Because avr-libc <errno.h> defines most error numbers with duplicate
values it's not sufficient to check #ifdef ENOTSUP when deciding which
std::errc constant to use for the filesystem library's __unsupported()
helper. Add a special case for AVR to always use the ENOSYS value.
libstdc++-v3/ChangeLog:
* src/filesystem/ops-common.h [AVR] (__unsupported): Always use
errc::function_not_supported instead of errc::not_supported.
inline error_code
__unsupported() noexcept
{
-#if defined ENOTSUP
+#if defined __AVR__
+ // avr-libc defines ENOTSUP and EOPNOTSUPP but with nonsense values.
+ // ENOSYS is defined though, so use an error_code corresponding to that.
+ // This contradicts the comment above, but we don't have much choice.
+ return std::make_error_code(std::errc::function_not_supported);
+#elif defined ENOTSUP
return std::make_error_code(std::errc::not_supported);
#elif defined EOPNOTSUPP
// This is supposed to be for socket operations