[ios::iostate]

using iostate = T2;

The type iostate is a bitmask type ([bitmask.types]) that contains the elements indicated in Table 104 .

Table 104 — iostate effects

Element	Effect(s) if set
badbit	indicates a loss of integrity in an input or output sequence (such as an irrecoverable read error from a file);
eofbit	indicates that an input operation reached the end of an input sequence;
failbit	indicates that an input operation failed to read the expected characters, or that an output operation failed to generate the desired characters.

30 Input/output library [input.output]