEPRECATED is now defined as FMT_HAS_CPP14_ATTRIBUTE(deprecated), as this attribute was introduced in C++14.
FMT_FALLTHROUGH is now defined as FMT_HAS_CPP17_ATTRIBUTE(fallthrough), as this attribute was introduced in C++17.
FMT_MAYBE_UNUSED is defined as FMT_HAS_CPP17_ATTRIBUTE(maybe_unused), as this attribute was introduced in C++17.
FMT_MAYBE_UNUSED has been applied to fix a couple of -Wunused-member-function warnings from clang.
FMT_STRING_IMPL has an internal helper named FMT_STRING, however FMT_STRING is also the name of the macro that invokes FMT_STRING_IMPL.
Renaming this helper avoids the appearance of a recursive macro.
Dair Grant