Created on2013-12-02.00:00:00 last changed109 months ago
[Moved to DR at the November, 2014 meeting.]
Proposed resolution (February, 2014):
Change 7.3.9 [conv.integral] paragraph 3 as follows:
If the destination type is signed, the value is unchanged if it can berepresented in the destination type(and bit-field width);otherwise, the value is implementation-defined.
Change 7.6.1.6 [expr.post.incr] paragraph 1 as follows:
...The result is a prvalue. The type of the result is the cv-unqualifiedversion of the type of the operand.If the operand is a bit-field thatcannot represent the incremented value, the resulting value of thebit-field is implementation-defined. See also7.6.6 [expr.add] and 7.6.19 [expr.assign].
Change 7.6.19 [expr.assign] paragraph 6 as follows:
When the left operand of an assignment operatordenotes a referencetoT, the operation assigns to the object of typeTdenoted by the referenceis a bit-field that cannot representthe value of the expression, the resulting value of the bit-field isimplementation-defined..
Change the final bullet of 9.5 [dcl.init] paragraph 17as follows:
The semantics of initializers are as follows...
...
...no user-defined conversions are considered. If the conversioncannot be done, the initialization is ill-formed.When initializing abit-field with a value that it cannot represent, the resulting value of thebit-field is implementation-defined. [Note: An expression oftype...
7.3.9 [conv.integral] paragraph 3 says, regarding integralconversions,
If the destination type is signed, the value is unchanged ifit can be represented in the destination type (and bit-fieldwidth); otherwise, the value is implementation-defined.
The values that can be represented in a bit-field are notwell specified, except for the correspondence with the values ofan enumeration in 9.8.1 [dcl.enum]. In particular, it isnot clear whether a bit-field has a sign bit and whether bit-fieldsmay have padding bits.
Another point to note in this wording: paragraph 1 describesthe context as
A prvalue of an integer type can be converted to a prvalueof another integer type.
However, prvalues cannot be bit-fields, so the applicability ofthe mention of “bit-field width” in paragraph 3 isunclear.
| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2017-02-06 00:00:00 | admin | set | status: drwp -> cd4 |
| 2015-05-25 00:00:00 | admin | set | status: dr -> drwp |
| 2015-04-13 00:00:00 | admin | set | messages: +msg5337 |
| 2014-11-24 00:00:00 | admin | set | status: ready -> dr |
| 2014-03-03 00:00:00 | admin | set | messages: +msg4805 |
| 2014-03-03 00:00:00 | admin | set | status: open -> ready |
| 2013-12-02 00:00:00 | admin | create | |