C++ named requirements: UnformattedInputFunction
From cppreference.com
Requirements
An UnformattedInputFunction is a stream input function that performs the following:
1)
Constructs an object of type
basic_istream::sentry
with automatic storage duration and with the
noskipws
argument set to
true
, which performs the following:
-
If
eofbit
or
badbit
are set on the input stream, sets the
failbit
as well, and if exceptions on
failbitare enabled in this input 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:
-
- Sets the number of extracted characters (gcount) in the input stream to zero.
-
If the function was called to write to an array of
CharT, writesCharT()(the null character) to the first location of the array.
- If the operator returns true , performs the input as if by calling rdbuf ( ) - > sbumpc ( ) or rdbuf ( ) - > sgetc ( ) .
-
-
If the end of the stream is reached (the call to
rdbuf
(
)
-
>
sbumpc
(
)
or
rdbuf
(
)
-
>
sgetc
(
)
returns
Traits
::
eof
(
)
), sets
eofbit. If exceptions oneofbitare enabled in this stream's exception mask ( ( exceptions ( ) & eofbit ) ! = 0 ), throws ios_base::failure . -
If an exception is thrown during input, sets
badbitin the input stream. If exceptions onbadbitare enabled in this stream's exception mask ( ( exceptions ( ) & badbit ) ! = 0 ), the exception is also rethrown.
-
- Exceptions thrown from basic_ios::clear are not caught or rethrown.
- If no exception was thrown during input, sets the number of extracted characters (gcount) in the input stream.
-
If the end of the stream is reached (the call to
rdbuf
(
)
-
>
sbumpc
(
)
or
rdbuf
(
)
-
>
sgetc
(
)
returns
Traits
::
eof
(
)
), sets
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 UnformattedInputFunction s .
- std::getline , except that it does not modify gcount.
- basic_istream::operator>> (basic_streambuf*)
- basic_istream::get
- basic_istream::getline
- basic_istream::ignore
- basic_istream::peek
- basic_istream::read
- basic_istream::readsome
-
basic_istream::putback
, except that it first clears
eofbit -
basic_istream::unget
, except that it first clears
eofbit - basic_istream::sync , except that it does not modify gcount
- basic_istream::tellg , except that it does not modify gcount
-
basic_istream::seekg
, except that it first clears
eofbitand does not modify gcount - std::ws , except that it does not modify gcount
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 61 | C++98 |
it was unclear whether throwing an exception because of
setting
eofbit
and/or
failbit
will result in setting
badbit
|
exceptions thrown from
basic_ios::clear
are not caught or rethrown |
| LWG 160 | C++98 |
the process of determining whether the exception caught
is rethrown mentioned a non-existing function
exception()
|
corrected to exceptions() |
| LWG 243 | C++98 |
the behavior when
sentry::operator bool()
returns
false
or the sentry object fails to be constructed was not specified |
specified |