C++ named requirements: FormattedOutputFunction

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C++ named requirements


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

  • 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.
  • 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 output takes place
  • If the sentry returned 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 the output could not be generated, sets failbit, If exceptions on failbit are enabled in this stream's exception mask, throws ios_base::failure.
  • 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 *this.
  • 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 FormattedOutputFunctions.