C++ named requirements: UnformattedOutputFunction

< cpp‎ | named req
C++ named requirements
Type properties
Container Elements

Stream I/O

Random Numbers


[edit] Requirements

A UnformattedOutputFunction is a stream output function that performs the following:

1) Constructs an object of type basic_ostream::sentry with automatic storage duration, which performs the following:
  • If eofbit or badbit are set on the output stream, sets the failbit as well, and if exceptions on failbit are enabled in this output stream's exception mask ((exceptions() & failbit) != 0), throws ios_base::failure.
  • Flushes the tie()'d output stream, if applicable.
2) Checks the status of the sentry by calling sentry::operator bool(), which is equivalent to basic_ios::good.
  • If the operator returns false or sentry's constructor throws an exception, no output takes place.
  • If the operator returns true, attempts to perform the desired output by inserting the characters into the output stream as if by calling rdbuf()->sputc(). Other public members of std::basic_ostream may also be used, but virtual members of rdbuf() except overflow(), xsputn() and sync() will never be called.
  • If an exception is thrown during output, sets badbit in the output 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 the value specified by the function.
3) In any event, whether terminating by exception or returning, the sentry's destructor is called before leaving this function.

[edit] Standard library

The following standard library functions are UnformattedOutputFunctions.

(since C++11)

[edit] 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 63 C++98 the exception-handling policy was missing added
LWG 160 C++98 the process of determining whether the exception caught
is rethrown mentioned a non-existing function exception()
corrected to exceptions()
LWG 165 C++98 the only virtual member allowed to be
called on rdbuf() was overflow()
also allowed
xsputn() and sync()