From cppreference.com
Requirements
An UnformattedInputFunction is a stream input function that performs the following:
1) Constructs an object of type
with automatic storage duration and with the noskipws argument set to true, which performs the following:
If
or
are set on the input stream, sets the
as well, and if exceptions on failbit are enabled in this input stream's
((exceptions()&failbit)!=0), throws
.
Flushes the tie()'d output stream, if applicable.
2) Checks the status of the sentry by calling sentry::operator bool(), which is equivalent to
.
If the operator returns false or sentry's constructor throws an exception:
Sets the number of extracted characters (gcount) in the input stream to zero.
If the function was called to write to an array of CharT, writes CharT() (the null character) to the first location of the array.
If the operator returns true, performs the input as if by calling rdbuf()->sbumpc() or rdbuf()->sgetc().
If the end of the stream is reached (the call to rdbuf()->sbumpc() or rdbuf()->sgetc() returns Traits::eof()), sets eofbit. If exceptions on eofbit are enabled in this stream's
((exceptions()&eofbit)!=0), throws
.
If an exception is thrown during input, sets badbit in the input stream. If exceptions on badbit are enabled in this stream's
((exceptions()&badbit)!=0), the exception is also rethrown.
Exceptions thrown from
are not caught or rethrown.
If no exception was thrown during input, sets the number of extracted characters (gcount) in the input stream.
3) In any event, whether terminating by exception or returning, the sentry's destructor is called before leaving this function.
Standard library
The following standard library functions are
.
, except that it does not modify gcount.
basic_istream::operator>>(basic_streambuf*)
, except that it first clears eofbit
, except that it first clears eofbit
, except that it does not modify gcount
, except that it does not modify gcount
, except that it first clears eofbit and does not modify gcount
, except that it does not modify gcount
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 it was unclear whether throwing an exception because of
setting eofbit and/or failbit will result in setting badbitexceptions thrown from
are not caught or rethrown
C++98 the process of determining whether the exception caught
is rethrown mentioned a non-existing function exception()corrected to
C++98 the behavior when sentry::operator bool() returns false
or the sentry object fails to be constructed was not specified specified