C++ named requirements: UnformattedOutputFunction

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

C++ named requirements

Basic DefaultConstructible MoveConstructible (C++11) CopyConstructible CopyAssignable MoveAssignable (C++11) Destructible Type properties ScalarType PODType TriviallyCopyable (C++11) TrivialType (C++11) StandardLayoutType (C++11)   ImplicitLifetimeType Library-wide BooleanTestable EqualityComparable LessThanComparable Swappable ValueSwappable (C++11) NullablePointer (C++11) Hash (C++11) Allocator FunctionObject Callable Predicate BinaryPredicate Compare

Container Container ReversibleContainer AllocatorAwareContainer SequenceContainer ContiguousContainer (C++17) AssociativeContainer UnorderedAssociativeContainer (C++11)   Container element DefaultInsertable (C++11) CopyInsertable (C++11) MoveInsertable (C++11) EmplaceConstructible (C++11) Erasable (C++11) Iterator LegacyIterator LegacyInputIterator LegacyOutputIterator LegacyForwardIterator LegacyBidirectionalIterator LegacyRandomAccessIterator LegacyContiguousIterator (C++17) ConstexprIterator (C++20) Stream I/O FormattedInputFunction UnformattedInputFunction FormattedOutputFunction UnformattedOutputFunction Formatters BasicFormatter (C++20) Formatter (C++20)

Random Numbers SeedSequence (C++11) RandomNumberEngine (C++11) RandomNumberDistribution (C++11) UniformRandomBitGenerator (C++11) RandomNumberEngineAdaptor (C++11) Concurrency BasicLockable (C++11) Lockable (C++11) TimedLockable (C++11) SharedLockable (C++14) SharedTimedLockable (C++14) Mutex (C++11) TimedMutex (C++11) SharedMutex (C++17) SharedTimedMutex (C++14) Ranges RangeAdaptorObject (C++20) RangeAdaptorClosureObject (C++20) Multidimensional View LayoutMapping (C++23) LayoutMappingPolicy (C++23) AccessorPolicy (C++23) Other CharTraits RegexTraits (C++11)   BitmaskType LiteralType (C++11) NumericType UnaryTypeTrait (C++11) BinaryTypeTrait (C++11) TransformationTrait (C++11) Clock (C++11) TrivialClock (C++11)

 

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.

Standard library

The following standard library functions are UnformattedOutputFunctions.

• basic_ostream::operator<<(basic_streambuf*)
• basic_ostream::put
• basic_ostream::write
• basic_ostream::flush

basic_ostream::tellp (except calls pubseekoff instead of output) basic_ostream::seekp (except calls pubseekoff or pubseekpos instead of output)

(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
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()