C++ named requirements: UnformattedOutputFunction


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, 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() or rdbuf()->xsputn(). Additionally, rdbuf()->overflow() and rdbuf()->sync() may be called, but no other virtual member function of std::basic_streambuf.
    • 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, 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.

Standard library

The following standard library functions are UnformattedOutputFunctions.

(since C++11)

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

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