C++ named requirements: FormattedInputFunction
Requirements
A FormattedInputFunction is a stream input function that performs the following:
- Constructs an object of type basic_istream::sentry
with automatic storage duration and with the noskipws argument set to
false
, which performs the following:- if eofbit or badbit are set on the input stream,
sets the failbit as well, and if exceptions on failbit are enabled in this input stream's
exception mask
((exceptions() & failbit) != 0)
, throws ios_base::failure. - flushes the tie()'d output stream, if applicable
- if ios_base::skipws flag is set on this input stream, extracts and discards characters from the input stream until one of the following becomes true:
- the next available character on the input stream is not a whitespace character, as tested by the std::ctype facet of the locale currently imbued in this input stream. The non-whitespace character is not extracted.
- the end of the stream is reached, in which case failbit and eofbit are set and if the stream is on for exceptions on one of these bits, ios_base::failure is thrown.
- if eofbit or badbit are set on the input stream,
sets the failbit as well, and if exceptions on failbit are enabled in this input stream's
exception mask
- Checks the status of the sentry by calling sentry::operator bool(), which is equivalent to basic_ios::good.
- If the sentry returned
false
or sentry's constructor threw an exception, no input takes place - If the sentry returned true, performs the input as if by calling
rdbuf()->sbumpc()
orrdbuf()->sgetc()
.- if the end of the stream is reached (the call to
rdbuf()->sbumpc()
orrdbuf()->sgetc()
returnsTraits::eof()
), sets eofbit. If exceptions on eofbit are enabled in this stream's exception mask((exceptions() & eofbit) != 0)
, throws ios_base::failure. - if an exception is thrown during input, sets badbit in the input stream.
If exceptions on badbit are enabled in this stream's exception mask
((exceptions() & badbit) != 0)
, the exception is also rethrown. - If no exception was thrown, returns
*this
.
- if the end of the stream is reached (the call to
- 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 FormattedInputFunctions.
- basic_istream::operator>>(int, long, double, void*, bool)
- operator>>(std::basic_istream, char&)
- operator>>(std::basic_istream, char*)
- operator>>(std::basic_istream, std::bitset)
- operator>>(std::basic_istream, std::string)
- operator>>, when called on the return value of std::get_money
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 160 | C++98 | the process of determining whether the exception caught is rethrown mentioned a non-existing function exception() | corrected to exceptions() |